SPECIAL PUBLICATION POTASSIUM IN INDIAN AGRICULTURE

International Symposium on Importance of Potassium in Nutrient Management for Sustainable Crop Production in India 3 -5 December, 2001 New Delhi

N.S. Pasricha & 5 K. Bansal

POTASH RESEARCH INSTITUTE OF INDIA

SINTERNATIONAL POTASH INSTITUTE SPECIAL PUBLICATION POTASSIUM IN INDIAN AGRICULTURE

International Symposium on Importance of Potassium in Nutrient Management for Sustainable Crop Production in India 3 - 5 December, 2001 New Delhi

N.S. Pasricha & S.K. Bansal

POTASH RESEARCH INSTITUTE OF INDIA

W INTERNATIONAL POTASH INSTITUTE Correct Citation: Pasricha, N.S. and Bansal, S.K. 2001. Potassium in Indian Agriculture, Special Publication, Potash Research Institute of India, Gurgaon, Haryana, India.

Published by the Potash Research Institute of India, Sector 19, Dundahera, Delhi-Gurgaon Road, Gurgaon-122001, Haryana, India

First printed 2001

Responsibility for the information in this publication rests with the individual authors.

Printed at Rakmo Press Pvt. Ltd., C-95, Okhla Industrial Area Phase-I, New Delhi-110020. Phone: 6814886, 6816282, Telefax: 6810424. Contents

I. Foreword 5

2. Preface 7

3. Kinetics of Potassium Release and Fixation in Soils 9 S.K. Sanyal and K. Majumdar

4. Potassium Availability in Relation to Soil Mineralogy in the Indo-Gangetic Plains 33 S.S. Mukhopadhyay and S.C. Dutta

5. Mineralogy and Dynamics of Potassium in Soils of Arid and Semi-Arid Regions of India 45 A.V Shanwal and S.P. Singh

6. Distribution and Availability of Potassium in Lateritic Soils of India 75 T.C. Baruah, K. Borakakati and H.C. Baruah

7. Distribution and Availability of Potassium in Red Soils of India 89 N.B. Prakash and R. Siddaramappa

8. Potassium Availability and Crops Response to Fertiliser Potassium in Hill and Mountain Soils of India 109 Patiram

9. Assessing Potassium Availability in Indian Soils 125 A. Subba Rao, TR. Rupa and S. Srivastava

10. Interaction of Potassium with Other Nutrients 159 A.N. Ganeshamurthy and Ch. Srinivasa Rao

11. Potassium Management in Rice-Wheat Cropping Systems in South Asia 175 Yadvinder Singh and Bijay Singh

12. Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 195 J.P. Singh, S.P Trehan and R.C. Sharma

13. Potassium Nutrition of Sugarcane in Relation to Yield, Quality and Abiotic Stress Tolerance 217 R.S Dwivedi 3 14. Potassium Fertility in Cotton Growing Soils of India and Its Influence on Yield and Quality of Cotton 241 M.S. Brar

15. Role of Potassium Fertilization in Improving Productivity of Pulse Crops 261 Masood Ali and Ch. Srinivasa Rao

16. Potassium Nutrition Management for Yield and Quality of Citrus in India 279 A.K. Srivastava and Shyam Singh

17. Influence of Potassium in Balanced Fertilization on the Yield and Quality of Vegetable Crops 321 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and S.K. Sharma

18. Potassium Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco 357 V Krishnamurthy; B.V Ramakrishnayya and K.D. Singh

19. Potassium Nutrition Management of Oil Seed Crops 379 B.A. Golakiya and M.S. Patel Foreword

Crop production in India has made a remarkable step forward in the last decades enabling to feed its steadily increasing population although the area of arable land remained almost the same. One of the driving forces behind the increased productivity of the available land is the use of mineral fertilizers. Consumption of mineral fertilizers almost doubled every decade reaching currently some 18 million tons of nutrients. Concomitantly, food grain production doubled in the last three decades to currently about 200 million tons, which not only kept the food production in line with the population growth but also increased the per capita output.

However, declining growth rates in crop yield raise concern on the efficiency of fertilizer use. A rather wide nutrient ratio in fertilizer use, as practised in India, fuelled the doubts. State-wide investigations showed indeed that, irrespective to the region, nutrient supply with mineral fertilizers and other sources is progressively less in balance with the nutrient removal by the harvested crops. This refers to potassium in particular. Negative K balances are widespread, the deficit tends to increase.

Continuous negative K balances mean soil K mining and ultimately loss in soil fertility and sustainability of the productivity of the cultivated land. This restricts full utilization of the genetic potential of the crops, which hinders income generation and prevents further rural development. The far-reaching consequences of unbalanced fertilization are enough reasons to bring the subject to the public knowledge. The Special Publication, which is issued on the occasion of the International Symposium on the "Importance of potassium in nutrient management for sustainable crop production in India", December 3-5, 2001 in New Delhi will address the public. Based on profound research, eminent scientists report on the behaviour of potassium in soils, its assessment, and the effect of balanced fertilization with potassium on yield and quality of crops and cropping systems.

With this publication, the decision-makers should be aware of the long-term consequences of unbalanced fertilization, consequences for food security, resource management, environment and the rural development. On the other hand, the consumer should also know that judicious and balanced use of mineral fertilizers, potassium in particular, contributes not only to produce high quality crops but safe food at the same time. Appreciatively, the Potash Research Institute of India, PRII, took the initiative to encourage and convince concerned scientists to collect the results and to prepare the manuscripts. Dr. Pasricha and his colleagues deserve our thanks and gratitude for issuing this Special Publication.

November, 2001 (Adolf Krauss) Director, IPI

5 Preface

This special publication on "Potassium in Indian Agriculture" released at the occasion of International Symposium on "'Importance of Potassium in Nutrient Management for Sustainable Crop Production in India" is a compilation of specific contributions from the scientists who have been working on one or the other aspects of potassium as a plant nutrient.

Future food production will be increasingly dependent on supplementing plant nutrients obtained from soil with mineral fertilizers. Mineral fertilizers have now become indispensable for ensuring sufficient food production and checking decline in soil productivity through nutrient depletion. The rapidly increasing population and consequent rise in food demand have rendered mineral fertilizers an integral part of our food supply chain. In a developing country like India, with increasing population and consequent decrease in per capita arable land, there is no alternative to a matching growth in food production as well. The challenge, therefore, is to sustain growth in food production whilst maintaining soil fertility and taking care of natural resources and environment. Balanced fertilizer application is, therefore, a must. Balanced fertilization entails supplying plants with precise and adequate amounts of nutrients needed for their optimal growth and development.

Consideration of size and readability have limited the amount of detail that can be presented on each aspect related to potassium nutrition, but it is our hope that this publication will contribute to improve our understanding of the complexities of potassium in soil, its role in plant nutrition and provide a basis for future research.

With the introduction of high yielding fertilizer responsive crop cultivars grown under intensive conditions, depletion of soil nutrients, like potassium, is taking place at an alarming rate without sufficient replenishment. Such a compendium on this vital plant nutrient is necessary since much new knowledge has accumulated in the recent time.

Dr. Adolf Krauss's generous contribution in writing the Foreword is gratefully acknowledged. We hope that the present publication will be useful to the researchers, students, extension worker, fertilizer industry, planners and administrators concerned with balanced fertilization, more particularly with potassium.

We also acknowledge our debt to those colleagues who put very sincere efforts in contributing different chapters.

November 2001 (N.S. Pasricha) 7 Director, PRII Kinetics of Potassium Release and Fixation in Soils

S.K. SANYAL AND K. MAJUMDAR* Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741252, West Bengal

INTRODUCTION

A large number of experimental studies have been conducted to probe the dynamic nature of equilibria between different forms of soil potassium (K), namely water-soluble K, exchangeable K, non-exchangeable K and the mineral or structural K. Most of these studies have employed a batch technique; allowing the system, namely soil K/solution K, to attain equilibrium at a constant temperature (and pressure). The ensuing distribution ratio (Goulding, 1983) has been related to the approximate thermodynamic equilibrium (K) constant. From the latter, as well as from a study of its temperature dependence, a number of 0 thermodynamic parameters (such as standard free energy change, AG ; enthalpy change, AH; and entropy change, AS) of K* exchange equilibria between soil solid and solution phases, have been computed. The negative sign of AG at a constant temperature and pressure of the ion-exchange reaction is taken to indicate the spontaneity of the given ion-exchange reaction, or the relative preference of ions, notably Ca 2 " the soil colloidal phase for K' ions over other exchangeable and Mg 2. Not withstanding the value of such thermodynamic studies, however, it is worth noting that thermodynamic parameters such as a large negative AG of product for the TY value merely suggests the formation of a large amount forward direction of the given reaction at equilibrium. It offers no idea as to how fast or how slow that equilibrium is attained at the given temperature. Although the AG of the reaction, H2 (g) + /202 (g) = H 20(g), is strongly negative at 25°C and I atm pressure, no detectable quantity of water vapour would be obtained on keeping a mixture of hydrogen and oxygen gases at 25°C and I atm pressure for a very long time. This is because the attainment of equilibrium of the forward reaction, being characterized by a high activation energy, is extremely slow. Indeed, for thermodynamic description of the rate processes, one has to have a recourse to irreversible thermodynamics (Katchalsky and Curran, 1965; Sanyal, 1981; Nanda and Sanyal, 1995), but this branch of thermodynamics has seldom been used in the description of soil processes. Thermodynamic considerations, leading to equilibrium constant, are, strictly speaking, applicable only to a closed system. Soil K being subject to fixation, release, leaching, plant uptake, and also addition through fertilizers, irrigation water and crop residues, does not satisfy the description of a closed system. Indeed, it is doubtful if even quasi- thermodynamic equilibrium between different forms of soil K is ever attained in

-Potash and Phosphate Institute of Canada (India Programme). BD-42, Sector I, Salt Lake City, Kolkata - 700 064, West Bengal 9 10 S.K. Sanyal and K. Majumdar a soil system, more so that at the root-soil interface of rhizosphere activities. The reversible thermodynamics do not also provide any information as to the mechanism or pathways of a process, such as K release or fixation in soil.

The study of kinetics of a process does not envisage equilibrium in the system, a state that is closer to the field situations with regard to soil K. Such studies also provide information on dynamics, on a time scale, of reactions between soil components, such as clay, and the added fertilizer, that largely govern the status of plant availability of the latter. Probing the kinetics of K release and fixation reactions in soil at different temperatures also leads to the energetics of the given reactions. The latter could very well afford one to explore the efficacy of management practices to facilitate K-release or fixation. The need for studying the kinetics of K release and fixation processes in soil thus hardly needs any overemphasis. However, a scan of the literature reveals that these studies date back to not more than 25 years or so. The need to stop a reaction between solid and solution phases at a given time before equilibrium is attained, followed by their immediate separation to discourage any further reaction is certainly more difficult as compared to the relative ease of allowing a reaction to proceed to the time-invariant equilibrium state. This may be one, among other reasons, for relative lack of interest in K-kinetic studies, compared to the equilibrium studies in the field.

BACKGROUND INFORMATION

Forms of Soil K

Before we deal with the subject matter of this chapter, salient aspects of K dynamics in soils are discussed.

It is generally agreed that plants take up K from or via soil solution. Of the different forms of soil K, the soluble and exchangeable forms contribute to the pool of readily available K, while the initially nonexchangeable K (NEK) serves as a reserve source of soil K. Only 1-2% of total soil K is generally present as readily available forms in soil. The equilibrium betwen different forms of soil K is generally present as readily available forms in soil. The equilibrium between different forms of soil K is disturbed by the removal of K from soil solution by plant and/or through leaching, and also by K addition through fertilizers, crop residues and also possibly through irrigation. The equilibrium between soluble K and exchangeable K is fast and is established within few minutes, but that between the exchangeable K and NEK is much slower, requiring few days to even few weeks to establish.

Potassium status and distribution in soils is almost entirely governed by soil mineralogy (Fanning et al., 1989). Indeed, the native soil K status depends, not only on parent material of the soil, but also on the subsequent stages of weathering Kinetics of Potassium Release and Fixation in Soils 11 of the parent material. That is, the weathering history of a mineral phase, rather than its mere presence, may be important factor to be reckoned with while relating the plant availability of soil K to the soil mineralogy (Sanyal, 2000). This applies not only to the dominant mineral species present in the clay and silt fraction of the soil, but also associated minerals of importance as well. The variability in K release behaviour observed within individual soil groups is often ascribed to the latter (Majumdar et al., 2001).

Mineral Sources of Soil K

The mineral sources of K in soils are the dioctahedral micas: muscovite, glauconite and hydrous mica or illite; the trioctahedral mica, namely biotite and phlogopite; and the feldspars, namely sanidine, orthoclase and microcline (Schulze, 1989). Microcline is the most common potash feldspar in soils. The feldspars may contribute 5-25% of the silt and sand fraction of soils, and may be less than 5% of the clay fraction of most agricultural soils. Their rate of K release by weathering is very slow, compared to that characterizing the micas.

Among the micas, biotite is more weatherable than muscovite. This is because of a shortened K-O bond in muscovite. Further, the (OH) groups of the octahedron in biotite are vertical to the basal plane, causing interlayer K to be less tightly bound in biotite than in muscovite. The presence of Fe2 ion in biotite that oxidizes during weathering reduces the structural stability due to charge imbalance. Weathering of micas/feldspars leads to the formation of secondary minerals with simultaneous release of K (Sparks and Huang, 1985; Sparks, 1987; Liu et al., 1997; Springob, 1999). Some of these secondary minerals also act as fixers of plant available K (Bertsch and Thomas, 1985). As one moves from micas to vermiculties via illites, the CEC increases, while fixation of added K through lattice entrapment leads to enrichment of the NEK pool, coupled with a fall in the CEC of the soil.

Results of numerous studies (Bertsch and Thomas, 1985; Bhonsle et al., 1992; Olk et al., 1995), suggest that for soils with trioctahedral mica parent material and a low intensity of weathering, K release to soil solution is rather high. For soils of dioctahedral mica parent material, and a moderate state of weathering, K release is less, but it is least for soils of low mica content or intensive weathering. Indeed, while formulating sound K fertilizer recommendations, it is imperative that the above K release characteristics of the soils be given due consideration.

Reserve Sources of K in Soil

Non-exchangeable K or reserve K is held between the adjacent tetrahedral layers of di-and trioctahedral micas, vermiculties and intergrade clay minerals. 12 S.K. Sanyal and K. Majundar

It is released to the exchangeable pool of soil K when the latter is depleted by crop removal and/or leaching. These Kt ions are bound coloumbically to the negatively charged interlayer surface sites, often in a dodecahedral state of coordination. Such binding force exceeds the characteristically low hydration energy of K' ions, thereby leading to a partial lattice collapse (Sparks and Huang, 1985), entrapping the interlayer K' ions.

Backett (1971) introduced the concept of 'intermediate K' as a fraction of the NEK that is held around the edges and wedge zones of micaceous minerals. Intermediate K may not be ordinarily extracted by neutral normal ammonium aerate (the conventional soil test extractant for plant available pool of soil K). It is released when K concentration in soil solution approaches a certain critical low value, known as the 'threshold' concentration (Datta and Sastry, 1988). The threshold value, independent of amount of K reserve, depends rather on the clay structure and degree of expansion (Datta and Sastry, 1990). Further, K fixation involves realignment of alumino-silicate layers of the expanded 2 : 1 mineral in the c-axis direction (Goulding, 1983). It is, therefore, likely that there will be a gap between release threshold level and fixation threshold level for soil K. The appropriate management practice has to evolve ways and means to maintain the exchangeable K level in soil somewhere at an optimum intermediate between these two threshold levels.

Release of such interlayer K* ions from mica to soil/exchangeable phase is thus both a cation exchange and diffusion process, requiring time for the exchanging cation to reach the site, and for the exchanged Kt ion to diffuse out from the wedge zones of the degraded micaceous minerals. The cationic diffusion of Kt through the negatively charged wedge zone being an essentially slower process [for instance, the diffusion coefficient of interlayer Kt ion in the illitic minerals lies in the range of 10-17 to 10-22 cm 2 sec- ' (Mengel, 1978), compared - 7 2 - to a value of the order of 10 cm sec in moist soil, the K release process tends to be diffusion-controlled (Martin and Sparks, 1983).

Further, on exchange, the concentration of the exchanging cation in the solution immediately adjacent to the exchanging surface falls. This creates a concentration gradient across the thin film of solution surrounding the soil particles, which leads to diffusion of the exchanging cation from the bulk solution to the surface of the particles across the thin films. A reverse scheme of the process occurs for the exchanged cation (Kf). Such diffusion is necessarily a slower process than the ion-exchange reaction at the exchange sites. The K fixation by soil also involves such sequence of elementary reactions/processes, but in the reverse order.

Therefore, it is imperative that one visualizes the overall process of release and fixation of K in soil as a sequence of different steps mentioned above, and then proceeds to examine as to why certain kinetic equations performed better than others in describing the rates of the processes concerned. Kinetics of Potassium Release and Fixation in Soils 13

Kinetic Equations to Describe Rates of Potassium Release and Fixation in Soil

Table 1. Summarn of kinetic equations used for potassium reaction with soil constituents Equation Assumptions First-order kinetics Rate of change in concentration is proportional either to the concentration in solution or to the number of empty exchange sites. Parabolic-diffusion equation Rate limiting step is the diffusion of K' ions either from the solution to the surface or from the surface to the interior of the particle. Modified Freundlich equation/ Potassium ions in soil system contained Power - function equation three compartments, A, B, and C, and react according to A ' B " C; rate limiting step is B ---) C Elovich equation Activation energy of K-adsorption/ desorption increases linearly with surface coverage Source: Adapted from Sanyal and De Datta (1991).

Table I gives a summary of kinetic equations used for describing reactions of K with soil components/soils. The equations used to describe the K release and fixation kinetics in soil are as the following:

(i) First-order kinetics (ii) Parabolic-diffusion equation (iii) Elovich equation (iv) Power-function relation (v) Zero-order equation

A. Potassium Release Kinetics

(i) First-order equation

For K release, this equation assumes that the K concentration at the exchange sites of the soil colloid is the determining factor for the release rate of K into soil solution. In the batch technique, the rate is given by 14 S.K. Sanyal and K. Majumdar

dK[/dt = kd (K 0 - K) (1)

Where Kt is the amount of K' ion released in time t, K., the amount of K' ion that could be released at equilibrium, while kd is the desorption rate coefficient.

For a miscible displacement or flow technique, the rate is given by

d(K/Ko)/dt = - kd K/K (2)

Where Kt and K0 denote, respectively, the amount of K' ion on the exchange sites of the soil colloid at time t and zero time of desorption.

On suitably integrating equations (1) and (2) and utilizing the initial and boundary conditions one arrives at the following integrated forms, namely

For batch technique:

In (K0 - K) = In K0 - kdt (3) For miscible displacement or flow technique:

In (K/K 0) = - kdt (4)

A plot of log (K0 - Kt) against t leads to a linear plot from the slope of which the specific release reaction rate (kd) is obtained in a batch technique. For flow technique, a plot of log (K/Ko) against t is used.

The first-order kinetics for K-fixation by soil/clays may also be described, e.g., for batch technique,

d (Ko - K,)/dt = k K t (5)

Where K, and K0 are the concentration of K in solution at time t and zero time, while k. is the adsorption rate coefficient.

For miscible displacement or flow technique, one has

d (K,/K0)/dt = k, (K, - Kt)/K,, = k. (1 - K/K_) (6)

Where K, and K_ are the amounts of K at the exchange sites of the colloid at time t and at equilibrium. The integrated forms are:

For batch technique:

In Kt = In K. - kat (7)

For miscible displacement or flow technique: In (I - K K ) =-kat (8) Kinetics of Potassium Release and Fixation in Soils 15

Thus, a plot of log Kt against t leads to ka from the slope of the resulting linear graph in a batch technique. The adsorption rate coefficient (k.), in miscible displacement technique, is obtained from the slope of the linear plot of log (1 - K/K_) vs. time.

The first-order kinetics have been used by a number of workers to describe the exchange-kinetics and K release from clay minerals, as well as surface and subsurface horizons of a number of soils (Sivasundaram and Talibudden, 1972; Jardine and Sparks, 1984; Sparks and Jardine, 1984; Elkhatib and Hern, 1988; Dhillon et al., 1989; Bhattacharyya and Poonia, 1996; Hundal and Pasricha, 1998; Majumdar and Datta, 1999; Sharma and Swami, 2000), and K release from NEK pool of soil (Martin and Sparks, 1983; Feigenbaum, 1986; Mehta and Singh, 1987; Dhillon and Dhillon, 1990; Hundal and Pasricha, 1993; Srinivasa Rao et al., 1995, 1997a, b, 1998, 1999; Manjaiah et al., 1996; Sharma and Swami, 2000).

While studying K-Ca exchange in a Ca-saturated soil sample, Jardine and Sparks (1984) observed that biphasic kinetics characterized the first-order plots with two simultaneous reactions, which were attributed to exchange sites with varying reactivity for K' and Ca2 ions. In support, these authors cited the reported existence of different types of K-binding sites in soils and clays such as illite (Bolt et al., 1963; Goulding and Talibuddeen, 1979). The external planer sites on clays accounted for rapid exchange kinetics while the interlattice exchange sites characterized the slow kinetics.

First-order kinetics were also used satisfactorily to describe the rate of K- Ca exchange in kaolinite, montmorillonite and vermiculite as well as soils (Sparks and Jardine, 1984). The K-adsorption rate was found to fall in the order: kaolinite >> montmorillonite > vermiculite.

The rate of K release from the micas, namely phlogopite and biotite. was similar to the rate of release of structural cations under acidic condition and " much higher under neutral condition (Feigenbaum et al., 1981). The rate of K release from muscovite was found by these authors to be about 5 and 15% of that from biotite and phologopite, respectively. These authors concluded that the mineralogical composition was more important than particle-size in determining the rate of K-bearing mineral dissolution.

While studying K-release from swell-shrink soils of Central India, Srinivasa Rao et al. (1998) observed that the first-order and parabolic-diffusion (see later) equations were equally successful in explaining the release data. These swell- shrink soils, having complex K availability under soybean-wheat cropping system, despite having high exchangeable K, often suffer from K stress. This indicates that the rate of crop uptake of K does not match with that of K release by soil. Rate of K release and maintenance of higher buffering capacity in soil are largely controlled by mineralogy of soils. 16 S.K. Sanyal and K. Majunidar

Dhillon el al. (1989) compared the efficiency of 0.01 M aqueous solutions of BaCI 2, CaC 2, NH 4CI and NaCi in extracting K from 15 untreated and pretreated surface samples of benchmark alluvial, red and black soils of India. The efficiency of these extractants was in the order: BaCI, > NH 4CI > CaCl, > NaCI. The pretreatment of soils with KCI resulted in an increased release of native K, more so in red soils than in the other two types. The desorption kinetics were adequately described by the first-order rate equations.

While examining the release of NEK from mineralogically different soils by using organic acids, Srinivasa Rao et al. (1997b) observed that the Vertisols showed the largest cumulative K release as well as the highest first-order release rate, followed by Inceptisols and Alfisols. The pattern of K release was found by these authors to consist of an initial rapid release, followed by subsequent slower release, corresponding to K release from edge and wedge zones, respectively, of the micaceous minerals.

It was argued by Feigenbaum (1986) that the rate of NEK release and its mechanism are controlled by the nature and amount of clay minerals, and the organic acids present in the soil environment. These acids are produced in soils during the decomposition of plant and animal residues, and extraction of NEK from soil by organic acids may thus simulate root extraction of soil K during cropping. The nature of K release from the mineral upon acid treatment is of significance, particularly in the root-soil interface, where H 3O' ions cause major release of interlayer K upon mineral alteration (Huang et al., 1968).

Non-exchangeable K release kinetics in illitic soil porofile were investigated by Hundal and Pasricha (1993), by using H-resin. More than 8% of total K in these soils was present in the mineral phase, which suggested the parent material origin for such K. The release of NEK was initially rapid, but decreased with increasing time and conformed to first-order as well as Elovich (see later) equations. Two simultaneous first-order equations were fitted, with slope containing both a rapid and a slow reaction. The rapid reaction conformed to first-order kinetics for initial 1.0 to 1.5 hr, accounting for 36-42% of total K release. Earlier, such first-order rate coefficient of release of NEK in two soils, similar in clay mineral suites and content, to H-resin was found to be quite similar (Martin and Sparks, 1983).

Manjaiah et al. (1996) explored the release of NEK from silt and clays of mica-dominated soils, and observed that irrespective of the method of extraction, K release was rapid in the first three extractions and then slowed down to a constant rate. The first-order rate constant also decreased sharply to a near constant value in both silt and clay fractions after the third extraction. The silt fraction of each soil was found to release less K compared to the corresponding clay fraction. These authors concluded that the particle-size, crystallinity of the mineral as well as the nature of the mica play important role in governing the K release rate from different sized soil particles, subjected to acid treatment. Kinetics of Potassium Release and Fixation in Snily 17

The first-order and the parabolic-diffusion (see later) equations, rather than Elovich and the zero-order (see later) equations, described the kinetics of NEK released by boiling HNO 3 from a number of soils (Srinivasa Rao et al., 1997a), in agreement with the earlier findings of Martin and Sparks (1983) and Elkhatib and Hem (1988), with the K release rate constants largely determined by the content and make-up of the given soil clays. Srinivasa Rao ei al. (1995) observed K desorption from three soil series to occur in two phases-an initial rapid phase, followed by a slower phase, apparently corresponding to the release of predominantly exchangeable K and NEK fraction, respectively. Such behaviour in respect of release of soil K was earlier noted by Talibudeen and Dey (1968), Feigenbaum and Levy (1977) and Mehta and Singh (1987). However, it has been argued by Elkhatib and Hern (1988) that several kinetic equations. differing in structure. may give equally good fit of experimental data (within limits of experimental error) since each of them may account for some factors, involved in or some changes, taking place during the said K release. Hence, models, based on theoretical considerations, would be preferable in order for elucidating the reaction pathways.

Continuous cropping in an Inceptisol without K and with recommended levels of N and P led to considerable decline in native K fertility of the soil, as evidenced by cumulative K release and the first-order K release rate constants (Srinivasa Rao et al., 1999). Application of NPK at the recommended doses and of FYM, @ 15 t/ha, maintained the K release rate constants despite small fall in cumulative K release at longer periods of cropping. These authers opined that used IM 3 M H2SO4 to be a better extractant for NEK than conventionally and boiling HNO 3 which may cause drastic dissolution of clay structure (Datta Sartry, 1993).

(ii) Parabolic-diffusion equation

The parabolic-diffusion equation reads,

Kt a+b 4t (9)

K0

Where K, is the cumulative K released in time t and K0 is the maximum K released, while a and b are constants. Thus, a plot of (Kt/K 0 ) against t should yield a straight line of slope b (Eq. 9). The latter is the overall diffusion coefficient of the ion concerned.

In a number of studies (discussed above), the parabolic-diffusion equation performed equally well or nearly so as the first-order kinetic equation in describing K release rates in soil (Feigenbaum et al., 1981; Martin and Sparks. 1983; Jardine and Sparks, 1984; Dhillon et al., 1989; Srinivasa Rao et al., 1997a, b, 1998, 1999). 18 S.K. Sanyal and K. Majumdar

Srinivasa Rao et al. (1998) reported an increase in diffusion rate of K, reflected in the value of the constant b (Eqn. 9), in cropped soil in response to a large diffusion gradient between the illitic interlayer (K source) and plant rood soil interface (K sink), via the exchange sites, a result of crop removal of K. Dhillon et al. (1989) reported the interparticle or surface-diffusion to be the rate-limiting step in the desorption of K in soils of their study mentioned above; in agreement the release rate of NEK from micas and vermiculitic clay mineral sources was found to be diffusion-controlled (Martin and Sparks, 1983). The parabolic-diffusion equation was also used successfully by Havlin et al. (1985) in describing, the kinetics of cumulative K release in calcareous soils to Ca- resin. The rate constants were highly correlated with mica content of soils and relative alfalafa yield and K uptake.

While using sorghum plant as an extractant of NEK in soil, rather than the conventional chemical extractants, Srinivasa Rao et al. (2000a) found the parabolic-diffusion equation to be most successful in describing the plant mobilisation rates of the reserve K in 15 semectitic soils. This tends to suggest that the plant-utilisation of interlayer K is a diffusion-controlled exchange process. Earlier, matching kinetics of K release from soil and that of K uptake by sugar beet and wheat (grown in the soils) from different pools of soil K were reported (Mayer and Jungk, 1993). Sharma and Swami (2000) observed that most of the soils of their study, as well as the corresponding soil fractions, on extraction with aqueous NaTPB, NH 4OAc, BaCl2 and oxalic acid released K, following the parabolic-diffusion equation.

The kinetic data on release of Mg and K on weathering from three Spodosols, with and without grain surface coating, were adequately described by a parabolic- diffusion equation (Courchesne et al., 1996). These authors suggested that the difference between the laboratory and field weathering rates could be substantially reconciled by taking due cognizance of the impact of surface coatings on release of cations.

(iii) Elovich equation

The integrated from of the Elovich equation reads

K, = (1/b) In (ab) + (1/b) In t (10)

Where K t is the amount of cumulative K released in time t, with a and b being constants. Equation (10) is based on the assumption that a b t >>> 1.0. A plot of Kt against In t gives a linear plot from the intercept and slope of which the constants a and b can be obtained (Eq. 10).

The Elovich equation is essentially an empirical equation which was used by a number of researchers to describe the kinetics of phosphate sorption and Kinetics of Potassium Release and Fixation in Soils 19 desorption in soils (Chien and Clayton, 1980. Hingston, 1982; Mouat, '1983; Sanyal and De Datta, 1991).

Havlin et al. (1985) were the first to employ this equation to describe successfully the kinetics of K release in calcareous soils. These authors opined that simple equations with two constants (such as Eq. 10) could satisfactorily replace the need of proposing the use of three or more simultaneous equations to describe the kinetics of K release. Indeed, Talibudeen et al. (1978) had employed an equation containing three simultaneous rate terms for the purpose. These authors suggested that the three functions represented K release from the soil surface, the weathered periphery, and the micaceous matrix. Goulding (1981), on the other hand, found the quantity of surface K, released to Ca-resin, to be the same as neutral N NH 4 OAc-extractable K, while the peripheral and matrix K to represent NEK. Such sets of three or more simultaneous equations were also proposed earlier to describe release or desorption kinetics of phosphate in soil (Amer et al., 1955; Sanyal and De Datta, 1991).

However, the simplifying assumption, namely abt >>> 1.0, does not hold equally well for the entire duration of the reactions, releasing K. Indeed, for applying the form of Elovich equation, given by equation (10), it is necessary to have accurate release/fixation data at short intervals (Havlin and Westfall, 1984). This fact ought to be given due consideration while assessing the success (or otherwise) of the Elovich equation in describing K release kinetics. Indeed, equation (10) is an approximate form, applicable at times for which abt >>> 1.0, of a more general form, namely

I K t = b In (1 + abt) (11)

t+I/ab or K, = I In

or K, = In t +;)b - In! (12)

Equation (12) reduces to equation (10) for abt >>> 1.0. Fixing appropriate values of (ab) is necessary for a good fit of experimental kinetic data to the Elovich equation (Sparks, 1987). The Elovich equation satisfactorily described the kinetics of release of NEK to H-resin in illitic soil profiles as well (Hundal and Pasricha, 1993). However, the Elovich equation failed in a number of cases as reported by several workers, examining the release rates of K in soils (Martin and Sparks, 1983; Sparks and Jardine, 1984; Elkhatib and Hern, 1988; Srinivasa Rao et al., 1997a, 1998; Sharma and Swami, 2000). 20 S.K. Sanyal and K. Majumdar

(iv) Power-function equation

The power-function equation (in double logarithmic form) reads,

In K =- In a + b Int (13)

Where K, is the cumulative K release in time t, with a and b being constants. The latter are obtained from, respectively, the intercept and slope of the linear plot of In K, against In t.

It is generally accepted that Havlin et al. (1985) first demonstrated the use of equation (13) in the studies of K release kinetics in calcareous soils. As stated earlier, these authors showed that the use of three or more simultaneous equations in describing K release kinetics can be replaced by simple equations with two constants such as the power-function equation (and for that matter, the parabolic- diffusion and Elovich equations discussed earlier). However, Sparks et al. (1980) successfully used a modified form of the Freundlich type of kinetic equation to study the kinetics of K exchange in an Ultisol. The equation, used by these authors, is essentially of the power-function type (much similar to the two constant kinetic equations proposed by Kuo and Lotse, 1974 and Kato and Owa, 1989 to describe the kinetics of phosphate sorption by soil minerals and soils), having two constants. Sparks et al. (1980) reported fall of K exchange rate constants with increasing ionic strength which thus conforms to the requirements of the Bronsted activity rate theory (Laidler, 1973; Sanyal et al., 1993). These rate constants were generally low for different soil horizons in the given vermiculitic soil.

Hundal and Pasricha (1993) also found the power-function equation useful in describing the kinetics of K release in illitic soil profiles to H-resin. Majumdar and Datta (1999), while studying the kinetics of K release in swell-shrink soils as a finction of mineralogy, observed that the first-order, parabolic-diffusion and power-function equations described the K desorption kinetics adequately. The K release behaviour of the given (untreated) soils was st ongly influenced by illite, vermicultite and associated minerals.

(v) Zero-order equation

The integrated form of the zero-order equation reads,

Ko -K, = a- bt (14)

Where K, is the cumulative K released in time t, K0 is the maximum K released, and a and b are constants. This equation has been relatively less used to describe the kinetics of K release or exchange in soils and minerals, and has also attained less success (Martin and Sparks, 1983; Sparks and Jardine, 1984; Hundal and Pasricha, 1993; Srinivasa Rao et al., 1997a, b). Kinetics of Potassium Release and Fixation in Soils 21

While studying the kinetics of mono-ammonium phosphate (MAP)-induced K release from Oxisols, Alfisols and Entisols, Zhou and Huang (1995) observed that the amount and the zero-order kinetic rate of such ammonium and phosphate- induced K release were related to the degree of weathering of the soils, and were in the order: Entisol > Alfisol > Oxisol. The findings suggested that the combined effect of ammonium, phosphate and protons (generated in situ on hydrolysis of MAP) on the alternation of K-bearing minerals was the major mechanism of such K release. This agreed with the earlier observations of these authors (Zhou and Huang, 1991) on MAP-induced alterations of mica and feldspars, leading to K release.

Srinivasa Rao et at. (1998) observed that the kinetics of K release from swell-shrink soils of India, subjected to cropping, can be described by the zero- order equation. Similar observations were reported (Srinivasa Rao el al., 1999) for the kinetics of release of NEK from an Inceptisol, subjected to long-term cropping. The equation performed better for explaining K release from soils over longer cropping periods, rather than for shorter periods.

Other studies

Brar et al. (1986) suggested that the important fractions of soil K, susceptible to absorption by plants during a growing season, are the soil solution K, K adsorbed on the external surfaces of the soil particles (loosely held K), K adsorbed on the edge (strongly bound K), and interlattice K (NEK). Such K supply to plants depends partly on the ease and the rate at which K is released into the soil solution. The ease of release depends inversely on the bonding strength. These authors reported the reserve K in soil and its release rate correlating with plant requirement of K and need for K-fertilisation in different soil series studied. This tends to suggest that a better understanding of the solution and exchangeable K relationship may help to refine the available soil K test criteria.

Onchere et al. (1989) examined the amount and rate of release of exchangeable short- and long-term reserves of K from a number of Kenyan soils by using a Ca-resin. The findings suggested that amounts and rates of K release varied greatly depending on the type of biannual wetting and drying cycles and the mica content of the clay and silt fractions of the soils studied. More generally, the Ca-resin technique has proved useful in determining both short- and long- term K release in the given semi-arid soils.

The release characteristics of NEK of a large number of agriculturally important benchmark soil series of India as a function of clay mineralogy and taxonomy were explored by Bhonsle et al. (1992). The K release pattern typically consisted of two parts - an initial rapid cumulative K release, followed by a slower release of K. Such release was the greatest in the illitic, and the least in the kaolinitic soils. The smectitic soils, despite showing high NH 4OAc-K. were 22 S.K. Sanyal and K. Majumdar characterised by moderate K release rates. Bhonsle et al. (1992) concluded that the shallow smectitic soils could experience K exhaustion and the need for K fertilisation earlier than the illitic soils.

Potassium depletion and replenishment capacity of a number of illitic soils under intensive cropping and at the corresponding minimal exchangeable K level was investigated by Srinivasa Rao and Khera (1994) and Srinivasa Rao et al. (1994). The K replenishment rates of the given soils at the minimal K levels showed highly significant correlation with minimal exchangeable K, but poor correlation with per cent clay content of the soils. The correlation with per cent illitic clay in the clay fraction of the given soils was, however, much better than that with per cent clay content.

Mechanisms of Potassium Release

While studying the mechanism of K release from sandy soils through the study of the corresponding kinetics, Sadusky et al. (1987) observed that much of the K release occurred from the sand fractions, high in potash feldspars. The mechanism of K release from the latter appeared to be via a surface-controlled process. This study demonstrated the usefulness of the K supplying power (to plants) of sand fraction in sandy soil.

Feigenbaum et al. (1981) suggested that a combination of two reactions, namely (i) a rapid exchange reaction between the adsorbed K* ion in illitic minerals and H ion in dilute (soil) solution, and (ii) a first-order transformation of the resulting H-clay to the product, is chiefly responsible for the diffusion- controlled mechanism for K release. The latter appears to be the factor responsible for the success of both the parabolic-diffusion and the first-order equations in describing the kinetics of K release from soils and minerals in a number of studies discussed earlier.

Much earlier, Scott and Smith (1966) observed that solution K level in soil, causing release of interlayer K from micaceous minerals, varies widely, being essentially in the order: muscovite > illite > biotite > phlogopite > vermiculite (hydrochlorite). The very low levels of dissolved K in soil solution, triggering off K release from muscovite and illite, account for the relative unavailability of most of such interlayer K.

A review of the mechanisms proposed for K release from primarily feldspars was given by Sparks (1987) which reveals rather tentative nature of the proposed mechanisms.

Springob (1999), in an attempt to understand the process and kinetics of K release from the clay interlayer in natural and arable soils, confirmed that large monovalent cations, especially NH4* and Cs', can reduce the rate of release of Kinetics of Potassium Release and Fixation in Soils 23

K' ions in K-Ca exchange, even if the former are present in concentrations of only a few gM. The author attributed the reported K deficiency in many vermiculitic alluvial soils to such blocked or suppressed release of K' ions, and suggested that substituting NH 4+-N by NO3-N fertilisers, if practicable, might cause more K to be released.

The kinetics of K extraction with a Ca-saturated resin, interpreted on the basis of a three compartment model (Goulding and Talibudden, 1979), suggest that sorbed K and K released by 'fast' and 'slow' processes, representing sites of low and high K selectivity, were assuciated with mineralogically distinct phases in the various particle-size fractions of the experimental soils.

B. Potassium Fixation

Kinetics of K fixation reactions have been less explored compared to the kinetics of K release in soils. Olk et al. (1995) examined the K fixation in a vermiculitic soil and the residual benefit from fertiliser K addition under different moisture regimes. The rates of K fixation conformed to the first-order kinetics, and demonstrated an increase of 107% corresponding to a change of matric suction from -0.03 MPa to -0.48 MPa. This was interpreted as being due to a concomitant increase in concentration gradient in soil that enhances the rate of diffusion-driven K fixation process in soil.

Hundal and Pasricha (1998) explored the adsorption-desorption kinetics of K in a typical alluvial profile of the Indo-Gangetic Plains of India. The cumulative K adsorption was reported to decrease with temperature in the range from 298 K to 313 K, especially at the lower depths due to corresponding higher content of vermiculitic and micaceous clay minerals. Chloride, compared to perchlorate as the background anion, facilitated K fixation owing to the fact that CI- ion, dominant in soil of the arid and semi-arid regions of the said Indo-Gangetic Plains, is known to form weak complexes with Ca2" ions, thereby, giving exaggerated values of K adsorption by these soils (Sposito et al., 1981).

Fixation of K in a number of swell-shrink soils was found to be negatively correlated with illite content and total K in these soils (Majumdar and Datta, 1999). These authors further suggested that satisfactory correlation between rate constants of parabolic-diffusion and power-function equations with soil parameters and per cent K fixation probably provides indirect evidence of suitability of these two equations in comparison to first-order equation.

Srinivasa Rao et al. (2000b) examined the K-fixation characteristics of major 22 benchmark soils of India. Surface soils of smectitic Vertisols and Vertic subgroup showed greater K fixation, followed by illitic Inceptisols, Alfisols, Entisols and Aridisols, while lower K fixation was reported for kaolinitic Alfisols and Inceptisols. Recovery rates of K per unit of added K were observed to be 24 S.K. Sanyal and K. Majurndar higher for kaolinitic soils, followed by smectitic soils, and lower for illitic soils.

Ramanathan et al. (1975) found that K fixation by a red soil was more under alternate wetting and drying condition, rather than under constant moisture level, + in contrast to NH 4 ion conforming to earlier reports (Ramanathan et al., 1973). Over an incubation period of four months, about a quarter of the added K was fixed in one day, which was in contrast to the earlier findings of Grewal and Kanwar (1967) that nearly 90 per cent K was fixed in one day with the equilibrium being established in seven days. Masilamani et al. (1993), while examining K- fixation characteristics of major soil series of Tamil Nadu, India, reported fixation of added K increasing up to four days of incubation, beyond which there was no conspicuous increase.

C. Methodologies

Reviews of methodologies, employed to examine the kinetics of K release/ fixation in soils and clays, have been presented by Ogwada and Sparks (1986), Sparks (1987), Eick et al. (1990), Bar-Tal et al. (1995), among others. These methods include batch, stirred, vortex batch, static and miscible displacement or stirred flow techniques. The type of kinetic technique used affects the time required for equilibrium to be attained in K-adsorption by soils and clays. Ogwada and Sparks (1986) reported that such time for equilibrium for different techniques follows the order: static > miscible displacement > batch > stirred > vortex batch.

The stirred-flow technique, developed by Carski and Sparks (1985), is a combination of batch and flow methods, and was tested by Bar-Tal et al. (1990) to measure the kinetics of reactions in soils. Eick et al. (1990), using tests of Bar-Tal et al. (1990), demonstrated that K-Ca exchange on montmorillonite was too rapid to be measured with stirred-flow technique, while exchange on vermiculite was kinetically controlled, and could be measured.

Bar-Tal et al. (1995) derived a mechanistic kinetic model for a reversible K- Ca exchange reaction, combined with transport processes in a stirred-flow chamber, and used it for determination of the rate coefficients of ion-exchange on, for instance, vermiculite.

Epilogue

A scan of literature affords one with several studies conducted during the last two decades or so, reporting the rate constants of K release or exchange in soils and clays, and less so for K fixation. A number of these investigations have been reviewed in the present chapter. As mentioned earlier, the need for visulasing Kinetics of Potassium Release and Fixation in Soils 25 the overall process as a sequence of different steps can hardly be overemphasised in the context of gaining an insight into the reaction pathways and mechanism. However, such an exercise is not apparent in a good number of studies, which more often than not do not go beyond establishing the superiority of one or more kinetic equations over others in describing the rates of the given processes. An attempt is made in this chapter to bring out the importance of mathematical models based on appropriate theoretical assumptions to understand the processes of K release and fixation in soils. Such understanding may also help in evolving the suitable management practices to facilitate release of potash in soil. Much remains to be done in this direction, and this could very well constitute an important thrust area of future research in the given field.

In some cases, what has passed for kinetics of a reaction, such as K release from soils over a prolonged period of several hundred hours, is actually a sequence of allowing the K-desorption system to attain equilibrium, followed by separation of the solid and the solution phases, and then a fresh run of desorption, leading, once again, to equilibrium, and so on. This certainly is not equivalent to monitoring K release from a given soil, on a time scale, without removing the products at regular intervals. Indeed the latter is what one may understand by a kinetic study that does not allow a reacting system to reach the time-invariant equilibrium state, whereafter no more time-dependent kinetic observations can be made. Appropriate care is, therefore, called for in designing the relevant kinetic experiments so as to avoid such possibilities.

References Amer, F., Boulden, D.R., Black, C.A. and Duke, F.R. (1955). Characterization of soil phosphorus by anion-exchange resin and 32P-equilibrium. Plant and Soil 6: 391-408. Bar-Tal, A., Sparks, D.L., Pesek, J.D. and Feigenbaum, S. (1990). Analyses of adsorption kinetics using a stirred-flow chamber: I. Theory and critical tests. Soil Science Society of America Journal 54: 1248-1253. Bar-Tal, A., Eick, M.J., Feigenbaum, S., Sparks, D.L. and Fishman, S. (1995). Determination of rate coefficients for potassium-calcium exchange on vermiculite using a stirred-flow chamber. Soil Science Society of America Journal 59: 760-765. Beckett, P.H.T. (1971). Potassium potential - A review. Potash Review Subject, 5: 30th Suite: 1-41. Bertsch, P.M. and Thomas, G.W. (1985). Potassium status of temperate region soils. In: Potassium in Agriculture (Munson, R.D., Eds.). Soil Science Society of America, Madison, Wisconsin, U.S.A., pp. 131-162. Bhattacharyya, D. and Poonia, S.R. (1996). Kinetics of potassium release in ammonium acetate in some soils of semi-arid and humid regions. Journal of the Indian Society of Soil Science 44: 44-48. 26 S.K. Sanyal and K. Majumdar

Bolt, G.A., Sumner, M.E., and Kamphort, A. (1963). A study of the equilibria between three categories of potassium in an illitic soil. Soil Science Society of America Proceedings 27: 294-299. Bonsle, N.S., Pal, S.K. and Sekhon, G.S. (1992). Relationship of K forms and release characteristics with clay mineralogy. Geoderma 54: 285-293. Brat, M.S., Subba Rao, A. and Sekhon, G.S. (1986). Solution, exchangeable and nonexchangeable potassium in five soil series from the alluvial soils region of Northern India. Soil Science 142: (4): 229-234. Carski, T.H. and Sparks, D.L. (1985). A modified miscible-displacement technique for investigating adsorption-desorption kinetics in soils. Soil Science Society of America Journal 49: 1114-1116. Chien, S.H. and Clayton, W.R. (19980). Application of Elovich equation to the kinetics of phosphate release and sorption in soils. Soil Science Society of America Journal 44: 265-268. Courchesne F, Turmel, Marie-Claude and Beauchemin, P. (1996). Magnesium and potassium release by weathering in Spodosols: Grain surface coating effects. Soil Science Society of America Journal 60: 1188-1196. Datta, S.C. and Sastry, T.G. (1988). Determination of threshold levels of potassium release in three soils. Journal of the Indian Society of Soil Science 36: 676- 681. Datta, S.C. and Sastry, T.G. (1990). Hysteresis effect in K - (Ca + Mg) exchange in soils dominated by different clay minerals. Journal of the Indian Society of Soil Science 38: 201-205. Datta, S.C. and Sastry, T.G. (1993). Potassium release in relation to mineralogy of silt and clays. Journal of the Indian Society of Soil Science 41: 452-458. Dhillon, S.K., Sidhu, P.S. and Bansal, R.C. (1989). Release of potassium from some benchmark soils of India. Journal of Soil Science 40: 783-797. Dhillon, S.K. and Dhillon, K.S. (1990). Kinetics of release of nonexchangeable potassium by cation saturated resins from red (Alfisols), black (Vertisols) and alluvial (Inceptisols) soils of India. Geoderma 47: 283-300. Eick, M.J., Bar-Tal, A., Sparks, D.L. and Feigenbaum, S. (1990). Analyses of adsorption kinetics using a stirred-flow chamber: 11. Potassium-calcium exchange on clay minerals. Soil Science Society of America Journal 54: 1278-1282. Elkhatib, E.A. and Hem, J.L. (1988). Kinetics of potassium desorption from Appalachian soils. Soil Science 145(1): 11-19. Fanning, D.S., Keramidas, V.Z. and EI-Desoky, M.A. (1989). Micas. In: Minerals in Soil Environment (Dixon, J.B. and Weed, S.B., Eds.). Soil Science Society of America, Madison, Wisconsin, U.S.A., pp. 552-634. Kinetics of Potassium Release and Fixation in Soils 27

Feigenbaum, S. (1986). Potassium distribution in a sandy soil exposed to leaching with saline water. Proceedings of the 13th Congress of International Potash Institute, Bern, pp. 137-144. Feigenbaum, S. and Levy, R. (1977). Potassium release in some saline soils of Israel. Geoderma 19: 159-169. Feigenbaum, S., Edelstein, R. and Shainberg, 1. (1981). Release rates of potassium and structural cations from micas to ion-exchangers in dilute solutions. Soil Science Society of America Journal 45: 501-506. Goulding, K.W.T. and Talibudden, 0. (1979). Potassium reserves in a sandy clay soil from the Saxmundham experiment: Kinetics and equilibirum thermodynamics. Journal of Soil Science 30: 291-302. Goulding, K.W.T. (1981). Potassium retention and release in Rothamsted and Saxmundham soils. Journal of Science and Food Agriculture 32: 667-670. Goulding, K.W.T. (1983). Thermodynamics and potassium exchange in soils and clay minerals. Advances in Agronomy 36: 215-283. Grewal, J.S. and Kanwar, J.S. (1967). Potassium fixation in some soils of Punjab, Haryana and Himachal Pradesh. Journalof the Indian Society of Soil Science 15: 237-244. Havlin, J.L. and Westfall, D.G. (1984). Soil test phosphorus and solubility relationships in calcareous soils. Soil Science Society of America Journal 48: 327-330. Havlin, J.L., Westfall, D.G. and Olsen, S.R. (1985). Mathematical models for potassium release kinetics in calcareous soils. Soil Science Society of America Journal 49: 371-376. Hingston, F.J. (1982). A review on anion adsorption. In: Adsorption of Inorganics at Solid-Liquid Surfaces (Anderson, M.A. and Rubin, A.J., Eds.). Ann Arbor Sci. Pub., Inc., Ann Arbor, Michigan, U.S.A., pp. 51-90. Huang, P.M., Crossan, L.S. and Rennie, D.A. (1968). Chemical dynamics of K release from potassium minerals common in soils. Transactions of the 9th International Congress of Soil Science 2: 605-612. Hundal, L.S. and Pasricha, N.S. (1993). Nonexchangeable potassium release kinetics in illitic soil profiles. Soil Science 156(1): 34-41. Hundal, L.S. and Pasricha, N.S. (1998). Adsorption-desorption kinetics of potassium as influenced by temperature and background anions. Geoderma 83: 215-225. Jardine, P.M. and Sparks, D.L. (1984). Potassium-calcium exchange in a multireactive soil system: I. Kinetics. Soil Science Society of A'merica Journal 48: 39-45. Katchalsky, A. and Curran, P.E (1965). Non-equilibrium Thermodynamics in 28 S.K. Sanyal and K. Majumdar

Biophysics. Harvard University Press, U.S.A. Kato, N. and Owa, N. (1989). Kinetics of phosphate adsorption by sandy and clayey soils. Soil Science and Plant Nutrition 35: 119-129. Kuo, S. and Lotse, E.G. (1974). Kinetics of phosphate adsorption and desorption by hematite and gibbsite. Soil Science 116: 400-406. Laidler, K.J. (1973). Chemical kinetics, Tata McGraw Hill Publishing Company, New Delhi. Liu, Y.J., Laird, D.A. and Barak, P. (1997). Release and fixation of ammonium and potassium under long-term fertility management. Soil Science Society of America Journal 61: 310-314. Majumdar, K. and Datta, S. (1999). Effect of mineralogy on potassium fixation and release in some Indian shrink-swell soils. Clay Research 18: 58-70. Majumdar, K., Sanyal, S.K. and Datta, S. (2001). Potassium release and fixation behaviour of mineralogically different soils of India. Communicated for presentation at the 17th World Congress of Soil Science, to be held at Bangkok, August, 2002. Manjaiah, G.S., Sidhu, G.S., Ghosh, S.K. and Datta, S.C. (1996). Nonexchangeable potassium release from silt and clays of some mica- dominant soils of Haryana. Clay Research 15: 38-44. Martin, H.W. and Sparks, D.L. (1983). Kinetics of nonexchangeable potassium release from two coastal plain soils. Soil Science Society of America Journal 47: 883-887. Masilamani, S., Muthiah, N.D. and Vijaylakshmi, K. (1993). Potassium fixation studies in major soil series of Pudukottai district in Tamil Nadu. Journal of Potassium Research 9: 228-232. Mayer, D. and Jungk, A. (1993). Plant availability of nonexchangable potassium - A new approach. Plant and Soil 149: 235-249. Mehta, S.C. and Singh, M. (1987). Potassium desorption kinetics in soils. Journal of the Indian Society of Soil Science 35: 524-526. Mengel, K. (1978). Potassium dynamics in the rhizosphere and-potassium uptake by roots. In: Potassium in Soils and Crops (Sekhon, G.S., Ed.). Potash Research Institute of India, Gurgaon, India, pp. 127-145. Mouat, M.C.H. (1983). Release of phosphate from soil measured by sequential desorption. New Zealand Journal of Agricultural Research 26: 321-326. Nanda, M. and Sanyal, S.K. (1995). Isothermal coupled transport processes in soils and clays. Journal of the Indian Society of Soil Science 43: 166-172. Ogwada, R.A. and Sparks, D.L. (1986). Kinetics of ion-exchange on clay minerals and soils: I . Evaluation of methods. Soil Science Society of America Journal Kinetics of Potassium Release and Fixation in Soils 29

50: 1158-1162. Ok, D.C., Cassman, K.G. and Carlson, R.M. (1995). Kinetics of potassium fixation in vermiculitic soils under different moisture regime. Soil Science Society of America Journal 59: 423-429. Onchere, J., Goulding, K.W.T., Wood, I.G. and Catt, J.A. (1989). Potassium and magnesium in some Kenyan soils: Their mineral sources and release to Ca- resin. Journal of Soil Science 40: 621-634. Ramanathan, K.M., Subbiah, S., Francis, H. and Krishnamoorthy, K.K. (1973). A study on the fixation of NPK by Noyyal Alluvium. 7th Annual Convention of the Indian Society of Agricultural Chemists, TNAU, Coimbatore. Ramanathan, K.M., Francis, H., Subbiah, S. and Krishnamoorthy, K.K. (1975). Fixation of NH 4, P and K by a red soil under two levels of moisture. The Madras Agricultural Journal 62: 458-466. Sadusky, M.C., Sparks, D.L., Noll, M.R. and Hendricks, G.J. (1987). Kinetics and mechanism of potassium release from sandy middle Atlantic Coastal Plain soils. Soil Science Society of America Journal 51: 1460-1465. Sanyal, S.K. (1981). Comments on the diffusion and non-equilibrium thermodynamic equations of water vapour in soils under temperature gradients. Soil Science 132: 376-378. Sanyal, S.K. and De Datta, S.K. (1991). Chemistry of phosphorus transformations in soil. Advances in Soil Science 16: 1-120. Sanyal, S.K., De Datta, S.K. and Chan, P.Y. (1993). Phosphate sorption-desorption behaviour of some acidic soils of South and Southeast Asia. Soil Science Society of America Journal 57: 937-945. Sanyal, S.K. (2000). Potassium availability of soils of West Bengal in relation to their mineralogy. Proceedings of the workshop on 'Potassium in Agriculture in West Bengal', held in Kolkata in April, 2000 under the auspices of PPIC (India Programme) and the Government of West Bengal (in press). Schulze, D.G. (1989). An introduction to soil mineralogy. In: Minerals in Soil Environment (Dixon, J.B. and Weed, S.B., Eds.). Soil Science Society of America, Madison, Wisconsin, U.S.A., pp. 1-34. Scott, A.D. and Smith, S.J. (1966). Susceptibility of interlayer potassium in micas to exchange with sodium. Clays and Clay Minerals 14th Conference, Pergamon Press, London, p. 69-81. Sharma, R.K. and Swami, B.N. (2000). Kinetics of potassium release from important soil series of Western Rajasthan of India. Journal of Potassium Research 16: 20-26. Sivasundaram, S. and Tahibudeen, 0. (1972). Potassium-aluminium exchange in acid soils: I. Kinetics. Journal of Soil Science 23: 163-176. 30 S.K. Sanyal and K. Majumdar

Sparks, D.L., Zelazny, L.W. and Martens, D.C. (1980). Kinetics of potassium exchange in a Paleudult from the Coastal Plains of Virginia. Soil Science Society of America Journal 44: 37-40. Sparks, D.L. and Jardine, P.M. (1984). Comparison of kinetic equations to describe potassium-calcium exchange in pure and mixed systems. Soil Science 138(2): 115-122. Sparks, D.L. and Huang, P.M. (1985). Physical chemistry of soil potassium. In: Potassium in Agriculture (Munson, R.D. et al., Eds.). Soil Science Society of America, Madison, Wisconsin, U.S.A., pp. 201-276. Sparks, D.L. (1987). Potassium dynamics in soils. Advances in Soil Science 6: 1-63. Sposito, G., Haltzelaw, K.M., Johnston, C.T. and Levesque, C.S. (1981). Thermodynamics of Na-Ca exchange on Wyoming bentonite at 298 K. Soil Science Society of America Journal 45: 1079-1084. Springob, G. (1999). Blocking the release of potassium from clay interlayers by small concentrations of NH4. and Cs+. European Journal of Soil Science 50: 665-674. Srinivasa Rao, Ch. and Khera, M.S. (1994). Potassium replenishment capacity of illitic soils at their minimal exchangeable K in relation to clay mineralogy. Z. Pflanzenernihr.Bodenk. 157: 467-470. Srinivasa Rao, Ch., Khera, M.S. and Subba Rao, A. (1994). Soil potassium depletion and K replenishment capacity under intensive cropping. Journal of Potassium Research 10: 229-235. Srinivasa Rao, Ch., Subba Rao, A. and Ganeshamurthy, A.N. (1995). Status and desorption kinetics of potassium in some swell-shrink soils. Journal of the Indian Society of Soil Science 43: 356-360. Srinivasa Rao, Ch., Subba Rao, A. and Takkar, P.N. (1997a). Kinetics of potassium release using boiling nitric acid from smectitic soils. Clay Research 16: 35- 40. Srinivasa Rao, Ch., Datta, S.P., Subba Rao, A., Singh, S.P. and Takkar, P.N. (1997b). Kinetics of nonexchangeable potassium release by organic acids from mineralogically different soils. Journal of the Indian Society of Soil Science 45: 728-734. Srinivasa Ran, Ch., Pal, D.K. and Takkar, P.N. (1998). Mathematical models to study the kinetics of potassium release from swell-shrink soils of Central India in relation to their mineralogy. Z. Pflanzenerndhr.Bodenk. 161: 67-72. Srinivasa Rao, Ch., Swarup, A., Subba Rao, A. and Raja Gopal, V. (1999). Kinetics of nonexchangeable potassium release from a Tropaquept as influenced by long-term cropping, fertilisation, and manuring. Australian Journal of Soil Research 37: 317-328. Kinetics of Potassium Release and Fixation in Soils 31

Srinivasa Rao, Ch., Subba Rao, A. and Rupa, T.R. (2000a). Plant mobilization of soil reserve potassium from fifteen smectitic soils in relation to soil test potassium and mineralogy. Soil Science 165(7): 578-586. Srinivasa Rao, Ch., Rupa, T.R., Subba Rao, A. and Bansal, S.K. (2000b). Potassium fixation characteristics of major benchmark soils of India. Journal of the Indian Society of Soil Science 48: 220-228. Talibudeen, 0. and Dey, S.K. (1968). Potassium reserves in British soils. Parts I and IT. Journal of Agricultural Science, Cambridge 71: 95-104, 405-411. Talibudeen, 0., Beasley, J.D., Lane, P. and Rajendran, N. (1978). Assessment of soil potassium reserves available to plant roots. Journal of Soil Science 29: 207-218. Zhou, J.M. and Huang, P.M. (1991). Kinetics and mechanisms of monoammonium. phosphate-induced potassium release from selected K-bearing minerals. American Society of Agronomy Abstract, p. 369. Zhou, J.M. and Huang, P.M. (1995). Kinetics of monoammonium phosphate- induced potassium release from selected soils. Canadian Journal of Soil Science 75: 197-203. Potassium Availability in Relation to Soil Mineralogy in the Indo-Gangetic Plains

S.S. MUKHOPADHYAY AND S.C. DATTA* Department of Soils, Punjab Agricultural University, Ludhiana-141004, India *Department of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi-110012, India

Abstract

As crop quality and environmental sustainability overwhelming agriculture at a fast pace, reexamining the concept of potassium availability and its henceforth vague relationship with soil mineralogy become presumptutous. We aimed to explain this relationship in the soils of the Indo-Gangetic plains (IGP). The 400,000 km2 plain could best be described basing agro-ecological regions. Lithologically, Pleistocene to Recent alluvium plain owes its deposits to the potassium rich sedimentary and metamorphic rocks. Perhaps soils of the west of IGP are least weathered, but despite high rainfall in the east, unaltered minerals dominate the scene. The potassium availability deciphered through NH 4OAc extractant was rarely low. But suspected hidden hunger and more importantly farm practices leading to K development vis-ci-vis weathering of K-minerals to a point of no return may soon pose a great threat. Existence of illite-vermiculite or illite-vermiculite-smectite or illite-smectite/chlorite-kaolinite phases undermine the advancement of weathering front, which could be further accelerated due to global climate change and acid rains.

Preamble

Present is forerunner of the future. The traditional postulation of soil minerals as principal repository of plant nutrients and receptacle through fertilizer source is fast changing with steady shift of land use to address diversification; and replacement of native vegetation by the utility oriented hybrid crops and more recently genetically engineered crops which have great capacity to withdraw large quantities of nutrients from soils. Very often than not, such farming systems have the capacity to leave soils in the lurch. This is especially a warning to potassium management, particularly in the Indo-Gangetic Plain where soils are very often exclusive supplier of K nutrition to plants and the aspect of soil deterioration with respect to K supplying power is largely overlooked. A quarter century ago, Singh and Brar (1977) showed that continuous cropping without K dressing decreased available K status from 166 to 85 kg ha-' in the soils of 33 34 S.S. Mukhopadhyay and S.C Datta

Punjab. Desspite this fact, there was no K response and it was because 90% of K demand was met by K release through non-exchangeable pool.

It is well known that potassium availability to plants is a function of quantitative mineralogical set-up, nature of complementary cation(s), and pedogenic environment (Schwertmann, 1982; Van Diest, 1985). In the context of Indian sub-continent, Sekhon (1982) summed up that both content and availability of K are related to the parent material, mineralogical make-up, particle size, degree of weathering and management practices.

The intricate problem in unlocking the relationship of K availability and mineralogy of soils is absence of reliable values for available K (Grimme, 1995; Evangelou, 1994) at one hand, and structural complexity out of crystal size, crystal disorder, ion substitution and surface characteristics on the other hand (Schwertmann, 1982).

These complexities are likely to be aggravated as part from provenance, pedogenic and neo-genic and seasonal minerals, foreign minerals are either incorporated or has a fair chance to find a place in the soil system through various sources. Some of these sources could be (i) slow release fertilizers (Johnson et al., 1983), (ii) pesticide carriers (David, 1996), (iii) irrigation water (Buddemeier and Hunt, 1988), (iv) wastes like sewage sludge and flyash (Dubey et al., 1998). The new thrust on incorporation of organic materials from plant sources (Schnitzer, 2000) and accelerated changes in climate are forcing soils to weather fast. Concern for environment quality may have the way for mineral materials supporting controlled ecological life support system (Golden and Ming, 1999) into the soils. Such materials are likely to change the scenario beyond comprehension. Keeping these apprehensions in mind, present chapter is casted to address the situation agro-ecological sub-region wise with. a forerunner, a bird's eye over view of the situation.

Indo-Gangetic Plain: Extent

The Indo-Gangetic Plain is spread from 670 to 960 E longitude and from ' 0 20054 to 33 22'E latitude (Schwartzberg, 1978). It extends from Assam and the Bay of Bengal on the east and to the Afghan border and Arabian sea on the west in between Himalayas on the north and minor hills or plateau on the south 2 covering 400,000 km , extending 2400 km from east to west and from 160 km width in the east to 500 km in the west. The vast plain covers Bangaladesh, India and Pakistan. It is a product of the continual deposits of alluvium in what was once a gulf between the peninsula and the Himalayas. The thickness of the alluvium deposits has never been conclusively ascertained. It may be as deep as 3000 m in places and is thought to be deepest closer to the mountains. The trough has been so filled over the ages that it looks like a level plain (Foreign Areas Studies Division, 1963; Spate and Learmonth, 1957). ill* So$

INDO-GANGETIC PLAIN cN

320 SCALE

91 11' so 0 100 200 ILES n.,

/Y So 0 100 200 300OKIMSm

REATNIA A |'

1" OHAR Y A Em ta

MALWA P LGITEAU RAN14 PLATEAU

r lAY OF E NG ALt o*e se' --72 e to, It..

Figure 1. lndo-Gangetic Plain 36 S.S. Mukhopadhyay and S.C Dana

BANGLADESH

The Bangladesh part of Indo-Gangetic Plain covers 115,000 km 2. It is a flood plain region and thereby, rice is extensively grown in cultivable lands (Ali et al., 1992). Islam (1992) reviewed the state of potassium in the soils in the four agro-ecological regions of Bangladesh and reported that about 50 per cent of the cultivated areas were low (0.17 cmol kg-'), 30 per cent areas were medium (0.18-0.34 cmol kg-') and 20 per cent areas were high (0.34-0.50 cmol kg-') to very high (>0.51 cmol kg-') in available K. Potassium availability appears to increase from the north to south of Bangladesh part of IGP. They found that the coastal saline and offshore soils were well supplied with it, while it was medium in terrace soils.

PAKISTAN

The popular extractant used for determination of available K in soils in Pakistan is 2.OM NH 4HCO 3 in 0.01M DTPA (AB-DTPA) as per recommendation of Soltanpour (1985). Soils of Pakistan as part of the Indo-Gangetic Plains posses adequate potassium status (Saleeny et al. 1989). The NH 4 OAc extractable K in calcareous soils was in medium (51-79 mg kg-') range (Rahmatulloh et al. 1998). It may however, become deficient under the global climate change and under acid rains. Rahatulla et al. (1995) observed that total K' as well as contents of mica and smectite decreased when acid was used to reclaim saline-sodic soils. In the global perspective, soils of Pakistan are rich in K reserve. Zia and Rahmatullah (1998) figured it out in the range of 2.65 to 3.55 per cent. The abundance of potassium vis-A-vis high K supplying power of soils was attributed to high amount of micas (about 50%) in sand and silt fractions (Aktar and Jenkins, 1999), and illite (about 50%) (Aktar and Jenkins, 1999) followed by kaolinite, montmorillonite, chlorite and vermicultie (Bajwa, 1989). Amongst the various size fractions, clay content had a strong influence on crop yields (Zia et al. 1990). It could however be deduced that soils supporting more than one crop are showing sign of K depletion (Zia et al., 1990). Soils of Pakistan as part of IGP experienced moderate level of weathering of provenance K-minerals as a large amount of applied K gets fixed (Raujha et al., 1992).

INDIA

Northern plain hot sub-humid (dry) Eco-region:

It is spread over central Bihar upto the border of Jharkhand, Central Uttar Pradesh and Sub-Himalayan parts of Uttaranchal, Haryana and Punjab. In this region rainfall decreases from east to west and north to south. The alluvium are Pleistocene of recent origin. Soils of the region belong to Alfisols, Entisols, Ineeptisols and Mollisols. The most of the soils are calcareous. Nor-calcareous Potassium Availability in Relation to Soil Mineralogy in the Indo-Gangetic Plains 37 soils occur on landscapes associated with well to excessively drained environment, are well developed and appear to have a close relationship with Alfisols. The 2 + soils being neutral to alkaline with high alkaline earth bases, Ca +-K exchange is an important driving force of K+ availability. The availability status reports are contradictory. For example, Ramamoorthy and Bajaj (1969) observed that the available K status was low except in Ambala district, where it was high. But review of Subba Rao and Srinivasa Rao (1996) suggests that soils of Punjab and Uttarchal parts are medium in exchangeable K and high to medium in non- exchangeable K, and soils of Haryana part (Ambala) are high in both exchangeable and non-exchangeable K. Ghosh and Hassan (1975) had reported medium to low available K status for the entire eco-region.

Mineralogically, coarse fractions are dominated by the quartz, micas, (both muscovite and biotite), feldspars (orthoclase and microcline in various proportions) with small amounts of accessory minerals. Sidhu (1982) observed that occurrence of these minerals were consistent with their percent materials, and that except biotite they had undergone very limited weathering in situ. Predominance of these minerals explains why these soils are rich in total potassium (For K content, review of Subba-Rao and Srinivasa-Rao, 1996). Although it is well established that coarse fractions release substantial amounts of K to soil solution (Munn et al. 1976), no attempt has been made to decipher its role in these soils -many of which are coarse, textured. These soils varied in their clay mineralogical composition widely. In Bihar, whereas smectite-illite- chlorite is most common clay mineral phase in the terraces, soil clays of flood plains and Rohtas and parts of Aurangabad are dominated by illite-smectire- chlorite phase (Mishra et al., 1996).

Northern plain hot semi-arid eco-region

The eco-region spreads on the south of the preceding eco-region over Punjab, Haryana, and Western Uttar Pradesh. The available K status was described by Ghosh and Hassan (1976) as high for Punjab and Haryana, medium for soils of U.P., and low for the remaining areas, whereas Ramamoorthy and Bajaj (1969) placed soils of Punjab in high and remaining soils in low available K categories. Mineralogically, sand fractions were dominated by the quartz, micas and feldspars in the decreasing order and small amounts of heavy minerals in the soils of Punjab and Haryana (Kanwar 1959, 1961, Kapoor et al., 1981 a,b,c, 1982; 1961, Kapoor et al., 1981; a,b,c, 1982; Murthy et al. 1982; Pundeer et al., 1974; 1978, Sehgal, 1974, Sehgal and De Conninck, 1979, Sharma 1981; Sidhu, 1982; Sidhu and Gilkes, 1977). Amongst micas, muscovite was more abundant than biotites (Sidhu, 1982). Silt fractions resembled sand fractions in their mineralogical make-up. Illite, vermiculite, and different amounts of smectite, chlorite, and kaolinite were common clay minerals in the region. The illites were predominantly dioctahedral (Kapoor et al. 1981; 1982, Sidhu and Gilkes, 1977). Most of the mineralogical work in the region was restricted to identification of crystalline minerals, which are detectable through X-ray. This left, para-crystalline, neogenic 38 S.S. Mukhopadhyay and S.C. Datta and accessory minerals unreported. Most of the soils of Punjab and Haryana (as also western Uttar Pradesh) contain carbonate minerals, although exact mineralogical configuration and their solubility are lacking in reports. Nevertheless, its influence was evident in K20 content in muscovite in some of the Punjab soils, which had 7.9 to 8.9% K20 (Sharma, 1981), far less than the ideal figure of10%. The entire AER is irrigated and both canal and tube-well water contain high amounts of K*. The impact of incorporation of K* through irrigation is evident through the minimal weathering of potash minerals, particularly illite. Mukhopadhyaya et al. (1992) observed formation of edge- wedge sites in K bearing minerals when K+ was removed through 18 successive cropping. On 28 cropping there was about 1% conversion of illite to vermicultie. Invariably, X-ray diffractograms of 1.0 nm peaks show broadening towards low angle, suggesting loss of interlayer K . A co-occurrence of illite and vermiculite also indicated that in spite of K incorporation through irrigation, crop residue and fertilizers, the minerals exist under K -Ioss domain. The scenario is alarming in view of the postulation of diversification from the present cereal based cropping system to fruits, vegetables and high value crop based systems.

Western plain hot arid eco-region part of IGP

The eco-region is on the north-east of Aravalli hills and cover south-west parts of Punjab and Haryana, and adjoining Rajasthan. All forms of potassium were substancially higher in this region than the adjoining Northern Plains (Table 1), reflecting the role of soil minerals particularly dioctahedral micas/illites and potash feldspars originating the weathering of the rocks of the Aravali hills and aeolian deposits. The mineralogical make-up showed higher proportions of trioctahedral micas than dioctahedral species in the soils of the arid region than the adjoining semi-arid region (Bhangu and Sidhu, 1993; Singh, 1993). Sekhon et al. (1992), however, warned that some of the benchmark series in this region are deprived of available K. Their study showed that Lukhi series (Gurgaon) became low in available K today its medium status reported earlier by Ghosh and Hasan (1976).

Table 1. Forms of Soil K in. the Western plain region* Site Soil No. of K forms (mg/kg) Taxonomy soils Water Exch. HNO 3 Non- soluble exch. Western Plain, Typic Ganaganagar, Torrifluvent 25 41 237 1278 1041 Rajasthan Northern Plain Udic Ludhiana, Punjab Ustochrepts 25 35.7 119 990 871 *Adapted from Sekhon et al. (1992) Potassium Availability in Relation to Soil Mineralogy in the Indo-Gangetic Plains 39

Assam and Bengal plain (hot sub-humid to humid) Eco-region

The soils of Assam were low whereas, soils of Bengal plains were medium in available K (Ghosh and Hassan 1976, and Ramamurthy and Bajaj,1969). Review presented by Mukhopadhyay and Mukhopadhyay (1982) showed that illite-vermiculite-kaolinite phases dominate the soils of Assam indicating K depletion state of the soils. On the other hand, it could be discerned that pH-pK region was narrower and smaller in the soils of Bengal plain, which were dominated by the smectite-illite (together 70-80% clays) phases with chlorite and kaolinite inter-phases.

Eastern Plain (hot sub-humid (moist) eco- region

In this region, laterization processes shaped the landscape resulting a kaolinite- illite-smectite phase (review by Mukhopadhyay and Mukhopadhyay, 1982). This makes available K status poor (Ramamoorthy and Bajaj, 1969).

Gangetic Delta

In the Gangetic delta of West Bengal, illite content (40-47%) exceeds smectite (24-30%) and they together constitute about 70% of the clay fractions. The remaining 30% is shared by vermiculite, chlorite, interstratified minerals, kaolinite and may be quartz (Ghosh and Datta, 1972, 1974). Both Ghosh and Hassan (1974) and Ramamoorthy and Bajaj (1969) reported K status as medium. Subramanium (1976) showed that all forms of potassium increased with the CEC implying the role of fine grain mineralogy. This depicts that greater available K index would be associated with the high charged minerals and as the weathering front advances, the availability of K would be falling.

CONCLUSIONS

Theoretically, it is well established that potassium availability in soils could be enumerated if precise mineralogical composite, their weathering state, release and kinetic characteristics are known. The only work in some soils of the IGP (Bhonsle et al., 1992) explained vividly the interdependence between the different K forms and its intricate relationship with dominant clay minerals (Figures 2 and 3). There is enormous scope if mineralogical features and properties are included in the plant growth model, especially at the present time, when precision agriculture is likely to determine the viability of Indian economy. There are a large number of publications on potassium forms and availability in soils, and K response to plants in the IGP, but very little is known about the topic under discussion. Many of these publications become redundant for future planning, because they did not report location precisely making mapping an impossible goal. Fortunately, variability of mineralogical make-up over a landscape is low. 40 S.S. Mukhopadhyay and S.C. Dat/a llZitic 70-CEo60 I

70 0 I(litic soils 2 *0 Mixed Y;-8.60 *0.292x, r :0.1 *0 - kx Mixed soils 0o ; Y=-1.68 *0216x , r2 =,0.72 ob-, 0 A Kaotinitic soils E so- - 0 Y=4.5 4 t0.143x , r 2 : 0.77' it ox Ia Smectitic soils 40 0i X Y=.80O.018x , r 2 =0.63 009 Kaollnitic

000 030 0 0 0 00 ONE

e)20 & * - Smectitic A o c •a a a g 0 cC an"~ co a a CC?0aC a a~;~.

SI I I I I I 100 zoo 300 400 Sao coo 700 Soo Ammonium acetate extractable K(ngkI ) Figure 2. Relationship between ammonium acetate extractable and water soluble K for some soil groups (Adapted from f/onsle et al., 1992) f 700

o Smectitic : 500 0 Iltitic soils a Y=43.17+0.048x r2:0.78 a Ix Mixed soils t 400 %& 1 Y=27.17+0.124x r 2 =0.80 C A Kaoinitic soil |oox a aY=42.08+0.087x Smectitic soils r 2 =0.65 -0 an a x U a x. Y=56.794,0.318x r2=0.82 2 x 9, Mixed

j 100 00 0 o0

400 800 1200 1800 2000 2400 2600 Nitric acid extractable K(mg kg- 1)

Figure 3. Relationship between K extracted in nitric acid and ammonium acetate for some soil groups (Adapted from Bhonsle et al., 1992) Potassium Availability in Relation to Soil Mineralogy in the Indo-Gangetic Plains 41

But, there is a need that whenever the pattern of K availability differ within the same landscape and mineralogical composition, its inherent cause, be it mineral state or hydraulic property, should be examined. It has become a necessity to map K availability in relation to mineralogical composition of the soils (not clay fraction alone) rather than doing it over a political boundary (like district). Soil testing laboratories in the IGP could be directed for this purpose.

REFERENCES Akhtar, M.S., Jenkins, D.A. (1999). Mineralogical characterization of the gluconitic sandstone from Chickali formation of surghan range. Pakistan Journal of Scientific and Industrial Research 42: 215-219. Alam, S.M., Ahmed, S., Azmi, A.R., Naqvi, S.S.M. and Sultana, R. (1998). Composition of underground water from southern part of Tharparkan dessert for cultivation of crops. Pakistan Journalof Scientific and Industrial Research 31: 830-832. Ali, M.F., Faiz, S.M.A., Karim, Z., Imamul Huq, S.M. and Hussain, M.S. (1992). p. 137-140. In Hussain, M.S., Imamul Huq, S.M. Iqbal, M.A. and Khan, T.H. (eds.) Proceedings of the Inter-Congress conference of Commission IV. Bangladesh Agricultural Research Council, Dhaka. Bajwa, M.F. (1989). Potassium mineralogy of Pakistani soils and its effect on potassium response. pp. 203-216. In NFDC Bulletin: 4-89. Bhonsle, N.S., Pal, S.K. and Sekhon, G.S. (1992). Relationships of potassium forms and release characteristics with clay mineralogy. Geoderma 54: 285- 293. Evangelou, V.P., Wang, J. and Philips, R.E. (1994). New developments and perspectives in soil potassium quantity-intensity relationships. Advances in Agronomy 52: 173-227. Foreign Areas Studies Division (1963). U.S. Army Area Handbook for India. Special operations Research Office, The American University, Washington DC. 802 pp. Grahm, E.R. (1941). Soil development and plant nutrition: I. Nutrient delivery to plants by the sand and silt separates. Soil Science Society of America Journal 6: 259-262. Grahm, E.R. (1943). Soil development and plant nutrition. 1I. Mineralogical and chemical composition of sand and silt separtes in relation to growth and chemical composition of soybean. Soil Science 55: 265-273. Islam, A. (1992). Review of soil fertility research in Bangladesh p. 1-18. In Hussain, M.S., Imamul Huq, S.M. lqbal, M.A. and Khan, T.H. (eds.) Proceedings of the Inter-Congress conference of Commission IV. Bangladesh Agricultural Research Council, Dhaka. 42 S.S. Mukhopadhyay and S.C. Datta

Kanwar, J.S. (1959). Two dominant clay minerals in Punjab soils. Journal of the Indian Society of Soil Science 7: 249-254. Kanwar, J.S. (1961). Clay minerals in saline alkali soils of Punjab. Journal of the Indian Society of Soil Science 9: 35-40. Kapoor, B.S., Goswami, S.C., Padmini, C.M. and Laxmi, V.V. (1982). X-ray studies on the distribution and characterisation of layer silicates in some alluvial soils. Journal of the Indian Society of Soil Science 30: 70-73. Kapoor, B.S., Singh, H.B. and Goswami, S.C. (1981a). Three component interstratification in sodic soils. Journal of the Indian Society of Soil Science 29: 123-124. Kapoor, B.S., Singh, H.B. and Goswami, S.C. (1981b). Distribution of illite in some alluvial soils of the Indo-Gangetic Plain. Journalof the Indian Society of Soil Science 29: 572-574. Kapoor, B.S., Singh, H.B., Goswami, S.C., Abrol, I.P., Bhargava, G.P. and Pal, D.K. (1981c). Weathering of micaceous minerals in some salt-affected soils. Journal of the Indian Society of Soil Science 29: 486-492. Khan, H.R. (1996). Fixation and release of K in twelve flood plain soils of Bangladesh as influenced by soil moisture regime, incubation times and application rate. Current Agriculture 20: 61-72. Mehdi, S.M. and Ranjha, A.M. (1997). Journal of PotassiumResearch 13: 297- 301. Mukhopadhyay, A.K. and Mikhopadhyay P. (1982). Mineralogy of soils of West Bengal, Assam and the Northeastern Hills. p 30-40. Mineralogy of Soil Potassium, PRRI Research Review Series I. Potassh Research Institute of India, Gurgaon. Mukhopadhyay, S.S., Sidhu, P.S., Bishnoi, S.R. and Brar, S.P.S. (1992). Changes of quantity-intensity Parameters on cropping. Journal of Potassium Research, 8: 21-34. Munn, D.A., Wilding, L.P. and McLean, E.O. (1976). Potassium release from sand, silt and clay soil separates. Soil Science Society of America Journal 40: 364-366. Murthy, R.S., Hirekerur, L.R., Deshpande, S.B., Venkata, Rao, B.V. and Shankaranarayana, H.S. (1982). Benchmark soils of India. Nagpur: National Bureau of Soil Survey and Land Use Planning ICAR, pp 108-109. Pundeer, G.S., Sidhu, P.S. and Hall, G.F. (1978). Mineralogy of soils developed on two geomorphic surfaces of the sutlej aluvium in the Central Punjab, N.W. India, Journal of the Indian Society of Soil Science 26: 151-159. Pundeer, G.S., Singh, M. and Randhawa, N.S. (1974); Mineralogy of the sand fraction of some flood-plain soils of Hoshiarpur District, Punjab. Journal of the Indian Society of Soil Science 22: 269-274. Potassium Availability in Relation to Soil Mineralogy in the lndo-Gangetic Plains 43

Rahmatulla, Salim, M. and Qureshi, R.H. (1995). Changes in potassium mineralogy of a calcareous saline sodic soil during reclamation with acids. Pakistan Journal of Agricultural Sciences 32: 270-273. Rahmatullah, Badur-Uz-Zuman, Salim, M. and Zia-M.S. (1998). Assessment of bioavailability of potassium in calcareous soils by plant growth and sodium tetraphenylboron. Arid Soil Research and Rehabilitation 12: 237-245. Ramamoorthy, B. and Bajaj, J.C. (1969). Available nitrogen, phosphorus and potassium status of Indian soils. Fertilizer News 14(8): 25-36. Ranjha, A.M., Mehdi, S.M. and Qureshi, R.H. (1992b). Potassium behaviour in some alluvial soil series of Pakistan. Journal ofAgriculturalResearch, Lahore 30: 101-110. Ranjha, A.M., Mehdi, S.M. and Qureshi, R.H. (1992a). Potassium behaviour in some alluvial soil series of Pakistan. Journalof Agricultural Research, Lahore 30: 101-110. Saleem, M.T., Davide, .G., Nabhan, H. and Hamid, A. (1987). Soil Fertilizer Use in Pakistan with Special Reference to Potash. Technical Bulletin National Fertilizer Development Centre 4-89: 19-39. Schwartzberg, J.E. (1978). A historical Atlas of South Asia. University of Chicago Press, Chicago, 352 p. Schwertmann, U. (1982). Soil mineralogy: a key to understand soils. p. 391-393. In Whither Soil Research Panel Discussion Papers, 12th International Congress of Soil Science, New Delhi. Sehgal, J.L. (1974). Nature and geographic distribution of clay minerals in soils of different moisture regimes in Pujjab, Haryana and Himachal Pradesh. Proceedings of the Indian National Science Academy 40B: 151-159. Sehgal, J.L. and De Coninck, F. (1979). Identification of 14A and 7A clay minerals in Punjab soils. Journal of the Indian Society of Soil Science 19: 159-166. Sekhon, G.S. (1987). Potassium availability in soils of North India. p 151-170. Technical Bulletin 1989. No. 4-99, Natiional Fertilizer Development Centre, Islamabad. Sharpley, A.N. (1989). Relationship between soil potassium forms and mineralogy. Soil Science Society of America Journal 53: 1023-1028. Sidhu, P.S. (1982). Mineralogy of potassium in soils of Punjab, Haryana, Himachal Pradesh and Jammu and Kashmir. p 7-14. Mineralogy of Soil Potassium, PRRI Research Review Series 1. Potassh Research Institute of India, Gurgaon. Sidhdi, P.S. and Gilkes, R.J. (1977). Mineralogy of soils developed on alluvium in the Indo-Gangetic plain (India). Soil Science Society of America Journal 41: 1194-1201. 44 S.S. Mukhopadhyay and S.C Dana

Singh, G. (1993). Pedogenesis in Arid Soils. M.Sc. Thesis, Punjab Agricultural University, Ludhiana. Spate, O.H.K. and Learmonth, A.T.A. (1957). India and Pakistan Methuen & Co. London 439 p. Subba Rao, A. and Srinivasa Rao, Ch. (1996). Potassium status and crop response to potassium on the soils of agro-ecological regions of India. Research Topics - International Potash Institute. No. 20, pp. 73, International Potash Institute, Switzerland. Zia, M.S. and Rahmatullah, Ali, A. (1998). Potassium release from soil clays by diammonium phosphate, ammonium bicarbonate and ammonium chloride. Journal of Agronomy and Crop Science, 180: 33-37. Zia, M.S., Aslam, M., Munsif, M. (1990). Potassium status of some soils under rice based cropping sequence. Journal of Potash Research 6(2): 56-59. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India

A.V. SHANWAL AND S.P. SINGH* Department of Soil Science, Chaudhary Charan Singh Haryana Agricultural University, Hisar-125004,India *National Bureau of Soil Survey and Land use Planning Regional Office, Indian Agricultural Research Institute Campus, New Delhi-110012, India

INTRODUCTION

Parent material and climatic conditions, the two major factors of soil formation greatly influence the potassium dynamics as these are also essential parameters to determine the physical and chemical functions of soil. The most important component of this dynamics is soil mineralogy, including primary and secondary minerals. The soil mineralogy depends on parent material and the extent of the pedogenesis. While the degree of pedogenesis operating in an area is entirely a function of climate. The status of different forms of potassium in soil, their release and fixation characteristics etc. are the other important component of K-dynamics which in turn are regulated by the soil mineralogical make up.

It is believed that the soils of Indo Gangetic plain in Arid and semi-arid regions (Table 1) are sufficient in potassium supply because of large amount of illite present in the clay fraction. But the presence of illite in a soil does not guarantee the availability of potassium to plants (Quirk and Chute, 1968). According to Sparks and Huang (1985), the role of potassium in soil is prodigious. More appropriately Albrecht (1943) termed this element as so nomadic that its

Table I. Range and median values for physico-chemical characteristics of soils from arid and semi-arid regions (Singh and Shanwal, 1997) S.No. Property Range Median

1. PH (1:2, Soil :H 20) 6.6-11.0 8.40 2. Electrical Conductivity (dSm - ') 0.03-82.5 0.30 3. Organic Carbon (%) 0.01-1.8 0.18 4. Calcium Carbonate (%) 0-35.0 - 5. CEC (Cmol (P+) kg- ') 1.1-37.3 10.2 6. ESP 0-100 9.1 7. Sand (%) 5.0-97.9 63.0 8. Silt (%) 0.5-78.0 18.0 9. Clay (%) 0.6-62.0 16.0 45 46 A.V Shanwal and S.P. Singh performance in any particular situation is difficult to interpret. Thus, by mere determination of any one component of K-dynamics, it is impossible to predict the behaviour of potassium in soil. Very often it is observed that the soils do not respond apparently to potassium application and normally its deficiency symptoms are also not shown by the growing crops (Bhumbla, 1978).

The objective of this chapter is to present a thorough overview of the dynamics and mineralogy of soil K in arid and semi-arid regions with particular emphasis to the recent literature in these areas.

MINERALOGY OF SOIL POTASSIUM

The K-containing minerals common in soils are the dioctahedral micas: muscovite, glauconite and illite (hydrous mica); the trioctahedral micas: biotite and phlogopite; and the feldspars: sanidine, orthoclase and microcline (Jackson, 1979). Transitional clay minerals and allophanes also contain small amount of potassium (-1%). A classification of the K-bearing minerals is given in Table 2.

Table 2. Classification of K-bearing minerals (Malavolta, 1985) Mineral Chemical composition K content (g/kg) Primary Feldspars

Orthoclase (KNa) Al Si 30 8 Sanidine KAI Si308 Microcline (Na,K) Al Si30 8 Leucite -110 Micas Muscovite KAI 2(AISi 3)0 10 (OH) 2 -80 2 Biotite K(Mg,Fe +)3(AISi 3)O10 (OH) 2 -70 Secondary Illite Dioctahedral 3 (KO. 58Xo. 17)(Al l 55Fe +o.2 0Mgo.25Al 0.5Si 3.5)O10(OH) 2nH20 Trioctahedral 2 (K 0.45X0 .21)(Mg 2.61 Fe +o.0 oAl 0.29Al .05Si 2.95)0 1 (OH) 2nH20 Transitional clay minerals Edge expanded illite Illite + Montmorillonitc lllite+ Vermiculete

Allophane I Si0 2.AI 20 3.2H 20

I 2SiO 2.AI 203.3H20 1.0-1.3 X = Cation held at edge site; n = number of water molecules Mm eralogv and Dynamics of posa jam in Soails of Soni Arid Regions of In dia 47

Except illite, transitional and allophane. all other species of silicate minerals are mainly concentrated in the coarser fractions of the soil.

Feldspars

The feldspars are aluminosilicate minerals having a framework of linked the framework to SiO 4 and Al203 tetrahedra, with sufficient opening in accommodate Na, K. Ca and Ba to maintain elctroneutrality (Rodoslovich, 1975). Feldspars may constitute 5-25 per cent of the coarser fractions of the soils and generally less then five per cent of the clay fraction of most soils (McLean and Watson. 1985).

Feldspars are important constituent of coarser fraction of soils and are the third most abundant minerals after quartz and muscovite in semi-arid regions of Punjab. Haryana and part of Uttar Pradesh (Pundeer el al., 1974, 1978; Ahuja er al, 1984; Sharma, 1981: Shanwal, 1984; Singh et al., 1985a; Raj Kumar et al, 1994 and Raj Kumar et al. 2000) as shown in Table 3. The major fractions of feldspars are microcline. orthoclase and albite-oligoclase. Microcline and orthoclase have undergone little alteration due to substitution reaction with sodium and calcium and retain much of their chemical composition (Singh and Shanwal, 1997 and Shanwal and Datta. 2001a) as shown in Fig. 1. Alterations are confined to edges. The feldspar flakes are fairly to moderately sorted with second cycle outgrowth of Himalaya (Ahuja et at.. 1984).

Table 3. Aineralogical tiornposition of the fine sand fraction (50-250 gin) of alluvial plains (Ahuja et al., 1984 Yadav, 1999) Site Minerals (9) Quartz Orthoclase & Albite- Muscovite Sericite Microcline oligoclase Patiala >60 <1-10 6-10 16-25 2-10 Armbala >60 2- I 2-10 6-25 6-10 Sirsa >60 2-10 60 <1-10 <1-5 16-25 2-I0 Hansi >60 6-1 0 6-10 6-25 6-10 Faridabad >60 6-10 2-10 6-25 6-10

In the soils of arid regions of Southern Haryana and Punjab and Eastern Rajasthan. feldspars are either in equal proportion or second most abundant mineral after quartz (Goswami and Bandvopadhyaya, 1978; Chaudhary et at.. 1989; Sekhon et al., 1992; Shanwal and Dutta, 2001a). Recently Singh and Shanwal (1997) and Shanw, al and Dutta (2001a) observed that fieldspars are the second dominant mineral in the 50-260 ilrn fraction of soils from acolian plains 48 V Shun wuland S tP gh

Figure 1.* {/PIi/,11 1,1 I11k,fjl 0 1 ...llII~I I L ,,d flke, 1 ,tIwk lt /dog..la I eld% (5tl0t¢p IO260pm Ir )II.. mg ru/huj , n,,j ijudemLu crnti ad Dutta,2001c

of Haryana and Rajasthan (Table 4). The alkali feldspars observed are of a range of chemical composition between the end members KALSI O, and NaAISi,),O as indicated by optical and analytical electron microscopy. From optical microscopy it is observed that alkali feldspars also include microcline showing typical cross-hatched twinning and perithitic feldspars (Fig. 2). Most feldspar grains exhibited little alterations and only few grains were partially weathered. It appears that structural conditions of feldspars (e.g. presence of Na, twinning etc.) favours their dissolution and some K is likely to be available to plants. 9 Singh et al. (1 85a) also reported feldspars (orthoclase and plagioclase) as the most abundant minerals in the sand fraction of soils of sand dune areas of Haryana bordering Rajasthan.

Table 4. Major minerals ol jine sand traction (50-260 Fin) of Tv C'i (Jstipvamment from aeolian plin, Hisat (Singh and Shanmil, 1997) Mineral Approximate content (%) Quartz 75 Alkali feldspars 10-15 Calcic feldspars 1-2 Muscovite 2-4 Biotite 1-3 MAinea ,, and Dvneam f Polonrium in Soll of Seui.-4d RqIVo al Ind'a 49

AA

4 e4

o4WtW2.ho ... jh , Iy .,rg 16

mi:...... ineil00-260 .. mnbfry aeohn,,pain rfouherpi Ilarvaua an Dwo.*

2001a)

Micas

Micas are phyllosilicates composed of a sheet of Al' octahedral sandwitched between two sheets of Si"+tetrahedral. Similar to that of feldspars, each fourth Si" tetrahedral is replaced by Al " , and the excess negative charge is neutralized by K*. Potassium occupies the pseudohexagonal or ditrigonal cavities between the tetrahedral sheets (Rich, 1968). The nature and quantity of cations occupying the octahedral sheet is of great significance in weathering and release of K in mica. The trioctahedral micas (biotite) are more weatherable than the dioctahedral micas (muscovite). A structurally ideal muscovite mica contains 9.8 per cent K Whereas, the micaceous minerals present in most soils generally range from 8.3 per cent K for soil micas to 3.3 per cent K for degraded micas (Fanning and Keramidas. 1977).

Micas (Primary) are widely distributed in soils, and mainly concentrated in the coarser fractions of the soils. In most soils, micas originate mainly from soil parent material and tend to weather to other minerals as they approach to finer fraction of soils. Therefore, they are in general more prevalent in younger and less weathered soils of arid and semi-arid regions than more weathered soils of humid and sub humid regions (Jackson, 1964).

Muscovite is the most abundant K bearing mineral in the coarser fraction of alluvial soils of semi-arid regions (Roonwal et al . 1967; Ahuja ei al. 1984: 50 A 1 Shm,d> ...' S.?, Imil/

SingI) and Shanwal, I990: Y'adav, I 999 and Shmxal and Dutta, 20(01a) MtLscovite Coitent taBOes liot 6 to 25 pCr ccut 'able 4. lowever, in acolian soils of P ahltx-itt, Raitathan aId I t tzi 1 ideh tlLtSCO\irc is less thani 5 per CoIn Anld il'trr tlds)pit it is semiO ito trttid nt K clittitltflt titt tJ (Chirudhar it ,, 19S,)I Stniig1 uld shao .I997 S~t .ikl and Dutta. 2}0a: Sekhon (t /., 1992) Iliotttc tithli Lt proteiltnj)h sitI1131r ttiOtII]s (< 21 ) compared to ttiiiucovtt\ aCltisb amztiteie imporittnt huctcmo oi heax moinueal , of and aid sill tudak, 1999i Bionic .itlwe itom 2 to 25 per cent and isdominant mineral .tir[ hornhlcnde in line sand fractionoit heavy minerals (Ahuja el a , 1984 and Yadav 1909o)

Muscovtle flakes in coarser fric tion, of aeolian as well as allIvial soils are mosl % fresh looking witlhout krinkles shialing no evidence (f exfoliation or setrlIing. on Cdges as obsCr1vtd by optical and Lannine electron microcoipy (Shanztlc,& DuIta, 2001a shown in Fig. 3. There existed a tango of particle size o" misco ite flakes in both sand and sill frac[tions. The biotile flakes in sand fraction ol Indo-Gangetic allial plain are partially weathered showking cracks and c cices and the edges of flakes show shattered effect wkith ecxrinction (Fig. 4). Whereas. biotitic flakes from aeidian plain are fresh and do not show any sign of iceathering fFig. 5),

itsa

ItI

c'n'/J !,, ,,,ha l idal< n . ... 11, 11~{l...... I fShlitn tal ,Ji NumI 200(1ai) K 4

/I ATUP' WI{~

K Si. 4KN~$KA~[r 52 ba, vl ?dt S. I. Si np/ lllite

In ost soils, natural reservs of zhe cSSL ntial elementi potassiun are contained in the mica like mineral in the clay fraction (t soil called ile (Quirk and Chute. 1968). StrLcturally illlie is similar to that of muscovite, however the isomorphic substitution ot Si by Al in tetrahedral laver is less (Schroeder. 1978). The tetrahedral replacement is higher in case of trioctahedral illite. The excess negative charge is neutralized by HO' and NH.,' apart from K'. Therefore, the K content in illite is low (upto 3.3%) compared to mica (8.3%).

During the last forty years mineralogy of clay fraction of soils in arid and semi-arid regions of India has been reasonably well investigated and reveals that illite is invariably the most abundant K bearing mineral and varies between 31- 73 per cent (Kanwar. 196 1 Gupta, 1968; Yadav and Gupta, 1974; Ghosh anti Dutta. 1974: Kapoor ef al., 1981, 1982; Ghosh and Kapoor, 1982: Chaudhary and Dhir. 1982: Chandhary ei al., 1985; Shanwal and Gbosh, 1987; Shanwal et al.. 1988: Shanwal and (bcosh, 1989; Sinh and Shanwal, 1997: Yadav. 1999: Pal et al, 1996 and Shanwal and Dutla, 2000, 2001a). From the intensity ratios of 10A and 5A: reflections. Kapoor et al. (1982) and Shanwal and Dutta (2001a) suggested the presence of both di and trioctahedral varieties of illite. Chaudhary and Dhir (1982) and Chaudhary et al. ( 1989) observed a symmetrical broadening of IOA peak towards low 2 0 angle due to replacement of interlayer potassium by hydrated cartons.

Sehgal and DeConick (1971) and Sehgal (1975) observed illite as major K bearing mineral with vermiculite or its chlorotised intergrade in soil clays of Punjab, laryana and Himachal Pradesh. However the presence of complex intergrade of chlorites in these soils was contradicted by Sidhu and Gilks (1977).

The high amount of illire in arid and semi-arid region reflects its low weathering intensity on which, mica has undergone some minor alterations and K is partially replaced by hydrated cations and just converted to illire of low K content (4-6%) and hydrated in structure (Shanwal and Ghosh. 1985). The electron micrograph of illite shows thin flakes of mica v ith sharp edges indicating physical disintegration (Fig. 6) and low chemical weathering. However, illite in alkali soils of old alluvial plain are partially transformed into smectites/vermiiculites through inter stratification (Fig. 7). The flakes of illite show sign of alteration and transformation into swelling clays. Fig. 8 show big aggregates of smectite with spheriodal to psendohexagonal particles of degraded illite and kaolinite.

Transitional Clay Minerals

Transitional clay minerals are intermediate product between the illites and the swelling minerals i.e. smectites and vermiculites. Generally these are referred to as interstratitied minerals. The interstratification may be regular or random. Sinera pgv and I) nanm , Poh ta is Mi in SlsIf S"o -Ard Re ii l oI India 53 I

Figiir, 6. Li ama:a i l jh ,I ,uaiiati;iliar edge, (<2Wmn) from Yamuna alluial tan irecent;. tlrvanc S h tan a Ia d Ghosh. 1985)

Figure 7. Isit I , Mi t...)iiQ t iti (4, <2 'Aa t flala a/linat plai n (old Har~atns shavwii tt....Jamnaii fl mlo ,svelink 21 nwero/ (Shua arnd Ghoh, 1985) Rogularl~l Isrt$io lcattot ni icmiicttite and imica- ermiculite is co1mm1onlV ohbscerd ill these soils (Kapoor (i alI 1QS. lQ92: Shanwal and Ghosh, 1985, 19 87, 1989 and[ Dutta aind Shanwal, 2001 ). High spacine tirrezular ilite'ITrJliIcautio is, lso teported In the soils of Indo-Gane'etic plain tilott)L,

All1phanes

Wlphanes are alorphous or ps.eudocrvsialine minerals 'ormcd during wet herinig prIcess. Thesc are hdrous lutninosilicates containitl discrele Si tthrid i and AloctahedralA! with A-i)-Si bonds, but lack regular structure.

fh content oti amorphouls mtial mosily globular in shape (Fig. 9) in lhe cla& iaL:tiorl of aijd and seti *arid loils 'aries hcrtxeen 5-20 per cent (Chaudharv Mid [)i l. i1,82: Shanwal and (io sh, 1 85, 19$?, 1989: Chaudfharv el /,, 198t): all( Dutl ol Shanwal, 2010 ). fie 1norphous lliCrial il fine clay is twice mosO iceous and predomnanlv cIoposed titrahedrllof component than in the coar el cls ll e 11 q V and(O 1)itii>( .. U... . , to ...... ii . .. S ,S, 4di t i .i n in i 55

Figuir 9. 0 ii wf 04s*. I , r "1of fI i1-, o "iI T (<2j[u'i nIf )mumni; ollutiiplainl (ol.d), itlallrol s.1tAn1ui vll .aId Gho f lhi95i

DYNAMICS OF SOIL POTASSIUM

The potassium immediately available to plant is of course present in the soil 50[kti()I. Hiowevcr, the concentration of soil 1olution K is niot sufficient it)meet the demand of plant at a ny one tine thu, the repienishment of the solution froar other phase> of K is of great importance in (dtermination the K fertility status of the soil, So the amotl of K pre'ent i the soil Solution depends on dvnailic eqtuilibri um01between various formis of K and perhaps moie oil the rate of release from reserve phase (Wic kander, 1954

Forms or Soil Potassium

Potassium inl soils can not be ea sily characterized in terms of different forms because its state throughout lhe soil is esenially ionic (K+). Sharp distinction between variou, fot n0 of K is not posstble and often there is an overlap between these forms (Scott and Smith, 1987 i. lhere e-,5ts a d.na miC equilibriurn bet ;een different forms of soil K tFig. 10).

In order of availability of K to pianis and microbes the different forms are water soluble or soluion K. exchangeable K, nonexchangeable or fixed K and 56 A VI Shanal and S P Sa kh

plant uptake Exchangeable K

Soil solution K* NoMn- Exchangeiible K'

[ -Le II] Mineral K*

Figure to. lyi. f\tiorwm icv~..... I

in eral or lattice K (S parks, 1987 ). The different formis of potassi umi available to plants have been determined by various workers (Sinugh et al_ 1985 b. Prakash and Sinugh, 1985; Majumndar and Sexana, 1987: Kumnar efciat., 1986, 1987, Tweajia rt al., 1989: Suhha Rao and Sekhon. 1990; Das cl W_, 1993: Sidhu and Bhangu. 1993: Sinugh ai tt, I 996a: Pal ci at. 1996 and Shanwal and DLutta, 2000a) in arid aind] semi-aridf region of' India. The distribution range of these forms of K is prese uted in 'Fable 5, The potassi uml content of all the forms in arid and semni

Table 5. Vor.)flflSt]pc)Uissiutii in soils Sr. Site (I at PuForms of K in soil (mg/kg)Lr," o. Water IExch- Non-exeb- Mineral Total Isoluble angeable angeable (/C) I . Aeolian plain 10-40 30-120 408-1027 1.15-2.16 1,20-2.28 (liaraa 2. Alluvial plain 2-50 25-150 131-1625 1.17-275 1,23-2.54 (Fayna )36-28 3. (Allfuvial Plain 10-41 47-237 3117 - .526.526 (Punjab) 4 Semiarid region 7-53 38-123 278-899 2.100-2.33 (Gularat 5 Arid region 7-156 35-42-0 254-3300 - 0,83-3,33 i(Gujarat) 6 Semiarid region 1';-23 71-1 16 390-5062 1-.21-164 (Western UP)

7. Arid region 3.2-16,4 37-190 - --

8. Arid region 7.8-31.2 58-109 319-760 0,35-1.29 0.70-1.49 (Aiwar) 9 Arid region 27.3-78 85-148 156-803 118-I 4a 1 25-1.47 (A juer) 10. Arird region 35-101 85-210 74-386 120-1 .60 1.20-1.70 (Churn) Mineralogy and Dynamics of Polassium in Soils of Semi-Arid Regions of India 57 arid range is generally much higher as compared to soils of humid and sub humid areas (Singh et al., 1989, 1998, 1999b and Shanwal and Dutta, 2000a) due to abundance of micaceous mineral (Main source of K).

Water soluble potassium

It is usually found in very low quantities (-0.2% of the total K). For arid and semi-arid region soils the water soluble K various between 2 to 56 (mg/kg) of soil in 1:2 soil water ratio and 0.1 to 2.8 (mmol/l) in saturation extract. The median values for saturation extract K and water soluble K of Haryana soils are 0.25 (mmol/l) and 9.8 mg/g soil respectively as reported by Singh and Shanwal (1997).

Exchangeable potassium

The exchangeable K refers as the K adsorbed to exchange site and normally extracted with salt solution such as NH 4OAc, MgCI2 , NaC1 or CaCl2 (McLean and Watson, 1985). Ammonium acetate is most widely used extractant now a days. The soils of Indo-Gangetic plain are generally rich in available K (Ramamoorthy and Bajaj, 1969). According to Ghosh and Hasan (1976) 38% of the soils are high, 42% medium and only 22% are low in potassium. The soils of Haryana, Punjab part of Rajasthan, Gujrat and Uttar Pradesh have varied content of available K (Singh and Kuhad, 1981; Singh et al., 1983, 1985b; Kumar et al., 1986, 87; Tewatia et al., 1989 and Shanwal and Dutta, 2000a) shown in Table 5. In an exclusive study, Bhandari et al., 1997 observed that about 92% soils of Haryana were tested high in available K status during the year 1975, but as a result of low K fertilizer application and changes in cropping system, only 61.5% of the soils are high in available K. The median value of exchangeable K for Haryana soils is 124.8 mg/g soil (Singh and Shanwal, 1997). The medium and heavy textured illitic soils contain significantly high amount of exchangeable K-than the coarse textured illitic soils (Subba Rao et al., 1993).

Nonexchangeable potassium

Non exchangeable potassium is held between adjacent tetrahedral micas and transitional and amorphous clay minerals (Sparks and Huang, 1985). Generally it is extracted with hot N HNO 3. The illite dominated soils of Indo-Gangetic plain generally contain high amount of nonexchangeable K (1150 mg/kg) followed by smectite and Kaolinite (Sekhon et al., 1992 and Bhonsle et al., 1992). The nonexchangeable potassium in Haryana soils ranges from 131 to 1625 mg/kg soil with a median value of 562 mg/kg soil (Singh and Shanwal, 1997). An identical range of this form is observed in soils of Punjab, Haryana, Eastern Rajasthan and Western Uttar Pradesh as shown in Table 5. 58 A. V Shanwal and S.P. Singh

Mineral potassium

More than 90 per cent of the total potassium is present as mineral or lattice K. It is structural component of K bearing minerals. The total potassium content of mineral soil range from 0.04 to 2.90 per cent (Jackson, 1964).

Similar to non exchangeable K, the total K content are also highest in illitic soils of Rajasthan, Punjab, Haryana and part of Uttar Predesh (Sekhon et al., 1992). On an average, these soils contain 1.72% but differ greatly (0.35 to 2.75%) from place to place. The values of total K in Haryana soils range from 0.11 to 4.0 per cent and the median value is 1.25 per cent (Singh and Shanwal, 1997 and Shanwal and Dutta, 2001a). The total K increases with the decreasing particle size. The median value for clay fraction is 2.46 for silt is 0.73 and for sand is 0.21 per cent. Very high amount of total potassium in different fractions of Uttar Pradesh and North Western India soils is observed by Mehrotra et al. (1973) and Sekhon (1985).

The results of total K with respect to various size fractions emphasize the importance of silt and sand fraction towards K nutrition in arid and semi-arid region soils. Most of the soils are light and sandy in texture. Therefore, sand and silt contribute a lot towards replenishment of K in soil solution (Mishra and Shrivastava, 1994; Shanwal and Dutta, 2001b). This has been indicated earlier by Kanwar and Grewal (1966). On the basis of above facts Srinivasa Rao et al. (2000) have advocated for inclusion of nonexchangebale K as a measure in soil test calibration and potassium recommendations.

Recently, Shanwal and Dutta (2001b) has shown relationship between K- bearing minerals and forms of potassium in these soils. A very high positive relationship exists between nonexchangeable K and illite plus mica (r = 0.75**) which slightly reduces with the addition of feldspar (r = 0.68*). It may be due to presence of albite and oligoclase feldspar in the coarser fraction of soils. Total potassium also shows similar relationship with the K-bearing minerals in these soils.

Kinetics of Potassium Release from Soil

The release of reserve potassium is actually not the result of dissolution of K-bearing minerals but in true sense is exchange reaction, which is so slow that can not be measured with normal methods of exchangeable K. During the course of growing season. K in soil solution is continually being replenished through release from exchangeable and nonexchangeable forms (Grimme, 1985).

Various methods and extractants (salts, ion exchangeable resins, sodium tetraphenyl boron, and organic and mineral acids) have been used to study the kinetics of K release from soil and different fractions (Sparks, 1987). Normally Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 59

HNO 3 extracts the highest amount of nonexchangeable K from these soils followed by H-resin, NaTPB, oxalic and citic acid (Shanwal and Dutta, 2001c). Potassium release (IN HNO 3) from various soils of India have been studied by various workers (Bhonsle et al., 1992; Mishra and Singh, 1992; Sekhon et al., 1992; Datta and Shastri, 1993; Pal and Durge, 1993; Mehta et al., 1995; Singh et al., 1996b; Das et al., 1997; Lal et al., 1998; Singh et al., 1999a; Srinavasa Rao et al., 2000; Sharma and Swami, 2000 and Shanwal and Dutta, 2001c). The release of potassium is directly governed by the amount and mineralogical composition of clay. The illitic soils showed the highest rate of K released followed by smectite and kaolinite, regardless of the content of exchangeable K in the soils. The release of K also increased with the concentration and temperature of the acid (HNO 3) in soils of Haryana (Mehta et al., 1995).

Shanwal and Dutta (2001c) investigated the kinetics of nonexchangeable K release from aeolian and alluvial soils using various extractants (IN HNO 3 , H- resin, citric and oxatic acid and NaTPB). Except H-resin, the K release obeyed first order kinetic equation. The nonexchangeable K release by H-resin obeyed Elovich equation and showed curvilinear pattern (Fig. 11). The high rate of desorption of K at the initial stage is mainly due to the external domain (surface and edges), while the slower rate of release to the restricted domain. The restricted domain (interlayer sites) controls the rate of diffusion (Sawhney, 1966). This pattern of K release in alluvial soils by H-resin is well supported by Hundal and Pasricha (1993) and Baruah et al. (1996). Samiel and Chahal (1986) used cation exchange resin saturated with counter ions to study the rate of K release in some alluvial soils of India. NH 4+ saturated resin extracted highest amount followed

1600" S-face(Chautala)H ---A-- Subsurface (Chautala) -.-... 1400 - Surface (Narnaul)

1200SD 1000.

800-• ,

400- -1

200j

Int Figure 11. Kinetics of nonexchangeable K release to H-resin as described by Elovich equation (Shanwal and Durra, 2001c) 60 A.V Shanwal and S.IP Singh

. by Na* and Ca The rate of release was more when illite was followed by chlorite than smectite within same textural class.

The K release by organic acids (oxalic, citric, malic and acatic acid) is more close to available K as they are common in rhyzosphere of plant roots. Srinivasa Rao et al. (1997) compared the organic acids for extraction of K in various soils of India. Malic acid extracted larger amount of K compared to citric and acetic acid. Oxalic acid extracted higher potassium than citric acid in soils of Indo- Gangetic plain (Mehta et al., 1995; Shanwal and Dutta, 2001c). The parabolic diffusion equation describes the rate of K release explicitly followed by 1st order equation in these soils. The ratio of cumulative K release at time 't' (Kt) to total K released (Ko) vesus square root of time for aeolian and alluvial soils (Fig. 12) shows a straight lime curve of parabolic diffusion kinetics of K release.

1.20- a Surface (Chautala) &-Surface (Bhiwuni) too- Surface CSatncli)

P0-

0.60-

0-40-

0.20-

0.OO7 , ....- ... 0 2 4 6 8 10 12 14 16 to-5 Figure 12. Parabolic diffusion kinetics of nonexchangeable K release in OG.IM citric acid (Shanwal and Duaa, 2001)

Sodium tetraphenyl boron is very effective for the release of nonexchangeable K by maintaining a low solution K concentration and thereby provide a mean of estimating plant available K in soils (Schulte and Correy, 1963). The illitic soils of arid and semi-arid regions of India, the rate of release of nonexchangeable K by NaTPB is less compared to H-resin and decrease with time (Samicl and Chahal, 1986; and Shanwal and Dutta, 2001c). The decreasing trend of K release following the 1st extraction might be due to easy replacement of K by Na from wedge and edge zones of micaceous minerals. First order equation was found as the best fitting model to explain the K release kinetic explicitly (Fig. 13) and exhibited a initial rapid and then gradual release of nonexchangebale K from the soil. Srinivasa Rao et al., (1998) observed that NaTPB extracts higher amount of K from illitic soils compared to semectitic soils. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 61

7.00. - Surface(Chautala) 6,• 0 -t-- _SurfSurface(whihani) ace (Satnali)

5.00

2 .00-

1.00-

0.00. 0 . 2 3 5 6 a' t (HOURS)

Figure 13.1st order kinetics of nonexchangeable K release in NaTPB (Shanwal and Dutta, 2001c)

Potassium Fixation in Soils

Fixation of potassium is conversion of soil solution or exchangeable K into nonexchangebale forms. Normally the fixation and release of K occur simultaneously (Mortland, 1961).The soils which contain appreciable amount of K-depleted micaceous and vermiculite minerals the fixation of added K can be appreciable. The swelling clay minerals (1.4 nm) when dried in the presence of K' ions, they lose their shell of water molecule and allows K + ions to enter the pseudohexagonal space between tetrahedral layer and become electrostatically bound and temporarily fixed.

Earlier it was believed that the fixation of applied K resulted in a drastic reduction of plant available K (Chaminade, 1936). But later, it has been demonstrated that the fixation of added K may be beneficial since it reduces K losses by leaching and luxury consumption and becomes available to subsequent crops (Black, 1968; McLean and Simon, 1958; Sekhon, 1985; Hundal and Pasricha, 1998).

The soils of arid and semi-arid regions of India are capable of fixing high quantity of potassium due to presence of depleted K illites and small amount of smeclite and varmiculite (Singh et al., 1987; Sharma and Dubey, 1988; Chakarvorh and Patniak, 1990; Srinivasa Rao and Khera, 1995). Bandyopadhyay and Goswami (1988) observed a fixation as high as 60 per cent in an black soil containing high amount of smectite followed by alluvial soil (45-48%) containing illite and laterite soil (38%) containing Kaolinite (Fig. 14). Wetting and dying 62 A. V Shanwal and S.P Singh

100- A LATERITE SOIL /

* ALLUVIAL SOIL so L BLACK SOIL

u1W

.0 . .-..--- ... . 0.60 4. -

i

20

I £ I I 0 0.2 0.4 0.6 APPLIED K-DOSES(m K/100g soil)

Figure 14.Fixation of K in soil at diJjerenl doses of applied K (Bandyopadhyay and Goswani, 1988) usually increase fixation by 2 to 3 folds in illite dominated alluvial soils (Singh et al., 1987).

Srinivasa Rao and Khera (1995) observed that potassium depleted illitic soils of alluvial plains fixed the applied potassium from 56 per cent to 93 per cent (Table 6). The K fixation increased with the increase in K fertilization rate from 20 to 200 (mg K g-' soil). This increase in fixation of added K with increase in K fertilization rate is irrespective of soil mineralogy (Srinivasa Rao et al., 2000). The surface soil of smectite dominated soils showed greater fixation (26-30%) than illitic (23-29%) and kaolinitic (17-23%). This substantial K fixation capacity of soils is mainly attributed to location of wedge zones in the mineral laltice.

Recently Hundal and Pastricha (1998) observed that the adsorption capacity of illitic soils of Indo Gangetic plain is greatly influenced by variation in temperature. Potassium absorption capacities of these soils are higher at lower temperation of 298 K as compared to 313 K (Fig. 15). Therefore, the relative low adsorption of K at higher temperature in these soils suggests that during hot Mineralogy and Dynamics of Potassium in Soils of Semi-A rid Regions of India 63 summer of semi-arid tropics leaching losses of K with percolating water might be quite extensive.

Table 6. K fixation (mg kg -' soil) and per cent K fixed at different rate of added K after depletion (Srinivasa Rao & Khera, 1995) - Soil series K added (mg kg ' soil) 20 40 90 140 200 Hamidpur 11.9 24.4 61.2 92.4 134.0 (59.5) (61.0) (68.0) (66.0) (67.0) Hisar 12.2 25.5 65.4 98.3 114.7 (61.0) (63.7) (71.5) (70.2) (57.3) Kakra 15.0 31.0 66.8 100.2 118.8 (75.0) (77.5) (74.3) (71.6) (59.4) Thaska 14.2 29.6 62.7 86.8 112.2 (70.9) (74.0) (69.7) (62.0) (56.1) Khoh 14.9 30.7 71.2 110.6 120.0 (74.8) (76.9) (79.8) (79.0) (60.0) Palam 18.7 36.9 82.4 128.9 156.8 (93.40) (92.4) (91.6) (92.1) (78.4) Mehrauli 11.5 24.5 56.7 98.0 118.0 (57.7) (61.4) (63.0) (70.0) (59.0) The figures in parenthesis are the per cent K fixed.

TIME (min) 0 8 16 24 32 36 0 -05 7 SURFACE -1.01 , (0-15cm) -1.5 I "X N(,

-- 2,0 r*298K 313 K 0

-0 N UB-SURFACE -1- '(125-150 cm)

-1.51 . 298 K

-2.0[ x 313 K -2.5

Figure 15. Istorder kinetics of adsorption of K as influenced by tempe- rature and background anions (Hundal and Pasricha. 1998) 64 A.V Shanwal and S.P. Singh

BIO-WEATHERING OF K-BEARING MINERALS

It is known fact that appreciable quantities of K release from feldspars occurs only when the weathering environment is very intense, as in the humid tropics, whereas, such release in arid and semi-arid region soils is quite small. Therefore, it is of relatively minor importance with respect to K nutrition in crop production.

The weathering of mica and its transformation to other mineral phases in soils of arid and semi-arid regions of India has been studied in great detail (Kapoor et al., 1981; Tomar, 1985; Shanwal and Ghosh, 1987, 1989; Shanwal and Dutta, 2000; and Dutta and Shanwal, 2001). It is not our intention to review this vast literature but rather to provide information about weathering of K- bearing minerals as a result of K removal by plants and contribution of coarser fraction towards K nutrition in addition to clay fraction.

Long back Mortland et al. (1956) observed direct transformation of biotite to vermiculite as a result of K uptake by wheat crop. Later on Hinsinger and co- workers (Hinsinger et al., 1992; Hinsinger and Jaillerd, 1993; Hinsinger et al., 1993) demonstrated the biological transformation of a reference phyllosilicates due to root induced release of interlayer potassium. Research done in arid and semiarid region of Indian concerns mainly to pot culture and field conditions.

Shanwal et at. (1996) observed transformation of illite to smectite in the soils of Indo-Gangatic alluvial plain due to continuous paddy cultivation under field condition. Recently Dutta and Shanwal (2001) have demonstrated the tranaformation of illite to smectite through root induced K release under field and pot experiment in soils of Indo-Gangetic plain. Under Long Term Experiment trials at CCS HAU, Hisar, the transformation of illite to smectite is evident in the soils which received no potassium fertilizer since 1975 (Fig. 16). However, Singh and Goulding (1997) could not observe transformation of mica despite continuous K removal by winter wheat in the Rothamsted Experiment Station which might be a effect of management factor.

Generally it is considered that the plant draws K from soil solution replenished by exchangeable K which is in equilibrium with nonexchangeable form of K (Fig. 10). However, some workers (Ganeshamurthy and Biswas, 1985; Anandswarup and Singh, 1987; Yadav and Swami, 1988; Pal and Mukhopadhyay, 1992; Sharma and Sekhon, 1992'and Srinivasa Rao et al., 2001) have shown substantial contribution of nonexchangeable K towards K uptake by a crop during a growing season. Recently (Mishra and Srivastava, 1994 and Shanwal and Dutta, 2001b) have demonstrated that mineral K of coarser fraction also replenishes soils solution under K stress in sandy soils. The contribution of coarser fraction of soil towards total K uptake under K stress is upto 60 per cent as observed in pot experiment (Table 7). Small amount of soils mixed with equal amount of quartz sand were exhausted for potassium by raising continuous intensive six crops of pearlmillet and wheat grown upto grand growth stage. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 65

n

Y K -300

3 5 7 9 11 13 15

n t n

4 y

K-SO0

•20._...

Figure 16.X-ray diffracrograms of clay fraction of the Long Term Experiment field CCS HAU, Hisar (a) with K plot (b) without K plot (Durta and Shanwal, 2001)

Table 7. Contribution from different fractions of soil to availability of K to pearlmillet and wheat (Shanwal and Dura. 2001b) Soils Per cent contribution from different fractions Sand Silt Clay Arid (Haryana) 4.7-57.8 6.7-42.0 35.5-59.6 Arid (Rajasthan) 13.6-50.0 7.0-27.1 37.5-59.3 Semiarid (Haryana) 7.1-54.2 10.8-38.9 34.9-64.8 Humid (Assam) 10.3-52.0 18.7-38.5 29.3-51.3 66 A. V Shanwat and S.RPSingh

SUMMARY

Arid and semi-arid region encompassing vast Indo-Gangetic alluvial plain, the grain bowl of the country, plays a vital role in Indian agriculture. The mineralogical analysis shows that feldspar, mica and illite are the prime K- bearing minerals in these soils. Mica and feldspar are found to be concentrated in the coarser fraction whereas, illite is the dominant mineral of the clay fraction. The soils of aeolian plain in arid region contain higher amount of K feldspar than alluvial soils of arid and arid region. The soils of this region are moderately rich and vary widely in their potassium status. The amount of K present is entirely a function of mineralogical composition of each particle size group. From the study it has been recognized that exchangeable K is an indifferent index of available K for most of the soils. Recently research efforts have been focused on the contribution of nonexchangeable and mineral K towards crop nutrition, particularly in sandy soils of arid and semi-arid region. The inclusion of nonexchangeable K in soil test calibration should pave a way for accurate prediction of available K to meet the demand of the crop for sustainable agriculture. High amount of K release and fixation capacity of these soils helps in maintaining the high K fertility status on one hand and reducing the losses and luxury consumption of potassium on the other hand, which makes it available to the next crop. With current emphasis on the contribution and importance of all the particle size fractions towards K nutrition of crops, future research should be focused on dynamics and modeling K release from sand and silt fractions in addition to clay to determine the site specific K fertilizer recommendations in arid and semi-arid region soils.

REFERENCE Ahuja, R.L., Garalapuri, V.N. and Khanna, S.S. (1984). Fine sand mineralogy in relation to landforms of the Ghaggar river basin in Haryana and Punjab. Journal of Indian Society of Soil Science. 32: 707-715. Albrecht, W.A. (1943). Potassium in soil colloid complex and plant nutrition. Soil Sci. 55: 13-21. Anand Swarup and Singh, K.N. (1987). Movement of K in a sodic soil profile influenced by long term use of inorganic fertilizer under rice-wheat rotation. Journal of Indian Society of Soil Science, 35: 253-256. Bandyopadhyay, B.K. and Goswami, N.N. (1988). Dynamics of potassium in soils as infunced by level of added K, Ca and Mg. Journal of Indian Society of Soil Science 36: 88. Baruah, H.C., Baruah, T.C. and Borah, N. (1996). Kinetics of nonexchangeable potassium release in major soil orders of Assam. Journal of Indian Society of Soil Science 44: 54-59. Bhandari, D.K., Sharma, J.C., Mehla, R.S., Suneja, B.K., Dev, G. and Sangwan, Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 67

O.P. (1997). Available Potassium in Haryana Soils. 1n: Gev, G. and Oswal, M.C. (eds) Use of potassium in Haryana Agriculture. Potash Phosphate Institute of Canada, India Programme. Gurgaon. India. pp 18 -26. Bhonsle, N.S., Pal, S.K. and Sekhon, G.S. (1992). Relationship of K forms and release characteristics with clay mineralogy. Geoderma, 54: 285-293. Bhumbla, D.R. (1978). Potassium in Soil-an Unpredictable Nutrition. In: G.S. Sekhon (ed) Potassium in soiLs and Crops. Potash Research Institute of India. New Delhi. pp. XXIX-XXXV. and Sons, New Black, C.A. (1968). Soil Plant Relatioship. 2 nd ed. John Wiley York. Chakravorti, S.P. and Patnaik, S. (1990). Fixation and release of potassium in flooded rice soils. Journal of Indian Society of Soil Science, 3: 243-247. Chaminade, R. (1936). La retrogradation du potassium dans les soils. Ann. Agron., 6: 818-830. Chaudhary, I.S. and Dhir, R.P. (1982). Clay mineralogy of dune and associated sandy plain soils of western Rajasthan. Journal of Indian Society of Soil Science 30: 342-348. Chaudhary, J.S., Sidhu, P.S., Dhir, R.P. and Ahuja, R.L. 1989. Chemical Composition and Mineralogy. In: Reviews of Research of Sandy Soils of India. Central Arid Zone Research Institute, Jodhpur. pp 65-84. Das, K., Singh, S.K. and Shyampura, R.L. (1993). Forms of K in relation to landforms and soil properties of basaltic terrain. Journal of Indian Society of Soil Science. 41: 557-559. Das, P.K., Acharya, N., Das, H.K. and Sahu, G.C. (1997). Potassium release characteristics of some soils in the watershed area of Phulbari district, Orissa, Journal of Indian Society of Soil Science. 45: 724-728. Datta, S.C. and Sastry, T.G. 91993). Potassium release in relation to mineralogy of silt and clays. Journal of Indian Society of Soil Science. 41: 452-458. Dutta, S. and Shanwal, A.V. (2001). Potassium depletion and illite transformation with time in Typic Haplustept under long term experiment. Hisar, India, Int. Symp. On Importance of Potassium in Nutrient Management for Sustainable Crop Production in India (Dec. 3-5, 2001), New Delhi. Fanning, D.S. and Keramidas, V.Z. (1977). Micas. In: J.B. Dixon and S.B. Weed (ed) Minerals in Soil Environment. Soil Science Society of America. Madison, WI. Ganeshamurthy, A.N. and Biswas, C.R. (1985). Contribution of potassium from non exchangeable source in soil to crops. Journal of Indian Society of Soil Science, 33: 60-66. Ghosh, A.B. and Hasan, R. (1976). Available potassium status of Indian Soils. 68 A.V Shanwal and S.P. Singh

Indian Society of Soil Science Bulletin No. 10: 164-169. Ghosh, S.K. and Dutta, N.P. (1974). X-ray investigation of clay minerals in the soils of West Bengal. Proceedings of Indian National Science Academy 40B: 138-143. Ghosh, S.K. and Kapoor, B.S.(1982). Clay minerals in Indian Soils. Rev. Soil Res. India. Part-Il. 12th InternationalCongress of Soil Science New Delhi. Goswami, N.N. and Bandyopadhyay, B.K. (1978). Potassium Dynamics in Alluvial Soils. In: G.S. Sekhon (ed) Potassium in Soils and Crops. Potash Research Institute of India. New Delhi. pp 35-45. Grimme, H. (1985). The dynamics of potassium in soil plant system. In: Potassiumin Agricultural System of the Humid Tropics. Proceedings of 19th Colloqium of International Potash International Bankok. Thialand. pp 127- 154. Gupta, R.N. (1968). Clay mineralogy of the Indo-Gangetic alluvium of UP. Journal of Indian Society of Soil Science. 16: 115-127. Hinsinger, P. and Jailard, B. (1993). Root induced release of interlayer potassium and vermiculization of phlogopite as related to potassium in the rhyzosphere of rye grass. Journal of Soil Science 44: 525-534. Hinsinger, P., Elsass, F., Jailard, B. and Rober, M. (1993). Root induced irreversible transformation of a trioctahedral mica in the rhyzosphere of rape. Journal of Soil Science 44: 535-545. Hinsinger, P., Jailard, B. and Dufey, J.E. (1992). Rapid weathering of a trioctahedral mica by the roots of rye grass. Soil Science Society of America Journal 56: 977-982. Hundal, L.S. and Pasricha, N.S. (1993). Nonexchangeable potassium release kinetics in illitic soil profiles. Soil Science. 156: 34-41. Hundal, L.S. and Pasricha, N.S. (1998). Adsorption-disorption kinetics of potassium as influenced by temperature and background anions. Geoderma, 83: 215-225. Jackson, M.L. (1964). Chemical Composition of Soils. In: F.E. Bear (ed.) Chemistry of the Soil. Van Nostrand Reinhold, New York. pp 71-141. Jackson, M.L. (1979). Soil Mineralogy. In: R.W. Fairbridge and C.W. Finkl, Jr. (eds) The Encyclopedia of Soil Science. Part 1. PP. 475-482. Kanwar, J.S. (1961). Clay minerals in saline alkali soils of Punjab. Journal of Indian Society of Soil Science. 9: 35-40. Kanwar, J.S. and Grewal, J.S. (1966). Relationship between forms of soil potassium and particle size. Journal of Indian Society of Soil Science. 14: 221-225. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 69

Kapoor, B.S., Goswami, S.C., Padmini, C.M. and Laxmi, V.V. (1982). X-ray studies on the distribution and characterization of layer silicates in some alluvial soils. Journal of Indian Society of Soil Science. 30: 70-73. Kapoor, B.S., Singh, H.B. and Goswami, S.C. (1981). Distribution of illite in some alluvial soils of Indo-Gangetic plain. Journalof Indian Society of Soil Science. 29: 572-574. Kumar, R., Singh, M., Kuhad, M.S. and Singh, R. (1987). Forms of Potassium in some soils of Central Haryana. Haryana Agricultural University Journal of Research XVII: 356-363. Kumar, V., Singh' B.P. and Singh, M. 1986. Depletion of soil potassium in some cropping system in arid soil. Journal of Potassium Research. 2: 132-135. Lal, B., Singh, D. and Hasan, R. (1998). Dynamics of soil potassium under intensive cropping as measured by step K and constant rate K. Journal of Indian Society of Soil Science. 46: 198-203. Majumdar, S.P. and Sexana, S.N. 1987. Determination of critical limits of soil solution concentration of K for wheat crops in some areas around Jaipur. Journal of Indian Society of Soil Science. 35: 313-315. Malavolta, E. (1985). Potassium Status of Tropical and Subtropical Region Soils. In: R.D. Munson (ed) Potassium in Soils and Crops. Potash Research Institute of India. New Delhi. PP. 163-200. McLean, E.O. and Simon, R.H. (1958). Potassium release and fixation in Ohio soils as measured by cropping and chemical extractions. Ohio Agricultural Experiment Station Research Bulletin, 824. McLean, E.O. and Watson, M.E. (1985). Soil Measurements of Plant available Potassium. In: R.D. Munson (ed) Potassium in Soils and Crops. Potash Research Institute of India. New Delhi. pp 277-308. Mehrotra, C.L., Singh, G. and Pandey, R.K. (1973). Relationship between different form of potassium in different particle size in broad soil groups of Uttar Pradesh. Journal of Indian Society of Soil Science. 21: 42-427. Mehta, S.C., Meel, P.K., Grewal, K.S. and Singh, M. (1995). Release of nonexchangeable potassium in Entisols. Journal of Indian Society of Soil Science. 43: 351-356. Mishra, A.K. and Shrivastava, A.R. (1994). Contribution from different size particles to availability of potassium to maize in alluvial soils of North Bihar. Journal of Potassium Research, 10: 255-262. Mishra, M.K. and Singh, M. (1992). Potassium release characteristics of some Benchmark soil of India. Journal of Potassium Research. 8: 1-10. Mortland, M.M. (1961). The dynamic character of potassium release and fixation. Soil Science, 91: 11-13. 70 A.V Shanwat and S.. Singh

Mortland, M.M., Newton, K. and Uehara, G. (1956). Alteration of biotite to vermiculite by plant growth. Soil Science 82: 477-481. Pal, D.K. and Durge, S.L. (1993). Potassium release from clay micas. Journal of Indian Society of Soil Science. 41: 67-69. Pal, S.K. and Mukhopadhyay, A.K. (1992). Potassium releasing power of soil as a tool to assess its supplying power. Journalof Indian Society of Soil Science, 40: 266-270. Pal, S.K., Schdev, C.B., Gaik, S.T. and Rana, K.P.S. (1996). Distribution of forms of K in Benchmark Pedons of Gujrat. Journalof Potassium Research. 12: 21-229. Prakash Chandra and Singh Vinay. (1985). Forms of potassium in alluvial soils of western Uttar Pradesh. Journalof Indian Society of Soil Science. 33: 911- 914. Pundeer, G.S., Sidhu, P.S. and Hall, F.G. (1978). Mineralogy of soils developed on two geomorphic surface of the Sutlej alluvium in the Central Punjab. Journal of Indian Society of Soil Science. 22: 269-274. Pundeer, G.S., Singh, M. and Randhawa, N.S. (1974). Mineralogy of the sand fraction of some flood plain soils of Hoshiarpur district. Punjab. Journal of Indian Society of Soil Science. 22: 269-274. Quirk, J.P. and Chute, J.H. (1968). Potassium release from mica like clay minerals. Transnational 9th International Congress of Soil Science 2: 671. Radoslovich, E.W. (1975). The cell dimensions and symmetry of layer-silicates: IV. Interatomic forces. American Mineral. 48: 76-99. Raj Kumar, Ghabru, S.K., Ahuja, R.L. and Singh, N.T. (1994). Elemental composition and mineralogy of alkali soils on the Swalik hill. Agropedology. 4: 59-68. Raj Kumar, Sidhu, P.S. and Sharma, B.D. (2000). Mineralogy of soils of Kandi area in the Siwalik hills of semiarid tract of India. Agropedology. 10: 24-33. Ramamoorthy, B. and Bajaj, J.C. (1969). Available nitrogen, phosphorus and potassium status of Indian soils. Fertiliser News. 14:1-12. Rich, C.I. (1968). Mineralogy of Soil Potassium. In: V.J. Kilmer (ed) The Role of Potassium in Agriculture. American Society of Agronomy. Madison. Roonwal, G.S., Khanna, S.S. and Prakash, A. (1967). Mineralogy of sand fractions in certain profiles of Hisar district (Haryana). Journalof Research of Punjab Agricultural Univeristy 4: 166-173. Samiel, A. and Chahal, D.S. 1986. Potassium release in alluvial soils. Journal of Indian Society of Soil Science, 34: 757-761. Sawhney, B.L. (1966). Kinetics of cesium sorption by clay minerals. Soil Science Society of America Proceedings 30: 565-569. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 71

Schroeder, D.(1978). Structure and weathering of potassium containing minerals in: Potassium Research Review and Trend. Proceedings of Congress of International Potash Institute 4: 43-65. Schulte, E.E. and Corey, R.B. (1963). Flame photometeric determination of K precipitated in soiil as potassium tetra phenyl boron. Soil Science Society of America Proceedings, 27: 358-360. Scot, A.D. and Smith, S.J. (1987). Visible changes in macro mica particles that occur with potassium depletion. Clay Mineralogy. 15: 357-73. Sehgal, J.L. (1975). Nature and geographic distribution of clay minerals in soils of different moisture regime in Punjab, Haryana and HP. Bulletin of Indian Water Science Academy 50: 151-159. Sehgal, J.L. and DeConinck, F.R. (1971). Identification of 14A' and 7A' clay minerals in Punjab soils. Journal of Indian Society of Soil Science. 19: 159- 166. Sekhon, G.S. (1985). Potassium in Indian Agriculture. Journal of Indian Society of Soil Science. 35: 754-768. Sekhon, G.S., Brar, M.S. and Subba Rao, A. (1992). Potassium in some benchmark soils of India. Potash Research Institute of India. Special Publication, Gurgaon, Haryana. India. Shanwal, A.V. (1984). Pedogenic characterization of Yamuna Alluvial Plain, Haryana Ph.D. Thesis. Indian Agricultural Research Institute, New Delhi. Shanwal, A.V. and Dutta, S. (2000). Potassium supplementation by coarser fractions of soils during crop growth. Crop Research 19: 530-533. Shanwal, A.V. and Dutta, S. (2001a). Forms of potassium and K-bearing minerals in soils of some agroclimatic zones of India. Int. Symp. On Importance of Potassium in Nutrient Managementfor Sustainable Crop Production in India (Dec. 3-5, 2001), New Delhi. Shanwal, A.V. and Dutta, S. (2001b). Contribution of different Oarticle size fractions of varied mineralogy soils towards potassium availability under intensive cropping. Int. Symp. on Importance of Potassium in Nutrient Management for Sustainable Crop Production in India (Dec. 3-5, 2001), New Delhi. Shanwal, A.V. and Dutta, S. (2001c). Potassium release kinetics arid soil mineralogy in aeolian and alluvial soils of North India. European Journal of Soil Science. (Communicated). Shanwal, A.V. and Ghosh, S.K. (1985). Smectite formation in catena of soils derived from micaceous alluvium. International Journal of Tropical Agriculture 3: 273-286. Shanwal, A.V. and Ghosh, S.K. (1987). Soils on surfaces differing in age, Yamuna 72 A.V Shanwal and S.R Singh

alluvial plain, India. Pedologie. XXXVII: 169-186. Shanwal, A.V. and Ghosh, S.K. (1989). Presence of fiberous minerals in the soils of dune shaped topography in Indo-Gangetic alluvial plain, India. Int. Symp. Monaging Sandy Soils. Central Arid Zone Research Institute, Jodhpur. Pp. 65-70. Shanwal, A.V., Kumar, V. and Karwasra, S.P.S. (1988). Clay mineralogy of soils of farm of HAU, Hisar, Haryana. Haryana Agricultural University Journal of Research. XVIII, 266-275. Shanwal, A.V., Pannu, B.S. and Sangwan, B.S. (1996). Changes in clay minerals in the genesis of paddy soils in the Indo-Gangetic alluvial plain, Haryana India. Agroforestry and Environment. 206-211. Sharma,'O.P. and Dubey. (1988). Potassium status of vertisol and associated soils of toposequence (M.P.). Journal of Indian Society of Soil Science, 36: 363-366. Sharma, R.R. and Swami, B.N. (2000) Studies on kinetics of potassium release in .surface horizons of three soil series of Rajasthan. Journalof Indian Society of Soil Science. 48: 472-477. Sharma, V.K. and Sekhon, G.S. (1992). Soil plant K interrelationship in six soil series differing in K status through short term adsoption studies with sorghum. Journal of Indian Society of Soil Science, 40: 317-320. Sidhu, P.S. and Bhaugu, S.S. (1993. Distribution of water soluble and exchangeable potassium in Benchmark soils of Punjab. Journal of Indian Society of Soil Science 41: 678-682. Sidhu, P.S. and Gilks, R.J. (1972). Mineralogy of soils developed on alluvium in the Indo-Gangetic plain (India). Soil Science Society of American Journal. 41: 1194-1198. Singh, A.P., Mehla, S.C. and Mittal, S.B. (1987). Potassium adsorption in some potassium depleted soils. Journal of Indian Society of Soil Science, 35: 375- 382. Singh, B. and Goulding, K. W.T. (1997). Changes with time in the potassium content and phyllosilicales in the soil of the Broadbalk continuous wheat experiment at Rothmasted. European Journal of Soil Science. 48: 651-659. Singh, B. and Shanwal, A.V. (1997). Potassium Scanario in Haryana Soils. In: G. Dev and M.C. Oswal (eds) Use of Potassium in Haryana Agriculture. Potash and Phosphate Institute of Canada, India Programme: Gurgaon. PP 27-41. Singh, B.P., Singh, M. and Shukla, U.C. (1983). Forms of potassium in some soils of different agroclimatic regions of Eastern Haryana. Journal of Indian Society of Soil Science. 31: 31-37. Mineralogy and Dynamics of Potassium in Soils of Semi-Arid Regions of India 73

Singh, R. and Kuhad, M.S. (1981). Available and potentially available form of potassium and their relationship with some of the physico-chemical characteristics of soils of Haryana. Haryana Agricultural University Journal of Research. XI: 75-76. Singh, S.K., Das, K., Shyampura, R.L. and Singh, R.S. (1996a). Forms of potassium in relation to soil moisture regime in Rajasthan. Journal of Indian Society of Soil Science. 44: 229-233. Singh, S.K., Das, K., Shyampura, R.L. and Singh, R.S. (1996b). The status and release behaviour of K as influenced by moisture regime. Journal of Indian Society of Soil Science 44: 392-397. Singh, S.P., Haldar, A.K. and Singh, N. (1989). Studies on forms of potassium in relation to soil characteristics in the soils of Mizoram. Indian Agriculture. 33: 55-58. Singh, S.P., Ram, J. and Singh, N. (1999a). Dynamics of potassium as influenced by moisture and fertilizer regimes in some soils of Nagaland. Journal of Potassium Research. 15: 48-53. Singh, S.P., Ram, J., Singh, N. and Haldar, A.K. (1998). Agropedology. 8: 90- 93. Forms of potassium in some soils of Arunachal Pradesh. Singh, S.P., Ram, J., Singh, N. and Sarkar, D. (1999b). Distribution of potassium in soils of Arunachal Pradesh. Journal of Potassium Research. 15: 15-24. Singh, Y.P., Singh, M. and Kumar, R. (1985a). Identification of potash bearing minerals in sand fraction of some soils of Haryana. Journalof Indian Society of Soil Science. 33: 732-734. Singh, Y.P., Singh, M. and Singh R. (1985b). Forms of soil potassium in western part of Haryana. Journal of Indian Society of Soil Science. 33: 284-291. Sparks, D.L. (1987). Potassium Dynamics in Soils. Advances in Soil Sci. Springer Verlag, New York. 6: 1-63. Sparks, D.L. and Huang, P.M. (1985). Physical chemistry of soil potassium. In: R.D. Munson (ed) Potassium in Agriculture. American Society of Agronomy, Crop Science Society of America and Soil Science Society of America, Madison, Wisconsin. PP. 201-276. Srinivasa Rao, C. and Khera, M.S. (1995). Fixation of added potassium and fertilizer K requirement of illite dominated soils as affected by K desorption. Journal of Indian Society of Soil Science, 43: 405-407. Srinivasa Rao, C., Bansal, S.K., Subba Rao, A. and Takkar, P.N. (1998). Kinetics of potassium desorption from important benchmark soils of India. Journal of Indian Society of Soil Science, 46: 357-362. Srinivasa Rao, C., Dutta, S.P., Subba Rao, A., Singh, S.P. and Takkar, P.N. (1997). Kinetics of nonexchangeable potassium release by organic acids 74 A.V Shanwal and S.P. Singh

from mineralogically different soils. Journal of Indian Society of Soil Science, 45: 728-734.

Srinivasa Rao, C., Rupta, T.R., Subba Rao, A. and Bansal, S.K. (2000). Potassium fixation characteristics of major Benchmark soils of India. Journalof Indian Society of Soil Science, 48: 220-228.

Srinivasa Rao, C., Subba Rao, A. and Bansal, S.K. (2000). Relationship of some forms of K with neutral normal NH 4OAc extractable K in mineralogically different Benchmark soil series of India. Journal of Indian Society of Soil Science. 48: 27-32.

Srinivasa, Rao, C., Subba Rao, A. and Rupa, T.R. (2001). Need for inclusion of non-exchangeable potassium as a measure in soil test calibration and potassium recommendations. Fertilizer News, 46: 31-38. Subba Rao, A. and Sekhan, G.S. (1990). Variability in potassium status of the soils developed on different parent materials. Journal of Indian Society of Soil Science. 38: 206-212. Subba Rao, A., Seshasai, M.V.R. and Pal, S.K. (1993). Nonexchangeable potassium reserve and their categorization in some soils of India. Journal of Indian Society of Soil Science. 41: 667-673.

Tewatia, R.K., Singh, N., Ghabru, S.K. and Singh, M. (1989). Potassium content and mineralogical composition of some salt affected soils. Journalof Indian Society of Soil Science. 37: 687-691. Tomar, K.P. (1985). High spacing irregularly interstratified layer silicates in the alluvial soil clays of Mearut, India. Clay Miner. 20: 115-124. Wicklander, L. (1954). Forms of potassium in soil. Potassium Symposium. 1: 109-12. Yadav, B.R. and Gupta, R.N. (1974). A comparative study of clay mineralogy in semiarid soils of western UP. Proceedings of Indian National Science Academy 40 B: 160-166.

Yadav, B.R. and Swami, B.N. (1988). Effect of potassium fertilization on dry matter yield and composition and uptake of nutrients by maize and changes in soil potassium on cropping in Rajasthan soil. Journal of Indian Society of Soil Science, 36: 739-742. Yadav, P. (1999). Pedogenic Characterization of Major Landforms of Haryana. Ph.D. Thesis. Chandhany Charan Singh Haryana Agricultural University, Hisar. Distribution and Availability of Potassium in Lateritic Soils of India

T.C. BARUAH, K. BORKAKATI AND H.C. BARUAH Department of Soil Science, Assam Agricultural University Jorhat-785013 (Assam)

INTRODUCTION

The subcontinent of India displays extreme variations in climate, vegetation, physiography and as a consequence various types of soil are found in the country. Based on physiographic and climatic variations, the soils of India can be divided into four broad soil groups viz., hill and forest soils of the Himalayan mountains, alluvium-derived soils of the great Indo-Gangetic plains, Black cotton soils, and red and lateritic soils of the Peninsula regions (Sehgal, 1988).

DEFINITION

Laterite soils: The word Laterite has originated from the Latin word Later which means Bricks. The name signifies the soils with laterite formation in the subsoil horizon. The laterite is a highly weathered material enriched in secondary forms of iron or aluminium, or both. It is either hard or subject to hardening upon exposure to alternate wetting and drying. The soils are poor in humus and largely depleted of bases and silica with or without diagnostic horizon and/or weatherable primary minerals or silicate clays. They generally qualify for Oxisols, Ultisols.

Lateritic Soils: The term is used for soils that do not necessarily have laterite as a subsoil horizon but reflect its occurrence in their morphological features. According to Soil Taxonomy (Soil Survey Staff, 1975) most of such soils qualify for Ultisols or Alfisols with kandic properties. Even with the recent revision of the limits of some diagnostic properties of Oxisols, most of the Lateritic soils of India are out of the ambit of Oxisols.

FORMATION

The laterites and lateritic soils are highly ferruginous soils formed in tropical and subtropical climates having alternate wet and dry seasons. The climatic conditions (heavy rains and high temperature) and basic parent rocks are conducive to the process of lateritisation. Laterite soils are usually shallow and generally at higher lands, but are very deep loam to clay soils in the valleys where good paddy crops are produced on them. 75 76 T.C. Baruah. K. Borkakati and H.C. Baruah

During weathering, the base and siliceous matter of the rock are leached away almost completely, with concurrent accumulation of sesquioxides (Fe and Al oxides). The resulting soils are rich in sesquioxides and devoid of bases and primary silicate minerals. The laterite layer is hard or capable of hardening when exposed to alternate wetting and drying. It is a compact to vesicular, rock- like material of Al- and Fe-oxides.

Soils that are formed from weathering of lateritic crusts on old land surfaces are called lateritic soils and are completely devoid of bases; those formed by laterization on

recent soils formed in situ from parent rock show variations in their base content, pH and accumulation of Fe and Al. Most of theses soils contain one or other heavy metals, such as Ni and Mn (William and Joseph, 1970; Schellmann, 1981) in addition to accumulated Fe and Al sesquioxides. Cation exchange capacity, base saturation, pH and organic matter decreases with increasing laterization of soils (Ranganathan, 1998).

CHARACTERISTICS

Lateritic soils are reddish in colour having maximum intensity of colour in the B horizon. The colour is due to the presence of haematite, and the yellow mottlings are due to limonite. They are deep or very deep, highly weathered soils. In the inland laterite region they are generally characterized by the presence of iron and laterite gravel in the form of a horizon, whereas in the coastal region the gravel is distributed throughout the depth. The depth of weathering may extend to several metres, with decreasing intensity of red colour and clay content. These soils have a high clay content (28 to 60 per cent) especially in the B horizon, which is due to in situ alteration and illuviation of clay. Weatherable minerals, on prolonged leaching, lose bases and silica with relative accumulation of sesquioxides. Laterite soils are deficient in basic elements viz., lime, magnesia, potash and nitrogen and available phosphorus.

Lateritic soils are acidic in reaction having moderate acidity (pH 5.0-6.5), toxicity of Al and Mn, and are deficient in phosphate due to high phosphate fixing capacity with very low silica/sesquioxide ratio (<2). They are low in available plant nutrients with Ca, Mg, B and Zn in deficient status and low organic matter. Kaolinite is the dominant clay mineral (Reddy et al., 1993).

The iron oxides of laterite soils fix P in forms unavailable to plants. Incorporation of well-decomposed organic matter into the soil for releasing the nutrients slowly has been suggested. Ranganathan and Biddappa (1991) suggested regular liming and maintaining thick mulch in the basins to keep the concentration of toxic ions such as Mn and Al at low levels. Lateritic soils are not sticky and plastic when wet. They are in excellent physical condition due to the presence Distribution and Availability of Potassium in Lateritic Soils of India 77 of hydrous oxides of iron and aluminium and kaolinite as the dominating clay minerals.

Distribution of lateritic soils of India

Lateritic soils occur in small patches in almost all the states of north eastern, eastern, southern and western India. They occur in parts of Kerela, Karnataka, Tamil Nadu, Maharashtra, Andhra Pradesh, Orissa, West Bengal, Bihar, Goa, North eastern states and in small areas of Madhya Pradesh (Velayutham and Bhattacharyya, 2000). In India, laterite soils occupy an area of 1,30,066 km 2. In India the well developed laterites are observed on hill-tops and plateau of Orissa, Maharashtra, Kerela, Tamil Nadu and North-Eastern region; such soils are locally observed in Andhra Pradesh, Karnataka and Assam. In Maharashtra, laterite soils occur in Ratnagiri. They are rich in coarser material and plant nutrients except lime. In Karnataka, laterite soils occur in the western part of Shimoga, Bangalore, Kadur, Kolar and Mysore districts. Some of them are well drained brown clay loam soil occurring in hill tops. Some of them are shallow brown loam soil.

Laterite soils are characterized by dry humid to moist humid climate with moisture availability that can support crop-growing period of 180-300 days in a year. They are formed from several kinds of rocks like basalt under a hot, humid climate when the basic elements and silica have been washed down and iron is precipitated and oxidized. Whenever drainage is restricted, a soft deposit of iron oxide occurs at or near the water table, which hardens when it dries. In some places like Malabar, this is cut in the form of bricks and used as a building material. This possesses an indurated honey comb mass of iron oxides. Laterite soils occur on nearly level land in the coastal plains and midlands as well as on undulating/rolling topography under tropical and subtropical climate with moderate to high rainfall and elevation ranging from 10 to 1000 metres above MSL. The natural vegetation consists of moist deciduous and evergreen forests.

Vertical distribution of K

Das et al. (1997) studied vertical distribution of K in some lateritic soils of Orissa belonging to taxonomic orders Alfisols and Inceptisols, taking profile samples from a sloping terrain having 3 to 5 per cent slope within different physiographic units comprising of foot hills, upper ridges, mid upland, medium land and medium valley lands. The general pedon characteristics together with K forms are given in table 1. Water soluble K decreased, whereas non- exchangeable K, lattice K and total K increased with soil depth. Non-exchangeable K, lattice K and total K were mainly contributed by the clay fraction in soil (Table 1). All the forms of K excepting water soluble K, were positively correlated with each other, while water soluble K was negatively correlated with others. Water soluble K/exchangeable K ratio decreased with depth in the profiles, but no specific trend in the ratio of other forms could be observed (Table 1). Table 1. Pedon characteristics and vertical distribution of K forms Genetic Depth Clay pH Org.C Forms of K (mg kg-' soil) horizon (cm) (%) (1:2) (%) Water sol. K Exch.K Non-exch. K Lattice K Total K Profile -1 Foot hills (Arenic Kanhaplic Haplustalfs) A 2 0-14 7.4 6.1 0.17 20.0(1.8) 40.0(3.6) 460(41.8) 580(52.8) 1100 B 21 14-40 11.4 5.8 0.17 19.5 (1.0) 70.5 (3.5) 510(25.5) 1400(70.0) 2000 B 22t 40-72 23.4 5.7 0.14 11.5 (0.5) 83.5 (3.5) 665 (27.7) 1640(68.3) 2400 B 23t 72-150 31.4 5.6 0.14 8.0(0.3) 97.0(3.2) 695 (23.2) 2200 (73.3) 3000 Profile-2 Upper ridges (Aridic Kanhaplustalfs) Ap 0-11 21.4 5.6 0.20 18.5 (0.7) 96.5 (3.7) 645 (24.8) 1840(70.8) 2600 B 21t 11-52 35.4 5.8 0.16 10.0(0.4) 110.0(3.9) 820(29.3) 1860(66.4) 2800 B 22t 52-88 36.4 5.9 0.15 6.5 (0.2) 93.5 (3.1) 860(28.7) 2040(68.0) 3000 B 23t 88-115 37.4 6.1 0.08 6.5 (0.2) 103.5 (3.6) 850(29.3) 1940(66.9) 2900 C 115-150 35.4 5.9 0.10 8.0(0.3) 107.0(4.0) 925 (34.3) 1660 (61.4) 2700 Profile-3 Mid upland (Aridic Kanhaplustalfs) Ap 0-14 15.4 5.5 0.39 17.5 (0.8) 62.5 92.8) 600 (27.3) 1520(69.1) 2200 B 21t 14-42 29.4 5.7 0.30 12.0(0.4) 83.0(3.0) 945 (33.7) 1760(62.9) 2800 fn B 22t 42-90 45.4 5.7 0.24 11.5 (0.4) 88.5 (2.9) 1100(36.7) 1800(60.0) 3000 B 23t 90-172 45.4 5.7 0.13 10.0(0.3) 100.0(2.9) 1130(32.2) 2260(64.6) 3500 Profile-4 Medium land (Aridic Kanhaplustalfs) Ap 0-14 15.4 5.5 0.33 13.5 (0.7) 71.5 (4.0) 675 (37.5) 1040(57.8) 1800 B 21t 14-27 17.4 5.5 0.28 13.0 (0.6) 62.0 (2.8) 765 (34.8) 1360 (61.8) 2200 B 22t 27-60 27.4 5.5 0.24 12.0 (0.5) 78.0 (3.1) 830 (33.2) 1580 (63.3) 2500 B 23t 60-150 47.4 5.9 0.23 7.5 (0.2) 67.5 (2.1) 1045 (32.7) 2080 (65.0) 3200 Profile-5 Medium valley land (Aridic Ustochrepts) Ap 0-14 13.4 6.1 0.40 15.5 (1.2) 39.5 (2.8) 505 (36.0) 840 (60.0) 1400 B 21 14-32 15.4 6.3 0.20 11.0 (0.7) 59.0 (3.9) 570 (38.0) 860 (57.4) 1500 B22w 32-84 31.4 5.8 0.14 10.5 (0.4) 94.5 (3.2) 775 (26.7) 2020 (69.7) 2900 C 84-155 37.4 6.0 0.15 10.0 (0.3) 105.0 (3.4) 885 (28.5) 2100 (67.8) 3100 Distribution and Availability of Potassium in Lateritic Soils of India 79

The decrease in water soluble K in spite of a general increase in exchangeable K with soil depth might be due to greater specific adsorption of K at the lower layers due to higher clay content (Table 1). Water soluble K was negatively correlated with clay and positively correlated with sand; whereas, all the other forms of K were correlated positively with clay and negatively with sand (Table 2). Non-exchangeable K, lattice K and total K were also positively correlated with silt, but the 'r' values were much less than that with clay, indicating that all these forms of K were mainly contributed by the clay fraction in soil followed by silt.

Table 2. Relationships of the forms of K with sand, silt and clay (n=21) X Y Soil separate Water sol. K Exch. K Non-exch. K Lattice K Total K Sand 0.76** -0.67** -0.90** -0.84** -O.91** Silt -0.39 NS 0.29 NS 0.44* 0.50* 0.5 1* Clay -0.78** 0.71** 0.92** 0.83** 0.91**

Potassium release from soils is quite inadequate. High N and K applications are required to sustain productivity. The effect of CEC could be kept at high levels by increasing the pH to 4.8 (optimum for tea) by liming, and by reducing pH by addition of organic matter and application of specifically adsorbed ions such as phosphate and silicate (Natesan and Ranganathan, 1990).

Studying the different forms of K, Kadrekar and Kibe (1973) observed that lateritic soils of heavy rainfall zones were generally found to be poor in different forms of K than the soils of transition zone.

Ray Choudhury and Loveday (1960) observed that the available K decreased with decreasing pH in lateritic soils. Rajakkamu et al. (1970) reported that there was no relation between available K and org. C in red soils. The amount of K fixed was comparatively more in black soils as compared to alluvial and red soil (Mitra et al., 1958; Verma and Verma, 1971; Aggarwal et al., 1979; Khurnana et al., 1982) or lateritic soils (Patil et al., 1976; Baleen and Sree Ramalu, 1979).

Gascuami et al (1976) pointed out that the differences in the magnitude of crop response to fertilizer K between various soil groups, laterite soils are the most responsive of all. Laterites and lateritic soils are the poorest in K availability.

Available K status of lateritic soils

States viz., Tripura, Meghalaya and Mizoram and Pondichary all come under the low category of available K. The K status is also low in 67, 58, 44 and 36% of the district of Assam, Kerela, Karnataka, Madhya Pradesh, Orissa and West 80 T.C. Baruah. K, Borkakati and HC. Baruah Bengal, 7 to 17% districts are low in K. The states with 71 to 82% of the district having a high status are Madhya Pradesh and Rajasthan. In Himachal Pradesh, Karnataka, Maharashtra and Tamil Nadu 20 to 46% are under the high category and so also 7 to 8% of the district of West Bengal. The K status is medium in Andhra Pradesh with 80% of the district in West Bengal and 85% in Orissa. The per cent distribution in the medium class ranges between 50 and 62 in Andhra Pradesh, Karnataka, Kerela, Maharashtra and Tamil Nadu. 33 to 43% in Assam. Somewhat lower figures of 18 to 28% are observed in Madhya Pradesh and Rajasthan. As regards the state of Bihar, the information is available in respect of 7 districts only, of which 72% are in medium class and the rest is high. The K status of lateritic soils of Eastern India has not been completed so far. In plateau region of Chotanagpur, 30% soils have been reported deficient. In general, soils have been reported to fix K in the order : alluvial > black > red and lateritic with 2:1 minerals dominating the process. Lateritic soils dominate in kaolinitic clay minerals and there the extent of fixation is less. Crop response to K fertilizers in the acid lateritic soils of West Bengal and Bihar is of the order of 7 kg grain kg-' K.

Ghosh and Hasan (1976) reported that nearly one-fifth of the districts of India measured low available K and most of these were located in regions dominated by red and lateritic soils. Even soils marked medium later turned to be low in available K (Table 3). Based on the data generated (Table 4), Sekhon et al. (1992) reported that lateritic soils of Nedumangad (Kerala) and Kumbhave- 5 (Maharashtra) were marginally medium in available K with a nodal value of 51-60 mg kg-'.

Table 3. Available K status of laterite in benchmark soil series Soil series PRII study (1990) Ghosh & Hasan (1976) Kumbhave-5 Low Medium Nedumangad Low Medium Source: Sekhon et al. (1992)

Table 4. Average available and reserve K contents of laterite in benchmark soil series Soil series K content (mg kg- soil)

NH 4 OAc HNO3 Non-exchangeable Kumbhave-5 70 ± 35 189 ± 72 119 Nedumangad 69 ± 33 120 ± 38 51 Source : Sekhon et al. (1992) Distribution and Availability of Potassium in Lateritic Soils of India 81

Factors affecting K availability in lateritic soils

Potassium availability in red and lateritic soils is governed by their mineralogy. Ningappa and Vasuki (1989) obtained low K-fixation ranging from 21.4-40.6 per cent on acid lateritic soils of Karnataka and attributed it to the dominance of kaolinite. Detailed mineralogical analysis of the benchmark soil series indicate that low to moderate levels of K in soil are maintained by small quantities of illite in clay fraction and mica and feldspars in silt fractions (Sekhon et al., 1992). In the absence of these minerals, the soils could have been completely devoid of available K as it is not the structural component of dominant kaolinite and amorphous clays; the negotiable K retention by these clays could have led to loss of labile K from the rhizosphere under high rainfall conditions.

Soil moisture has an important role in K fixation and release behaviour. Drying of soil causes fixation of added K (Grewal and Kanwar, 1967), but is also known to promote its release (Kadrekar and Kiibe, 1973). Response to K has been found in many areas in the country, the extent being generally higher with rice than in wheat.

Soil acidity is another factor affecting K availability in lateritic soils. It has been shown that percentage of potassium saturation (PPS) on clay complex gives a better indication of K availability as compared to other forms of K. Potassium saturation in most of the laterite soils is found to be low ranging from I to 3 per cent. Presence of low potash bearing minerals coupled with adverse soil conditions like soil acidity determine the K availability in these soils. In general, laterite soils are dominant in kaolinite type of clay minerals with limited mica content. Moreover, release of K from these meager quantities of mica and its conditions, the K selective binding sites are occupied by Al and Al-hydroxy cations and their polymers, and the extent to which these exist is a function of soil pH (Panda and Koshy, 1982).

Srinivasa Rao and Subbaiah (1997) studied PPS, exch. K and total K in relation to soil acidity and mica content in six laterite profiles of Nellore district. Presence of high exch. acidity (All' and H+) resulted in lower PPS on clay complex as revealed from significant negative correlation (r=0.59*) between these two parameters. Higher sesquioxide inhibits the K retention on clay as revealed from negative correlation between sesquioxide content and PPS. Total K in surface soils had highly significant correlation (0.97**) with mica content of soils.

The sesquioxides (R 20 3 = A120 3 + Fe20 3) are the striking feature of laterite soils affecting K availability. In mature laterites, sesquioxdes accumulate in the form of crust and concretions. A negative relationship (r = 0.40) between sesquioxide content and PPS was reported by Srinivasa Rao and Subbaiah (1997) in six laterite profiles of Nellore district. High contents of sesquioxide together 3 with acidic soil condition increased exch. A and H* content and on further 82 T.C. Baruah, K. Borkakati and H.C. Baruah

hydrolysis, resulted in lower retention of bases on exchange complex of clay minerals.

Non-exchangeable K reserve and its categorization in some lateritic soils of India

On the basis of K reserve, the soils are categorized into five classes, viz., very low, low, medium, high and very high. These soil classes may serve as the basis for soil test calibration and crop response studies.

The exchangeable K content is low in lateritic soils and the soils developed on laterite have low content of K-bearing minerals. In lateritic soils, K content is larger in sand and silt sized fractions compared to clay. Thus, in lateritic soils where the clay fraction is depleted of K rich micaceous minerals, the proportion of K release by HNO 3 may be smaller than in the illitic and smectite dominant soils. The lateritic soil (Kunbhave-5) with relatively larger amounts of mica K with corresponding small amounts of step K indicate that reserve K in these soils is not readily mobilizable for plant uptake (Table 5).

Table 5. Different forms of K and K release parameters of red and lateritic benchmark soil series of India Series K mg kg-' K mg kg - ha -' Ratio Exch. Non- Mica Step K- Mica K Step K exch. release Non- Non- exch.K exch.K Vijayapura 68 62 1234 152 17 19.9 2.4 Nedumanged 69 51 1161 152 7 22.8 3.0 Kumbhave-5 70 119 2240 149 49 18.8 1.2 Tyamagondalu 76 292 3889 801 117 13.3 2.7 Doddabhavi 92 957 1648 2007 272 12.2 2.1

Among all the soils Doddabhavi soil and Tyamagondalu released more amount of non-exch. K. Lateritic soils of Nedumanged and Kumbhave-5, had lower rates of non-exch. K release (and also step K) indicating that these soils are poorer in K supply compared to others. Doddabhavi soil had high reserve K (step K) but moderate K release rate showing the possibility for less depletion of K reserve. Almost similar behaviour can be expected in case of Tyamagondalu soil also.

Release characteristicsof K

Since the deep rooted crops absorb nutrients from the deeper part of soil, information on K-release behaviour of soils at the sub-surface horizons seems Distribution and Availability of Potassium in Lateritic Soils of India 83 essential. Das et at. (1997) studied the K-release behaviour of some lateritic soils of Orissa belonging to taxonomic orders Alfisols and Inceptisols, taking samples from surface and sub-surface horizons from a sloping terrain having 3 to 5 per cent slope within different physiographic units comprising of upper ridges, mid upland, medium land and medium valley lands.

K-release parameters for the soils like total extractable K and total step K increased with increase in clay content from surface down the profile (Table 6). Total extractable K per cent and total step K per cent were positively correlated with non-exchangeable K: lattice K ratio in soil. Positive correlations of all the K-release parameters with non-exchangeable K having high 'r' values indicated that non-exchangeable K may serve as a good index of the K-supplying capacity of the soils (Table 7).

Table 6. Changes in the values of K release parameters with depth in the profiles Genetic Depth Total Total CR-K % of non-exch. K + lattice K horizon (cm) extract. K step K Total Total CR-K extract. K step K Profi rs) Ap 0-11 1365 1325 04 54.9 53.3 0.2 B 21t 11-52 2008 1768 24 74.9 66.0 0.9 B 22t 52-88 2228 1908 32 76.8 65.8 1.1 B 23t 88-115 2466 2066 40 88.4 74.1 1.4 C 115-150 2505 2105 40 96.9 81.4 1.5 Pr ilfs) Ap 0-14 1348 1188 16 63.6 56.0 0.8 B 21t 14-42 2085 1845 24 77.1 68.2 0.9 B 22t 42-90 2776 2216 56 95.7 76.4 0.9 B 23t 90-172 2882 2282 60 85.0 67.3 0.8 Pro Ilfs) Ap 0-14 1432 1352 08 83.4 78.8 0.5 B 21t 14-27 1629 1389 24 76.7 65.4 1.1 B 22t 27-60 2106 1786 32 87.4 74.1 1.3 B 23t 60-150 2709 2069 64 86.7 66.2 2.0 Profil repts) Ap 0-14 1109 909 20 82.5 67.6 1.5 B 21 14-32 1390 1070 32 97.2 74.8 2.2 B22w 32-84 1787 1587 20 63.9 56.8 0.7 C 84-155 2185 1865 32 73.2 62.5 1.1

Total extractable K was positively correlated with non-exchangeable K, lattice K and total K (Table 7). Total extractable K per cent was positively correlated with non-exchangeable K : lattice K ratio, which might be due to weaker binding 84 TC. Baruah, K. Borkakati and H.C. Baruah

Table 7. Relationship of the K-release parameters with forms of K (n = 17) Y) (X) K-release parameters Non-exch. K Lattice K Total K Total extractable K 0.96** 0.73** 0.84** Total step K 0.95** 0.79** 0.89** CR-K 0.80** NS 0.58** energy of K at the non-exchangeable sites than those inside the crystal lattice resulting in easier release of K from non-exchangeable sources than from the lattice sources.

Pal et al. (2001) assessed the reserve and release of non-exch. K by repeated extraction with boiling IN HNO 3 in 21 cultivated surface lateritic soils occurring widely in Narasinghpur area of Cuttack district of Orissa. K release parameters varied widely in different locations indicating a wide variation in K supplying capacity of these soils. Both the K release parameters were positively correlated with non-exch. K, lattice K and total K. Significant correlations of total extractable K and total step K with non-exch. K (r = 0.944** and 0.989**, respectively) indicate that the non-exch. K may serve as a good index of the K supplying capacity of these soils.

Crop response to applied Potassium

Responses to K application have been reported by Leelavathi et al. (1986) on lateritic soils (Table 8). Bhargava et al. (1985) found that on soils of humid to semi-arid Western Ghats and Karnataka plateau, application of 60 kg K20 per ha over N and P gave 5.1-8.3 and 2.3-5.6 kg rice and wheat grains, respectively, per kg of applied K20. Application of 1 kg K20 on Alfisols of Tamil Nadu produced 118-125 kg cane (Perumal and Sonar, 1987) and annual addition 200- 400 g K20 per plant increased the weight of banana bunch in both main and ratoon crops (Subramanyam and Iyengar, 1978).

Table 8. Yardstick on HY and locally improved varieties of rice to applied K (60 kg K20 ha-') in lateritic soils No. of districts - No. of experiments kg grain kg ' K20 Kharif rice (H.Y.) 11 884 5.1 Rabi rice (H.Y.) 11 1118 5.1 Kharif rice (locally improved) 2 179 2.9 Distribution and Availability of Potassium in Lateritic Soils of India 85

The magnitude of response to K determined by the initial K status of the soils (Goswami et al., 1976; Tandon and Sekhon, 1988). On lateritic soils of Kerela, application of 100 kg K20 ha-' to cassava produced maximum response and the response to 50 kg K20 ha-' was the highest in soils testing low in available K.

Potassium as an antidot

Toxicity of Fe is common in lateritic soils under submerged conditions, especially in the foothills where application of increased K levels alleviated this disorder (Dev and Rattan, 1998). In managing Fe toxicity, the two approaches used are : (i) cultivation of Fe-tolerant varieties, and (ii) use of additional level of K fertilizer. Application of K on F-toxic soils increased yield (Mitra et al., 1990), reduced Fe uptake and Fe/K ratio in rice plants (Table 9) (Dev, 1993). The results show that the use of Fe-tolerant varieties and increased level of applied K under Fe-toxic conditions in lateritic soils provide handy management practices.

Table 9. Effect of K application on grain yield (q ha -') and Fe:K ratio in grain yield of rice varieties Level Kharif* Rabi**

(kg K20 Jaya Mahsuri Pathara Parijat ha-') Yield Fe:K Yield Fe:K Yield Fe:K Yield Fe:K ratio ratio ratio ratio

0 10.3 2.3 18.2 1.6 19.0 2.2 24.4 1.4 40 13.8 1.1 22.1 0.9 22.2 0.7 30.0 0.6 80 19.4 0.8 22.7 0.5 27.2 0.4 31.9 0.4 120 22.1 0.6 26.5 0.4 29.9 0.4 33.9 0.2 160 24.4 0.3 28.8 0.2 32.4 0.2 36.3 0.2 Mean 18.0 1.0 23.58 0.7 26.2 1.4 31.5 0.5 CD (5%) K 2.53 2.42 V 2.69 1.13 KxV 1.52 NS = Average of 2 years; ** = Average of 3 years Source: Mitra et al. (1990)

Management of laterite soils vis-A-vis K management

As discussed earlier, laterite soils are inherently acid and are poor in exchangeable bases. Lateritic soils are among the nutritionally poor soils. Deficiency in lateritic soils is due to excessive leaching owing to high rainfall. 86 TC. Baruah, K. Borkakati and I[C. Baruah

The various nutrient deficiencies must be corrected through application of nutrients in a suitable proportion in order to sustain desired high levels of crop production. K as well as N fertilizers, which tend to leach with high rainfall or irrigation water supplies, should be applied in splits to ensure maximum efficiency.

Maintaining organic matter is essential to sustain productivity. Hence, sustainable nutrient supply system should revolve around soil organic matter maintenance and buildup, and making up the resultant deficit with supplementary dressings of fertilizers in order to ensure efficiency of application and availability to plants of various nutrients in appropriate amount and balance.(Sekhon, 1998).

Liming to increase the pH to near neutrality is not advocated, for this may even result in yield reduction. The three strategies used to address acid soil stress are:

* Liming to reduce Al-saturation below toxic level for the specific farming systems. * Liming to supply Ca and Mg and to promote their movement into the subsoil and * Use of plant species tolerant to Al, Fe and Mn toxicities

The quantity of lime to be added to an acid laterite soil depends on the amount of KCI-exch. Al in the soil. Liming recommendations are commonly given to supply Ca equivalent to 1.5 times the exch. Al. In terms of t ha-' CaCO 3, this will be equal to approx. 1.65 x exch. Al expressed in cmol (p') kg - . High soil pH (>6.5) normally enhances the substitution of K+ for Ca2 than Al" . Hence, liming to about pH 6.5 becomes necessary to reduce the leaching losses of K in acid tropical soils.

Balanced use of NPK is superior to N or NP use alone in increasing grain yield of rice in acid lateritic soils,.and liming sustained the highest productivity.

REFERENCES Bhangu, S.S. and Sidhu, P.S. (1993). Potassium mineralogy of five benchmark soils of central Punjab. Journal of Potassium Research 9: 105-112. Bhargava, P.N., Jain, H.C. and Bhatia, A.K. (1985). Response of rice and whaet to potassium. Journal of Potassium Research 1: 45-61. Das, P.K., Sahu, G.C. and Das, N. (1997). Vertical distribution and release characteristics of potassium in some lateritic soils of Orissa, I. Vertical distribution of potassium. Journal of Potassium Research 13(2): 105-110. Das, P.K., Sahu, G.C. and Das, N. (1997). Vertical distribution and release characteristics of potassium in some lateritic soils of Orissa, 11. Release Distribution and Availability of Potassium in Lateritic Soils of India 87

characteristics of potassium. Journal of Potassium Research 13(2): 111-116. Dev, G. (1993). Annual Report (1992-1993), Potash and Phosphate Institute of Canada-India Programme, Gurgaon. Dev, G. and Rattan, R.K. (1998). Nutrient management issues in red and lateritic soils. In the proceeding Red & Lateritic Soils Vol.1 Managing Red and Lateritic Soils for sustainable Agriculture (Eds. J. Sehgal, W.E. Blum and K.S. Gajbhiye) pp. 321-337. Ghosh, A.B. and Hasan, R. (1976). Available potassium status of Indian soils. Bulletin of Indian Society of Soil Science 10: 1-5. Goswami, N.N., Bapat, S.R., Leelavathi, C.R. and Singh, R.N. (1976). Potassium deficiency in rice and wheat in relation to soil type and fertility status. Bulletin of Indian Society of Soil Science 10: 186-194. Kadrekar, S.B. and Kibe, M.M. (1973). Journal of Indian Society of Soil Science 21: 161. Leelavathi, C.R., Bapat, S.R. and Narain, P. (1986). Revised yardsticks of additional production of rice due to improved measures, Indian Agriculturel Statistics Research Institute, New Delhi. Mitra, G.N., Sahu, S.K. and Dev, G. (1990). Potassium chloride increases rice yield and reduces symptoms of iron toxicity. Better Crops International, 6(2): 14-15. Ningappa, N. and Vasuki, N. (1989). Potassium fixation in acid soils of Karnataka. Journal of Indian Society of Soil Science 37: 391-92. Pal, A.K., Pattnaik, M.R., Santra, G.H. and Swain, N. (2001). Stuides on potassium releasing power of lateritic soils of Cuttack district. Journal of Indian Society of Soil Science 49(1): 7-74. Panda, N. and Koshy, M.M. (1982). Chemistry of Acid Soils. In: Review of Soils Research in India - I. 12th International Congress of Soil Science. New Delhi. pp. 160-168. Perumal, R. and Sonar, K.R. (1987). Potassium availability in soils growing sugar cane. Potash Research Inst. of India Review Research Series, No. 4: 65-69. Pillai, K.G.K. (1989). Research Highlights, Research Gaps and Future Strategies of All India Coordinated Agronomic Research Project, Indian Council of Agricultural Research, New Delhi. Ranganathan, V. Suitability of red and lateritic soil landscapes for tea. In Red and lateritic soils Vol. I. Managing red and lateritic soils for sustainable agriculture. (Ed. Sehgal, J, Blum, W.E. and Gajbhiye, K.S.). pp. 203-206. Reddy, P.S.A., Naga Bhushana, S.R., Krishnan, P., Natarajan, A., Shivaprasad, C.R., Venugopal, K.R., Prabhakara and Urs, M.S.D. (1993). Distribution, 88 TC. Baruah, K. Borkakati and H.. Baruah

Characterization and Classification of Red and Lateritic Soils of India. In: Red and Lateritic Soils of India - Resource Appraisal and Management (Eds. J. Sehgal, V.A.K. Sharma, R.K. Batta, K.S. Gajbhiye, S.R. Nagabhushna, K.R. Venugopal), NBSS Publ. 37, pp. 15-26. Sehgal, J.L. (1988). Major soils of India and Soil-Biota relationship, 1 0 th International Soil Zeology Colloquium, August 7-13, 1988, Bangalore, India. Sekhon, G.S., Mrar, M.S. and Subba Rao, A. (1992). Potassium in some benchmark soils of India, Sp. Publication 3, Potash Research Institute of India, Gurgaon. Sekhon, G.S. (1998). Sustainable nutrient supply systems for managing red and lateritic soils. In: Red and lateritic soils Vol. 1. Managing red and lateritic soils for sustainable agriculture. (Eds. Sehgal, J, Blum, W.E. and Gajbhiye, K.S.). pp. 313-320. Srinivasa Rao, Ch. And Khera, M.S. (1994). Consequences of potassium depletion under intensive cropping. Fertilizer News. 39: 23-29. Srinivasa Rao, Ch., Subbaiah, G.V. (1997). Association of some forms of potassium with soil acidity and mica content in six profiles of laterite soils. Journal of Potassium Research 13(1): 12-20. Srinivasa Rao, Ch., Subbaiah, G.V. and Pillai, R.N. (1991). Nutrient status of black soils of Telegu Ganga project area in Nellore district of Andhra Pradesh. Andhra Agric. J. 38(2 & 3): 210-215. Subba Rao, A. and Sekhon, G.S. (1991). Influence of soil acidity and organic matter on water soluble and exchangeable potassium and their relationship in acid tropical soils. Journal of Potassium Research 7: 20-26. Subramanyan, T.R. and Iyengar, B.R.V. (1978). Response of fruit crops to fertilizer potassium. Proc. PRI! Symposium Potassium in Soils and Crop, 347-365. Tandon, H.L.S. and Sekhon, G.S. (1988). Potassium research and agricultural production in India, Fertilizer development and consultation organization, New Delhi. Velayutham, M. and Bhattacharyya, T. (2000). Soil Resource Management. In Natural Resource Management for Agricultural Production in India. International Conference on Managing Natural Resources for sustainable Agricultural Production in the 21st Century, Feb. 14018, 2000, New Delhi. pp. 3-129. Distribution and Availability of Potassium in Red Soils of India

N.B. PRAKASH AND R. SIDDARAMAPPA Department of Soil Science & Agricultural Chemistry, University of Agricultural Sciences, GKVK, Bangalore

Introduction

Potassium (K) is one of the major plant nutrient often recognized for its influence on the qualities of produce. The importance of K in Indian Agriculture is increasing with the passage of time. The available Soil Survey data indicate that, majority of Indian soils are medium to low in Potassium. The long term fertilizer experiments have further strengthened by a positive crop response to potassic fertilizer application.

The distribution of potassium differs from soil to soil and is a function of dominant clay minerals present. The potassium content varies according to parent material, particle size distribution, degree of weathering and management practices (Sekhon et al., 1992).

National Bureau of Soil Survery and Land Use Planning in collaboration with the State Soil Surveys and SAU's have been able to prepare state soil resource maps (Sehgal, 1998). Based on the state soil resource map, a map of red and lateritic soils has been compiled (Figure 1). Red and lateritic soils pose several soil degradation problems, especially erosion, nutrient depletion, soil depth; the shallow to moderately shallow soils occupy about 45 per cent of the total area. Red and lateritic soils of India are classified under six Soil Orders (Alfisols, Ultisols, Oxisols, Inceptisols, Mollisols and Entisols), 13 suborders, 38 Great Groups and 71 Subgroups.

Red soils are the major soil group in the southern, eastern and north eastern parts of the country, coming under agro-ecological regions characterized by dry humid to moist humid climate with moisture availability that can support crop growing period of 180-300 days in a year.

Indian soils have been characterized on the basis of potassium fertility by Ramamoorthy and Bajaj, (1969) Ghosh and Hasan, (1976) and Sekhon et al., (1992). Further, Subba Rao and Srinivasa Rao (1996) made an attempt to compile available information on potassium dynamics in soils of each agro-ecological regions of India.

The knowledge of potassium chemistry and supplying power of soils is essential to formulate sound fertilizer recommendations for potassium. But no 89 14 0 Simk

3.. SState Boundar

Red & Lateritic Soil.

comprehensive sludy onl potassium distribution and availability has been done in dilferent soils. This study at templs to compile the information regarding the distribution and availability of potassium in. red soils of India. The study would be of great importance in appraisal of available potassium stats ill red soils distributed in different ago-ecological legions of India,

Mineralogy of red soils in relation to total K

PotassiNu status of soils is determined by parent muterial and the extent of pedogCnesis which a soil has undergone (Graham and Fox, 1971). Yoig soils derived iom materials rich in K bearing minerals are abmdant in K. In terms Distribution and Availability of Potassium in Red Soils of India 91 of mobility of soil K, a number of different K fractions can be identified. These include K in the crystal structure of minerals, K adsorbed on the surface of soil colloids and K in the soil colloids and K in the soil solution. Soils also vary in their capacity to release K from the reserves in non-exchangeable forms.

Potassium availability in red soils is largely governed by their mineralogy. Red soils exhibit the dominance of Kaolinite (sometimes 80-97%) with mica being associated mineral and very small amounts of chlorite, vermiculite, mixed layer minerals, quartz and feldspars (Ghabru, 1981). Bhattacharya et al., (1983) found more than 65 per cent of kaolinite in the clays of red soils developed from granite gneiss with mica being the next dominant mineral (22-33%). Sahu and Krishnamurthi (1984) reported the presence of significant amounts of amorphous ferrialumino silicates in addition to kaolinite in oxidizing environment of soils of Kerala. Further, detailed mineralogical analysis of the bench mark soils series of India indicated that, the low to moderate levels of K in soil are maintained by small quantities of illite in clay fraction and mica and feldspars in silt fractions (Sekhon et al., 1992)

The K content and its fractions in soil mainly depend on the nature of parent material, mineralogical make up, particle size distribution, degree of weathering and topographical features of the area. The total K contents of red soils of India varied from 0.36 to 4.5 per cent (Table 1). The total potassium content in the soil varies from soil to soil, locations and geomorphological units. The higher content of total K may be attributed to the presence of substantial amounts of K bearing minerals, subjected to less intense weathering (Mehrotra and Singh, 1970). A review of clay mineral research in Andhra Pradesh revealed that, feldspars account for 90 per cent of K bearing minerals present in coarse fraction

Table 1. Total K content of red soils in different states of India State Total K (%) Reference Kerala 0.37 Maheswari & Sekhon (1986) Tamil Nadu 1.72 Sekhon et al., (1992) Tamil Nadu 0.79-2.16 Ramanathan (1977) Karnataka 0.36-2.12 Sekhon et al., (1992) Karnataka 2.16 Ranganathan & Satyanarayana (1980) Karnataka 0.44-3.05 Maheswari & Sekhon (1986) Karnataka 1.78-2.12 Dhillon & Dhillon (1994) Andhra Pradesh 0.62-2.87 Dhillon & Dhilon (1994) Andhra Pradesh 4.65 Sekhon et al., (1992) Maharashtra 0.41 Sekhon & Mahatim Singh (1982) Maharashtra 1.33 Kadrekar & Kibe (1972) Maharashtra 0.69 Raskar & Pharande (1997) Uttara Pradesh 2.29 Mehrotra & GulabSingh (1970) Uttara Pradesh 2.69 Sekhon et al., (1992) Bihar 1.70 Roy et al., (1990) 92 N.B. Prakash and R. Siddaramappa of red soils (Padmaja and Sreenivasa Raju, 1999). The potassium from feldspars becomes available to plants only when its three dimensional structure is broken down during the process of weathering, which is difficult and time consuming (Rao and Raju, 1984).

The potassium content in sand, silt and clay fractions varied from 12.8 to 82.1, 29.5 to 87.2 and 17.7 to 40.0 cmol kg-' respectively (Table 2). The silt fraction of all red soils studied contained highest amount of total K and the per cent contribution of sand fraction towards total K content is very high than other fractions. The high amounts of K in the sand and silt fractions of red soil may be attributed to presence of less weathered K bearing minerals (Prasad et al., 1967). The highest contribution of sand fraction towards total K as observed in the samples of red soils could be attributed to the sand content of these soil samples. Maheswari and Sekhon, (1986) observed variation in soil K with depth and contribution to total K by particle size fractions which was attributed mainly to the textural variations and partly to K content of the particle size distribution.

Table 2. Total potassium content in sand, silt and clay and the per cent contribution of these fractions towards total potassium in red soils of south India (Dhillon and Dhillon 1996) Total K (cmol kg-') % Contribution Sand Silt Clay Soil Sand K Silt K Clay K Tyamagondalu sl 46.2 74.4 24.1 45.6 68.4 21.2 10.4 Tyamagondalu s 53.9 87.2 22.3 54.4 87.0 10.9 2.1 Channasandra sl 12.8 29.5 17.7 15.9 85.0 25.0 20.0 Patancheru sl 82.1 83.1 28.7 73.6 80.1 14.8 5.1 Patancheru 1 37.2 51.3 40.0 42.6 38.3 42.0 19.7 Mean 46.4 63.1 26.7 46.4 65.7 22.8 11.5 sl - Sandy loam soil, s - Sandy soil I - loamy soil

The pattern of distribution of potassium in different red soils in relation to depth revealed that available K decreased with depth in red soil of Tyamagondalu and increased considerably with depth in Vijayapura series. In Vijayapura and to some extent Tyamagondalu series, reserve K showed an increase with depth (Subba Rao and Sekhon, 1990). A decrease in exchangeable K and an increase in non-exchangeable K with depth was reported in twvo soil series from red soil areas in Tamil Nadu (Ekambaram et al., 1975). The increase in available K in Vijayapura and reserve K in both Tyamagondalu and Vijayapura could be due to the increase in clay content with depth (Subba Rao and Sekhon, 1990).

Potassium status of red soils

The impact of cropping with or without potassium application is reflected not only in crop yields and potassium uptake, but also in the amounts of potassium Distribution and Availability of Potassium in Red Soils of India 93 in different fractions in the soil. Thus both depletion and buildup of potassium can be observed by monitoring the changes in K fertility over a period of time.

The long term fertility experiments which have been carried out in India from 1970 at a number of sites representative of different agro-ecological conditions on intensive cropping system have indicated (Nambiar and Ghosh, 1987) that after 5-13 years, in 6-8 locations, most of the crops started showing responses to K whereas in the beginning only at one site (cereals) and at two sites (potato) showed such responses. The observations clearly demonstrated that on continuous cropping, despite the same high input of NPK year after year, the crops had to draw upon K reserves of the soil, as the annual K input was not adequate to meet the demand (Table 3).

Table 3. Potassium balance in experimental plots under intensive cropping over the 1971/83 period. (Nambiar and Ghosh, 1987)

Soil type No of K20 (Kg ha-') (Location) crops Added Removed Balance Mean annual harvested K balance NPK NP Plots Plots Alluvial (Ludhiana) 35 1490 3346 -1856 -66 -229 Black (Jabalpur) 23 654 3722 -3068 -434 -481 Red (Hyderabad) 19 565 2002 -1437 -151 -215 Laterite (Bhubaneswar 23 1369 2434 -1065 -92 -133

Ghosh and Hasan (1996) reported that nearly one fifth of the districts of India measured low available potassium and most of these were located in regions dominated by red and lateritic soils. Even soils marked as medium later on turned to be low in available K (Table 4). The scenario of K fertility status of red and lateritic soils appeared to have changed as evidenced by decline in K fertility status at different locations of long term fertilizer experiments (Nambiar and Hegde, 1993). Widespread crop responses to application of potassic fertilizers were observed in cultivators' fields during early eighties (1977-1982) compared to earlier period (Bhargava et at. 1985). Many research workers felt the need to revise the rating limits based on the crop responses. Hence, there is a need to compile all soil test data of K on all India level and bring out a new K fertility map for the country with revised rating limits (Shivaprasad et al., 1995).

However, regular application of potassic fertilizers is very essential to achieve good yield besides maintaining the fertility status of soils. Monitoring of red loam soils of Ranchi after two years of cropping (Roy et al., 1990) indicated buildup of almost all the forms of K; the extent of accumulation in exchangeable K content being 6 to 22 per cent over the initial soil value. 94 N.B. Prakash and R. Siddaramappa

Table 4. Long term fertility changes in available K status in red soils of South India Soil type/Series Fertility status 1971 1976* 1980 1985 1991"* 1994 Kodad (Andhra Pradesh) M L Vijayapura (Karnataka) M L Tyamagondalu (Karnataka) M L Doddabhavi (Tamil Nadu) M M Shallow red soils of Karnataka*** Khanapur (Belgaum) M M M L Athani (Belgaum) H H M L Kudlagi (Bellary) H M M M Shiratti (Dharwar) M M M L Shapur (Dharwar) H M M H - High, M - Medium, L - Low *Ghosh & Hasan (1976) **PRII study (1991) ***Shivaprasad et al. (1995)

Forms and Distribution of Potassium in red soils

Use of IN NH4OAc at pH 7.0 to extract the exchangeable + water soluble K is the most wide spread of all methods used to estimate the so called plant available K. However, to categorize the soils in different agro-ecological regions on the basis of available K (1N NH 4 OAc extractable) and non exchangeable K (IN boiling HNO 3 extractable minus IN NH 4OAc extractable as described by Jackson (1968); Subba Rao and Srinivasa Rao (1996) employed the following norms:

Low Medium High Reference Available K (mg kg -') 0-50 50-110 >110 Muhr et al., (1965) Non exchangeable K(mg kg - ') 0-300 300-600 >600 Subba Rao et al., (1993)

Accordingly, the potassium status of red soils in different soils in different agro-ecological regions is furnished in Table 5 and Figure 2.

Region 4: Soils of Southern Rajasthan occupying Durgapur, Banswara, parts of Chittorgarh and Udaipur districts with great groups Haplustalfs are low to high in available K.

Region 7: These are low to high in available K. Soils of many districts of Andhra Pradesh of this region need greater attention as they are poor in both available and reserve K and may respond to K fertilizers. Shallow and deep red Distribution and Availability of Potassium in Red Soils of India 95

14 1

.d 1 d. CHOWl

ff g. KALGI NDA

10 0 h.ii. NAZANAMUSUTYHFRAD 0. TAflOtdJ C. MBHOAL 9.k. SELCAUMPAo S•Imdi m.BEtL.AW • n.VUA.Y tRA o. rmAaGONDML X-R49h p.MYSORE q. COIDAWIE t ITWIAN DRUM • . s. NEYAT11NKARA shallowrd soils egularly Figure 2. Available potassiutm status in red soils of different agro-ecological regions of India

soils of North Karnataka belonging to this region are low and high in both exchangeable and reserve K respectively and needs proper attention for fertilizing shallow red Soils regularly.

Region 8: Red soils are dominant group in this belt (Tamil Nadu and Karnataka) and these are medium to high in available K but low to high in reserve K. Crop responses to K have frequently been reported in this region.

Region 10: Haplustalfs of this region (Madhya Pradesh) are high in available K and medium in non-exchangeable K. Table 5. Potassium status of red soils in different agro-ecological regions of India State/Region Soil/Soil No. Water Exch- HNO 3- Non Reference group of soluble K K Exch- soil K K South Rajasthan Haplustalf 30 1.2-29 39-269 L-H - - Yadav & Swamy (1987) Andhra Pradesh Nalgond Typic paleustalf 25 10.7 65 M 269 204 L Sekhon et al (1992) Rangareddy Alfisols 12 23.4 10.14 L 2476 - Padmaja & Sreenivasaraju (1999) Mahaboobnagar Alfisols 8 27.3 132.6 H 2691 - Padmaja & Sreenivasaraju (1999) Medak Alfisols 4 31.2 195 H 3455 - Padmaja & Sreenivasaraju (1999) Patanacheru Udic Rhodustalfs 15.6 113.2 H 401.7 - Dhillon & Dhillon (1994) Karnataka Vijayapura Oxic Haplustalf 25 16.2 55 M 140 95 L Sekhon et al. (1992) Tyamagondalu Oxic Paleustalf 25 205 61 M 380 299 L Sekhon et al. (1992) Channasandra Oxic Rhodustalf - 19.5 93.6 M 448.5 - Dhillon & Dhillon (1994) Deep red soils Paleustalfs 304 - 110.5 H - 1394.5 H Shivaprasad et al. (1995) (Bellary, Mysore Rhodustalf Bangalore) Ustropepts Shallow red soils Lithic Ustropepts 394 - 44.25 L - 112.5 L Shivaprasad et al. (1995) (Belgaum, Dharwar, Mysore) Tamil Nadu Coimbatore Udorthentic 25 15 77M 1074 982 H Sekhon et al., (1992) Madhya Pradesh Bhopal Haplustalf 18 - 263H 737 474 M Srinivasa Rao et al (1995) Table 5. (Coned.)

State/Region Soil/Soil No. Water Exch- HNO3- Non Reference group of soluble K K Exch- soil K K Bihar Ranchi Red soil 24 7.8 98M - 17.6 L Roy & Ajaykumar (1993) Ranchi Alfisol - 3.95 56M 122.4 66.35 L Roy et al. (1990) Kerala Trivandrum Alfisols 15 117 171H 321 150 L Prabhakumari & Aiyer (1993) Vellayani Haplustalf 15 11 28.8L - 50.1 L Sudharmai Devi et al (1990) Neyyattinkara Oxic Ustropepts 15 15.3 56.2L - 57.9 L Sudharmai Devi el al. (1990) Maharashtra Taldco Udic Haplustalf - 35 179H - 473M Raskar & Pharande (1997) Chikali Udic Haplustalf - 12.3 318 H - 610 H Raskar & Pharande (1997) Pali Udic Haplustalf - 10.7 87 M - 273 L Raskar & Pharande (1997) Kumbharoshi Udic Haplustalf -. 8.7 179 H - 267 L Raskar & Pharande (1997) L - Low; M - Medium; H - High 98 N.B. Prakash and R. Siddaraniappa

Region 12: These red soils are medium in available K and low in non- exchangeable K. Soils in this belt (Bihar) showed large responses to applied K and there is a great potential for K fertilization

Region 19: Red soils of this region are largely medium in available but low in non- exchangeable K. Agricultural, horticultural and plantation crops in this region respond to K application. The red soils of Kerala requires the application of potassic fertilizers, especially in view of the fact that the major crops (coconut and cassava) grown on them are heavy feeders of this nutrient element.

Red soils of Maharashtra with great groups of Udic haplustalfs are medium to high in available K and low to high in non-exchangeable K and need proper attention of K management.

The information on potassium status in red soils of other agro-ecological regions is meager and limited efforts have been made to delineate them from other laterite/lateritic soils.

Methods of extraction of soil potassium and its relation to soil properties

Soil analysis methods for K have been reviewed by Johnson and Goulding (1990). Total K can be determined after dissolving the soil with HF but such data are rarely useful. Perhaps the one exception is when estimating K requirements of plantation crops grown on very sandy soils with very little total K. Exchangeable K together with that in the soil solution, is determined by the use of extractants with excess cations, usually NH4 *, capable of exchanging with K+ on cation exchange sites in soil. There is no widely accepted method for determining non exchangeable or not readily soluble K. This is unfortunate because the quantity of K in this pool and its rate of transfer to the exchangeable pool have major implications for K manuring.

While most laboratories use a measure of exchangeable + water soluble K as an index of K availability in the soil, some laboratories use an estimate of non-exchangeable K for the same purpose. There appears a merit in combining the two estimates and examine a measure of exchangeable + water soluble K in the light of information on non-exchangeable K.

The measurement of exchangeable K alone may not give a reliable estimate of K supplying capacity of soil. The neutral IN NH4OAc extractable K measures only the amount of K that may be immediately available to plant and cannot predict the rate of release of K from non-exchangeable source to the exchangeable or solution form (Boruah et al., 1990).

Potassium desorption using electro-Ultra filtration has shown (Brar and Sekhon, 1986; Brar et al., 1986) that soil having similar amounts of NH4 OAc-K Distribution and Availability of Potassium in Red Soils of India 99 could release different amounts of K depending upon their content of non- exchangeable K. Table 6 group the soils according to their HNO 3-K:. Looking at the modal value of NH 4OAc-K estimates of various soil groups in the light - of HN0 3-K one finds that most of the kaolinitic soils were low in both HNO3 only modest K and NH 4OAc-K and had low K release rates. Smectitic soils had K- amounts of HNO 3-K but were associated with high NH 4OAc-K and moderate release rates. Hence, it appears useful to consider the amount of both the exchangeable and non-exchangeable K and clay mineralogy of soils in arriving at a judgment of K release and availability in soil.

Table 6. Distribution of soils in different categories of HNO 3-K and modal values of NH 4OAc-K (Bhonsle et al., 1992) - Soil series Per cent soils with Boiling HNO3-K NH 4OAc-K (mg kg ') value <600 600-1200 >1200 Modal <- mg kg -1 > Kaolinitic 98.57 1.43 - 21-63 (700) (690) (10) Smectitic 17.16 75.33 7.34 181-440 (600) (103) (452) (44) lllitic 0.25 38.25 61.50 81-100 (400) (1) (153) (246) Figures in Parenthesis indicate total number of soil samples analysed in each category.

Mishra and Mahatim Singh (1992) reported that the illitic soils having lower having higher amount of NH 4OAc-K showed faster K release than smectitic soils release than illitic amount of NH 4OAc-K. The kaolinitic soils showed slower K as well as smectitic soils. This might be the probable reason for the response of the crops to K application in the soils having higher values of K availability index and to some extent the behaviour of non-responsive nature of crops to K application in the soil testing low to medium in K availability index.

Changes in estimates of K by water soluble, NH 4OAc and HNO 3 extractions as per textural class in four soil series are given in Table 7. The relationship between exchangeable K and water soluble K indicated a faster K release in alfisols of Kodad and Doddabhavi as compared to two vertisols (Bansal et al., 1996).. Effect of texture on different forms of K was seen prominently in Kodad and Noyyal soil series. Both NH 4OAC and HNO 3- extractable K increased with fineness of texture in these series which was in confirmation with results of Subba Rao and Sekhon (1989). In general, there was an increase in water soluble K with time in all the textural classes of these four Soil series possibly due to cropping, which enhances the release of K. Reserve K decreased with time in all the textural classes of Kodad, Noyyal and Kalathur series though the magnitude of decrease varied with texture to some extent only. It could perhaps Table 7. Changes in K extracted by different extractants according to textural classes in four soil series over a period of time and Nutrient Index Value based on their NH4OAc-K content (Bansal et al., 1996) Soil series Soil K (mg kg-') xtracted b classification Textural Water NH 4OAc HNO 3 class Earlier* 1993 Earlier* 1993 Earlier* 1993 NIV* Kodad Typic sl 9.3 12.0 46 71 245 231 1.75 (Nalgonda, A.P) Paleustalf scl 12.6 12.9 82 93 291 268 Doddabhavi Rhodusta s 18.7 27.2 93 117 983 1002 (Coimbatore, T.N) 2.10 Is 17.3 33.0 93 101 1078 1016 sl 13.1 21.1 103 70 1140 1200 Noyyal Udoorthenti cl 77.5 85.3 658 683 2285 2233 3.00 (Coimbatore, T.N) Chromuste sicl 88.3 110.0 939 954 2475 2450 c 91.3 81.2 702 750 2559 2590 Kalathur Udic cl 13.2 26.5 212 168 833 810 3.00 (Thanjvur, T.N) Chromust c 10.7 20.6 190 172 905 891 *earlier: Kodad - 1987, Doddabavi - 1988, Noyyal - 1985, Kalathur - 1988 sl - sandy loam , scl - sandy clay loam, - s sandy , Is - loamy sand , c - clay, sicl - silty clay, cl - clay loam (% samples low x 1)+ (% samples medium x 2) + (% samples high x 3) 2 *NIV = 100 Distribution and Availability of Potassium in Red Soils of India .1O1 be inferred that depletion of K with cropping in the same soil series is less with increase in heaviness of the soil texture. Bansal et al., (1996) confirmed that soils dominant with kaolinite clay mineral have a faster dynamic equilibrium than those of the smectitic dominant ones. They inferred that such soils which are coarse in texture and are kaolinitic, receiving less external K supplies and growing heavy K removal crops, are likely to be depleted of their K'fertility much faster than other. Hence, their K management needs to be regularly monitored to sustain the crop productivity.

The available forms of K showed positive and significant correlations with silt and organic carbon content (Table 8). The significant correlation with organic carbon content indicates the possible role of some of the components of organic matter in fixation and release of native K, showing the beneficial effect of organic matter on K availability. A positive correlation with silt indicates a higher proportion of K rich primary minerals in this fraction such as feldspars, which are known to occur mainly in 50 to 2gm fractions. However, the forms of K were non-significantly correlated with pH, CEC and clay contents of these soils. The wider variation in clay content of these soils might have resulted in non significant correlation between clay and K content. Similar non-significant correlations were also reported for red soils by Singh et al.,(1989). However, Mengel, (1978) reported higher amounts of water soluble K in sandy soils than in clayey soils.

Table 8. Relationship among forms of K and salient characteristics of red soils of Andhra Pradesh (Padmaja & Sreenivasa Raju,1999) Forms of K organic carbon silt clay

NH 4OAc-K 0.608** 0.418* NS Water soluble-K 0.637** 0.420* NS Exchangeable-K 0.583** 0.453* NS : 5 per cent level of significance ** I per cent level of significance NS Non significant

Shankayan and Bhardwaj, (1987) indicated that IN NH 4OAc is not suitable extractant for available K in Inceptisols and Alfisols of Himachal Pradesh. The superiority of H2SO 4 over NH 4OAc as the extracting reagent had also been reported by Datta and Kalbande (1967).

Comparison between plant and soil analysis in red soils

The plant uptake of K is not solely based on the available soil K status as the plant K nutrition is depended upon various other soil, plant and environmental factors (Singh and Sekhon, 1989). It was indicated by Singh and Sekhon (1989) that alfisols which may be medium as per soil test K but the crops growing there 102 N.B. Prakash and R. Siddaramappa may still be deficient in K. Moreover, the crops respond to K fertilization only when applied along with sulphur.

The data presented in Table 9 is in confirmity with that of Brar et al., 1986 where a slightly higher per cent deficiency of K indicated by plant analysis in sorghum crop grown on red soils is possibly due to low available and reserve K in these soils. The plant analysis of wide range of crops growing in highly divergent soils and the differences between soil and plant test results indicated the need for rechecking the soil and plant K critical limits which may be soil and crop specific. However, the complete plant analysis can effectively supplement soil test in diagnosing the nutrient problems (Bansal and Shahid Umar, 1998).

Table 9. Potassium content in leaves, distribution of plant samples in different categories and comparison between plant and soil analysis for potassium based on nutrient index values in different red soils (Bansal and Shahid Umar, 1998). Soil series Crop Plant Per cent samples in Plant Fertility indicated categories Nut- Rating K rient (%) H S SD MD ED Index Plant Soil Index ana- ana- lysis lysis Kodad Rice 1.36 0 3 65 32 0 1.68 MM L Kumbhave-5 Rice 1.55 0 26 63 10 1 1.89 M M Vijayapura Sorghum 2.19 0 30 21 35 14 1.51 L L Tyamagondalu Sorghum 2.55 2 60 19 17 2 1.83 M L H - High, S - Sufficient (10% yield reduction) SD - Slightly Deficient (10-20% yield reduction) MD - Moderately Deficient (20-40% yield reduction) and ED - Extremely Deficient (> 40% yield reduction) MM-Marginally Medium, M-Medium, L-Low

Routine soil testing for specific fertilizer K recommendations is still not widely used in the country. Thus, decisions by farmers about K applications largely depend on personal preferences. Fertilizer market conditions or government regulations rather than on knowledge of soil K status and K demand by the crop.

Conclusion

The red soils are distributed in southern, eastern and northeastern parts of the country. They exhibit wide variation in K status and availability to crops. Soil factors such as depth, soil texture and mineralogy are known to influence availability of K in soil. Distribution and Availability of Potassium in Red Soils of India 103

The soils may be high or medium as per soil test K but the crops growing there may still be deficient in K. The crops do respond to the application of K fertilizers despite soils showing high fertility. Hence there is a need to recheck the methods of estimation for K recommendation.

Shallow red soils are relatively poorer in available potassium and hence consideration of soil depth should also be made routinely in future. There is need to bring out K fertility map for the country with revised rating limits by compiling all soil test data of K in different soils at All India level.

Soils which are lighter in texture and are kaolinitic, receiving less external K supplies and growing heavy K demanding crops, are likely to be depleted of their K fertility much faster than others. Hence their K management needs to be regularly monitored to sustain the crop productivity.

There is a need to monitor the potassium status in selected red soil series in each agroecological region and delineate their potassium supplying power.

Soil test crop response studies should be conducted on important crops for the well-defined red soil series in each region to prescribe location specific potassium fertilizer recommendation.

REFERENCES Bansal, S.K., Gautam Debnath and Shahid Umar. (1996). Monitoring changes in potassium fertility of five bench mark soil series from southern India. Journal of Potassium Research, 12: 337-344. Bansal, S.K, and Shahid Umar. (1998). Nutrient indexing of crop plants grown on twenty six benchmark soil series of India. Journalof Potassium research, 15: 7-18 Bhargava, P.N., Jain, H.C. and Bhatia, A.K. (1985). Response of rice and wheat to potassium. Journal of Potassium research, 1: 45-61. Bhattacharyya, T., Ghosh, S.K. and Prakash, N. (1983). Chemical and morphological charactgeristics of amorphous materials present in red soils derived from granite gneiss. Clay Research, 2: 20-27 Boruah, H.C., Bora, D.K. and Nath, A.K. (1990). Potassium release characteristics of three major soil orders of Assam. Journal of Potassium research, 6: 139- 144. Brat, M.S. and Sekhon, G.S. (1986). Desorpition of Potassium from five soils of North India using electro utrrafiltraion. Journal of Soil Science, 37: 405- 411 Brar, M.S. Subba Rao, A. and Sekhon, G.S. (1986).Solution, exchangeable and 104 N.B. Prakash and R. Siddaramappa

non-exchangeable potassium in five soil series from the alluvial soil region of Northern India. Soil Science, 142: 229-234 Datta, N.P and Kalbande, A.R. (1967). Correlation of response in paddy with soil test K for different Indian soils. Journal of the Indian Society of Soil Science 15: 1-6. Dhillon, S.K. and Dhillon, K.S. (1994). Forms of Potassium in some benchmark soils of India. Journal of Potassium Research, 10: 1-11. Ekambaram.S., Kothandaraman, G.V and Krishnamoorthy, K.K. (1975). Studies on the distribution of different forms of potassium in red soil. The Madras Agricultural Journal, 62: 243-247. Ghabru, S.K. (1981). Genesis and transformation of minerals in some red and black soils of Karnataka developed under varying conditions of relief and parent material. Ph.D. Thesis. IARI, New Delhi. Ghosh, A.B. and Hasan. (1976). Avaiable potassium status of Indian soils. Bulletin of Indian Society of Soil Science, 10: 1-5 Graham and Fox. (1971). Tropical soil potassium as relate to labile pool and calcium exchange equilibria. Soil Science, 111: 318-332. Hanway, J. Heidal, H. (1952). Soil analysis method as used in Iowa State College Soil Testing Laboratory. Iowa State College Agriculture Bulletin. 57: 1-13. Jackson, M.L. (1968). Soil chemical analysis, Prentice Hall of India private Ltd. New Delhi. Johnston, A.E. and Goulding, K.W.T. (1992). Potassium concentrations in surface and ground waters and the loss of potassium in relation to land use. In: Potassium in Ecosystem, Biogeochemical fluxes of cations in Agro and Foresi systems. InternationalPotash Institute, Basel, 135-158. Kadrekar, S.B. (1991). Use of potassium in Maharashtra agriculture. Potash and Phosphate Institute of Canada. Indian programme, Gurgaon. Kadrekar, S.B. and Kibe, M.M. (1972). Soil potassium forms in relation to agro- climatic condition in Maharashtra. Journal of Indian Society of Soil Science, 20: 231-240 Maheswari, R.K. and Sekhon, G.S. (1986). Potassium reserves in some red and lateritic soils of southern India and their significance to potassium nutrition of crop plants Clay Research 2 : 93-100 Mehrotra, C.L., Gulab Singh and Pandey, R.K. (1973). Relationship between different particlessize in broad soil groups of Uttara Pradesh. Journal of Indian Society of Soil Science 21: 423-427. Mehrotra, C.L. and Singh, G. (1970). Forms of potassium in broad soil groups of Uttar Pradesh. Journal of Indian Society of Soil Science 18: 327-334. Distribution and Availability of Potassium in Red Soils of India 105

Mengel:K., (1978). Potassium availablity and its effect on crop production (In Potassium in soils & crops, Potash Research Institute of India, New Delhi, pp 71-79). Mishra, M.K. and Mahatim Singh. (1992). Potassium release characteristics of some benchmark soils of India. Journal of Potassium Research, 8: 1-10. Muhr, G.R., Datta, N.P., Shankara Subramoney, H., Leley, V.K. and Donahu, R.L. (1965) Soil Testing in India, USAID. New Delhi. ppl20. Nambiar, K.K.M. and Hegde, D.M. (1993). Potassium response studies in major cropping systems. International Symposium on Decade of Potassium Research. 18- 2 0 h, November, New Delhi NBSS Staff (1993) Red and Laterite Soil map of India, compiled by NBSS Staff of the NBSSLUP - Regional Centre, Bangalore. Padmaja, G. and Sreenivasa Raju, A. (1999). Status of potassium found in alfisols of southern telangana zone of Andhra Pradesh. Journal of Potassium Research, 15: 25-32. Pal, S.K. and Mukhopadhyay, A.K. (1990). Forms of potassium in some Alfisols of West Bengal. Journal of Potassium Research, 6: 180-184. Prabhakumari, P. and Aiyer, R.S. (1993). Soil test and crop responses studies for potassium in laterite/red loam soils of Kerala. Journal of Potassium Research, 9: 62-66. Prasad, d., Sinha, H. and Mandal, S.C. (1967). Fractions of potassium in Bihar soils. Journal of the Indian Society of Soil Science, 15: 173-179. Ramanathan, K.M. (1977). Studies on dynamics of soil potassium. Ph.D., thesis submitted to TNAU, Coimbatore, Tamil Nadu. Ramamoorthy, B and Bajaj, J.C. (1969). Available nitrogen, phosphorus and potassium status of Indian soils. Fertilizer News, 14: 24-33 Ranganathan, A. and Satyanarayana. T. (1980). Studies on potassium status of soils of Karnataka. Journal of Indian Society of Soil Science, 28: 148-153. Raskar, B.N. and Pharande, A.L. (1997). Different forms of potassium and their distribution in some important soil series of vertisol and alfisol of western Maharasthtra. Journal of Potassium Research, 13: 21-30. Rathore, H.S., Khatri, P.B. and Swami, B.N., (2000). Comparison of methods of available potassium assessment for Ustochrepts in Rajasthan. Journal of Indian Soceity of Soil Science, 48: 621-623. Roy, H.K. and Ajaykumar. (1993). Quantity/Intenstity relations of potassium in texturally different acid red loam soils. Journal of Indian Soceity of Soil Science, Roy, H.K. Ajaykumar and Kishore Sinha. (1990) Response of wheat to potassium 106 N.B. Prakash and R. Siddaramappa

in red loam (alfisols) soils of Ranchi. Journal of Potassium Research, 6: 23- 28. Rao, A.P. and Raju, A.S.(1984). The mineralogy and dynamics of potassium in soils of Andhra Pradesh. In clays and clay minerals research in Andhra Pradesh published by the Clay Minerals Society of India, Hyderabad Unit: 25-38. Sahu, D. and Krishnamurthey, G.S.R. (1984). Clay mineralogy of a few laterites of north Kerala. Southwest India. Clay Research, 3: 81-83 Sehgal, J.L. (1998). Red Soil and laterite soils ; an overvidew. In Vol. 1 Managing red and laterite soils for sustainable agriculture, edt. by Sehgal. J., Blum. E. and Gajbhiye. K.S., pp 1-21 Sekhon, G.S., Brat, M.S. and Subba Rao, A. (1992) Potassium some benchmark soils of India. Special Publication 3, Potash Research Institute of India, Gurgaon. Sekhon, G.S. and Mahaatim Singh. (1982). Potassium status of soils and crop responses to potassium in India. Fertilizer News, 27: 53 Shankayan. S.D. and Bhardwaj, S.K. (1987). Studies on forms of potassium, methods of extraction and crop response in some Alfisols and Inceptisols of Himachal Pradesh. Journal of Potassium Research, 3: 10-16. Shivaprasad, C.R., Niranjana, K.V., Dhanorkar, B.A., Swamynatha, R., Naidu, L.G.K., Hanumantha Rao, P.S. and Sehgal. J. (1995). Available potassium status of major soils of Karnataka. Journal of Potassium Research, 11: 219- 227. Singh, M. and Sekhon, G.S. (1989). Potassium indexing of sorghum grown in three benchmark soil series of southern India. Journal of Potassium Research, 5: 92-97. Singh, S.P., Singh, N., Das, A.L. and Ram, J. (1989). Potassium distribution in some dominant soils of chotanagpur region in Bihar. Journal of Potassium Research, 5: 53-60. Subba Rao, A. and Sekhon, G.S. (1989). Potassium availability in soils differing in mineralogy and texture. Journal of Potassium Research, 5: 143-151. Subba Rao, A. and Sekhon, G.S. (1990). Pattern of distribution of potassium in different soils in relation to depth of sampling for fertility investigations. Journal of Potassium Research. 6: 43-50 Subba Rao, A., Sesha Sai, M.V.R. and Pal, S.K. (1993). Non-exchangeable potassium reserves and their categorization in some soils of India. Journal of Indian Society of Soil Science, 41: 667-673 Subba Rao. A and Srinivasa Rao. Ch. (1996). Potassium status and crop response to potassium on the soils of agro-ecological regions of India. International Potash Institute Research Topics No. 20: pp:57. Distribution and Availability of Potassium in Red Soils of India 107

Sudharmai Devi, C.R., Korah, P.A., Usha, P.B. and Saraswathi, P. (1990). Forms of potassium in two soil series of South Kerala. Journal of Potassium Research, 6: 9-15. Yadav, B.S. and Swami, B.N. (1987). Studies on potassium in some red soils (Haplustalfs) of Southern Rajasthan. Journal of Potassium Research, 3: 1- 9. Potassium Availability and Crops Response to Fertiliser Potassium in Hill and Mountain Soils of India

PATIRAM ICAR Research Complex for North Eastern Hills Region, Umroi Road, Umiam-793103, Meghalaya

ABSTRACT

In India, hills and mountain cover 21.3% of the geographical area and distributed over the Himalayas from northwest (Jammu and Kashmir) Arunachal Pradesh in east, northeastern hills and in south Western Ghats. The sub-Himalayan areas of Himachal Pradesh and Uttaranchal, northeastern hills and Western Ghats (facing towards the Arabian Sea) receive rainfall more than 2,000 mm in a year. The soils of this zone belong to soil orders of Ultisols, Alfisols, Entisols, Inceptisols and Mollisols. Most of the soils of are acidic in nature and low to medium in potassium availability as a result of humid climate. The soils developed on granites, gneisses, charnokites, khondalites and laterites of Western Ghats are generally poor in K reserves compared to Himalayan and northeastern hills. The field trials allover the country revealed that wheat and rice in general were more responsive to potassium application in hill and mountain soils than the rest of the area. From the long-term as well short term field experiments indicated that the yield of crops can be maintained by the application of potassium fertilisers along with recommended doses of N and P to achieve the optimum sustainability of soil productivity.

Key words: hill and mountain soils, potassium availability, K status, response of crops to K fertilisers.

INTRODUCTION

The Planning Commission for hill Area and Western Ghats Development Programme (an area having elevation of more than 500 m) have adopted 101 districts in the country distributed over the Himalayas from Jammu and Kashmir to Arunachal Pradesh, the Patkai and other ranges in the northeastern hills and plateau of Meghalaya and Sahyadri (Western Ghats) (Table 1). The Himalayan and northeastern hill and mountains cover an area of 533,407 sq. km amounting 16.23% of the total geographical area of the country and similarly Western Ghats cover area of 166,564 sq. km (5.07%). Thus these areas account 21.3% of the country's land (699,971 sq. km). 109 110 Patiram

Table 1. Hill and mountainous areas of India (sq. km) (Anon. 1999) State Districts Geog. Area Arunachal Pradesh All 83,743 Assam Karbi Anglong, North Cachar Hills 17,484 Himachal Pradesh All 55,673 Jammu and Kashmir All 222,235 Karnataka Kannada Uttara, Kodagu, Shimoga, 40,588 Chickmaglore, Kannada Dashina Kerala Cannanore, Khozokode, Wynad, 31,745 Idduki, Ernakulam, Malapuram, Palghat, Qilon, Trivendrum Maharastra Kolhapur, Nasik, Pune, Ratangiri, 69,905 Satara, Raigarh Manipur All 22,327 Meghalaya All 22,429 Mizoram All 21,081 Nagaland All 16,579 Sikkim All 7,096 Tripura All 10,486 Tamilnadu Coimbatore, Madurai, Nilgiri, 24,326 Kanyakumari Uttaranchal All 51,125 West Bengal Darjeeling 3,149 Total 699,971 % Hills and mountains 21.3 of India

Himalayas are the world youngest and largest east-west mountain system, extending almost uninterruptedly for a distance of 2500 km and covering about 500,000 sq. km with the convex side towards North Indian Plains. The western zone starts from the Indus watershed and comprising of Jammu and Kashmir and Himachal Pradesh; central zone consists of Uttaranchal and Nepal and eastern zone starts from Singlila range (Sikkim) upto Arunachal Pradesh including Brahmputra watershed. The Patkai and associated mountain ranges run to the south of Assam Himalayan along the Indo-Burma border. They are known under different names in different parts of Arunachal Pradesh, Nagaland, Manipur, Mizoram and Tripura and collectively can be grouped Purvanchal (Purva, east and anchal, mountain). The Meghalaya Plateau is really an eastward extension of the massive block of peninsular India lying to the east of the great gap of Archaean terrain. The central plateau of Khasi Hills cover about 5000 sq. km, its outer limit defined roughly by a 1500 m contour line. K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 111

The Sahyadri, with an average height of 1200 m, run for about 1600 kin, along the western border of Daccan from near the Tapti mouth in the north to Cape Camorin (Maharastra to Kerala), the southern most point of India and running more or less parallel to the coast. In the southern part of the peninsula and to the north of Coimbatore, the hills rise to over 2440 m and are known as the Niligiris or Blue Mountain. The Nilgiris continue northward as the mountains of Coorg.The Travancore hills of Kerala separate the district of Dindigul, the Annimallai, south of Coimbatore, Sevagiri southeast of Madurai. The continuity of Ghats is disturbed by the Palghat, which is believed to be abandoned valley of an old river, and the Shencottah Gap. South of Palghat Gap, Western Ghats is known as South Sahyadri.

GEOGRAPHY AND GEOLOGY

The Himalayan mountain chain, all along its longitudinal axes, is arranged into three main series of parallel ranges some time refer to as the Great Himalayas, the lesser Himalayas and the Sub-Himalayas and at the other the inner, the middle and the outer Himalayan. These ranges are separated by intervening space occupied by longitudinal valleys of tectonic origin connected with the Himalayan uplift or plateaus making the erosion surface of an earlier age.

The Tibetan zone composed of fossil bearing sedimentary rock ranging from Paleozoic to Eocene of the Pleistocene era, lies to the north of Great Himalayan. The Great Himalayan zone is composed of crystalline and metamorphic rocks, such as granites, schistose and gneisses and sedimentary deposits are also not uncommon. This is succeeded by Himalayan Nappe zone (Kashmir, Himachal and Garhwal section) where large bodies of older rock have been physically displaced and thrust on the newer ones along the recumbent fold over large area. The outer or Sub-Himalayan zone corresponding to Siwaliks is composed of the sedimentary deposits belonging to have been derived from the eroded material of the main Himalayan ranges themselves. The Karewas of the Kashmir valley have thick deposit of glacial clay and other material embedded over long distances. Many U-shaped and hanging valleys found at elevation much lower than the existing glaciers. Extensive moraine deposits along the river valleys, which in many areas form well developed terraces, particularly on the flanks of the surrounding mountain ranges in Kashmir valley. The terraces of the Himalayan rivers furnish enough evidence of this phase of increased fluvial activity.

The hills of Western Ghats are composed of granites, gneisses, charnokites, khondalites and laterites. The yellowish/reddish laterite rocks form low fault tapped ridge covering the crystalline and tertiary sediments on the foothills.

The great rivers, IndusGanga and Brahmputra together with their tributaries have their source in the glacial of Himalayas. 112 Patiram

AGRO-CLIMATIC ZONES

The Highest rainfall occurs along the Western Ghats and decreases in the leeward side of hills towards the east. Sub-Himalayan areas of Himachal Pradesh and northeast, Purvanchal and the hills of Meghalaya receive rainfall more than 2,000 mm in a year. In Cherrapunji and Mawsynram of Khasi hills the rainfall exceeds 10,000 mm. It however, drops to 2,000 mm or even below in Brahmputra valley and adjoining hills. The eastern Himalayas, in general, provide moisture surpluses from direct runoff of the abundant summer monsoon rainfall; the snowmelt contribution is comparatively insignificant. In northwest Himalayan snow melt water becomes critically important. The cold deserts of Laddakh and Kargil districts of Jammu and Kashmir, parts of Kinnaur (Lahul and Spiti) of Himanchal Pradesh, precipitation occurs in the form of snow during winter. Some parts of Kargil and Kinnaur receive some rain during summer and rainy season.

An agro-ecosystem is essentially a man made ecosystem which is evolved to meet the basic human needs of food, fodder, fuel, fiber, timber, medicinal and commodity crops and also giving some economic returns. The agro-climatic zones of the hill areas of India vary from perpetual snow cover at high elevations of Himalayas to cold arid, alpine, sub-alpine, temperate, sub-tropical temperate, sub-tropical and tropical hill zones with valleys under different altitudes.

SOILS

The soils of hills have developed under varying climatic, vegetative, lithological and topographic conditions. The differences in local geological formations and microclimate as a result of relief, type and amount of vegetation produced under different plant communities have brought about great changes in morphology and properties of soil. Most of the hill soils are Inceptisols, Alfisols, Ultisols, Entisols and Mollisols.

The mountain meadow soils of Jammu and Kashmir, Himachal and Uttranchal at high elevations are shallow, sandy loam in texture and neutral alkaline in reaction. The Kashmir valley is covered by comparatively fine textured moist soils almost neutral in reaction. The soils of the rest of the area are acidic in reaction and rich in organic matter content and later has the tendency to increase with rise in elevation. The soil acidity of Himalayas increases from west to east with increasing rainfall. The acidic soils of Western Ghats support plantation crops, such as coconut, arecanut, coffee, pepper, rubber, cashewnut, tapioca and small cardamom.

The soils developed in Quaternary deposits of the sub-Himalayan region of Jammu and Kashmir and Himachal Pradesh belong to Alfisols, Mollisols, Inceptisols and Ultisols. They are in general micaceous with considerable amount K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 113 of vermiculite, smectite, chlorite and mixed layer minerals; the presence of kaolinite is, however, occasional. The Kashmir valley clayey soil developed on loess is dominated by vermiculite plus smectite followed by mica, mixed-layer minerals, chlorite and kaolinite. The soils of northeastern hills are dominated in micas and kaolinite.

Soils developed on Deccan basalt, under acidic weathering environment in humid climate, smectite/kaolinite interstratification is an important ephemeral stage during the transformation of smectite to kaolinite. The Alfisols developed in humid climate on basalt, dominated by kaolinite and/or gibbsite have been very rare and mostly enriched with interstratified smectite/kaolinite where in the kaolinite portion is most dominant. The clay minerals in soils peninsular gneiss are rich with kaolinite and mica. Spatially associated red (Alfisols) and black (Vertic Inceptisols) soils as distinct entities with similar microdepressions topographical conditions occur on the Bhimashankar plateau (1100 m) of the western Ghats, the presence of zeolite has provided sufficient bases to prevent the transformation of smectite to kaolinite. The soils developed on mounds are generally deep, sandy clay loam to clay, yellowish brown to red with low base saturation and hill soils are moderately deep, sandy clay to clay, strong brown to reddish brown with high base saturation. Soils developed on laterite landscape are deep, sandy clay loam with 25-43% base saturation. Soils on khondalite landforms are moderately deep to deep, sandy clay loam to loam with high base saturation.

POTASSIUM STATUS

The status of soil available K analysed by the State Soil Testing Laboratories of country reflected that most of hill soils are low to medium in availability excepting Maharastra, Tamil Nadu and Arunachal Pradesh which are medium to high in availability category (Ghosh and Hassan, 1976). The soils of the other states of the North Eastern Hills are low to medium in availability (Prasad et al., 1981). Singh et al. (1999) and Misra and Saithantuaanga (2000) also reported medium to high availability of available K in the soils of Arunachal Pradesh and Mizoram. Literature pertaining to different forms of potassium in hill soils is meagre. Most literature reveals only with the available fraction, which by and large, is considered to be exchangeable potassium. In general, the soils derived from granite-gneiss have a low K supply because of intensive weathering of parent material and high rainfall.

Western Ghats

Bolan and Sreeramulu (1981) recorded total, lattice, non-exchangeable, exchangeable and water soluble form soil K from 505-6975, 450-6708, 13-1120, 14-750 and 1-20 ppm for the high altitude Nilgiris soils, respectively. There 114 Patiram existed negative relationship between rainfall and all forms of K. The total and available K content of the major soil series of red soils of Coimbatore district has been reported that it varied from 0.15-0.57% and 0.004-0.006%, respectively and both increased in subsoils (Mayalagu and Sreeramulu, 1983). The available K ranged from medium to high in Ootacamund, Conoor and Kotagiri and low to medium in Godlur blocks of the Nilgiris districts. Under the condition of heavy rainfall prevailing in Kerala the soils are highly depleted of potassium. The deficiency of K was particularly marked in the laterites. Sreedevi and Aiyer (1974) reported 5.1-49.1, 0.17-2.58 and 0.02-1.20 me/100 g soil of total, difficult exchangeable and exchangeable K in the acid soils of Kerala. Giri et al. (1998) found that available K of Kerala soils ranged between 25-100 ppm in laterites, charnokites and granite-gneiss area and 100-175 ppm in khondalites.

Almost all the hill soils of Karnataka are low in available K due to acidic parent rocks containing only small percentage of K-bearing minerals and leaching of K due to high rainfall. The liberal application of potassium fertilisrs is necessary to raise good crops of potato, tobacco, coconut, fruits and vegetables. The soil available K (water soluble + exchangeable K) of North Kananda and South Kannada districts analysed ranged between 0.043 and 0.320 me/100 g soil (Perur, 1996) and increased with increasing soil pH, electrical conductivity and clay content. The hill districts of humid region of Maharastra are poor in available K and low fixation capacity compared to other type of soils (Kadrekar, 1976).

North-west Himalayas

In Himachal Pradesh state, the available potassium varied from from 6.8- 1740 kg K20/ha (Marwaha, 1996). The ammonium acetate extractable K of brown hill soils of Shimla found to be vary from 53 to 775 ppm, fixed K 0.096- 0.554% and HCI soluble K 0.275-1.050% (Negi et al., 1979). Q/1 relationship revealed that low buffering capacity of soils suggested the importance of K fertilisation. Grewal and Sharma (1980) found 120 ppm critical limit of soil available K (NH 4 OAc extractable) below which the potatoes can respond to potassium fertilisation. Total K 2 0 content of temperate zone of Himachal Pradesh soils was found to vary from 1.1-2.4% due to presence of potash rich minerals (Gupta and Tripathi, 1992). High status of potassium has been reported from the alkaline soils of Leh, Seru and Nubra valleys of cold desert of Laddakh (Yadav and Kumar, 1999). The soils under alpine vegetation of Tehri Garhwal had the high amount of exchangeable potassium and ranged from 0.4-1.7 me/100 g soil in surface and decreased with depth (Murthy and Sharma, 1992).

North eastern hills

Almost all the soils are acidic in reaction due to leaching of bases from the exchange complex under the prevailing high rainfall and hilly topography (Prasad K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 115 et al., 1981). Generally the soils of higher altitude and with high rainfall are more acidic. The total as well as HCI-soluble K content of soils are also high in the north eastern per-humid hills compared to Western Ghats (Table 2), suggesting the presence of substantial quantity of potash bearing minerals in this region. Singh and Datta (1986) and Singh et al. (1989; 1999) reported positive relationship between the total soil K and ilt fractions, which indicated higher proportion of potash rich minerals in the silt size particles as feldspars. All forms K were highest in Typic Udifluents occurring on active flood plains under rice cultivation compared to Typic Udorthents of Arunachal Pradesh, attributed to deposition of new sediments year after year in the case of former (Singh et al., 1999). Reverse trend was found in Inceptisols and Alfisols compared to soils occurring on hill slopes under thin forest cover or shifting cultivation. Almost similar trend was noticed in Meghalaya soils (Patiram and Prasad, 1984) where as Manipur valley soils are rich in available potassium compared to hill soils (Prasad et al., 1981). It was also found that lower altitude soils had higher available K compared to soils from higher altitude sandstone parent materials and high rainfall (Lyngdoh and Shukla, 1993).

Table 2. Forms of potassium in northeastern hill soils Forms of States 3 Nagaland Sikkim5 Darjeeling K (ppm) Arunachal Megha- Mizoram 6 Pradesh' laya2 hill Total (%) 1.53-4.91 2.66-5.51 0.81-2.60 HCI soluble %) 0.28-0.69 0.25-0.75 0.10-0.63 0.22-0.94 Non- 84-1314 310-941 205-2120 856-9169 exchangeable Exchangeable 43-471 37-250 160-390 90-461 40400 16-164 Water soluble 12-53 2-24 10-31 6-58 8-70 Available 68-524 185-421 Step 172-1695 72-275 199-1940 Constant rate 1 44-350 126-92 46-580 _j Singh et al. (1999), 2Patiram and Prasad (1986), 3Singh et. al. (1989), 4Ghosh and Ghosh (1976), 5Patiram and Prasad (1991), 6Sahu and Gupta (1988)

Potassium supplying power of soils

The release of non-exchangeable potassium has been used to evaluate the long-term K supplying power of soil and there exists close relationship between the total K uptake and uptake of non-exchangeable K by crops under exhaustive cropping in pot experiments. Exhaustive cropping was used to assess the release of non-exchangeable K from the soils of Meghalaya and Sikkim (Patiram and Prasad, 1983a; 1991). The exchangeable K decreased up to 2-4 crops, thereafter 116 Patiram

the removal of K by plant occurred through the release of non-exchangeable K. The per cent uptake of non-exchangeable K had the tendency to increase with decreasing soil exchangeable K. However, total K removed and dry matter yield were significantly and negatively related to the per cent K removed from non- exchangeable sources, indicated that the higher yield of crops could not be realise depending on the release of non-exchangeable K to meet the demand. Further this suggested that when crop removes the exchangeable K below certain characteristic level for a given soil, the rate of release of non-exchangeable K would often be inadequate to the maximum yield of the crops taken.

Availability indices

Various chemical extractants used to extract the available K from soils for availability indices indicated that even available K extracted in Bray P, (0.03 N NH 4F + 0.025 N HCI) seems to be most suitable (though slightly inferior to IN NH 4OAc) for the acid soils of Meghalaya and Sikkim (Patiram and Prasad, 1983b; Patiram et al., 1989). The Bray P, can serve the dual purpose of extracting the soil available P and K. The response of maize and rice to K could be expected when soil available K (IN NH 4OAc) dropped below 0.30 and 0.22 meq/100 g soil, respectively and it was 0.13 meq/100 g soil for Bray P, to maize (Patiram et al., 989).

The availability of labile soil K is considered to be influenced by the parameters of intensity (I) and quantity (Q) of labile K present in the soil. So this parameter has been used to represent the K status of soils. The Q/IT parameters of K were studied in the soils of Meghalaya, Nagaland and Sikkim (Patiram and Prasad, 1981; Gupta et al., 1983; Patiram, 1991). These studies indicated that measuring the Q/I parameter which is more time consuming and cumbersome did not offer any advantage over more easily measured neutral ammonium acetate extractable exchangeable K to predict the K availability to plants.

RESPONSE OF CROPS TO POTASSIUM FERTILISERS

The varied ecological and environment of Himalayas and northeastern hills have led to a great diversity in crop production. To sustain the life of traditional nomadic and tribal communities they're with long history and diverse culture. In northeastern hills, rice is the main staple crop followed by maize and wheat. Wheat is cultivated in small areas of Meghalaya, Arunachal Pradesh, Sikkim and Tripura only. In contrast to northeastern hills, in north western Himalayas (Jammu and Kashmir, Himachal Pradesh and Uttaranchal) wheat is the major crop followed by rice, maize and millets.

The response of crops to potassium fertilisers is generally found to vary according to certain soil types, time of application, method of application, crop K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 117

varieties/types etc. Light soils are frequently more responsive compared to heavy clayey soils. However, it depends on potassium status of soils and its supplying power to plants from exchangeable and non-exchangeable forms. The high yielding crop types respond better to potassium application than the lower yielding" ones. The response of rice and wheat to applied potassium @ 60 kg K20/ha in the country is given in Table 3. It can be seen from the Table 3, that the response of wheat and rice (kg grain/kg K20) increased from 1967-71 and 1981- 82 tremendously irrespective of different regions as a result of increased N fertiliser use and introduction of improved high yielding crop varieties. Table 3 also revealed that the response of potassium was much more in the hill zones compared to others.

Table 3. Response of rice and wheat to applied potassium (kg grain/kg K20) Region Kharif rice Wheat 1969/70 1977/78 1969/70 1977/78 to to to to 1970/71 1981/82 1970/71 1981/82 Humid West Himalayan 6.7 8.9 4.2 10.6 Humid West Bengal-Assam 2.0 4.4 4.1 8.0 Humid East Himalayan 5.3 7.7 Sub-humid Sutlej-Ganga 4.0 5.8 2.8 6.5 Alluvial plains Sub-humid/humid East and 3.7 8.2 1.7 5.9 S.E. Uplands Arid Western Plains 1.5 5.4 2.2 5.6 Semi-arid lava Plateau 3.5 8.9 3.2 6.0 Humid/semi-arid W. Ghats 5.1 8.1 3.1 5.6 and Karnataka Plateau Source: Tandon and Sekhon, 1988

North-West Himalayas

In north-west humid Himalayan region, wheat responded well to potassium application and grain yield increased from 4.2 kg/kg K20 during 1969-70 to 10 kg/kg K20 in 1980-81 and it was 3.1 to 5.6 kg in humid to semi-arid Western Ghats and Karnataka plateau at 60 kg K2 0ha (Bhargava et al., 1985). Dixit and Sharma (1995) obtained economical optimum yield of wheat, soybean and linseed on an acid soil of Palampur at 30 kg K20 compared to 60 kg K2O/ha and response was 13.3, 10.3 and 6.3 kg grain/kg K20. Crop response to long-term potassium application in rice-wheat crop sequence and manuring under "All India Coordinated Agronomic Research Project (AICARP)" at R.S. Pura also 118 Patiram

revealed that 10 kg and 18.8 grain/kg K.0, could be obtained, respectively (Pillai et al., 1985).

The long-term field experiment with maize-wheat sequence at Palampur (sub-humid wet temperate climate) revealed drastic reduction in grain yield of both crops in the absence K after 3-4 years. The application of balance NPK (Table 4) sustained the yields around 30-35 and 25-30 q/ha for maize and wheat crops, respectively. However, highest and sustained yield was found with the integrated use of organic and inorganic (NPK + FYM). This long-term experiment highlighted the continuous mining of K in the absence of potassium fertiliser and resulted depletion of its source to meet the crop requirements and ultimately reduced the crop yield. Therefore, the response of crops during the latter years of production increased and also maintained the positive soil K balance. Similarly continuous 24 years field experiment on a sandy loam soil in Almora, the response of soybean and wheat (residual) gradually increased with increasing years (Ghosh et al., 1998). However, soybean was more susceptible to potassium deficiency as compared to wheat. The contribution from non-exchangeable K to crop removal varied from 32.5-86.0 and 12.4-93.6 per cent, respectively.

Table 4. Effect of different fertilizer treatments on grain yield (q/ha) of maize and wheat from 1973-1996 (5 years moving average) (Sharma et al., 1998) Treatments Moving years average 1 5 t0 15 20 Maize Control 4.2 1.5 2.0 2.3 2.1 N 22.8 6.0 1.5 0.6 0.2 NP 34.0 22.7 19.6 11.1 13.0 NPK 35.2 27.5 33.1 36.5 27.4 NPK + FYM 49.5 37.8 52.2 51.4 40.3 Wheat Control 7.0 2.8 2.1 2.2 3.5 N 13.9 4.4 2.4 1.2 0.5 NP 28.0 17.7 15.9 15.8 14.1 NPK 29 20.5 25.4 28.2 19.8 NPK + FYM 37.3 25.5 33.5 35.1 29.9 120-150, 60-100 and 40-100 kg/ha and 90-120, 60-120 and 30-60 kg/ha N, P205 and K20 during the 25 years for maize and wheat, respectively.

North Eastern Hills Region

In the northeastern hill states of India, rice is the main staple food crop excepting Sikkim where maize occupied the largest area (Table 5). The K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 119 productivity of rice in this region is highest in Manipur followed Tripura more than the national average yield. In the other states it is far below the national average. It can be seen from the Table 6, that the productivity of rice is directly related to the use of chemical fertilisers. The lowest yield of Arunachal Pradesh (1079 kg/ha) is the result of the lowest use of fertiliser (2.5 kg/ha). Thus there is a much scope to increase the productivity of crops in this region.

Table 5. Area ('000 ha) and productivity (kg/ha) of food crops in north eastern hill (NEH) state (1997-98) State Rice Total Food Crops Oilseeds Area Prod. Area Prod. Area Prod. Arunachal Pradesh 120.0 1079 183.3 1145 24.1 954 Manipur 157.9 2227 161.5 2259 3.1 549 Meghalaya 105.2 1427 132.8 1447 9.1 648 Mizoram 68.1 1624 80.4 1600 9.1 1352 Nagaland 145.0 1290 205.2 1166 28.5 870 Sikkim 15.9 1367 78.3 1344 9.6 792 Tripura 257.8 2078 271.0 2018 10.3 806 All India 143420.2 1895 124406.5 1551 26214.2 840 Prod. = Productivity

Table 6. Use of chemical fertilisers (kg/ha) in NEH states State 1997-98 1998-99 1999-2000 Arunachal Pradesh 2.3 2.5 2.5 Manipur 65.0 84.2 100.5 Meghalaya 13.5 17.8 19.4 Mizoram 8.9 10.6 19.1 Nagaland 2.3 3.3 3.4 Sikkim 5.8 6.5 6.7 Tripura 22.8 21.3 23.2 All India 85.4 88.6 96.9

The deficiency of K occurs on sandy, degraded ill-drained and highly reduced valley soils. Loss of top fertile soils from terraces and sloppy lands by runoff water also causes its deficiency in upland crops. Even the trials conducted during 1958-67, the increase in yield of rice was more than 300 kg/ha at 40 kg K20/ ha applied in north-eastern hill region (Raheja et al., 1970). From field experiments it has been observed that the application of 60-80 kg K/ha produced the optimum yield of wetland rice (Patiram and Prasad 1983c, Patiram et al., 1987a, Laskar et al., 1983) and which in turn also improved the efficiency of applied N (Singh and Patiram, 1987). The application of potassium in different ratio to nitrogen increased the yield significantly irrespective of nitrogen levels 120 Patiram

(Figure 1). The interaction N x K20 was significant and maximum yield of rice was obtained when potassium was applied one and half times more than nitrogen at all levels of N (Singh and Patiram, 1988). Although maximum benefit was obtained with 120 kg N and K20/ha, yet 40 kg K20/ha gave the maximum return. The split application of 30 kg K/ha in equal amount at 10 days after transplanting, tillering initiation, tillering and maximum tillering stages of rice at Upper Shillong had produced almost similar yield as that of 60 kg K/ha as basal application (Patiram and Prasad, 1989). The maximum benefit of potassium can be obtained by the application of 60 kg K/ha either in two equal doses at transplanting and at active tillering stage or in three equal splits at transplanting, active tillering and panicle initiation stages of rice growth at medium elevation of Meghalaya. (Patiram and Prasad, 1985). Split application of K at these stages of rice growth maintained higher K concentration throughout the growth of plant. In the potato-rice crop sequence of the central plateau of Meghalaya, the application of 80 and 60 kg K/ha, respectively in rotation was necessary for most profitable yield of crops and to maintain the balance of native soil K removed (Patiram and Prasad, 1983c). 50 ~40 -94040 kg N/ha

v30 - 0 80kg N/ha C; , 0120kg N/ha 20 0160kg N/ha 10 ,,, 0 NoKo 0 , 0q!

01:00.5 01:01.0 01:01.5 N: K20 Figure 1. Effect of different N :K0 ration on rice yield

The yield of upland rice in Meghalaya increased linearly upto 213 kg available K/ha, and this amount could be considered as the critical level of available K for upland rice Patiram et al., 1987b). Added K increased linearly upto 90 kg K/ha application in soil which had 133 kg available K/ha and at higher fertility levels (213-263 kg available K/ha), the added K did not increase the yield significantly (Figure 2). Irrespective of soil available K, the application of 30 kg K/ha produced the optimum yield of rice and did not differ from 60 and 90 kg K/ha application. It also indicated that a higher yield of rice could be obtained at higher fertility level without addition of fertliser K because native soil available P also increased from 4.7 to 82.5 kg P/ha as the soil available K increased.

Maize is the next important cereal crop in northeastern hills region after being the major crop in Sikkim. Maize responded favourably to 30-50 kg K/ha K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 121

-- 0 --- 30 -'-60 90 -60 50 "-"40 .6 30 "' 20 C *0

I-I

133 167 213 263 Soil available K (kg K/ha)

Figure 2. Response of upland rice to applied K (kg K/a) at different levels of soil available K

in Meghalaya and Sikkim (Patiram and Prasad, 1987, Patiram et al., 1990). In Sikkim, the soil, which had the 0.12 me K/100 g, responded well to K application upto 50 kg K/ha, but only 25 kg K/ha in the soils, which had almost double amount the amount of exchangeable K than the former. The sufficiency level of K in the ear leaf samples taken at 50% silking stage for getting the 90-100% yield was 1.7-2% K. The maximum yield of wheat crop was obtained at 80 kg K20/ha in Sikkim (Prasad et al., 1981) and highest yield response of 10.9 kg/ kg K2 0 was recorded at 40 kg K20/ha in the hill zone of Assam (Paul et al., 1998).

From the preceding pages, it is very much evident from the long-term as well as farmers' field trials and short term experiments, the productivity of major cereals crops (rice, wheat and maize) of hill and mountain soils of our country can be increased to a great extent with balance use of chemical fertilisers. Potassium fertiliser has the important role to maintain the productivity of crops in the acidic and poor in available potassium reserve soils.

REFERENCES Anonymous (1999). State of Forest Report. Survey of India, Dehra Dun. Bhargava, P.N., Jain, H.C. and Bhatia (Mrs) A.K. (1985). Response of rice and wheat to potassium. Journal of Potassium Research 1: 45-61. Bolan, N.S. and Sreeramulu, U.S. (1981). Potassium status and its relationship with various soil properties in Nilgiris soils. Madras Agriculture Journal 68: 256-259. 122 Patiram

Dixit, S.P. and Sharma, D.K. (1995). Effect of lime and potassium on lime and phosphate potential and crop yield on an Alfisol. Journal of the Indian Society of Soil Science 43: 78-80. Giri, J.S., Singh, R.S., Jain, B.L. and Shyampura, R.L. (1998). Soil resource mapping of the rubber growing areas of Kerala. Annual Report, National Bureau of Soil Survey and Land Use Planning, Nagpur, 175-178. Ghosh, A.B. and Hasan, R. (1976). Available potassium status of Indian soils. Bulletin Indian Society of Soil Science 10: 1-5. Ghosh, G. and Ghosh, S.K. (1976). Potassium in some soils of Nagaland. Bulletin Indian Society of Soil Science 10: 6-12. Ghosh, B.N., Prakash, V. and Singh, R.D. (1998). Yield response and nutrient use efficiency on soybean-wheat system in a long-term manurial experiment. Proceedings of the Long-Term Fertility Management Through Integrated Plant Nutrient Supply, Indian Institute of Soil Science, Bhopal, 277-282. Grewal, J.S. and Sharma, R.C. (1980). Evaluation of soil test methods for potassium in acidic brown hill soils for recommending fertiliser doses for potatoes. Journal of the Indian Society of Soil Science 28: 355-360. Gupta, R.D. and Tri[pathi, B.R. (1992). Genesis of soils in wet temperate and sub-alpine/moist-alpine climatic zones of the northwest Himalayas. Journal of the Indian Society of Soil Science 40: 505-512. Gupta, R.K. Datta, M. and Sharma, S. (1983). Different forms of quantity- intensity parameters of potassium in acidic soils of Nagaland. Journal of the Indian Society of Soil Science 31: 305-357. John, P.S. and George, M. (1990). Fertiliser use in west coastal plains and Ghats region, FertiliserNews 35(6): 61-64. Kadrekar, S.B. (1976). Soil of Maharastra state with reference to the forms and behaviour of potassium. Bulletin Indian Society of Soil Science 10: 33-37. Lyngdoh, J.C. and Shukla, L.M. (1993). Fertility status of some Alfisols. Journal of the Indian Society of Soil Science 41: 707-709. Marwaha, B.C. (1996). Acid soils of the north western region of India - their characteristics and management. In: Acid Soils of India, Indian Council of Agricultural Research, New Delhi, 165-173. Mayalagu, K and Sreeramulu, U.S. (1983). N, P and K (total and available) status of major series red soils of Coimbatore district, Tamilnadu. The Madras Agriculture Journal 70: 51-53. Misra, U.K. and Saithantuaanga, H. (2000). Characterization of acid soils of Mizoram. Journal of the Indian Society of Soil Science 48: 437-446. Murthy, J.R. and Sharma, A.K. (1999). Role of physiography on characteristics and development of soil under pine vegetation and their classification. Journal of the Indian Society of Soil Science 40: 143-149. K Availability and Crops Response to Fertiliser K in Hill and Mountain Soils of India 123

Negi, A.S., Sharma, R.C. and Sud, K.C. and Grewal, J.S. (1979). Journal of the Indian Society of Soil Science 27: 268. Patiram and Prasad, R.N. (1981). Quantity/intensity parameters of potassium'in the soils of Meghalaya. Journal of the Indian Society of Soil Science 29: 446-452. Patiram and Prasad, R.N. (1983a). Potassium supplying power of soils from East Khasi hills of Meghalaya. Journal of the Indian Society of Soil Science 31: 506-510. Patiram and Prasad, R.N. (1983b). Evaluation of available potassium in acid soils of India. Journal of the Indian Society of Soil Science 31: 628-631. Patiram and Prasad, R.N. (1983c). Yield responses to fertilizer potassium and balance sheet of potassium in potato-rice sequence. Journal of the Indian Society of Soil Science 31: 502-505. Patiram and Prasad, R.N. (1984). Forms of potassium in the soils of East Khasi hills of Meghalaya. Journal of the Indian Society of Soil Science 32: 168- 171. Patiram and Prasad, R.N. (1985). Efficacy of time of potassium application in lowland rice on Haplaquent of Meghalaya. Indian Journal of the Agricultural Science 55: 338-341. Patiram and Prasad, R.N. (1985). Response of potato to potash at different levels of potassium and nitrogen on an Alfisol of central plateau of Meghalaya. Journal of the Indian Society of Soil Science 33: 935-937. Patiram, Prasad, R.N.and Singh, R.P. (1987a). Effect of potassium on yield and its contributing characters in rice grown on Haplaquent of Meghalaya. Indian Journal of the Agricultural Science 57: 943-945. Patiram, Prasad, R.N.and Singh, R.P. (1987b). Response of rainfed direct seeded rice to potassium on an Alfisol of Meghalaya. Annals of Agricultural Research 8: 214-220. Patiram and Prasad, R.N. (1987). Response of maize to applied potassium on Alfisol of Meghalaya. Annals of Agricultural Research 8: 158-161. Patiram and Prasad, R.N. (1988). Effect of topdressing of potassium on rice grown in valley soils of Meghalaya. Indian Journal Hill Farming 2: 21-24. Patiram, Rai, R.N. and Prasad, R.N. (1989). Suitability of extractants for available K to maize in the acid soils of Sikkim. Patiram, Rai, R.N., Singh, K.P. and Prasad, R.N. (1990). Response of maize (Zea mays) to potassium in Sikkim soils. Indian Journal of the Agricultural Science 60: 601-604. Patiram (1991). Q/I relationships and potassium availability in acid soils. Journal of the Indian Society of Soil Science 33: 935-937. 124 Patiram

Paul, S.R., Sarma, N.N. and Sarma, D. (1998). Effect of seed hardening and K levels on grain yield of rainfed wheat in the hills zone of Assam. Journal of Potassium Research 15: 54-58. Perur, N.G. (1996). Acid soils of Karnataka. In Acid Soils of India, Indian Council of Agricultural Research, New Delhi, 165-173. Pillai, K.G., Devi, S. and Setty, T.K.P. (1985). Recent achievements of All India Coordinated Agronomic Research Project. Fertiliser News 30 (4): 26-34. Prasad, R.N., Patiram, Barooah, R.C. and Ram, M. (1981) Soil Fertility Management in North Eastern Hill Region. Technical Bulletin No.9, ICAR Research Complex for northeastern hills region, Shillong. Raheja, S.K., Seth, G.R. and Bapat, S.R. (1970). Crop responses to potassium fertilisers under different agroclimatic and soil conditions. Fertiliser News 15(2): 15-33. Sharma, S.P., Sharma, J. and Subehia, S.K. (1998). Long-term effects of chemical fertilisers on crop yields, nutrient uptake and soil environment in Western Himalayan soils. Proceedings of the Long-Term Fertility Management Through Integrated Plant Nutrient Supply, Indian Institute of Soil Science, Bhopal, 125-138. Singh, O.P. and Datta, B. (1986). Forms of potassium in some soils of Mizoram. Journal of the Indian Society of Soil Science 34: 187-190. Singh, R.P. and Patiram (1987). Response of wetland rice to applied potassium on an Haplaquent of Meghalaya. Indian Journal of the Agricultural Science 57: 398-403. Singh, R.P. and Patiram (1988). Response of rice to potassium fertilisation in relation to nitrogen on Haplaquent of Meghalaya. Indian Journal of Hill Farming 1-A: 23-26. Singh, S.P., Haldar, A.K. and Singh, N. (1989). Studies on forms of potassium in relation to soil characteristics in the soil of Mizoram. Indian Agriculturist 33: 55-58. Singh, S.P., Ram, J., Singh, N. and Sarkar (1999). Distribution of potassium in soils of Arunachal Pradesh. Journal of Potassium Research 15: 54-58. Sreedevi, S. and Aiyer, R.S. (1974). Potassium status of acid rice soils of Kerala state. Journal of the Indian Society of Soil Science 22: 321-328. Tandon, H.L.S. and Sekhon, G.S. (1988). Potassium Research and Agricultural Production in India. Fertiliser Development and Consultation Organisation, C/10 Greater Kailash, New Delhi. Yadav, J. and Kumar, N. (1999). Status of major nutrients in alluvial soils of Leh, Seru and Nubra valleys under cold arid conditions of Laddakh region. Journal of the Indian Society of Soil Science 47: 799-801. Assessing Potassium Availability in Indian Soils

A. SUBBA RAO, T.R. RUPA AND S. SRIVASTAVA Indian Institute of Soil Science, Nabibagh, Berasia Road, Bhopal-462038, Madhya Pradesh, India

INTRODUCTION

Fertiliser nutrient is applied when the demand for a nutrient exceeds the amount which the soil can supply within a growing season. Soil tests for potassium (K) are carried out to determine the K supplying ability of the soil and to arrive at the quantity of fertiliser that must be applied to overcome any deficiency/ shortcoming. There are many soil testing methods and a great deal of work has been expended in the search for the 'best' method. A number of workers have used chemical extraction procedures which selectively extract one or more of soil K fractions for the purpose of assessing their contribution to plant K uptake. Such studies have helped in devising better methods of soil K evaluation and also in understanding the K release under varying soil, environmental and cropping conditions. In the present paper an attempt has been made to review the basis for potassium extraction, details of soil test procedures, ability of the methods to measure K in different soils, correlations between soil tests and plant indices, inclusion of subsoil K and non-exchangeable K in soil test calibration, critical limits of K and the soil test based fertiliser recommendations.

2. BASIS FOR POTASSIUM EXTRACTION

Four important fractions of soil K are removed to a varying extent by the various chemical and physico- chemical methods. A list of methods used to measure soil K fractions is in Table 1, compiled from Grimme and Nemeth (1978), McLean and Watson (1985) and Sparks and Huang (1985).

2.1 Potassium concentration in the soil solution

Potassium (K) concentration in the soil solution is an important index of K availability to crop plants because K diffusive flux towards the roots takes place in the soil solution and the rate of diffusive flux depends on the concentration gradient that develops in the soil adjacent to an actively absorbing root. However, the amount of K present in the soil solution at a particular instance represents only a very small proportion of the total soil K and is much less than a crop requires in a growing season. A measurement of the K concentration in solution does not reveal whether this concentration is well buffered or not and how much fertilizer K need to be added when the concentration is considered inadequate. 125 126 A. Subba Rao, TR. Rupa and S. Srivastava

Table 1. Methods for measuring soil K K fraction Method Solution Batch equilibration or column leaching with water, extraction by pressure membrane or centrifugation (extracts soil solution K) Activity ratios Exchangeable Batch equilibration or leaching with dilute salt solutions (especially NH 4 ) and acids (citric, nitric) Electroultrafiltration (EUF) Silver thiourea Mehlich I (HCI + H2S0 4) and 2 (acetic acid, ammonium fluoride, ammonium chloride, HCI) Ammonium bicarbonate + DTPA Bray I Exchange isotherms and other equilibrium data Potassium potentials Calcium acetate lactate (CAL-K) Double lactate (DL-K) Non-exchangeable Exhaustive cropping Leaching with dilute acids and salts Boiling with dilute acids Boiling with concentrated acids Repeated extractions with NaTPB Repeated extractions with oxalic acid Repeated extractions with Ca or H resins Sodium cobaltinitrite Hot MgCI 2 Electroultrafiltration (EUF) Electrodialysis Mineral Selective dissolution with Na-pyrosulphate fusion Total HF digestion Multi-fraction Quantity-intensity (Q/I) curves EUF Sequential extraction by resins Boiling HNO 3

2.2 Exchangeable K

A variety of extracting solutions viz., neutral unbuffered electrolyte solutions and weak or strong acid solutions are in use to measure exchangeable K. Exchangeable K represents the fraction adsorbed on external charge sites and accessible internal surface of clay colloids. So, it is mainly the clay content and the clay mineralogy which modifies the availability of exchangeable K (McLean, 1978) so that the relation between exchangeable K and K uptake is very much Assessing Potassium Availability in Indian Soils 127

improved if exchangeable K is expressed as a fraction of cation exchange capacity (CEC).

2.3 Non-exchangeable K

The plant-available non-exchangeable K reserves are usually extracted with strong acids (De Turk et al., 1943) which give a measure of the long-term K supplying power of soils (Haylock, 1956). Electrodialysis, exchange resins and Na-tetraphenylboron (NaTPB) have also been used (Quemener, 1979) to measure non-exchangeable K. It is only when growth rates are low i.e. low yield situations that non-e:changeable K can be considered as a useful K source. In many cases yields are reduced, if a large proportion of the K requirement has to be met by non-exchangeable K, because the release rate is too low to meet the K demand of a vigorously growing crop (Grimme, 1974).

2.4 Mineral K

Micas and feldspars occurring predominantly in sand and silt fractions of soil are major source of reserve K. Small amounts of feldspars and micas present in fine sand and silt fractions may serves as a source of slowly-available K. Extraction with NaTPB can be used to assess the magnitude of K release from mineral sources. Haylock (1956) proposed step K and constant rate K as measures of K availability. Step K measures the plant-utilizable non-exchangeable K whereas constant rate K gives an idea about the rate of K release from mineral lattice. The amount of step K far exceeds the non-exchangeable K measured by the conventional single extraction with boiling iN HNO 3. It appears that step K also includes the K present in easily-soluble micaceous minerals.

The data on different forms of K in benchmark soil profiles of India (Sekhon et al., 1992) (Table 2) revealed that exchangeable K is generally higher in

Table 2. Forms of potassium expressed as proportion of total potassium in different soils Form of K (% of total K) Soil Water- Exchange- Non- Total K soluble able exchangeable (me 100 g') Alluvial Calcareous illitic (8)* 0.12 0.28 7.52 57.43 Acidic kaolinitic (2) 0.32 0.78 2.34 10.25 Vertisols and vertic type Smectitic (7) 0.25 2.12 5.56 35.38 Red and lateritic Kaolinitic (5) 0.19 0.49 3.14 26.41 Source: Sekhon et al.. 1992; *No. of soil samples 128 A. Subba Rao. T.R. Rupa and S.Srivastava

Vertisols and vertic type soils and in the fine-textured alluvial soils than in the red and lateritic soils, acidic alluvial soils with kaolinite as dominant clay mineral, and light-textured alluvial soils. Whereas the concentration of non-exchangeable K was greater in illite dominant alluvial soils followed by smectite-dominant soils. The total K was most abundant in illitic alluvial soils, followed in order by smectitic Vertisols and vertic type soils, kaolinitic red and lateritic soils, and kaolinite dominant acidic alluvial soils. The order was similar for the non- exchangeable K fraction as a proportion of the total K. However, the exchangeable K proportion was the highest in Vertisols and vertic type soils and the lowest in illitic alluvial soils. Although total K was least in kaolinitic acidic alluvial soils, a relatively larger proportion of it existed in water-soluble form.

The concentration of different forms of K in different soil types indicated a wide variation. In general, Vertisols had higher total K concentration followed by water-logged soils and lateritic soils. Potassium fractions in soils exist in equilibrium with each other. Upon waterlogging, the amount of water-soluble K increases as a result of exchange reaction due to increase in Fe2+ and Mn 2 concentrations (Verma et a., 1994).

3. POTASSIUM SOIL TEST PROCEDURES

Any soil test that accurately reflects the K* available to crop plants in a growing season must measure the amount in solution plus that is replenished to the soil solution and taken up during the growing period (McLean and Watson, 1985). There have been several attempts to characterize the K supplying power of soils by simulating the feeding action of plant roots and to determine that fraction of the nutrient in the soil. Quite a number of soil test methods are used for assessing the available K status of different soils, but none of these is applicable to all soils, as the available K in soils is influenced by the heterogeneous character of the soils as well as the forms of K in soils.

A wide range of chemical extractants have been used for assessing plant- available K (Table 3). The most commonly used one is IM NH 4OAc method. Other extractants which received considerable attention are, Morgan's (NaOAc- HOAc) reagent, Olsen's reagent (0.5 M NaHCO 3) or modified Olsen's reagent (0.5N NaHCO3 + 0.01M EDTA) and Bray P1. These have also been tried as extractants for simultaneously estimating both available P and K.

Schachtschabel and Heinemann (1974) proposed 0.025 N CaC12 as an extractant for available K, and was shown to be a good indicator of the K status of soils by Grimme and Nemeth (1976). The proportion of total exchangeable K extracted varies from 40 to 80% and depending on clay content and clay mineralogy. Dilute organic acids are considered to be better extractants to simulate plant-available K in soil as these represent feeding mechanism similar to plant roots in extracting soil K around root vicinity. Assessing Potassium Availability in Indian Soils 129

Table 3. Details of some soil test procedures Extractant Soil : Shaking Reference extractant time ratio Water 1:5 5 min Jackson(1973) Water 1:10 30 min MacLean (1961) Dilute salt solutions O.01M Calcium chloride 1:10 30 min Woodruff and McIntosh (1960) 0.01M Barium chloride 1:10 30 min Peech et al. (1947) IN Sodium acetate (pH 7.0) 1:5 5 min Conyers and MacLean (1969) IN Magnesium acetate (pH 7.5) 1:5 5 min Hanway and Heidel (1952) IM Ammonium acetate, pH 7.0 1:5 5 min 0.03M Sodium tetraphenyl boron 1:10 16 h Schulte and Corey equili- (1965) bration Organic acids 1% Citric acid (pH 2.5) 1:10- 7 days Dyer (1894) equili- bration 0.OIN Citric acid 1:10 30 min Zhu and Leo (1993) 1.01N Oxalic acid 1:10 30 min Strong mineral acids Pratt (1957) 1.38 N H2SO 4 1:26 30 min Hunter & (1957) 6N H2SO 4 1:3.5 30 min Hunter & Pratt Concentated H2SO4 1:2 30 min Hunter & Pratt (1957)

IN boiling HNO 3 1:10 10 min Wood and DeTurk (1940)

0.5M HNO 3 1:5 30 min Oommen (1962) Buffered solutions Morgan's reagent (pH 4.8) 1:2 1 min Morgan (1941) Ammonium acetate + 1:5 5 min MacDonald et al. Acetic acid (pH 5.0) (1978) Electro-ultrafiltration EUF 10 5 min Nemeth (1979). EUF 30 30 min Nemeth (1979) EUF 35 35 min Nemeth (1979) 130 A.Subba Rao, TR. Rupa and S. Srivastava

Next to NH 4OAc, IM boiling HNO3 method is perhaps the most widely used procedure for studying soil K supplying capacity to meet plants need. While comparing NaTPB with mineral acids, Beegle and Baker (1987) stated that the NaTPB would simulate better the plant need of K than strong mineral acids because it would not destroy the mineral structure. Among the methods to assess the non-exchangeable K reserves viz., strong acids, NaTPB, ion exchange resins and dilute electrolytes, the methods based on boiling IM HNO3. 0.01M HCI and 0.01M CaCI 2 indicated superiority.

Electroultrafiltration (EUF) method of soil analysis is the only method in practice, which takes dynamic aspects of nutrient supply into account. It allows the determination of intensity, quantity and buffering capacity parameters (Nemeth, 1976). Electroultrafiltration extraction method is a combination of electrodialysis and ultrafiltration of the cathode and anode dialysis at chosen voltage and temperature (Nemeth, 1979). Nemeth (1985) reported that one of the major achievements of EUF as compared to conventional soil testing method is the fact that the availability of K is determined by two fractions viz., EUF- K-200C and the EUF-K-80oC/20oC quotient. However, Srinivasa Rao et a. (1995) showed that EUF-K-quotient as a measure of buffering power has limitations and can only be used for soils with similar cropping history as well as K fertilization. Extended period of extraction at 800C and 400 V provides information on nonexchangeable K reserves (Subba Rao et al., 1988).

Currently, multinutrient extractants are becoming more popular because they save the time and cost of estimation of available nutrients (Table 4). In a single

Table 4. Universal soil extractants and soil adaptability Extractant Soil : Soil type Shaking Reference extractant time ratio Olsen's reagent 1:20 Neutral, alkaline 30 min Olsen et al. and calcareous soils (1954) Mehlich 1 1:4 Acid sandy soil 5 min Mehlich (1953) Mehlich 3 1:10 All acid soils 5 min Mehlich (1984) Morgan-wolf 1:2 All acid soils 5 min Wolf (1982) Organic soils AB-DTPA 1:2 Alkaline soils 15 min Soltanpour & (pH 7.6) Schwab (1977) 1:10 Wide range of soils 30 min Simard and Deschenes (1992) Sr-citrate 1:5 Neutral, alkaline and 10 min Hunter (1972) calcareous soils Olsen's modified 1:10 All acid soils 30 min Morgan (1941) reagent (NaHCO 3+EDTA) Morgan Assessing Potassium Availability in Indian Soils 131 extraction, they extract several nutrient elements and/or pollutants, in addition to K. The amounts of exchangeable bases (K, Na, Mg and Ca) determined by the Mehlich 3 method are nearly identical to those obtained by IM NH 4OAc (Michaelson et al., 1987). Liu and Bates (1990) found AB-DTPA to be slightly better than ammonium acetate and Mehlich 3 to evaluate available K for lucerne. The Sr-citrate extracted more K than IM NH 4OAc or Mehlich 3 in soils with CEC's of less than 15 cmol kg-' and less K in soils with larger CEC (Simard and Zizka, 1994). It was found best for predicting K uptake from low CEC (<15 cmol kg-') soils and adequate for higher CEC soils using alfalfa as test crop in Quebec, Canada. Ammonium acetate extracted slightly higher amounts of K than the modified Olsen's reagent extraction (Ananthanarayana et al., 1989).

3.1 Ability of soil tests to measure K in different soils

Soils vary in their available K status depending on parent material, stage of weathering and clay mineral composition. Different extractants extract K to varying extent from the diverse soils. The extent of variability in extractable potassium concentrations estimated by IM NH 4OAc, boiling IM HNO 3 and EUF methods in twenty soil series developed on a variety of parent materials and occurring in intensively cultivated areas of India was investigated by Subba Rao and Sekhon (1990). The variability measured by the coefficient of variation percentage was more in NH 4OAc-K as compared to HN0 3-K. The variability in basis the HNO 3-K is the minimum and soil series can be distinguished on the of this fraction of K. Swell-shrink (black) soils and illitic alluvial soils with medium or high available K showed variation in NH 4OAc-K within the limits of accuracy (±10% of mean) while kaolinitic red, lateritic and acid alluvial soils with coarse to medium texture and medium to high K status showed larger variation. EUF-K showed more or less similar variability as NH 4OAc-K. Variability in NH 4 OAc-K and EUF-K can be reduced by assessing the K status of soil types within a soil series.

3.1.1 Alluvial soils (Micaceous mineral dominant soils)

In soils dominant in micaceous minerals, large amounts of potassium are released during crop growth in the absence of fertilizer K. For making accurate fertilizer K recommendations in alluvial soils intensively cropped over long periods, both exchangeable K and K release from non-exchangeable sources should be taken into consideration.

Studies of Krishna Kumari and Khera (1989) on relative efficacy of soil test methods to measure changes in K status due to uptake, addition and release of potassium in micaceous soils showed that the status of available K in soil was in the decreasing order: boiling IM HNO 3 > IM NH 4OAc > Morgan's reagent > 0.01 M CaCI2. Boiling IM HNO 3 can be recommended for use on micaceous 132 A. Subba Rao, TIR. Rupa and S. Srivastava

soils where there is substantial release and utilization of K from non-exchangeable forms under intensive cropping.

Talukdar and Khera (1996) screened soil tests of K on K depleted Ustochrepts of Delhi. The amount of K extracted by eight conventional extractants varied - from as low as 7.8 mg kg ' soil with distilled water to as high as 99.0 mg kg- with Mehlich-I extractant. Based on average K extractability, these methods could be arranged in the following increasing order : Distilled water < 0.01M CaCI2 < Modified Olsen's reagent < IN MgOAc < IM NH 4OAc < 0.5M HNO 3 < 1.38N H2SO 4 < Mehlich 1I. Non-conventional methods based on non- exchangeable K release removed a part of non-exchangeable form of soil K and could be arranged in the following decreasing order: IM HNO 3 (boiling) > 0.01M HCI (leaching) > cation exchange resin.

Tiwari et al. (1995) also evaluated the relative efficacy of soil test methods for measuring K in 30 soils (Typic Ustochrepts) of Uttari series of Kanpur (U.P.). The extraction capacity of various extractants can be arranged in the descending order as : Boiling IM HNO 3 > Olsen's reagent > modified Olsen's reagent > IM NH 4OAc > 0.75 M HCI > IM NaOAc > distilled water > 0.01M CaCI2.

Ghosh and Mukhopadhyay (1996) studied the forms of K in Belar and Bankati series of West Bengal having a varied pH. On an average the water- soluble and available K concentrations of soils were higher in Bankati series in which pH was closer to acidic range than in the Belar series. Whereas, the reserve and non-exchangeable K corcentrations showed a reverse trend. A study of Nath and Purkaystha (1988) on the suitability of some commonly used soil test methods for assessing available K in alluvial soils of Assam revealed that the K extracting capacity of different extractants was in the following order : IM HNO 3 > 0.5M HCI > 1.38N H SO 2 4 > neutral IM NH 4OAc > 0.025M CaCI2 > Morgan's reagent > 0.01M CaCI 2 > distilled water.

3.1.2 Red and laterite soils (Kaolinite dominant soils)

Forms of potassium and suitability of some soil test methods for assessing available K in lateritic soils of Phondaghat soil series in south Konkan (Maharashtra) was studied by Sutar el al. (1992). In general, the extractants involving mineral acids (IM HN0 3, conc. H2SO4 , 1.38N H2SO 4) recorded higher K concentrations compared to those containing the salts (IM NH 4OAc, 0.01M CaCI2 , 0.5M NaHCO3, Morgan's reagent). The higher K concentrations with acid extractants could be attributed to the fact that besides exchangeable K, these extractants also bring some non-exchangeable K into solution by the breakdown of soi l minerals (Bhadoria et al., 1986). Even though the Bray P1, Bray P2 and Olsen extractant are the popular soil P tests, they were observed to be the promising soil K test methods too (Maharana et al., 1976 and Patiram et Assessing Potassium Availability in Indian Soils 133 at., 1989). The data showed that the K extractability of Bray P2 resembled closely that of IM NH 4OAc.

3.1.3 Vertisols (Smectite dominant mineral soils)

Surekha et at. (1997) compared different indices of K availability for Vertisols of Andhra Pradesh and indicated that the K extracted was in the following order: Boiling IM HNO 3 > 0.IM HNO 3 > IM NH 4OAc > 0.M HCI = O.1N H2SO 4 > 1:5 soil water extract > saturation extract. The EUF (10-30) K > EUF (30-35) K > EUF (10) K. They also reported that IM NH 4OAc was the best index to estimate available K and boiling IM HNO 3 was the best measure of long-term release from non-exchangeable forms in Vertisols of Andhra Pradesh. Ramanathan and Krishnamurthy (1981) found that 0.IM HNO 3 was the best index of K availability for black soils of Tamil Nadu.

3.1.4 Waterlogged soils

Studies of Verma et al. (1994) on evaluation of chemical methods for the determination of K in waterlogged soils indicated that the 1.5M HNO 3 extracted higher amount of K followed by IM HNO 3 (Table 5). The mean values of K extracted by all the methods, except two (IM HN0 3 and 1.5M HNO3 ), from waterlogged soils were greater than those extracted from air-dry soils. By contrast, IM HNO 3 and 1.5M HNO 3 extracted slightly higher amount of K in air-dry soils than in waterlogged soils. The greater mean values of K extracted by the other five methods may be attributed to more efficient extraction by these methods under waterlogged conditions. Since IM and 1.5M HNO 3 extracted most of soil K from non-exchangeable and residual fractions under waterlogged conditions and some portion of these two forms of K had changed to exchangeable and

Table 5. Potassium extracted (mg kg-') in air-dry and water-logged soils Extractant Range Mean Waterlogged Air-dry Waterlogged Air-dry soil soil soil soil

IM NH 4OAc 60.4-243 50.2-177.0 139.9 94.2 IM HNO 3 500-2336 570-2400 1014 1082 1.38N H2SO 4 55.5-146.1 46.4-146 97.6 88.1 1.5M HCI 50.5-134.0 25.2-99.1 83.5 57.6 1.5M HNO 3 650-2600 610-2650 1195 1218 10% NaOAc+3% CH 3COOH (pH 4.8) 40-110.0 42.4-96.0 63.0 56.7 0.75M HCI 34.8-130.0 40.5-109.0 73.4 66.2 Source: Verma et al., 1994. 134 A. Subba Rao, T.R. Rupa and S. Srivastava

water-soluble K, these two methods extracted relatively lower amounts of soil K under waterlogged conditions. The maximum increase in the values of extracted K by five chemical methods due to waterlogging was observed to be in IM NH 4OAc and minimum in 0.75M HCI.

3.2 Correlation between soil tests and plant indices

The choice of a soil test method is mainly done from correlation studies between soil test values and crop yield and/or uptake from a number of trials conducted in various soils of different fertility levels. In the interpretation of soil test data, it is also necessary to know critical soil test level for a nutrient below which the probability of an economic response of a crop to added fertilizer is high. Widely used procedure to get such information is to compute correlation coefficients for the relationship between per cent yields and soil test values using several chemical extractants.

Subba Rao and Ghosh (1983) in an investigation to examine the changes in available K status on an alluvial soil under intensive cropping and fertilizer use for seven years, using water, 0.01M CaCI2. neutral IM NH 4OAc and NH 4F + DTPA as soil tests showed that all the four tests employed were fairly effective. IM NH 4 OAc methods proved to be the best. in detecting the treatmental differences. Singh and Ghosh (1982) evaluated the efficiency of 19 soil test procedures for measuring the potassium availability through correlation with dry matter yield, total K uptake and per cent K concentration in maize, cowpea and wheat crops grown in greenhouse using 10 soils of alluvial origin. The amount of K extracted by IN magnesium acetate solution (pH 7.5) was closely correlated with plant K uptake. Olsen's reagent, modified Olsen's reagent and Mehlich's diacid extractant proved quite reliable in majority of the cases.

-Correlation co-efficients between soil test values by various conventional ard non-conventional methods and crop response parameters indicated that 0.5M HNO 3, 1.38N H2SO 4 and 1M NH 4OAc methods could be considered as better methods for testing K availability in K-depleted alluvial soils (Talukdar and Khera, 1996).

The coefficients of correlation between extractable K in 30 solis (Typic Ustochrepts) of Uttari series and the Brays' per cent yield and the concentration and uptake of K in 6-week old plants, and in grain and straw of wheat worked out were generally higher with boiling IM HNO 3, IM NH4OAc (pH 7.0), 6M H SO , 0.13M 2 4 HCI and modified Olsen's reagent. Out of these, IM NH4OAc (pH 7.0) and boiling IM HNQ 3 were found most suitable for determining available soil K. Further IM HNO 3 was found superior to IM NH 4OAc (Tiwari et al., 1995). Tiwari et al. (1996) evaluated different soil test methods for determining available K using chickpea as a test crop in 30 soils (Typic Ustochrepts) of Uttari series of Kanpur. Of the 14 extractants tested, IM HNO 3, IM NH4OAc Assessing Potassium Availability in Indian Soils .135

(pH 7.0), 0.13 N HCI and IM NaOAc (pH 7.0) showed high degree of correlation with Bray's per cent yield and the concentration and uptake of K in plant, grain and straw. Tiwari et al. (1999) conducted a greenhouse experiment with rice on 30 soils (Udic Ustochrepts) of Uttari series of Kanpur to evaluate suitability of soil test methods for K and to establish critical limits of K in soils and plants. For verification multilocation field experiments were conducted on cultivators' fields. Correlation of fourteen soil test methods with plant indices indicated superiority of boiling IM HNO 3 and IM NH4OAc (pH 7.0) over others. Between the two best extractants, IM HNO 3 showed better correlation with Bray's per cent yield and K uptake than IM NH 4OAc.

Panda and Panda (1993) evaluated some soil test methods for rice in a Fluventic Ustochrept of Puri district. The relationship between various soil test values and the plant parameters suggested that IM NH4 OAc and 0.5M HNO 3 methods which estimate mostly the readily-available fraction of soil K are the better methods for estimating available K in Fluventic Ustochrepts.

A study by Nath and Purkaystha, (1988) revealed that except 0.5M HCI, all other extractants showed a significant positive correlation with Bray's per cent yield and per cent K uptake and significant negative correlations with Bray's per cent response in rice. A comparison of r values both at K0 level and Bray's approach showed that the extractants 0.01M CaCI2, neutral IM NH4 OAc and 0.025M CaCI2 were superior to all others for assessing available K and predicting response of rice to applied K in alluvial soils of Assam.

Evaluation of suitable soil testing methods for determining available K in the lateritic/red loam soils of Kerala indicated that neutral IM NH 4OAc, 0.01M CaCI2, and 0.5M HCI were found to the be the best methods for determining K availability followed by water and IM HNO 3. The correlation coefficients obtained between laboratory estimates of K and K uptake by Neubauer crop were in the following order: Neutral 1M NH 4OAc (r = 0.503) > 0.01 M CaCI2 (r = 0.431) > 0.5N HCI (r =0.384) > water (r = 0.374) > 6N H2SO4 > Morgan's reagent (r = 0.252) > IM HNO 3 (r = 0.146) (Prabha Kumari and Aiyer, 1993).

Of the twelve different extractant methods tested, six namely conc, H 2SO 4, 6% NH 3 + 7% CH3COOH, 0.75M HCI, Morgan's reagent, Bray P2 and IM NH 4OAc had higher correlation coefficients with rice grain yield (r = 0.597 to 0.664), Bray's per cent yield (r = 0.74 to 0.802) and K uptake (r = 0.72 to 0.812) on lateritic soils (Sutar et al., 1992).

Srinivasa Rao and Takkar (1997) evaluated the suitability of different extractants for K on Vertisols using sorghum as a test crop and found that while IM NH 4OAc - K can be used as a measure of plant-available K, multinutrient extractants and dilute organic acids can also serve as equally good measures of available K in soils. 136 A. Subba Rao, T.R. Rupa and S.Srivastava

Akolkar and Sonar (1994) evaluated the soil test methods of K for sorghum in 16 soils belonging to Ottur series (Typic Chromusterts) in Maharastra. The highest correlation values were observed between NH 4OAc and per cent grain yield (r = 0.941**) and NH 4OAc and per cent K uptake (r = 0.843**). The next best method was found to be NaOAc.

The suitability of soil test methods studied by Verma et al. (1994) in relation to rice plant growth parameters in air-dry and waterlogged soils of Himachal Pradesh indicated that the non- exchangeable K was the most important K fraction contributing to K nutrition of rice and the exchangeable K was next in importance. IM HNO 3 extractant was the most effective in air-dry and waterlogged soils and this method correlated well with all the plant growth parameters.

3.3 Inclusion of subsoil K in soil test calibration

Truog (1937) expressed the view that subsoils fertility to be of considerable importance to deep-rooted plants. Deeply rooting species such as alfalfa, soybean and cotton possess a higher potential for subsoil K exploitation. Hanway et al. (1962) observed that inclusion of the amount of exchangeable K in the soil below six inches (15 cm) improved the correlations. Black (1965) elaborated the Mitscherlich equation to include the contribution of nutrient concentrations at different depths in the soil profile. Kapur and Sekhon (1985) created variation in nutrient availability in the field, by physically mixing N, P and K fertilsers in the 0-15, 15-30 and 30-45 cm soil layers. The correlation between dry weight of roots in different soil layers and the respective crop yield and nutrient uptake was good in the 15-30 cm soil depth. According to Tamhane and Subbaiah (1962), if a close correlation exists between the subsoil and the surface soil nutrient values, there is little advantage in drawing samples from lower depths. However, in soils where surface soil, sufficient in K, lies on the top of a subsoil, grossly insufficient in K and the crop is a deep-rooted one, there is obvious need to sample both surface and subsurface soil, separately.

Srinivasa Rao et al. (2001) studied the subsoil K in relation to surface soil K in 22 benchmark soil series of India. Potassium availability in sub-soils in comparison to surface soil K (which is taken as 100%) is shown in Figure 1 which indicates the potential of subsoil K supply to crop plants. In kaolinitic soils 6N H2SO 4 extracted higher levels of K from subsoil than surface soil. The overall per cent of K from subsoil to the surface soil varied from 71 to 96, 62 to 90 and 60 to 82 in kaolinitic, illitic and smectitic soils. The higher subsoil K as a percentage of surface soil K in kaolinitic soils could be due to down ward movement of added K or released from non-exchangeable fraction of surface soils and accumulated at lower depths. The movement of K to deeper layers of loamy sand profile in a long term fertilizer experiment was reported earlier by Ganeshamurthy and Biswas (1984). The relationship between subsoil K and surface soil K in mineralogically different soils showed highly significant Assessing Potassium Availability in Indian Soils 137

soil[ Surface Kaollnitic E]Subsurface 150-

100

50

WS, diric LM N PB d NHAOAC

im

40~

Smectitic soils F IIIurac

EIudsace 120

. 100 80

-. 60

4080 CA 20

Figure 1. Subsoil K content as percentage of surface soil K in three mineralogically different soil groups 138 A. Subba Rao, TR. Rupa and S.Srivastava correlation (r2 = 0.89-0.940). The slope values of regression equations connecting surface and sub-surface soil K (including all the forms of K examined were found to be 0.74 for kaolinitic, 0.85 for illitic and 0.66 for smectitic soils. This subsoil K source become very important when surface soils are K deficient as in kaolinite dominant red and lateritic soils. In other soil groups, deep rooted crops can utilise K from subsoil. Therefore results suggests that K recommendations for different crops/cropping systems could be improved by including subsoil K.

Distribution of K in different Indian soils showed characteristic differences according to depth of sampling (Subba Rao and Sekhon, 1990). Available and reserve K tended to decrease with depth in calcareous alluvial soils from Bihar and Rajasthan (Table 6). In alluvial soils from Indo-gangetic plains, available K was larger in surface layer (0-20 cm) as compared to lower layers (20-40 and 40-60 cm), whereas the reserve K showed a definite increase with depth. In swell shrink soils, both available K and reserve K contents decreased with depth. Except in red soils of Vijayapura, in red and lateritic soils, available K decreased with depth. Reserve K increased with depth in red soils while it decreased in lateritic soils. Sekhon et al. (1994) studied the vertical distribution of potassium in the Jodhpur Samana and Gahri Bhagi soils of district Bathinda. Although these soils have generally sufficient K, there is a progressive decline with depth in the amount of water-soluble and exchangeable K.

Table 6. Distribution of availableand reserve K in the different depths of selected soils Depth (cm) 1) Soil Series NH 4OAc K (mg kg-') HN0 3 K (mg kg- 0-20 20-40 40-60 0-20 20-40 40-60 Alluvial soil Rarha 88 82 83 1113 1293 1447 Swell shrink soil Pemberty 268 247 176 840 750 600 Red soil Vijayapura 29 36 53 110 116 135 Source: Subba Rao and Sekhon, 1990

When subsoil contains very little available K, the plant will have to rely largely on fertiliser K added in the plough zone. If subsoil is high in K, only enough fertiliser K to start plant growth may be necessary. Workers in some states in USA, subsoils of major soil series in respect of levels of P and K have been characterized and adjusted their recommendations accordingly. There is an urgent need to take up such studies in India. Assessing Potassium Availability in Indian Soils 139

3.4 Inclusion of non-exchangeable K in soil test calibration

Recommendations of K fertilizer are done based on available (neutral IM NH 4 OAc extractable) K status of soils in different soil testing laboratories in India. However, recent studies employing a variety of measures of non- exchangeable K indicated a very substantial contribution of non-exchangeable fraction of soil K to crop K uptake.

3.4.1 Relationship of non-exchangeable K release with K uptake

The K release from 30 soil samples of East Kashi hills of Meghalaya was assessed by exhaustive cropping, successive extractions with 0.01M HCI and boiling IM HNO 3. The level of exchangeable K decreased by 13.2 to 80.0 per cent after five croppings of maize and finger-millet. The removal by the first two crops almost accounted for the loss of exchangeable K and the remaining three removed the K from non-exchangeable form. Both exchangeable and released non-exchangeable K were significantly correlated with K uptake and dry matter yield. The maximum amount of K, which could, be released by successive extraction with 0.01M HCI, was highly correlated with K uptake by the plants (Ram and Prasad, 1983).

Nath and Dey (1982) observed that the K intensity values of three alluvial soils under exhaustive cropping with rye-grass decreased progressively during the initial cropping period whereas dry matter yield, K uptake and K concentration in harvested material increased. Thereafter the intensity values tended to increase to their original levels for a period when dry matter yield, K uptake and K concentration of harvests decreased gradually. During the later cropping period, these parameters declined slightly until soils reached exhaustion levels. The estimated uptake of non-exchangeable K during exhaustive cropping varied between 0.9 and 2.74 me K/100 g soil. The lowest and highest uptake coinciding with the shortest and largest periods of cropping at which exhaustion signs were exhibited.

Subba Rao et al. (1983) studied the K release pattern in eight representative soil groups by repeated extractions of soils for five times with 0.01M CaC 2 and IM NH 4OAc at 24 hour intervals. The K supplying power of the soils was evaluated in a green house experiment by raising five crops in succession each for a duration of 30-35 days on the same soils. Correlation study revealed that constant rate K obtained with 0.01M CaCI2 had significant positive relationship with K uptake by the fifth crop. Subba Rao et al. (1986) evaluated parameters influencing K availability in seven representative soils of Andhra Pradesh by taking eight crops of 30-35 days duration continuously in a green-house. Of the various extractable forms of K, IM NH 4OAc extractable K bore significant positive relationship with K uptake by the eight crops. Among potassium parameters, K extracted by IM HNO 3 methods had a positive relationship with K uptake by the eighth crop. 140 A. Subba Rao, T.R. Rupa and S.Srivastava

Sachdev and Khera (1980) reported substantial contribution of non- exchangeable K to crop nutrition in illite-dominant alluvial soils to the extent of 80-90%. In a field experiment, Talukdar and Khera (1991) showed that if only contribution from surface soils (0-15 cm) was taken into account the contribution of non-exchangeable K in plant K uptake by maize and bajra crops varied from 77.5-88.9% whereas if the contribution from 60 cm of soil was included, the non-exchangeable K contribution came down to the range of 54-76%. However when the same soil was employed in a green house study, the contribution extended to 89% in both maize and bajra. The contribution of non-exchangeable K from eight illitic soils during 245 days of exhaustive cropping with sudan grass was 70% in first harvest (during initial 35 days) and it reached the highest level of 90% between 2nd and 4th harvests when exchangeable K attained minimal level (Figure 2). After reaching the minimal level of exchangeable K, the pattern of crop K uptake and release of non-exchangeable K was almost identical (Srinivasa Rao et al., 1994).

Krishna Kumari et al. (1984) reported that wheat crop utilised about 86% of the total K uptake from non-exchangeable source. But this contribution was negligible when K fertilizer was applied. At higher levels of K application, there was a build up in the non-exchangeable K. In the case of pearimillet, when no K was applied, the crop utilized about 95% of the K from non-exchangeable source and it decreased to 59% at 53.5 mg K kg -' soil and to 13 and 22% at 107 - and 160.5 mg K kg ' levels, respectively. The non-exchangeable K utilized by the rice plant grown in pots in the green house ranged from 40.8 to 95.2% under

Is[ Nonexchangeable K 120 j Exchangeable K 100

o 80 f 60 C o 40 20

0

Soil series

Figure 2. Relative contribution of non-exchangeable K towards total K uptake by plants from different soil series during 245 days of exhaustive cropping in green house Assessing Potassium Availability in Indian Soils 141

exhaustive cropping and when K fertilizer was applied the K utilized by rice from non-exchangeable source was found reduced (Ramanathan, 1977). To an alfalfa crop when more potassium was applied through fertilizers less potassium was released from non-exchangeable source. At higher rates of applied K, it was fixed instead of releasing (McLean, 1978).

Change in non-exchangeable K of soils under cropping has been observed in many long-term experiments irrespective of the available K status and doninant minerals of soils. Ten cycles of maize-wheat cropping on alluvial soil at Ludhiana substaintially reduced the non-exchangeable.K espectially under higher level of N and P application whereas application of 100 kg K/ha decreased the extent of change in non-exchangeable K (Ganeshamurthy, 1983). Studies also showed that contribution of non-excheangeable K to crop removal decreased with increase in the level of applied K in wheat-sorghum (fodder) system on an alluvial soil (Subba Rao et al., 1993). Similar trend of reduction in non-exchangeable K under long-term cropping of finger millet-maize-cowpea system sequence was observed in Vertic Inceptisol at Coimbatore (Santhy et al., 1998) and under soybean-wheat-cowpea systm at Jabalpur (Bansal and Jain, 1988). In both the cases reductions were of larger magnitude in the absence of K supply (NP treatment) as compared to 100% NPK+FYM treatment. Non-exchangeable K release rate constants of an Inceptisol at Hyderabad as influced by 14 years of rice-rice cropping, fertilization and manuring indicated considerable decrease in non-exchangeable K release due to cropping (Srinivasa Rao et al., 2000a).

The literature cited above clearly brought out that especially in soils containing good amounts of micaceous minerals, the non-exchangeable content of the soils should duly be taken into account while recommending K fertilizer rates. The fertilizer rates to be applied get reduced in proportion to the amount of non-exchangeable K in micaceous minerals.

3.4.2 Soil test calibration based on non-exchangeable K

Studies on soil test calibration, interpretation and fertilizer recommendations based on boiling nitric acid or other measures of non-exchangeable K are very limited. The non-exchangeable K reserves, can be used as a measure to compare soils with respect to their capacity to supply K to crops. Categorization of soils based on non-exchangeable K reserves aid in making correct fertilizer recommendations for different crops/cropping systems. Subba Rao et al. (1993) categorized the 21 surface soils of well-defined soil series of India developed on a variety of parent materials on the basis of non-exchangeable K reserves.

To categorize non-exchangeable K reserves, parameters of reserve K and K release rate, which showed very good positive relationships with non- exchangeable K, were chosen as the primary determinant and the other indices were compared against this. The soils were categorised into very low, low, 142 A. Subba Rao, T.R. Rupa and S. Srivastava medium, high, and very high using <150, 151-300, 301-600, 601-1200 and >1200 mg kg-' K respectively, of nonexchangeable K as limits (Table 7). Nonexchangeable K reserves were higher in illite-rich soils followed by smectitic soils, while kaolinitic soils contained smaller amounts. Non-exchangeable K reserves place kaolinite dominant red, lateritic and acidic alluvial soils with coarse or fine texture in the very low category. Red soils and acidic alluvial soils with considerable amount of mica may fall in the category of low. Smectite-rich soils are essentially medium in their reserve K. A few soils with appreciable amounts of illite were placed in the high to very high categories. Except coarse textured soil of Lukhi and acidic alluvial soil of Bagru, all the other illitic alluvial soils with medium to fine texture were high to very high in their K reserves.

The categorization of soils into classes makes the soils more homogeneous in their K release for plant uptake. Fertilizer recommendations formulated on the basis of soil test calibration and crop response studies carried out on soils

Table 7. Categorizatin of soils on the basis of non-exchangeable K status of soils Category Non- exhangeable K (mg kg-') Soil series Description Very low < 150 Balisahi Kaolinite dominant red, Kharbona lateritic and acidic alluvial Vijayapura soils with coarse or Nedumangad fine texture Kumbhave-5 Low 151-300 Tyamagondalu Red soils and acidic alluvial Bagru soils with considerable amount of mica Medium 301-600 Pithvajal Smectite-rich swell- Kamliakheri shrink soils and coarse Sarol textured alluvial soils Pemberty Lukhi High 601-1200 Doddabhavi Smectite soils with Shendvada appreciable amounts of Kalathur illite and illitic-alluvial soils Nabha Masitawali Very high > 1200 Rarha Medium to fine illitic Khatki alluvial soils and smectite Noyyal soils with high mica or illite Source: Subba Rao et al., 1993 Assessing Potassium Availability in Indian Soils 143 classified using non-exchangeable K could be extended to other areas for advisory purposes. Soil test calibration studies for K need to be conducted on each category of soils having similar mineralogy and K supplying power to provide for better K recommendations. Methods for boiling soil-acid suspension were recently evaluated (Srinivasa Rao et al. 2000b) and showed that boiling on hot plate was better than on heating mantle and burner.

3.5 Critical limits of K for diagnostic purposes

Usually soils analyzing less than 120 kg ha-' of NH4 OAc extractable K (144 kg K20) are rated low in available K, between 120 and 280 kg ha - 1 K (144-336 kg K20) medium and above 280 kg ha-' (336 kg K20) as high in available K (Muhr et al., 1965). Unfortunately, these rating limits are irrespective of crops or soils. For delineation of fertility status and to isolate responsive soils from non-responsive ones, critical limits for different crops in soils of various agro- ecological regions are needed. Table 8 and Table 9 provide critical limits of available K in different crops on some well-defined soils of the country.

Table 8. Critical levels of available (NH4OAc) K in different soils for different crops Crop Soil and state Critical Reference level (mg kg- ') Rice Medium black soil (A.P.) 100 Venkatasubbaiah et al. (1976 Red soils (A.P.) Dubba & Chalka 75 Subba Rao et al. (1976) Light soils of Kodad (A.P.) 67.5 Venkatasubbaiah et al. (1991 Alluvial soils (A.P.) 190 Subramanyeswara Rao and Rajagopal (1981) Rarha series, alluvial soil (U.P.) 117 Tiwari (1985) Uttari series, alluvial soils (U.P.) 120 Tiwari et al. (1995) Calcareous soils (Bihar) 58 Sinha (1985) Phondaghat series, lateritic soils 76 Sutar et al. (1992) (Maharashtra) Udic Ustochrepts, Uttari series 110 Tiwari et al. (1999) (U.P.) Lateritic soils, Kumbhave series 86.6 Kale and Chavan (1996) (Maharashtra) Fluventic Ustochrept (Orissa) 64 Panda and Panda (1993) Khatki series Typic Haplustalf Sharma et al. (1995) (Uttar Pradesh) Belar series, Vertic Haplaquept 71 Ghosh and Mukhopadhyay (West Bengal) (1996) Bankati series, Aeric Ochraqualf 50 Ghosh and Mukhopadhyay (West Bengal) (1996) 144 A. Subba Rao, TR. Rupa and S. Srivastava

Table 8. (Contd.) Crop Soil and state Critical Reference level 1 -__ _(mg kg- ) Wheat Uttari series, Typic Ustochrepts 100 Tiwari et al. (1995) (Uttar Pradesh) Rarha series, alluvial soil (U.P.) 95 Tiwari (1987) Jagdishpur Bagha, calcareous 60 Prasad (1990) soil (Bihar) Umendanda soil series (Bihar) 50 Roy (1987) Puto series, Alfisol (Bihar) 48 Roy et al (1989) Khatki series, Typic Haplustalf 71 Sharma et al. (1995) (Uttar Pradesh) Maize Haplustalfs, Rajasthan 47 Yadav and Swami (1984) Valuthalakudi series 71 Jeyabaskaran and (Tamil Nadu) Raghupathy (1993) Jagdishpur Bagha, calcareous 81 Prasad and Prasad (1995) soil (Bihar) Sor- Islamnagar series 3 & 4 240 Srinivasa Rao and Takkar ghum (M.P.) (1997) Typic Chromusterts 335 Akolkar and Sonar (1994) (Maharashtra) Pearl Medium black soil (A.P.) 95 Venkatasubbaiah et al. (1976) millet Black calcareous soils (Gujarat) 60 Meisheri et al. (1995) Alluvial soils (A.P.) 160 Sailakshmiswari (1984) Ground- Light soils of Kodad (A.P.) 60 Subramanyeswara Rao and nut Rajagopal (1981) Black calcareous soils (Gujarat) 65 Golakiya (1999) Potato Submontane soils (H.P.) 120 Grewal and Sharma (1980) Cotton Tulewal and Samana series, Sidhu and Brar (1989) alluvial soils (Punjab) 50 Chick- Rarha series, alluvial soil (U.P.) 137 Tiwari (1985) pea Uttari series, 105 Tiwari et al. (1996) Typic Ustochrepts (U.P.)

The data show a great diversity in the critical limits ranging from 48 for an Alfisol to 335 mg kg-' for a Vertisol. It is also seen that there is lack of sufficient information on critical limits for K on Vertisols for important crops. Solankey et al. (1992) studied the response of two wheat varieties to potassium on farmer's fields in swell-shrink soils. Though these soils were adequate in ammonium acetate soluble K, crop responded to 30 kg ha-' K20. They have established a critical limit of 14.4 kg ha -t' K water-soluble K but failed to establish a critical limit based on ammonium acetate K. Gajbhiye et al. (1993), using cotton, sorghum Assessing Potassium Availability in Indian Soils 145

Table 9. Critical levels for non-exchangeable (IM HN0 3) K in different soils and crops Crop Soil and State Critical Reference level (mg kg-') Rice Uttari series, 1275 Tiwari et al. (1995) Udic Ustochrepts (U.P.) Khatki series, 960 Sharma et al.(1995) Typic Haplustalf (U.P.) Jagdishpur Bagha, 1600 Prasad and Prasad (1990) Calcareous soil (Bihar) Wheat Uttari series, 1200 Tiwari et al.(1999) Udic Ustochrepts (U.P.) Jagdishpur Bagha, 1580 Prasad (1990) Calcareous soils Maize Valuthalakudi series 326 Jeyabaskaran and Raghuparty (Tamil Nadu) (1993) Haplustalfs, Rajasthan 339 Yadav and Swami (1984) Jagdishpur Bagha, 1940 Prasad and Prasad (1995) Calcareous soils Chickpea Uttari series, 1280 Tiwari et al. (1996) Udic Ustochrepts (U.P.) I I

- of and wheat as a test crops, established a critical limit of 165 mg kg 1 soil ammonium acetate K in Vertisols. They also showed that the yield of test crops increased beyond the level of 200 mg K kg-' soil. They attributed the lack of - hunger' for K response below 200 mg kg ' NH 4OAc K to the state of 'soil (Figure 3). Akolkar and Sonar (1994), in a field experiment conducted on Ottur series (Typic Chromusterts) having ammonium acetate K from 437 to 1992 kg - for ha', established a critical limit of 750 kg K ha ' (335 mg kg-') sorghum.

The fore-mentioned three studies indicate the need for initiating more elaborate studies on Vertisols, grouped on the basis of water soluble K.or the mg kg-') to test upper limit based on NH 4OAc for the 'state of soil hunger' (200 the response of crops on Vertisols and establish calibration system for K fertilizer recommendations.

3.6 Soil test based fertillser potassium recommendations

General fertilizer recommendations result in application of excess a'mounts of fertilizer in such areas where it is not needed and insufficient amounts in 146 A. Subba Rao, TR. Rupa and S. Srivastava

100 -o--o- Cotton Sorghum 90 - Wheat 80 C-7 0o

050

t tMinimum ettaJnable 30 value olK So hunger lor K I 20 (Zero response- - of crop) 't I Crop rosponses to 1 I0V Increasing soil K

I I I1 | I -- - I 100 120 140 160 180 200 220 240 260 280 300

Available K20 (ppm)

Figure 3. Crop response curve to soil K some others areas where it is needed. Soil test based recommendations are essential to economise fertiliser use and to optimize production on a sustainable basis without polluting the environment. Among the various methods of fertiliser recommendation, the one based on yield targeting is unique in the sense that this method not only indicates soil test based fertiliser dose but also the level of yield the farmer can hope to achieve if good agronomic practices are followed in raising the crop. The essential basic data required for formulating fertiliser recommendation for targeted yield are (i) nutrient requirement in kg/q of produce, grain or other economic produce (ii) the per cent contribution from the soil available nutrients (iii) the per cent contribution from the applied fertiliser nutrients (Ramamoorthy et al., 1967).

The above mentioned three parameters are calculated as follows:

Nutrient requirement of N, P and K for grain production

kg of nutrient/q of grain = Total uptake of nutrient (kg) Grain yield (q) Assessing Potassium Availability in Indian Soils 147

Contribution of nutrient from soil (kg ha-') x 100 % Contribution from soil (CS) = Total uptake in control plots Soil test values of nutrient in control plots (kg ha-') % Contribution of nutrient from fertilizer

Contribution from (CF) Total uptake of - (Soil test values of nutrients in treated nutrients in fertiliser plots treated plots x CS)

CF % Contribution from fertiliser = Fertiliser dose (kg ha-') x 100

Calculation of fertiliser dose

The above basic data are transformed into workable adjustment equation as follows : Nutrient requirment in kg/q of grain % CS Fertiliser dose= x 100 x T - x soil test value %CF %CF

= a constant x yield target (q ha-') - b constant x soil test value (kg ha-')

Hence, the fertiliser doses can be calculated once the soil test values and yield targets are known. Such type of fertiliser recommendations are depicted in Tables 10 and 11 for rice and wheat, respectively. It can be clearly seen from the tables that the fertiliser recommendations change with the soil test values. They are also different for different soils. Similar type of soil test based fertiliser recommendations are available for many crops on different soils (Subba Rao and Srivastava, 2001).

4. FUTURE LINES OF WORK

* Soil test calibration work for potassium in general and that involving non- exchangeable K parameters in particular is very limited. So there is urgent need to calibrate soil tests for K based on non-exchangeable K under field conditions. The calibration needs to be developed employing different statistical models.

* There is a need to evaluate the multinutrient soil 'tests to save energy and cost of soil testing. 148 A. Subba Rao. TR. Rupa and S. Srivastava

Table 10. Soil test based fertiliser potassium (K 20) requirement for rice on different soils of India Target Soil test values (kg/ha) Soil Site (t/ha) 100 150 200 250 300 350 400 Acid Alfisol Kangra (H.P.) 4.5 59 25 Alluvial soil Punjab 6.0 54

Mollisol and Uttaranchal, 5.0 36 20 3 - - Inceptisol Wertern U.P. Black M.P. 5.0 * * 69 60 51 42 33

Old alluvial Bihar 4.0 50 38 26 - - - - gray light textured soil

Recent alluvial Parts of Bihar 4.0 52 33 13 - - - - non calcareous non saline Old alluvial -do-- 4.0 38 18 heavy textured Calcareous Parts of Bihar 4.0 92 72

New alluvial Parts of W.B. 3.5 60 46 32 - - - - Old alluvial -do- 4.0 45 25 6 - - - - Black Guntur (A.P.) 5.0 * * 42 33 23 11 01 Inceptisol Jagitiyal 5.0 * * 94 76 58 40 22 Sandy clay loam Nellore 5.0 * * 55 45 35 25 15 (alluvial) Black soil Nandyal 6.0 * * 50 44 38 32 26 Red/alkaline Parts of 4.0 75 70 65 60 55 50 45 Karnataka Black clayey Bellary, 4.0 90 88 86 84 82 80 78 Raichur districts of Karnataka Alluvial (alfisol) Coimbatore 6.0 * * 68 49 33 17 01 Red Parts of TN 6.0 * * 69 39 10 0 0 (Irugur series) Black Parts of TN 7.0 * * 91 71 51 31 11 (Adanur series) Source: Subba Rao and Srivastava, 2001 • Means the soils of this region do not have these soil test values - Means no fertiliser K requirement Assessing Potassium Availability in Indian Soils 149

Table 11. Soil test based fertilizer potassium (K20) requirement for targeted yield of 3.5 i/ha of wheat on different soils of India Soil test values (kg/ha) Soil Site 100 150 200 250 300 350 400

Acid Alfisols M. P. 66 57 47 38 --- Neutral Inceptisol -do--- 52 38 24 10 --- Acid alluvialfInceptisol -do-- 107 85 64 42 --- Alluvial/Inceptisol Delhi 49 33 17 ---- Mollisol/inceptisol Uttaranchal 47 Wetern U. P. Typic Chromusterts Maharashtra * * 33 21 09 - Black (Vertisols) M.p. * 57 49 41 33 25 Source: Subba Rao and Srivastava, 2001 * Means the soils of this region do not have these soil test values - Means no fertiliser K requirement

Soil test based fertiliser recommendations for K need to be developed for different crops, cropping systems on diverse soils. The recommendations should be site specific and crop/cropping system specific.

There is need for generating K recommendations on soil test basis for dryland crops as K has beneficial role in efficient utilization of water and survival of the crop under limited moisture conditions.

It is also desired to generate integrated K recommendations involving soil supply (non-exchangeable K, subsoil K), fertilizer K and manure K.

REFERENCES Akolkar, R.D. and Sonar, K.R. (1994). Calibration of soil test methods for available potassium in Vertisols for sorghum. Journal of Potassium Research 10: 63-67. Ananthanarayana, R., Raghavendra Rao, K. and Mithyantha, M.S. (1989). A

common extractant for determination of available P20, and K20 in the acid soils of Karnataka. Journal of Indian Society of Soil Science 37: 66-69. Beegle, D.B. and Baker, D.E. (1987). Different potassium buffer behaviour of individual soils related to potassium corrective treatments. Communications in Soil Science and Plant Analysis 18: 371-385. Bhadoria, U.P.S., Bansal, K.N. and Singh, D. (1986). Screening of soil test methods for potassium in some alluvial soils of Madhya Pradesh. Journalof Potassium Research 2: 24-30. 150 A. Subba Rao, TR. Rupa and S. Srivastava

Black, C.A. (1965). Methods of Soil Analysis. Americal Society of Agronomy, Inc. Publ., Madison, Wisconsin, USA. Conyers, E.S. and McLean, E.O. (1969). Plant uptake and chemical extractions for evaluating potassium release characteristics of soils. Proceedings of Soil Science Society of America. 33: 226-230. De Turk, E.E., Wood, L.K. and Bray, R.H. (1943). Potash fixation in corn-belt soils. Soil Science 55: 1-12. Dyer, B. (1894). On the analytical determination of probably available mineral plant food in soil. Journal of Chemical Society 65: 115-167. Gajbhiye, K.S., Gaikawad, S.T., Seghal, J.L., Bhaskar, K.S. and Gupta, R. (1993). Studies of available potassium and crop response in soils of Sawangi watershed in Vertisol region of Vidarbha. Journal of potassium Research 9: 233-240. Ganeshamurthy, A.N. (1983). An estimate of the uptake of subsurface soil potassium by crops in two long term experiments. Journal of Agricultural Sciences, Cambridge. 101: 495-497. Ganeshamurthy, A.N. and Biswas, C.R. (1984). Movement of potassium in an Ustochrept soil profile in a long term fertiliser experiment. Journal of Agricultural Sciences, Cambridge. 102: 393-397. Ghosh, B.N. and Mukhopadhyay, A.K. (1996). Critical limit of potassium in rice plant in Belar and Bankati series of West Bengal. Journal of Indian Sociery of Soil Science 44: 286-289. Golakiya, B.A. (1999). Potassium fertilization of groundnut in Saurashtra region, India. Proceedings of workshop C oreganized by the International Potash Institute at the 16th World Congress of Soil Science, Montpellier, France, 20-26 August 1998. Grewal, J.S. and Sharma, R.C. (1980). Evaluation of soil test methods for potassium in acidic brown hills soils for recommending fertiliser doses for potatoes. Journal of Indian Society of Soil Science 28: 355-360. Grimme, H. (1974). Potassium release in relation to crop production. Proceedings of 10th Congress, International Potash Institute, Bern pp. 1 3 1-136. Grimme, H. and Nemeth, K. (1976). Beziehungen zwischen K (CaC 2) Gehalten im Boden und dem Ertrag im Gefass-Kleinparzellen-und Feldversuch, Landw. Forsch. 29: 13-20. Grimme, H. and Nemeth, K.I. (1978). The evaluation of soil K status by means of soil testing. Proceedings of l1th Congress, International Potash Institute, Bern pp. 99-108. Hanway, J. and Heidel, H. (1952). Soil Analysis Methods as used in Iowa State College Soil Testing Laboratory. Iowa State College of Agriculture Bulletin 57: 1-13. Assessing Potassium Availability in Indian Soils 151

Hanway, J.i., Barbar, S.A., Bray, R.W., Caldwell, A.C., Fried, M., Kurtz, L.T., Lwatron, K., Pesek, J.J., Pretty, K., Reed, M. and Smith, F.W. (1962) North Central Regional Potassium Studies. Ill. Field Studies with Corn. North Central Regional Publication No.35. Iowa Agriculture and Home Economics Experiment Station Research Bulletin 503. Iowa State University, Ames., Iowa, U.S.A. Haylock, O.F. (1956) A method for estimating the availability of nonexchangeable potassium. Proceedings of the 6th International Congress of Soil Science, Part B: 402-408. Hunter, A.H. and Pratt, P.F. (1957) Extraction of potassium from soil by sulphuric acid. Soil Science Society of America Procedings 21:. 595-598. Hunter, A.H.(1972) Technical Report North Carolina Aricultural Experiment Station. Jackson, M.L. (1973) Soil Chemical Analysis, Prentice Hall of India Private Limited, New Delhi. Jeyabaskaran, K.J. and Raghupathy, B.J. (1993) Critical limits of potassium for maize in Valuthalakudi series. Journal of Potassium Risearch 9: 353-359. Kale, V.B. and Chavan, A.S. (1996) Critical limit of potassium in relation to paddy yield in Kumbhave soil series of Konkan, India. Punjabrao Krishi Vidyapeeth Research Journal 20: 90-93. Kapur, M.L. and Sekhon, G.S. (1985) Rooting pattern, nutrient uptake and yield of pearl millet and cotton as affected by nutrient availability from the surface and sub-surface soil layers. Field Crops Research 10: 77-86. Krishna Kumari, M. and Khera, M.S. (1989) Relative efficacy of soil test methods for potassium to measure changes in K status to uptake, addition and release of potassium in micaceous soils. Journal of Indian Society of Soil Science 37: 495-498. Krishna Kumari, M., Khera, M.S. and Ghosh, A.B. (1984) Studies on potassium release in an Inceptisol soil (Holambi series) at the minimum level of exchangeable potassium Plant and Soil 79: 3-10 84. Liu, L and Bates, T.E. (1990) Evaluation of soil extractants for the predication of plant-available potassium in Ontario soils. Canadian Journal of Soil Science 70: 607-613. MacLean, A.J. (1961) Potassium supplying power of some Canadian soils. Canadian Journal of Soil Science 41: 196-206. MacDonald, G.E., Rock, N.H. and Vittum, M.T. (1978) Communications in Soil Sciuence and Plant Analysis. Maharana, D.P. Mukherjee, S.N., Mutatkar. V.N. and Dhua, S.P. (1976) Soil test crop response correlation for potassium on rice growing soils in old alluvial tracts of Bihar. Bulletin of the Indian Society of Soil Science 10: 293-298. 152 A. Subba Rao, TR. Rupa and S.Srivastava

McLean, E.O. (1978) Influence of clay composition on potassium availability. In: Potassium in Soils and Crops, Potash Research Institute, India pp. 1-19. McLean, E.O. and Watson, M.E. (1985) Measurments of plant-available potassium. In: Potassium in Agriculture (Ed. R. D. Munson), Madison, USA, pp. 277-308.

Mehlich, A. (1953) Determination of P, Ca, Mg, K, Na and NH 4. In: Handbook of Reference Methods for Soil Testing. The Council on Soil Testing and Plant Analysis, 1974. Mehlich, A. (1984) Mehlich 3 soil test extractant: A modification of Mehlich 2 extractant. Communications in Soil Science and Plant Analysis 15: 1409- 1416. Meisheri, M.B., Hadvani, G.J., Talavia, B.P. and Shiroya, M.K. (1995) Potassium response and its critical limit for pearl millet in calcareous soils. Gujarat Agricultural University Research Journal 21: 41-46. Michaelson, G.J., Ping, C.L. and Mitchell, G.A. (1987) Correlation of Mehlich 3, Bray I and ammonium acetate extractable P, K, Ca, and Mg for Alaska agricultural soils. Comminications in Soil Science and Plant Analysis 18: 1003-1015. Morgan, M.F. (1941) an improved universal extracting solution and its use for diagnositic soil fertility. Bulletin Connecticuf Ariculture Experiment Station, 450. Muhr, G.R., Datta, N.P., Sankarasubramany, H., Dever, R.P., Leley, V.K. and Donahue, R.L. (1965) Soil Testing in India, United States Agency for International Development Mission in India, New Delhi pp. 120. Nath, A.K. and Purkaystha (1988) A study on soil test and crop response in respect of potassium in acid alluvial soils of Assam. Journal of Indian Society of Soil Science 36: 120-124. Nath, A.K. and Dey, S.K. (1982) Studies on K-releasing pattern in various textural types of alluvial soils of Assam by the exhaustive cropping. Journal of Indian Society of Soil Science 30: 291-295. Nemeth, K. (1976) The determination of effictive and potential availability of nutrients in the soil by electro-ultrafilatration. Applied Science Development 8: 89-111. Nemeth, K. (1979) The availability of nutrients in the soils as determined by electro ultra filtration (EUF). Advances in Agronomy 32: 155-187. Nemeth, K. (1985) Recent advances in EUF research (1980-1983). Plant and Soil 83: 1-19. Olsen, S.R., Cole, CV., Watanabe, F.S. and Dean, L.A. (1954) Estimation of available phosphorus extractable. Nature (London) 213: 418-419. Assessing Potassium Availability in Indian Soils 153

Oommen. P.K. (1962) Correlation between soil test values for potassium crop responses to potassic fertilizers by paddy and wheat in Indian soils. Journal of Indian Society of Soil Science 10: 155-159, Panda, M. and Panda, A.K. (1993) Evaluation of some potassium soil tests for rice in a Fluventic Ustochrept. Journal of Indian Society of Soil Science 41: 188-189. Patiram, Rai, R.N. and Prasad, R.N. (1989) Suitability of extractants for available K to maize in the acid soils of Sikkim. Journal of the Indian Society of Soil Science 37: 841-843. Peech, M., Alexander, L.T., Dean, L.A. and Reed, J.F., (1947) Circ USDA., 757.. Prabha Kumari, P. and Aiyer. R.S. (1993) Soil test and crop response studies for potassium in laterite/red loam soils of Kerala. Journalof Potassium Research 9: 62-65. Prasad, B. (1990) Availability and critical limits of potassium in wheat and Jadishpur Bagha soil series (calciorthents) of Bihar. Journal of Potassium Research 6: 96-105. Prasad, B.and Prasad, C.R. (1990) Critical limits of soil K for rice in Jagdishpur Bagha soil series. Annual Report, Potash Research Institute of India, Gurgaon (Haryana) for the year 1989-90, pp. 30. Prasad, B. and Prasad, J. (1995) Critical limits of potassium for winter maize in calcareous soils. Journal of Potassium Research 11: 319-326. Quemener, J.(1979) The measurement of soil potassium. Research Topics No. 4. International Potash Institute, Bern, Switzerland. Ram, P. and Prasad, R.N. (1983) Yield response to fertiliser potassium and balance sheet of potassium in a potato-rice crop sequence. Journal of the Indian Society of Soil Science 31: 512-515. Ramamathan, K.M. and Krishnamurthy, K.K. (1981) An appraisal of potassium availability indices in soils of Tamil Nadu. Journal of Indian Society of Soil Science 29: 477-480. Ramamoorthy, B., Narsimham, R.L. and Dinesh, R.S. (1967) Fertiliser application for specific yield target of Sonara-64. Indian Farming 1: 43-45. Ramanathan, K. (1977) Studies on dynamics of soil potassim. Ph.D. Thesis, Tamil Nadu Agricultural University, Coimbatore (1977). Roy, H.K., Kumar, A. and Sarkar, A.K. (1989) Critical limits of potassium in soil and plant and response of wheat in soils of puto series (Alfisol) of Ranchi. Journal of Potassium Research 5: 157-163. Roy, H.K. (1987) Soil and fertiliser potassium in relation to crop growth. Potash Research Institute of India Annual Report 1986-87, Gurgaon, India.. 154 A. Subba Rao, Tit. Rupa and S. Srivastava

Sachdev, C.B. and Khera, M.S. (1980) Utilization of potassium from non- exchangeable sources in soil under intensive wheat-bajra cropping system. FertiliserNews 25: 6-10. Sailakshmiswari, Y. 1984. Evaluation of various quantity and intensity parameters of potassium availability in texturally different alluvial soils. M.Sc. (Ag) Thesis, Andhra Pradesh Agricultural University, Hydrabad. Santhy P., Sankar, S.J., Muthuvel, P. and Selvi, D. (1998) Long term fertiliser experiments - Status of N, P and K fractions in soil. Journal of Indian Society of Soil Science 46: 395-398. Schachtschabel, P. and Heinemann, C.G.. (1974) Beziehungen Zwischen den Kaliumgehalten in Boden und in Jungen Haferpflanzen. Z. Pflanzenernahr. Bodenk. 137: 123-134. Schulte, E.E. and Corey, R.B. (1965) Extraction of potassium from soils with sodium tetraphenylboron. Soil Science Society of America Proceedings 29: 33-35. (s4

Sekhon, G.S., Bhangu, S.S., and Sidhu, P.S. (1994) Contribution of subsoil to potassium nutrition of cotton. I. Vertical distribution of potassium in two soils of Bathinda. Journal of Potassium Research 10: 343-349. Sekhon, G.S., Brar, M.S. and Subba Rao, A. (1992) Potassium in some banchmark soils of India. Potash Research Institute of India, Gurgaon, Haryana, India. pp. 1-82. Sharma, R.D., Sikander, A. and Ali, S. (1995) Potassium critical limit and response to rice and wheat in Khatki soil series of Uttar Pradesh. Journal of Potassium Research. 11: 143-153. Sidhu, P.S. and Brar, M.S. (1989) Native soil potassium and crop response to potassium. Potash Research Institute of India Annual Report 1988-89, Gurgaon, India. pp. 30-33. Simard, R.R. and Deschenes, M. (1992) Strontium chloride-citric acid extraction procedure for agricultural and environmental purposes. Communications in Soil Science and Plant Analysis 23: 2207-2223. Simard, R.R. and Zizka, J. (1994) Evaluation of plant-available potassium with strontium citrate. Communications in Soil Science and Plant Analysis 22: 1779-1789. Singh, D. And Ghosh, A.B. (1982) Evaluation of some soil test methods for estimation of plant utilizable potassium in soils. FertiliserNews 27: 38-42. Sinha, M.K. (1985) Response of crops in the recommended and locally practised cropping systems in selected soil associations differing in mineralogy, physical and chemical properties. In: Annual Report PRII, Gurgaon (Haryana) for the year 1984-85, pp. 35-36. Assessing Potassium Availability in Indian Soils 155

Solankey, B.S., Shinde, D.A., Yadav, K.S. and Singh, J.(1992) Response of wheat to K application in swell-shrink soils in relation to water-soluble K contents. Journal of Potassium Research 8: 328-333. Soltanpour, P.N. and Schwab, A.P. (1977) A new soil test for simultaneous extraction of macro and micro nutrients in alkaline soils. Communications in Soil Science and Plant Analysis 8: 195-207. Sparks, D.L. and Huang. P.M. (1985) The physical chemistry of soil potassium. In: Potassium in Agriculture (Ed. R.D. Munson), American Society of Agronomy, Madison, Wisconsin, pp. 201-276. Srinivasa Rao, Ch. and Khera, M.S. and Subba Rao, A. (1994) Soil potassium depletion and K replenishment capacity under intensive cropping. A. Journal of Potassium Research 10: 229-235. Srinivasa Rao, Ch. and Takkar, P.N. (1997) Evaluation of different extractants for measuring the soil potassium and determination of critical levels for plant-available K in smectitic soils for sorghum. Journalof the Indian Society of Soil Science 45: 113-119. Srinivasa Rao, Ch., Rupa, T.R. and Subba Rao, A. (2001) Subsoil potassium availability in 22 benchmark soils of India. Communications in Soil Science and Plant Analysis (in press). Srinivasa Rao, Ch., Subba Rao, A. and Ganeshamurthy. A. N. (1995) Status and release kinetics of potassium in swell-shrink soils of Islamnagar series. Journal of Indian Society of Soil Science 43: 356-360. Srinivasa Rao, Ch., Subba Rao, A., Swarup, A., Bansal, S.K. and Rajagopal, V. (2000a). Monitoring the changes in soil potassium by extraction procedures and electroultrafiltration (EUF) in a Tropaquept under twenty years of rice- rice cropping. Nutrient Cycling in Agroecosystems 56: 277-282. Srinivasa Rao, Ch., Subba Rao, A.and Singh, S.P. (2000b) Extraction of nonexchangeable potassium from soils with boiling one molar nitric acid: Evaluation of different modes of boiling the soil-acid suspension. Communications in Soil Science and Plant Analysis 31: 905-911. Subba Rao A., Bhonsle, N. S., Singh M. and Mishra, M. K. (1993) Optimum and high rate of fertiliser and farmyard manure application on wheat and sorghum (fodder)yields and dynamics of potassium in an alluvial soil. Journal of Potassium Research 9: 22-30 Subba Rao, A. and Ghosh, A.B. (1983) Available potassium content in soil under intensive fertiliser use as revealed by some soil tests. The Madras Agricultural Journal 70: 24-27. Subba Rao, A. And Sekhon, G.S. (1990) Pattern of distribution of potassium in different soils in relation to depth of sampling for fertility investigations. Journal of Potassium Research 6: 43-50. 156 A. Subba Rao, TR. Rupa and S. Srivastava

Subba Rao, A. and Srivastava, S. (2001) Soil Test Based Fertiliser Recommendations For Targetted Yields of Crops. Indian Institute of Soil Science, Bhopal, India. Subba Rao, A., Brar, M.S. and Sekhon, G.S. (1988) Desorption pattern of potassium from five soil series developed on different parent materials. Journal of Indian Society of Soil Science 36: 239-245. Subba Rao, A., Krishna Kumari, G., Adinarayana, V. And Pillai, R.N. (1983). Long term potassium supplying power of soils of Andhra Pradesh. Indian Potash Journal 8: 2-7. Subba Rao, A., Krishna Kumari, G., Satyanarayana P.H. and Gopichand, S. (1986) Evaluation of parameters influencing potassium availability in representative soils of Andhra Pradesh. The Andhra Agricultural Journal 33: 106-110. Subba Rao, A., Sesha Sai., M.V.R. and Pal, S.K. (1993) Nonexchangeable K reserves and their categorisation in some soils of India. Journal of Indian Society of Soil Science 41: 667-673. Subba Rao, I.V., Venkateswarlu, J., Seetharama Rao, V., Srinivasa Raju, A. and Nishat Mukhlis (1976) Potassium fertilization in Pochampad project area. Potassium in soils, crop and fertilizers, Indian Society of Soil Science, Bulletin No. 10, New Delhi, pp1 9 5-19 9 . Subramaneyeswara Rao, A. and Rajagopal, V. (1981) The Andhra Agricultural Journal 28: 200. Surekha, K., Subba Rao, I.V. and Shantaram, M.V. (1997) Comparison of different indices of potassium availability for Vertisols of Andhra Pradesh. Journalof Potassium Research 13: 123-130. Sutar, V.S., Dongale, J.H. and Chavan, A.S. (1992) Forms of potassium and evaluation of soil K test methods along with critical limits of K in leteritic soils. Journal of Potassium Research 8: 187-199. Talukdar, M.C. and Khera, M.S. (1991) Contribution of surface and subsurface soil potassium to maize and bajra crop production. Journal of Potassium Research 7: 214-220. Talukdar, M.C. and Khera, M.S. (1996) Screening soil tests for wheat grown on potassium depleted Ustochrepts. Journal of Potassium Research 12: 146- 151. Tamhane, R.V. and Subbiah, B.V. (1962) Correlation of soil tests with pot and field trials in the evaluation of soil fertility. Soil Science and Plant.Nutrition 8: 97-106. Tiwari, A. Tiwari, K.N. and Mishra, S.G. (1995) Soil test methods and critical limits of potassium in soil and plants for wheat grown in 'lhpic Ustocrepts. Journal of the Indian Society of Soil Science 43: 408-413. Assessing Potassium Availability in Indian Soils 157

Tiwari, A. Tiwari, K.N. and Mishra, S.G. (1999) Compairison of soil test methods and potassium critical limits for rice in Udic Ustochrepts of Kanpur: Uttari series. Journal of Potassium Research 15: 75-82. Tiwari, K.N. (1985) Changes in potassium status of alluvial soils under intensive cropping. Fertilizer News 30: 17-23. Tiwari, K.N. and Dcv, G. (1987) Potassium availability in soils growing wheat. Potash Research Institute of India, Gurgaon, India. Research Review Series. 4: 29-44. Tiwari. A., Misra, S.G. J. and Tiwari, R. (1996) Calibration of soil test methods and assessment of critical limits of potassium I n soils and plants of chickpea. Journal of Indian Society of Soil Science 43: 408-413. Truog, E. (1937) Availability of essential soil elements - a relative matter. Soil Science Society of America Proceedings 1: 135-142. Venkatasubbaiah, V., Sreenivasa Raju, A. Badrinarayana Rao, M. Geoffrey, T.P., Nageswara Rao, L. and Bhaskara Rao, B.R. (1991) Paper presented in Seminar on potassium held in Nov. 91 at Hyderabad. Venkatasubbaiah, V.,Venkateswarlu, J. and Sastry, V.V.K. (1976) Potassium supplying power of black soils of West Godavari, Andhra Pradesh. Potassium in soils, crops and fertilizers, Indian Society of Soil Science, Bulletin No. 10, New Delhi. 219-226. Verma, T.S. , Bhagat, R. M. and Kanwar, K. (1994) Evaluation of chemical methods for the determination of available potassium in waterlogged soils. I. Potassium availability indices in relation to potassium fractions. Journal of Potassium Research 10: 12-22. Wolf, B. (1982) An improved universal extracting solution and its use for diagnosing soil fertility. Communications in Soil Science and. Plant Analysis 13: 1005-1033. Wood, L.H., and DeTurk, E.E. (1940) The absorption of potassium in soils in non-exchangeable forms. Proceedings of the Soil Science Society of America 5: 152-161. Woodruff. C.F. and Mc Intosh, J.L. (1960) Testing soil for potassium. Transactions 7th International Congress Soil Science Madison. III: 80-95. Yadav, B.S. and Swami, B.N. (1984) Critical limits of soil potassium for maize crop in red soils (Haplustalfs) of Dungarpur district of Rajasthan. Proceedings of International Symposium on Soil Test Crop Response Correlation Studies, Dhaka, Bangladesh, pp. 84-96. Zhu, Y.G. and Leo, J.X. (1993) Release of nonexchangeable soil K by organic acids. Pedosphere 3: 269-276 Interaction of Potassium with Other Nutrients

A.N. GANESHAMURTHY and CH. SRINIVASA RAO Indian Institute of Pulses Research, Kanpur-208024, Uttar Pradesh, India

ABSTRACT

The phenomenon of nutrient interactions is a common feature in crop production. Potassium owing to its diversified role in plant metabolic processes, interacts with almost all other essential plant nutrients. These interactions can either be synergistic or antagonistic and become increasingly important in farming for high yields. The interaction of K with N and P have been extensively studied, and is generally synergistic. Intensive cultivation with increased use of N and P resulted in heavy depletion of soil K. On soils which are deficient or marginal in N and K or P and K or N, P and K synergistic interaction between the two or three applied nutrients spectacularly improved their uptake and increased crop yields. The form of available N, N0 3-N and NH,-N significantly influenced the behavior of N x K interaction causing consequential changes in the relationship of absorbed Ca and Mg. No direct physiological relationship between P and K in plant system has yet been established but the synergistic interactions between the two become increasingly important in achieving high yields. Antagonistic interactions of K may occur between K and Ca or K and Mg: the three are complementary cations. Potassium application consistently reduced the absorption of Ca and Mg and indeed lowered their tissue concentrations. On soils marginal in Ca and Mg supply, yield responses to applied K tundoubtedly decreased tissue Ca and Mg because of dilution effect. 'Aplilichtion of S increased the tissue concentration of K in several crops. But there is no direct evidence of a K x S interaction in plant system except for maintaining a cation-anion balance. Although several studies have reported interaction of K with micronutrients, these are not fully characterized. By and large K application resulted in reduced uptake of Fe, B and Mo and increased the utilization of Zn, Cu and Mn. Most of these interaction studies are made in the green house. There is a need to validate the same under field conditions before drawing any meaningful conclusions for economic exploitation of these interactions.

INTERACTION

Interaction of nutrients may be stated as the effect of applying two or more nutrients together is more (synergistic) or less (antagonistic)than the sum of the individual effects of nutrients when applied alone. There is less research on 159 160 A.N. Ganeshamurthy and Ch. Srinivasa Rao interactions including K owing to the fact that nitrogen and phosphorus have occupied the center stage. Until 1930 crop yields were modest everywhere. Fertilizer use started on a large scale only after the Second World War - Phosphorus and nitrogen deficiencies first attracted attention. Though synergistic interaction of K with N and P are documented some studies indicate its positive interaction with S and micronutrients as well. The knowledge of such interactions is helpful in developing strategies for sustainable agriculture. An attempt has been made in this paper to bring in to focus the interaction of K with other nutrients. Randhawa and Pasricha (1975) reviewed the interaction of K with micronutrients.

INTERACTION OF POTASSIUM WITH MACRONUTEITNTS

Nitrogen

Nitrogen is one essential plant nutrient, which is absorbed in both cationic (NH4*) and anionic (NO 3 -) forms. This presents the unique possibility of observing both a cation-cation and a cation-anion interaction. Since, fertilizers are increasingly becoming costly the integrated management of N and K interaction assumes of special significance. The N x K interaction essentially operates at a high levels of crop productivity. Soils are well supplied with K where sizable additions through applications of available farm yard manure (FYM) and ashes, crop residues and irrigation waters usually occur and it is unusual to find large responses to K fertilizers. However, the high yields obtained now through use of N fertilizers do impose a strain on potassium supplies.

An example of N x K interaction in rice is shown in Fig. 1 (Mondal, 1982). It demonstrates that at every rate of N, application of K increased the yields: the increase was more at higher amounts of N. Further more, the N x K interaction was larger in dry season than in wet season due to favorable growing conditions, and higher yield potentials.

8 I 7 r--+- Dry Season

VweLs '153 on

V_ 2 --- 120 - 40 .2 1 80 - -- 40

0 40 80 120 160 N Applied (kg/ha) . Figure 1. Nitrogen and potassium interaction in rice in two major growing seasons in West Bengal Interaction of Potassium with Other Nutrients 161

In another set of 15 field trials on rice in Bihar, application of 20 kg K20 ha' in combination with N resulted in a mean yield increase of 300 kg ha -' over 40 kg N, 750 kg hat over 80 kg N and 910 kg ha' over 120 kg N thus clearly demonstrating the positive N x K interaction (Umar et al., 1986). This is also an example of a cation (K*)-cation (NH 4 ) interaction because in rice soils most of the N is present in NH4* form. This study indicated that K does not compete with NH 4 for selective binding sites. Ajay et al. (1970) working with tomatoes in hydroponics and Mengel et al. (1976) working with rice also concluded that K* does not compete with NH4 in the absorption process. The increase in yield with increased K in treatments allowed for rapid assimilation of absorbed NH 4 in plants maintaining a low non-toxic level of NH 3. This has led to increased uptake of N at higher levels of N resulting in increased yield (Dibb and Welch, 1976) where NH4 has reduced K concentration of plants (Raizy, 1976). The positive N x K interactions resulted from the necessity of adequate K levels with increasing N rates for metabolization of absorbed N, because K is required for metabolization of absorbed N. In Saline soils though rice responded to applied N, high levels of N (180 kg N ha -') had depressing effect on yields. However, maximum yield could be obtained at highest level of applied N with highest level of applied K (42 kg ha-I) (Anand Swarup, 1996).

In upland crops the observed N and K interaction indicates the necessity of additional K at increasing N rates which thus is a case of cation-anion (K-NO 3) interaction as NO 3 is the main form of N absorbed by plants under such situations, cassava which is not particularly responsive to N application but moderately responds to K dressing, responds to N and K when used in combination (Muthuswamy and Chiranjivi Rao, 1979).

In a long term experiment on tea at Toklai experimental station, the yields started declining after 25 years in plots receiving only N (20 kg N-') and more so with higher amounts of N (55 kg ha-'). The yield decline could be arrested when the estate was dressed with 56 kg K ha' (Fig. 2). In South Indian Tea soils, which are poor in K supplies, even a modest tealeaf yield is not possible 12

c 6 * 4 -4-N:K=I:0.6] " -i-#-N:K=1 :0.5 2 00 0 180 240 3D0 360 N Applied (kg/halear) Figure 2. Response of young tea to K at different N K ratios 162 AN. Ganeshamunhy and Ch. Srinivasa Rao

with N alone. The N : K ratios have been optimized (Table 1) for various stages of tea plants by Ranganathan and Natesan (1985). In young tea bushes, the highest leaf yield over a range of N levels was achieved at a I : 1.5 = N, : K20 application ratio owing to an improvement in the vigour and health of the bushes and NH 3 metabolism in plants.

Table 1. Optimum N:K ratios for tea in south Indian soils. Stage of tea crop N: K Tea nurseries 1.00: 0.83 Young Tea plants (depending on soil pH and K 1.00: 0.83 to 1.25 availability in soil) Mature Tea plants in prune year 1.00 1.25 to 1.66 (depending on the type of pruning) Mature Tea plants (other than prune year 1.00 : 0.42 to 0.83 depending upon N source and yield level) Source: Raanganathan and Natesan (1985)

In pine apples, in West Bengal soils where N an K were applied individually the yield increase was 8.8 t ha- ' with 600 kg N/ha and 1.2 t ha' with 200 kg - K20/ha, respectively. But the yield increased dramatically by 18.4 t ha ' when N and K were applied together (Roy et al., 1986).

Phosphorus

Very few K x P interaction studies have been reported perhaps due to lack of evidence for a K x P interaction in plant metabolism except for maintaining ionic balance (Adams, 1980). In a 4 year field experiment with tea, responses to applied K was observed only when P was applied along with K; the degree of response increased when N:K 20 ratio was increased from 2:1 to 1:1 (Ranganathan and Natesan, 1985). Similar observation was made in coconuts by Khan and Bavappa (1986).

The need for an appropriate balance between P and K was emphasized (Table 2) for soybean by Jones et al. (1977) and for Bermuda grass by Welch et al (1981). This suggests that in crop production an adequate level of K is required for obtaining maximum responses to added P.

In a solution culture study it was shown that P absorption site on the plant roots are activated by K (Adepetu and Akapa, 1977). In cowpea, a marked decrease in P uptake in K deficient solutions was found despite adequate levels of P supply in the solution. Addition of K increased the P uptake while addition of another cation Mg did not do so. In a field experiment involving soybean- wheat system on Vertisols, increasing levels of P resulted in the increase in the Interaction of Potassium with Other Nutrients 163

Table 2. P and K interaction for higher yields. Crop P K Yield Reference Soybean 0 0 1735 Jones et al. (1977) 15 0 2072 0 112 3105 15 112 3694 Bermuda grass 0 0 6000 Welch et al. (1981) 0 336 5900 112 0 7300 112 336 10200

K content of straw and K uptake by soybean grain and straw. Increasing levels of depletion in soil available K was observed with increasing levels of applied P (Srinivasa Rao and Subba Rao, 1999).

Potassium is known to reduce the P induced Zn deficiency in soils, a common problem faced where high P fertilizers are applied. Higher levels of K also increased the uptake of Mn (Ward et al., 1963) as well as Mn and Zn in the soil solution. However, it is not clear whether the former or the latter or both are the factors responsible for this phenomenon. Adriano et al. (197 1) observing similar effect of K on P-Zn relationship concluded that while K favoured P uptake more than Zn and Fe, but could enhance the release of exchangeable Zn in soil there by alleviating Zn deficiency.

INTERACTION OF K WITH SECONDARY NUTRIENTS

Calcium and Magnesium

Calcium, Mg and K perform one non-specific function of maintaining a level of ionic balance in plant system. The preference of these cations in plants deferrers with species, and varieties and the concentration of the three cations in the substrate. The 'viets effect' named after F.G. Viets who first observed, states that higher Ca concentration in the outer solution either enhances the uptake of K or reduces the loss of K ions. Hence the tissue K concentration increases. Thus, in the event of better supply of one cation, the uptake of the other two is reduced. The crop response accordingly depends upon the extent of such antagonism. Application of K beyond the optimum level leads to its luxury consumption with a corresponding reduction in the concentration of [Ca + Mg] (Fig. 3). The antagonistic behaviour of K with Ca ad Mg has been reported *among others by Mandal and Sinha (1968) and Sekhon et al. (1975). Vinay Singh and Tomar (1994) reported that application of K to wheat, barley, oats and linseed reduced the content of Ca and Mg in these crops. Increase in yields of these crops with K application was associated with increase in K : Ca and K : 164 AN. Ganeshamurthy and Ch. Srinivasa Rao 3.53

2.5

82

1.5 • o=--t3-- Ca+Mg UptakeH cc 1

0 0 31.2 62.4 93.6 124.8 156 187.2 K Applied (kg/ha) Figure 3. The effect of K on uptake of Ca and Mg by wheat

Mg ratios. Nutrient indexing surveys of wheat area from Punjab showed low concentration of 0.096% Mg associated with 2.8% K in plant and high concentration of 0.14-0.24% Mg with 2.4% K (Sekhon et al., 1975).

Negative K x Mg interaction has been reported in grapes (Bhargava, 1987), cassava (CTCRI 1986), coconuts (Hameed Khan et al., 1986) (Table 3) and coffee in certain areas. Hence fertilizer schedules for horticultural crops have to be revised after ascertaining the soils and leaf nutrient status once in 3-4 years.

Table 3. Effect of NPK application on nutrient content (%) of coconut leaf. Annual treatment (kg palm- ') K Mg Na Ca Control 0.7 0.23 0.25 0.23 0.5 N + 0.5 P20 5 + 1.0 K20 1.0 0.17 0.13 0.33 1.0 N + 1.0 P20 5 + 2.0 K20 1.1 0.15 0.13 0.27 Source: Hammed Khan et al., 1986.

Sulphur

Although there is no direct evidence of a K and S interaction, application of S has been found to increase some times the concentration of K in rice, mustard and groundnut (Rathee and Chahal 1977; Kumar et al., 1981). A significant positive interaction between S and K in rapeseed was reported by Aulakh and Pasricha (1978). In sand culture studies, Umar and Bansal (1995) found that when K was deficient in soil, application of S did not influence the yield of rice. But under adequate K supply in the soil, application of S significantly increased the yield. Sulphur deficiency in soil results in very poor uptake of K. Interaction of Potassium with Other Nutrients 165

With improvement in S nutrition from deficiency to sufficiency, the K content in plant tissue decreased for the same level of yield. One significant observation made by them was that with increasing K levels, there was significant increase in S physiological efficiency index (Fig. 4) and the same was not affected by S application. This allows us to conclude that by supplying K in optimum amounts the PEI of S could be enhanced considerably.

K Physiolgical Efficiency Index E 30 0D0.5SK 103.0 K 2 E3]4.0 K IM6.0 K -- 25 e.0 15 0)CD 15 cc 15 l uJ CL 5 - 0, 0.5 1.5 3 4 S In Nutrient Medium (mval)

S Physiological Efficiency Index 60 E3 0.5 K m3.0K . ,0 500 M*4.0 K f6.0 K *9 a 400 . 300 u') 200. CL 100- 0.0

0.5 1.5 3 4 S In Nurlent Medium (mval) Figure 4. Effect of K and S application on physiological indices (PEI) of K and S (g grain gram-i nutrient absorbed)

MICRONUTRIENTS

Several studies indicated that K interacts with micronutrients. These interactions influence assimilation and utilization of nutrients and crop production. However, apparently there is relatively less organized research on micronutrients x K interactions in India. 166 A.N. Ganeshamunhy and Ch. Srinivasa Rao

Zinc

In soils deficient in both K and Zn synergistic interaction of Zn x K was observed on the grain yield of wheat (Gupta and Raj, 1983). Application of K decreased the grain yield while application of Zn or Zn + K increased the grain yield indicating growth limitation caused more due to lack of Zn than K (Table 4). The interaction was significant above 50 mg K pot' partly due to increase in solution concentration of Zn.

Table 4. Effect of Zn and K on grain yield' of wheat in pots. Treatment Zn/K (mg kgl Grain yield 0 25 50 100 0 13.4 12.4 13.0 12.3 5 17.3 17.5 17.9 19.7 10 17.8 18.2 16.3 20.2 LSD (0.05) Zn x K = 0.5 Source: Gupta and Raj, 1983

Application of K to maize decreased zinc concentration in roots but increased it in stover showing increased Zn absorption and translocation. Uptake of Zn by both maize and wheat increased with K application but beneficial effect was evident only in maize (Biswas et at., 1977). Application of K to potato grown on alluvial soil, low in Zn and marginal in K status, the response to K varied only from 254 to 543 kg ha - . But when K was applied with 2.5 kg Zn ha' the response increased to 521-1125 kg ha -' (Fig. 5). In case of peas application of K and Zn significantly increased their content and uptake. However, application of K alone decreased Zn concentration and increased its uptake. Uptake of K also increased by application of low levels of Zn. The K : Zn ratio increased with K and decreased with Zn addition (Vinay Singh et al., 1992).

1 -- IMZnO 0I Zn2.5 IMZn 5 - 10

4

2

0 0 25 50 100 K Applied (kg/ha) Figure 5. Effect of K and Zn on potato yield Interaction of Potassium with Other Nutrients 167

In contrast to upland crops, Zn absorption in rice seedlings decreased with increasing levels of K in solution concentration. Translocation of Zn from roots to shoot also decreased with a rise in K level and the nature of this inhibition was reported to be non specific (Sadana and Takkar, 1984).

Copper

Generally application of K increased Cu concentration in plants when crops were supplied well with phosphorus (Waddington 1972). Limited amount of information showed that excess Cu inhibited the uptake of K in maize and wheat (Bujtas and Cseh, 1982). Smith (1975) reported a reduced Cu level in the alfalfa forage when K was top dressed under adequate supply of P. This may be due to dilution effect.

Iron

A synergistic interaction between K and Fe exists and is found to be due to the physiological relationship that exists between Fe, K and organic N. Application of Fe increased the uptake of K by different cultivars of rice up to 20 kg FeSO4 ha' but it decreased at 40 kg Fe ha'. Increasing level of K supply decreased Fe content in paddy. K application is also known to correct Fe toxicity in rice grown on Fe rich acid soils as it improves metabolic activity and Fe excluding power of plant roots (Tanaka and Tadano, 1972; Patro, 1985; Mitra et al, 1991). But synergistic effects occurred when both K and Fe were applied resulting in increased rice yields as well as K and Fe uptake (Gupta, 1986).

Sahu and Mitra (1992) in their pot studies reported that the elasticity of synergism has an upper limit of 100 ppm Fe in the soil. The yield of rice increased with Fe application up to 50 mg kg -' soil beyond which the yield drastically reduced. Application of K could overcome the Fe toxicity effects up to 100 mg Fe kg- ' soil beyond which this effect ceased (Fig. 6). At higher Fe

9 ,- ,. - K O I m =" 78 - .. -- ,K30

6 K60 .25 _e=,45 \\\ K90

C3 2

0 FeO Fe5O Fel 00 Fe200 Fe300 Fe400 Fe Level (mglkg)

Figure 6. Effect of increase in Fe and K level in soil on dry matter yield of rice (glpol) 168 A.N. Ganeshamurthy and Ch. Srinivasa Rao concentration there is drastic reduction in yield and nutrient uptake because the roots are heavily coated with ferric hydroxide which blocks exchange sites and blocks uptake of other ions. Kawaha and Ostojarati (1965) reported that K application increases the oxidizing power of rice roots which results in conversion 2 of Fe " to Fe3 and the exclusion of Fe3" from uptake. This was confirmed from field survey that as Fe content in the soil increases, satisfactory levels of yields could be achieved only when soil K content was above 150 mg kg -' soil. However, in acid sulphate soils where Fe content exceeded 350 ppm though K content was excessively high, rice yields were very low (Ganeshamurthy, 2001).

Manganese

K along with Ca and Mg is known to regulate the absorption of Mn by plants. Under situations of Mn deficiency in soils, application of K promoted absorption of Mn by plants where as when Mn level in soil is toxic to plants, K, Ca and Mg application effectively decreased Mn uptake (Ramani 'and Kannan, 1974). In arable crops, K application has increased Mn levels in crops (Smith, 1975, Legget et al., 1977). Application of K increased Mn level in alfalfa but decreased a host of other nutrients (N, Ca, Mg, Na, Cu, Zn and B) and increased the yield from 6.46 to 9.88 t ha - '. In tabacco leaf yield and quality were improved. The K content increased by 560 per cent (Table 5). Though the Mn content increased by 20 per cent at highest rate of 448 kg K ha' it was not consistent at lower rates of K application (Legget et al., 1977).

Table 5. Effect of K application on yield and chemical composition of burkley tobacco leaf Rate of K (kg ha -') Leaf yield (kg ha - ) K (g kg -' dry leaf) Mn (ppm) 0 2569 147 572 112 2925 262 556 224 2967 440 572 448 3073 820 686 Source: Leggettee et al. (1977)

Randhawa and Pasricha (1975) reported a consistent reduction in Mn content of rice with increasing levels of K. Similar findings were reported in bent grass turf by Waddington et al. (1972). However, under the conditions of these experiments the magnitude of change was not considered critical.

Boron

Published work shows both synergistic and antagonistic interaction between K and B. When plants were grown on soils with low B and high K levels or with added K, the B levels in plants decreased (Table 6) and the B deficiency symptoms in crops intensified (Woodruff et al., 1960). In their results they could find no Interaction of Potassium with Other Nutrients 169

Table 6. Effect of K and B applicationon the composition of the second trifoliate . leaf of soybean. % K saturation Composition of leaf on dry weight basis No B B B K Ca Mg B K Ca Mg 0 11 4 14 15 75 4 16 14 2 34 10 8 6 54 15 14 8 20 Tr 31 3 4 - 30 10 8 Source: Woodruff et'al. (1960) suitable explanation for the relationship between K and B based on soil chemical properties and concluded that the relationship must be associated with the physiology of the elements in the plant. This calls for balanced nutrient application keeping in view the available B status of the soil.

In another study in a sand culture the dry weight of 30 day old rice increased with application of K and B upto 2.5 mg B kg - ' and 60 mg K kg- ' soil. The B content also increased from traces to 108.7 mg kg-' with B application and from 37.7 to 46.2 mg kg- ' with K application (Kumar et al., 1981).

In chickpea, wheat and lentil, B application progressively increased the K content from 3.78 to 7.02, 5.50 to 6.87 and 3.90 to 5.50 per cent, respectively in a sandy soil under screen house conditions (Yadav and Manchanda, 1979; Singh and Singh, 1983). The results of a typical synergistic effect of K and B in a field experiment on calcareous soils with black gram are summarized in Table 7. Maximum yield of 1238 kg ha -' was obtained with a combined - application of 30 kg K20 and 2 kg B ha '.

Table 7. Effect of K20 and B application on grain yield of black gram. - - Boron kg ha ' K20 kg ha 1 0 30 60 Mean 0 642 675 743 687 1.0 767 790 850 802 1.5 775 867 813 818 2.0 857 882 708 816 Mean 760 804 770 CD (0.05) for B = 49, K = NS, K x B = 86 Source: Sakal et al. (1988) 170 A.N. Ganeshamurthy and Ch. Srinivasa Rao

Molybdenum

Application of potassium is known to reduce the Mo content of crops. In a field study K application to alfalfa decreased the Mo content in the herbage but its concentration was still high enough to cause Cu deficiency in ruminants. In corn, as well the yield increased by 236 per cent but plant Mo levels dropped by 75 per cent. This could have been a dilution effect (Jones 1965). In a review Loue (1978) reported a positive interaction between Mo and K and Mo stimulated uptake of K in alfalfa and wheat.

Sodium

A significant negative interaction between K and Na is observed in plants that respond to Na like sugarbeets and coconuts. In such cases both K and Na are required for obtaining maximum yields (Mozafar et at., 1970).

CONCLUSION

Potassium is a unique plant nutrient, which is absorbed by plants in large quantity, yet is not a constituent of any bio-molecules. But it plays a diversified role in plant metabolic processes and interacts with all other essential plant nutrients absorbed absorbed from soil. Due to its abundance in Indian soils application of K in crop production is not looked at par with N and P. However, full benefit of fertilization can only be realized when interaction effects are taken into consideration. This has become abundantly clear from the results of long term fertilizer experiments. The main reason for the neglect of interaction effects for commercial exploitation is that most of these studies are conducted in green houses. There is hence need to validate these results under field conditions for economic exploitation of these interaction effects.

FUTURE LINE OF WORK

To increase the productivity of crops on soils deficient in one or more nutrients, enhanced application of deficient nutrients is very important. Consequently the studies pertaining to nutrient interactions under different soil- crop conditions have proved beneficial. These can be used to stress the need for balanced nutrient application schedule, which maximizes positive interactions and minimizes antagonistic effects. Research gaps still persist on scientific managements of nutrient interactions. This needs to be strengthened to harvest the effects of interactions on productivity of crops. Some of these researchable aspects are given below:

* The database on nutrient status of soils particularly of N, P and K are outdated. This information has to be updated along with secondary and micronutrients and interpreted on agroecological region basis. Such information supplemented with nutrient budgeting helps in identifying and Interaction of Potassium with Other Nutrients 171

forecasting of the kind of nutrient interaction which may exist or may appear in future in different agroecological regions. * Varietal development for specific purpose like quality, pest and disease resistance etc. is the today's thrust areas with breeders. However, the kind of nutrient mining ability of such varieties and its effect on nutrient interactions has received least attention. This aspect needs to be studied in detail. * There is need to bridge the information gap on interaction of K with other nutrients in plantation, fruit, pulse, medicinal and aromatic, flower and beverage crops in different agro ecosystems. * The effect of interaction of K with other nutrients on quality of economic produce has not received the kind of attention it deserves. Hence well- planned research work needed to be initiated in this area in collaboration with plant physiologists and biochemists. * Studies on the influence of nutrient interactions on nurtient uptake and use efficiency have been grossly neglected. In all nutrient interaction studies these aspects should receive due attention. " In grain legumes there is need to quantify the effect of nutrient interaction on nodulation and N fixing capacity. " The effect of nutrient interaction on the efficiency of beneficial micro- organisms like microrrhizae, PSB, azotobactor etc. need to be investigated. " There is need to study in depth the interaction effects of nutrients in rice- wheat rotation and its effect on sustainability of the system.

REFERENCES

Adams, F. (1980). Interaction of P with other elements. In (Eds. Khasawneh et al.). The role of P in agriculture. American Society of Agronomy, Crop Science Society of America Madison, WI. P 661. Adepetu, L.A and Akapa, L.K. (19.77). Root growth and nutrient uptake characteristics of some cowpea varieties. Agronomy Journal 69: 940-943. Adriano, D.C., Paulsen, G.M. and Murphy, L.S. (1971). P-Fe and P-Zn relationships in corn seedlings as affected by mineral nutrition. Agronomy Journal 63: 56-59. Ajayi, 0., Maynard, D.N. and Barker, A.V. (1970). The effect of potassium on ammonium nutrition of tomato. Agronomy Journal 62: 818-821. Anand Swamp (1996). Influence of nitrogen and potassium on yield, available soil N and K and their uptake by wheat in a saline soil under sub-surface drainage system. Journal of Potassium Research 12: 199-204 Aulakh, M.S. and Pasricha, N.S. (1978). Inter relationship between S, Mg and K in rapeseed. I. Yield, concentration and uptake of South Indian Journal of Agricultural Science 47: 577-581. 172 A.N. Ganeshamurthy and Ch. Srinivasa Rao

Bhargawa, B.S. (1987). Potassium availability in soils growing grapes. PRRI Research Rev. Series No. 4. 85-92. Biswas, C.R., Rajinderjit Singh and Sekhon, G.S. (1977). Zinc availability to maize and wheat in relation to P and K status of the soil in a long-term fertilizer experiment. Journal of Indian Society of Soil Science 21: 414-421. Bujtas, C. and Cseh, E. (1982). Effect of Cu on the K ion uptake system of wheat roots. Mogy. Tud. Akad. Biol. Tud. Oszt. Kozl. 25: 609-622. CTCRI (1986). Annual report for 1985. Central Tuber Crops Research Institute, Trivandrum, pp 151. Dibb, D.W. and Welch, L.F. (1976). Corn growth as affected by ammonium vs. nitrate absorbed from soil. Agronomy Journal 68: 89-94. Faizy, S.E.D.A. (1979). N-K interaction and net influx of ions across corn roots as affected by different NPK fertilizers. In: Soils in Medeterranian climate and their yield potential. Proceedings of Colloqium of International Potash Institute 14: 409-421. Ganeshamurthy, A.N. (2001). Field survey of rice soils (Unpublished data) Gupta, M.L. (1986). Effect of Fe-K interaction on yield and nutrient content of paddy in alluvial soil. Oryza. 23: 126-128. Gupta, V.K. and Raj, H. (1983). Zinc-potassium relationship in wheat. Haryana Agricultural University Journal Research 13: 140-146. Hameed Khan, H., Gopalasundaram, P., Joshi, O.P. and Nelliat, E.V. (1986). Effect of NPK fertilization on the mineral nutrition and yield of three coconut genotypes. FertiliserResearch 10: 185-190. Jones, J.B., Jr. (1965). Molybdenum content of corn plants exhibiting varying degrees of potassium deficiencies. Science 148-94. Jones, G.D., Lutz, Jr. J.A. and Smith, T.J. (1977). Effect of P and K on soybean nodules and seed yield. Agronomy Journal 69: 1003-1009. Kawaha, S. and Ostojara. K. (1965). Studies on the oxidizing ability of root hairs in rice plants. Crop Science Society of Japan Proceedings 33: 168-173. Khan, H. and Bavappa, K.V.A. (1986). Management of P in plantation crops. Proc. IMPHOC-FAI seminar on crop production techniques and fertilizer management in rainfed agriculture in South East Asia. New Delhi. 513-528. Kumar, S., Arora, B.R. and Hundal, H.S. (1981). Potassium boron synergism in the nutrition of rice. Journal of Indian Society of Soil Science 29: 563-564. Leggett, J.E., Sims, J.L., Arsett, D.R., Pal, U.R. and Bennes, J.F. (1977). K and Mg nutrition effects on yield and chemical composition of Burkley tobacco leaves and smoke. Canadian Journal of Plant Science 57: 159-166. Loue, A. (1978). The interaction of potassium with other growth factors, particularly with other growth factors, particularly with other nutrients. In potassium research, review and trends, Proceedings of Congress of International Potash. Institute 11: 407-433. Interaction of Potassium with Other Nutrients 173

Mandal, S.C. and Sinha, M.K. (1968). Potassium nutrition of plants in a limited soil. Journal of Indian Society of Soil Science 16: 37-40. Mengal, K., Viro, M. and Hehl, G. (1976). Effects of potassium on uptake and incorporation of ammonium N of rice plants. Plant Soil. 44: 547-558. Mitra, G.N., Sahu, S.K. and Dev, G. (1990). Potassium chloride increases rice yields and reduces symptoms of iron toxicity. Better crops International 6: 14-15. Mondal, S.S. (1982). Potassium nutrition at high levels of N fertilization on rice. Potash Rev. Subject 9. Suite 52. Mozaffar, A., Goodin, J.R. and Derth, J.J. (1970). Sodium and potassium interaction in increasing the salt tolerance of Atriplex haliums. II : Na and K uptake characteristics. Agronomy Journal 60: 481-484. Muthuswamy, P. and Chiranjivi Rao (1979). The influence of nitrogen and potassium fertilization on tuber yields and starch production in cassava varieties. Potash Revised Subject 27. Suit 91. Patro, B.N. (1985). Iron-Potassium-Manganese interaction in rice and rice soils. Ph.D. Thesis. Behrampur University, Behrampur. Ramani, S. and Kanna, S. (1974). Effects of certain cations on manganese absorption by excised rice roots. Common. Soil Science and Plant Anal. 5: 435. Randhawa, N.S. and Pasricha, N.S. (1975). Interaction of potassium with secondary and micronutrient elements. Bull No. 10. Indian Society of Soil Science 227-240. Ranganathan, V. and Natesan, S. (1985). Potassium nutrition of tea. In Potassium in Agriculture. ASA, Madison. 981-1022. Rathee, O.P. and Chahal, R.S. (1977). Effect of P and S application on yield and composition of groundnut in Ambala Soil. HAU Journal Research 7: 173- 177. Roy, R. (1986). Field response of Kew pineapples to N, K and plant density. Maharashtra Journal of Horticulture 3: 38-43. Sadana, U.S. and Takkar, P.N. (1984). Effect of Na and K on 65Zn absorption and translocation in rice seedlings. Indian Journal of Plant Nutrition 3: 255-261. Sakal, R., Singh, A.P. and Verma, M.K. (1988). Effect of boron application on blackgram and chickpea production in calcareous soil. Fertiliser News 33(2): 27- 30. Sekhon, G.S., Arora, C.L. and Brar, M.S. (1975). Nutrient status of wheat crop in Ludhiana. Soil Science Plant Nutrition 6: 609-618. Singh, V. and Singh, S.P. (1983). Effect of applied boron on the chemical composition of lentil plants. Journal of Indian Society of Soil Science 31: 169-170. 174 AN. Ganeshamurthy and Ch. Srinivasa Rao

Smith, D. (1975). Effect of potassium top dressing a low fertility silt loam soil on alfalfa herbage yield and composition and on soil K values. Agronomy Journal 67: 60-64. Srinivasa Rao, Ch. and Subba Rao, A. (1999). Effect of different levels of farmyard manure and phosphorus application on potassium uptake by soybean-wheat cropping system on Vertisol. Journal of Indian Society of Soil Science 47(1): 176-178. Still Well, T.C. (1975). Response to K fertilization of three Punjab soils. Indian Journal of Agricultural Science 45: 149-151. Tanaka, A. and Tadano, T. (1972). Potassium in relation to iron toxicity of rice plant. International Potash Institute Revision Subject 9, 21st Suite: 1-12. Tiwari K.N., Vandana, N. and Pathak, A.N. (1982). Effect of K on drymatter production and nutrient uptake by potato variety "Kufli chandramukhi" in an alluvial soil of Uttar Pradesh. Plant Soil. 65: 141-147. Umar, S.M., Prasad, B. and Prasad, B. (1986). Response of rice to N, P and K in relation to soil fertility. Journal of Indian Society of Soil Science 34: 622- 624. Vinay Singh, Betra, T.D., Singh, R.P. and Mehta, V.S. (1992). Effect of graded dose of P and K on yield and their uptake by pea. Journal of Potassium Research. 8: 144-147. Vinay Singh and Tomar, J.S. (1994). Effect of potassium application on the yield and content of calcium and magnesium in wheat, barley, oats and linseed. Journal of Potassium Research 10: 78-82. Waddington, D.V., Moberg, E.L. and Duich, J.M. (1972). Effect of N sources, K sources and K rates on soil nutrients level and growth and elemental composition of penncross creeping bent grass. Agrositis Plustris Huds. Agronomy Journal 64: 562-566. Ward, R.C., Langin, E.J., Olsen, R.A. and Stukenholtz, D.D. (1963). Factors responsible for poor response of corn and grain sorghum to phosphorus fertilization: III. Effect of soil compaction and other properties on P-Zn relations. Soil Science Society of America Proceedings 27: 326-329. Welch, C.D., Gray, C. and Pratt, J.N. (1981). Phosphorus and potassium fertilization for coastal barmuda grass hay production in East Texas. Fact Sheet L 1861. Texas Agric. Ext. Serv. Woodruff, C.M., Mclntish, J.C., Miculcik, J.D. and Sinha, H. (1960). How potassium caused boron deficiency in soybeans. Better Crops Plant Food 44(4): 4-11. Yadav, O.P. and Manchanda, H.R. (1979). Boron tolerance studies in gram and wheat grown on a sierozem sandy soil. Journal of Indian Society of Soil Science 27: 174-180. Potassium Management in Rice-Wheat Cropping System in South Asia

YADVINDER SINGH AND BIJAY SINGH Department of Soils Punjab Agricultural University, Ludhiana-141004, India

ABSTRACT

Rice-wheat is a dominant cropping sequence practiced essentially under irrigated conditions spread over 12 million ha in Indo-Gangetic Plains of India, Pakistan, Nepal and Bangladesh. Since, over 1.2 billion people rely on this cropping system for a large share of their daily caloric intake, income, and employment, the importance of studying sustainability of rice-wheat systems in terms of nutrient balance and productivity is immense. Present population in the Indo-Gangetic Plains (South Asia) is increasing at 1.8% per year resulting in an increasing demand for rice and wheat cereals at 2.5% per year which is expected to result in a short fall of 20 million tons by the year 2020 (Yadvinder- Singh and Bijay-Singh, 2001). During 1960 to 1990, genetic improvements leading to development of highly fertilizer responsive rice and wheat varieties and improved management strategies resulted in a dramatic rise in productivity and production from rice-wheat system. The system in fact, is now showing signs of fatigue and is no longer exhibiting increased production with increases in input use. Both rice and wheat are exhaustive feeders, and the double cropping system is heavily depleting the soil of its nutrient content. A rice-wheat sequence that yields 7 t ha-' of rice and 4 t ha - ' of wheat removes more than 300 kg nitrogen, 30 kg phosphorus, and 300 kg ha-' of potassium from the soil. Even with the recommended rate of fertilization in this system, a large negative balance of potassium still exists. On all India basis, if one takes into account only the K content of the harvested food grains, production of about 200 million t food grain would lead to a deficit of about 7 million t K20 removed from the soil without being replenished. In both low- and high-resource .input conditions, both crops must use the nutrients contained in the soil as well as applied through fertilizers and manures efficiently to reach their yield potential under this system. The potassium requirements for high rice and wheat yields vary depending on soil and climatic conditions.

FERTILIZER USE IN RICE-WHEAT SYSTEM

Yadav et al. (2000) have reported that farmers are using very high doses of 175 176 Yadvinder Singh and Bijay Singh

N (130 to 195 kg N ha-') to rice in Punjab, Haryana and western Uttar Pradesh in India (Trans-Gangetic plain and parts of Upper Gangetic plain). In most cases application of K fertilization is limited. In Middle Gangetic plain (eastern Uttar Pradesh and Bihar), 23 to 46 kg N hac- is applied as basal dressing and 23 to 46 kg N ha-' is top dressed in 2-3 splits. In Lower Gangetic plain (West Bengal) fertilizer use is very low. Rice and wheat receive 34.5- 46 kg N ha-' as basal dressing and only 23 kg N is applied as top dressing. In wheat, use of 95 to 200 (average 153) kg N ha - ' and 13 to 24 (average 17) kg P ha' is common throughout the rice-wheat system in South Asia. Potassium fertilizers are rarely used in these areas. Recommended fertilizers are hardly adopted by rice-wheat farmers in the Indo-Gangetic plain. Fertilizer consumption in Bangladesh has increased from 65000 t of muriate of potash in 1986-87 to 147000 in 1990-91 (BBS, 1992).

Fertilizer use pattern for rice-wheat system in the Indo-Gangetic plains varies greatly from one part to another (Yadvinder-Singh and Bijay-Singh, 2001). For example in out of 30 districts in Punjab and Haryana states in the northwestern India, 18 districts consumed more than 150 kg (N + P20 5 + K20) ha-'. On the other hand, in 82 out of 120 districts of the eastern part comprising Uttar Pradesh, 1. Bihar and West Bengal consumed less than 100 kg (N + P20 5 + K20) ha- Although fertilizer use in all the Indian states where rice-wheat system is practiced is consistently increasing over the years, N/P 20 5 and N/K 20 ratios were widened with passage of time. It is true all over the Indo-Gangetic plains, although extent is more in western India where fertilizer use is conspicuously more than in eastern side (Table 1). Reduction in subsidies on phosphate and potash in India adversely affected their consumption, while nitrogen remained heavily subsidized. This resulted in continued imbalanced fertilizer use, the N: P205 : K20 ratio in 1996/97 was 9.9:2.9:1 compared to 6.3:2.3:1 in 1970/71 (FAO, 1998). There is unbalanced consumption of K in southeast and south Asia. In India, only 14% of the total K removal by food grains is supplemented by K fertilizers.

Table 1. Ratios of N:P2O5:K 2 O and nutrient consumption per ha of cropped area (Yadvinder-Singh and Bijay Singh, 2001) State 1984-85 1991-92 1997-98

N:P 20 5 : N+P 20 5+ N:P 20 5 : N+P 20 5 + N:P 20 5 : N+P 20 5 +

K20 K 20 K20 K20 (20 K20 (kg ha-') (kg ha-') (kg ha-') Punjab 33.9:11.9:1 151.2 51.5:17.7:1 168.4 45.2:12.9:1 170.9 Haryana 35.8:7.4:1 57.7 62.6:31.8:1 112.8 171.0:47.8:1 140.1 Uttar Prades 14.7:3.4:1 65.1 16.8:4.4:1 88.7 26.0:6.3:1 117.7 Bihar 7.8:1.8:1 35.9 9.1:2.8:1 57.9 11.5:2.9:1 87.2 West Bengal 3.9:1.4:1 54.8 2.5:1.3:1 90.5 3.2:1.5:1 112 Potassium Management in Rice-Wheat Cropping System in South Asia 177

SOIL FERTILITY

Soils in the Indo-Gangetic plain generally contain sufficient exchangeable K and K bearing minerals (illite) able to release exchangeable K to meet crop requirements. Total K in alluvial soils of IGP ranges from 1.28 to 2.77% and exchangeable K contents of 78-273 mg kg-' soil (Tandon and Sekhon, 1988). Of the about 0.2 million soil samples analyzed in Punjab (India), 8.2% soil samples low, 45.4% medium and 46.4% high in available potassium (Brar, 1998). tested - Of the 73 samples analyzed, 52% contained 0.15 cmol of K kg ' (Kawaguchi and Kyuma, 1977). Potassium is now becoming a limiting factor in crop production in intensively cropped areas producing high yields of rice and wheat in many south Asian countries. Most of the soils in Bangladesh are low in exchangeable K (Islam, 1995). In Myman Singh, percentages of soil samples below the critical soil test value for K were 75%. Potassium has not yet received adequate attention and may be limiting yields of rice and wheat in Bangladesh. Only 27% of the K required is being applied (Bhuiyan et al., 1993). The most extensive nutrient deficiencies in soils of Nepal are those of N, P and K because these are the nutrients which rice and wheat absorb in large amounts. The IN ammonium acetate- extractable K in lowland rice soils ranges from 0.05 to 2 c mol kg -' (x 391 = mg kg-').

POTASSIUM REMOVAL BY RICE-WHEAT SYSTEM

- Rice-wheat cropping system annually removes 132-324 kg K ha ' (Table 2). The nutrient removal depends on the production level, soil type and whether crop residues are removed or recycled in the soil. Optimum application of N increased K uptake by 57% over control plots and N and P application increased K uptake by 145% (Tandon and Sekhon, 1988). Removal of K by rice-wheat system far exceeds its additions through fertilizers and recycling. The quantities of nutrient removed by rice and wheat crops are important parameters for evaluating the fertilizer requirement. The observed average K removal in irrigated - 1 rice systems in Asia is about 20.6 kg K t grain yield, assuming agrain: straw - ratio of 1:1.25 (Table 3). Therefore, a rice crop yielding 7 t ha ' takes up - 145

Table 2. K removal by rice-wheat cropping system Cropping system Total K Reference productivity uptake (t ha-') (kg ha-') Rice-wheat 13.2 287 Kanwar and Mudahar (1986) Rice-wheat-cowpea 9.6 + 3.9 324 Nambiar and Ghosh (1984) (dry fodder) Rice-wheat-jute 6.9+2.3 (fibre) 212 Nambiar and Ghosh (1984) Rice-wheat 8.8 280 Sharma and Prasad (1980) Aman rice-wheat 5.7 132 Saunders (1990) Aman rice-wheat-Aus rice 8.1 185 Saunders (1990) 178 Yadvinder Singh and Bijay Singh

Table 3. K uptake and K content of modern rice and wheat varieties Plant part Typical observed range Observed average Rice& Wheatb Rice a Wheat"

K uptake (kg/ t grain/ straw yield) Grain 2-3 4-5 2.5 4.5 Straw 12-17 9-12 14.5 10.5 Grain + straw 14-20 13-17 17.0 15.0 K content (%) Grain 0.22-0.3 1 0.35-0.50 0.27 0.43 Straw 1.17-1.68 0.85-1.151 1.39 1.00 aDobermann and Fairhurst (2000), 'Yadvinder-Singh (unpublished data)

kg K ha-' of which 80% remains in straw. If the grain only is removed and straw is returned to the field, K removal is - 2.5 K t' grain yield. Similarly, observed average K removal in irrigated wheat is about 20.3 kg K t' grain yield, assuming a grain: straw ratio of 1:1.5 (Table 3). A rice crop yielding 5 t ha-' will take up - 100 kg K ha-'.

The high K reserves in the alluvial soils in northern India are heavily tapped when potassium is omitted. Results from a long-term field experiment in Haryana showed that for soils in the control non-exchangeable K decreased from about 4500 kg K ha-' to around 1000 kg K ha-' within 12 years of cropping (Grewal and Mehta, 1996). Depletion of the soil K reserves alters the configuration of soil minerals and increases the K fixation. The amount of K required for per cent increase in the available K in exhausted soils is 3-5 times more than in the fertile soils (Krauss, 1998). With the depletion of the exchangeable K fraction, the crop has to rely increasingly more on K released from reserves (Yadvinder- Singh and Khera, 1998).

POTASSIUM TRANSFORMATIONS IN SOILS

Soil potassium is often considered to exist in solution, exchangeable and non-exchangeable (fixed and structural K) forms. The amount of solution and exchange K is usually a small fraction of total K (1-2% and 1-10%); the bulk of soil K exists in K-bearing micas and feldspars (Sekhon, 1995). The amount of K present in the soil solution is often smaller than the crop requirement for K. Thus continuous renewal of K in the soil solution for adequate nutrition of high yielding varieties of rice and wheat is obvious. Similarly, exchangeable K component has to be continuously replenished through the release of fixed K and weathering of K minerals. Hence, K availability to crops is a function of the amounts of different forms of K in soil, their rates of replenishment and the degree of leaching. The release of K from illitic materials through weathering may account for the apparent lack of response to K in alluvial soils of the Indo- Potassium Management in Rice-Wheat Cropping System in South Asia 179

Gangetic plain: Dynamic equilibrium reactions occurring between different forms of K have a profound effect on the chemistry of soil K. The direction and rate of these reactions determine the fate of applied K and release of non-exchangeable K. Under certain conditions, added K is fixed by the soil colloids and is not readily available to plants. Clays of 2:1 type can readily fix K and in large amounts. The mechanisms governing K fixation and especially in flooded soils are not clearly understood.

Available K is kept at relatively high levels in flooded soils because of large 2 amount of soluble Fe2+ and Mn * ions brought into solution displace cations from the clay complex, and exchangeable K is then released into the soil solution. In fields with adequate drainage, K and other basic cations are lost via leaching. Leaching losses of K are a major concern on highly permeable wetland rice soils with low cation exchange capacity (Yadvinder-Singh and Associates). Abedin Mian et al. (1992) reported from Bangladesh that leaching losses could be as high as 0.1-0.2 kg K ha- ' day-'. Leaching losses of K will depend on soil solution concentration and percolation rates. Percolation rates are further enhanced et al., when fertilizer K as KCI or K 2SO4 is applied to the soil (Komal-Singh 2001) The increase in K availability in flooded soils also enhances K uptake by rice. Water regime is highly dynamic in rice-wheat system and it may influence availability and fixation of K in soils. In a long-term experiment with rice-wheat rotation in the Tarai plain of Southern Nepal, the proportion of added K that was fixed in the soil ranged from 46 to 56% in a wet/dry equilibration, and fixation - was linear with addition rates up to 25 mM K kg ' soil (Regmi, 1994).

Flooding of dry lowland soils containing vermicullite, illite, or other K- fixing minerals (2:1 layer clay minerals) may increase K fixation and reduce the solution concentration, so that rice depends on non-exchangeable reserves for K uptake. Rice roots, however, cause acidification in the rhizosphere, which increases the release of nonexchangeable K (because K is displaced from interlayer positions by H ions).

ASSESSMENT OF SOIL K-SUPPLYING CAPACITY

Soil testing is being widely used in the Indo-Gangetic plain to estimate amount of K that becomes available to plants during rice and wheat cropping seasons. Use of IM ammonium acetate at pH 7.0 to extract plant available K (exchangeable + water soluble K) is still the most used soil K availability index for rice and wheat. But its suitability as a measure of plant available K remains controversial, especially when soils with different textures and clay mineralogy are considered together (Kemmler, 1980; Dobermann et al., 1996). For example, in Gurdaspur (India), 40% of soil samples were found to be deficient in K while only 7% of the plant samples could be called deficient in K (Tandon and Sekhon, 1988). Critical levels for IM ammonium acetate-extractable K for rice soils has - been reported to vary from 0.17-0.21 cmol K kg ' (Prasad and Prasad, 1992). 180 Yadvinder Singh and Bijay Singh Soils have been grouped into 3 categories of low, medium and high on the basis of soil test values. Usually diverse soils analyzing < 55 mg kg kg-' soil by IM ammonium acetate solution are rated as low in available K and soils analyzing >110 mg kg-' soils are rates as high in available K. Depending on soil texture, clay mineralogy, and K input from natural resources, however, critical levels of ammonium acetate- extractable K can vary from 0.1 to 0.4 cmol K kg- 1 soil. The critical levels are larger in soils containing large amounts of 2:1 clay minerals. Critical ranges with general applicability are as follows: a. Soils with exchangeable K < 0.15 cmol /kg are low in K status, and response to K fertilizer is certain,

b. Soils with exchangeable K 0.15-0.45 cmol/kg are medium in K status and, response to K fertilizer is probable, and c. Soils with exchangeable K > 0.45 cmol/kg are high in K status, and response to K fertilizer can only be expected at very high yield levels (> 8 t/ha). On lowland rice soils with high K fixation and release characteristics (e.g. vermicullitic soils), IN ammonium acetate-extractable K is often small (<0.2 cmol kg-') and not a reliable soil test to asses K supply. K saturation (% of total CEC) is often a better indicator of soil K supply than the absolute amount of K extracted with IN ammonium acetate, because it takes into account relationship the between K and other exchangeable cations (Ca, Mg, Fe). The proposed ranges for rice as suggested by Dobermann and Fairhurst (2000) are as follows:

i. K saturation <1.5% - low K status, response to K fertilizer is certain, ii. K saturation 1.5 -2.5% - medium K status, response to K fertilizer is probable, and

iii. K saturation >2.5% - high K status, response to K fertilizer is unlikely. The critical level of I N HNO3 (slow release K) is 0.25 cmol K/kg. Soils containing (Ca + Mg) : K ratio > 100 may indicate low soil K availability to rice. Most of the soils in the Indo-Gangetic plain contain illite as dominant clay mineral. The high root density, relatively high maximum influx and low minimum solution concentrations for K uptake indicate that rice and wheat depend on non- exchangeable fraction for much of their K supply in such soils (Meelu et al., 1995). Hence, it appears desirable to include a measure of non-exchangeable K in our estimate of plant available K. A measure of non-exchangeable K in soil is determined by boiling IM HNO 3, but results are not always correlated to grain yields and total K uptake.

There is now considerable information to show that sub-soil K fertility Potassium Management in Rice-Wheat Cropping System in South Asia 181 makes a significant contribution to plant nutrient, and differences in the mineralogy and reserve K and relationship between exchangeable K and water soluble K among soil series and soil types suggest the need for different rates of critical limits for different soils (Sekhon, 1995). In addition, ammonium acetate- extractable K for soil testing should include soil properties such as clay content, cation exchange capacity and organic matter content. On alkaline soils, reduced K activity in soil solution due to preferential K adsorption may contribute to low K uptake by rice, when ample K is available (Dobermann et al., 1996). Other methods such as QII relationship and electro-ultra filtration are laborious and/or expensive and not used in routine analysis of soils for rice-wheat cropping system.

Tandon and Sekhon (1988) suggested that soils with low available K (<100 mg kg-' soil) are expected to readily respond to K application. Soils with low available K and high in reserve K (>1000 mg K kg-' soil) status will need lower - rates of K application and soils with high available K (>100 mg K kg ' soil) and low reserve K status can support crops for some years without K fertilizer application.

All chemical soil tests used for K for rice and wheat production have theoretical limitations, including that; (1) nutrient availability in irrigated rice- wheat ecosystem is extremely dynamic and tests on air-dried soil may not fully reflect nutrient status after submergence, (2) differences in clay mineralogy and physical properties have a strong impact on desorption characteristics and plant availability (3) unextracted nutrient pools may also contribute to plant uptake, (4) diffusion is a key process of K (and P) transport to the root surface, (5) external mechanisms such as root-induced solubilization of P by acidification contribute significantly to uptake by rice and wheat roots, and (6) kinetics of nutrient release are not measured. Dynamic soil tests overcome many of the theoretical limitations associated with rapid chemical extractions (Dobermann et al., 1998). The resin capsule, for example, integrates intensity, quantity and delivery rate measures of P and K supply to the rice and wheat roots and it provides parameters that help to assess both short and long-term nutrient supplying power in a dynamic manner. Perhaps the major advantage of this method is that it can be used as an universal soil test for simultaneous extraction of N, P, K, S, Ca, Mg, Fe, Mn, Zn, Cu and other nutrients across very different soil types in situ without the need for collecting and processing soil samples.

In spite of conclusive evidence of role of non-exchangeable K in plant nutrition and the role of soil texture on K release, most soil testing laboratories yet do not seem to be taking these into account while making K recommendations. The question of critical limits of K in soil continues to first problem of interpretation. More work is required to developing field applicable critical limits for diagnosing the K deficiencies in soils and crops. 182 Yadvinder Singh and Bijay Singh

FERTILIZER K MANAGEMENT FOR RICE-WHEAT SYSTEM

Crop response to applied K

Most of the alluvial soils in the Indo-Gangetic plain are generally reported as medium to high in extractable K. But K deficiency is now increasing even in alluvial illitic soils of India (Tiwari, 1985). Response to applied K depends upon crop, variety, soil fertility status, soil texture, cation exchange capacity, soil depth, soil moisture and application of other nutrients. Due to the dense rooting system, cereals often fail to respond to K in short-term field experiments. The yield levels and thus demands for K also determines the response to K. Beaton et al. (1992) reported that with increasing yields the response to K improved. At - rice yields increasing 8t ha ' the recommended rate of 75 kg K ha-' was not sufficient to meet crop K requirement. Earlier studies conducted on large number of farmers fields in India showed that application of 50 kg K ha-' gave response of 290 and 240 kg grain ha-' in wheat and rice, respectively (Randhawa and Tandon, 1982). Average agronomic response of 6 kg grain kg-' K to the application of 37.5 kg K ha-' was observed in rice and wheat. In later studies, Meelu et al. (1992) reported that response of rice to 25-50 kg K ha - ' ranged from 210-370 kg grains ha-' in northern states of India comprising Punjab, Haryana and W. Uttar Pradesh. Dobermann et al. (1995) reported significant yield increase of 12% to K application in rice at Pantnagar. From a 5-year field study on a sandy loam soil testing 123 kg available K ha - ', mean increase in the yield of rice and wheat by 280 and 160 kg grain ha-', respectively, due to - application of 25 kg K ha ' (Meelu et al., 1995). The low responses to fertilizer K observed in rice and wheat on alluvial soils of the Indo-Gangetic plain suggest that release of native K from illitic minerals in these soils could meet the K needs of these crops.

A large proportion of area (about 2.8 million ha) in the Indo-Gangetic Plains is highly alkaline (pH > 8.5) and contains excessive concentration of soluble salts, high exchangeable sodium percentage (> 15) and CaCO 3. Swarup and Singh (1989) found that application of fertilizer K did not significantly increase crop yields in rice-wheat rotation on reclaimed sodic soils in Haryana even after continuous cropping for 12 years. However, in salt affected soils of Kanpur, application of 25 kg K ha-' to both crops produced additional grain yield of 0.50 and 0.61 t ha-' of rice and wheat, respectively (Tiwari et al., 1998).

Using time series analyses, Bhargava et al. (1985) showed that response to K has been increasing with time. The response to K in wheat was in the range of 6.7-12.7 kg grain kg-' K during 1977-1992 as against 2.0-5.0 kg grain kg-' K during 1969-1971. The corresponding values for rice were 5.3-10.7 kg and 1.8-8.0 kg grain kg-' K. The increasing trend in response to K over the years suggests the need for its application in intensive rice-wheat cropping system. In another long-term studies in India, response to K application increased with time, while that of N decreased (Table 4). During 1975-1979, Kemmler (1980) Potassium Management in Rice-Wheat Cropping System in South Asia 183

Table 4. Response of crops to N, P and K application over time in rice-wheat cropping system in long-term experiments in India Crop Year Control yield Response to applied nutrient (kg ha-') (kg ha-') N120 P23 K33 Location: Faizabad (PDCSR, 1990) Rice 1977-78 1008 2905 500 50 1989-90 820 2642 925 231 Wheat 1977-78 833 2625 617 35 1989-90 602 2141 1169 398 Location: RS Pura (Hegde and Sarkar, 1992) Rice 1981-82 1490 2499 654 -250 1989-90 1550 880 989 666 Wheat 1981-82 980 873 458 66 1989-90 730 423 1191 2250 reported average increase in rice yield > 0.4 t ha-' due to K application in 400 out of 500 trials in Bangladesh. Long-term studies in Bangladesh showed that requirement of fertilizer K will increase overtime. The fertilizer K requirement for each of the rice and wheat crop in the cropping system recommended was 66.7 kg K/ha.

Dobermann (1995) suggested that yields of irrigated rice in Asia must be raised to 8.0 t ha - ' from a present level of 4.9 t ha-'. Similarly, the yields of wheat must be raised to 6.0 t ha -'. Hence large quantities of fertilizer K will be needed in the future to achieve such high yields of rice as well as wheat.

Effect of K fertility status of soils on response to potassium

It is a common finding that responses of rice and wheat to K application are higher on soils testing low in IM ammonium acetate-extractable K than on high K soils (Tandon and Sekhon, 1988; Yadvinder-Singh and Khera, 1998). Significant responses of wheat to applied K were observed up to 25 kg K ha-' on soils testing low in available K in Punjab, but no significant increase in wheat yield was observed on soils testing medium and high in available K (Sharma et al., 1978). From another study at Gurdaspur in the Indian Punjab, Azad et al. (1993) - reported that whereas wheat yield increased significantly up to 75 kg K ha 1 on soils testing low in available K, significant increase in wheat yield was observed only at 25 kg K ha-' on soils testing medium as well as high in available K. - Rana et al. (1985) observed that rice responded to 50 kg K ha ' on soils testing low and medium in available K, but no significant response to applied K was observed on soils testing high in available K. Tandon and Sekhon (1988) concluded that response of high yielding varieties of rice and wheat to K 184 Yadvinder Singh and Bijay Singh application in soils rated medium in available K were only marginally lower than responses in low K soils. Such results emphasize the need for fresh look at soil fertility limits used for categorizing soils into low, medium and high with respect to available K, particularly for highly productive rice-wheat cropping system.

Field experiments conducted at different locations in the Indian Punjab showed that rice responded more to applied K in north-eastern districts (Gurdaspur, Amritsar, Kapurthala and Hoshiarpur) than in central and south- western districts (Ludhiana, Bathinda, Sangrur, Ferozepur) (Singh and Bhandari, 1995). The values of available K in soil ranged from 150-180 kg K ha-' in northwestern districts and 112-165 kg K ha- 1 in central and southwestern districts. The lower rates of K release from clay minerals as well as lower rates of K fixation could be possible reasons for the greater responses to applied K in northeastern districts as compared to control and southwestern districts. Recent study (1997-2000) conducted at two locations in Punjab showed that both rice and wheat responded significantly to K application up to 50 kg K ha-' on loam soil at Gurdaspur, whereas no significant increase in crop yields was observed on sandy loam soil at Ludhiana (Table 5, Yadvinder-Singh and associates). Soils at both the locations tested low in available K. These studies suggest that same test values represent different K supplying capacity of different soils.

Table 5. Response of crops to potassium application in rice-wheat cropping system on two locations in Punjab, India Rate of Grain yield of rice (t ha- 1) Grain yield of wheat (t ha-') K 20 (kg ha-') 1997 1998 11999 2000 1996-9 1997-9 1998-9 1999-0( 1. Ludhiana (sandy loam soil) 0 5.4 4.4 5.7 6.3 4.2 4.9 4.5 6.1 30 5.3 4.6 5.7 6.4 4.3 5.1 5.1 6.5 60 5.4 4.6 5.6 6.4 4.1 5.0 5.0 6.5 LSD (0.05) NS NS NS NS NS NS 0.16 0.17 2. Gurdaspur (loam soil) 0 5.5 5.7 6.2 5.2 2.9 3.3 4.5 4.4 30 5.9 5.9 6.6 5.5 3.2 3.5 4.8 4.7 60 6.2 6.2 6.6 5.4 3.3 3.7 5.0 4.8 LSD (0.05) 0.441 0.34 0.30 0.27 0.32 0.22 0.18 0.29

Time and method of K application

Common recommendation is to apply full dose of K as basal at puddling for rice and at sowing of wheat. When cation exchange capacity of soil is low and drainage in soil is excessive basal application of K to rice should be avoided. Because rice and wheat require large quantities of K, a sustained supply is Potassium Management in Rice-Wheat Cropping System in South Asia 185

necessary up to heading stage when the reproduction stage is complete. On coarse textured soils, split application of fertilizer K in both rice and wheat may give higher nutrient use efficiency than its single application due to reduction in leaching losses and luxury consumption of K (Tandon and Sekhon, 1988). In Punjab, Kolar and Grewal (1989) reported a yield advantage of 250 kg grains ha-' by split application of K (half at transplanting + half at active tillering stage) as compared with single application at transplanting. Some other studies also showed distinct benefit of applying K in split doses (Tandon and Sekhon, 1988). Similarly, in sandy loam soil of Uttar Pradesh, Singh and Singh (1987) reported a yield.advantage of 440-490 kg grain ha -' in wheat by split application of K as compared to a single application. The number of splits required depend on the soil K buffering capacity, crop establishment method used and amount of fertilizer K to be applied. If the amount of K fertilizer required is small (<30 kg K/ha), all can be supplied as a basal application. In the direct seeded rice, the first K dose should be applied at about 10-15 DAS.

Fertilizer K at sowing of wheat and transplanting of rice is normally applied by drilling, placement or broadcast followed by incorporation.

Interactions of potassium with other nutrients

The interaction among plant nutrients is a common feature of crop production. Potassium plays an important role in ensuring efficient utilization of N. At insufficient K supply, NO 3- accumulates in the root, being partially reduced and converted into amino acids. The build up of the latter signals in a feed back effect on the plant to further reduce N uptake. As a consequence, with increased K depletion yield decreases and N use efficiency decreases. Large quantities of N used in intensive rice-wheat cropping system encourage crop uptake of N and K and in turn heavy depletion of soil K. Application of N and P resulted in 145% increase in K uptake as compared to control (Tandon and Sekhon, 1988). If insufficient N and P or other essential plant nutrients restrict the crop development, amount of K present even at low soil test values may be sufficient to meet crop needs. Tiwari et al.(1992) reported that response to K application in rice increased with increasing rate of N application. In order to obtain high yields need for applying increasing rate of K with increasing levels of N was suggested.

GENERAL K MANAGEMENT

K management should be considered part of a long-term soil fertility management, because K is not easily lost from or added to the root zone by the short-term biological and chemical processes that affect the N supply. K management must ensure that N use efficiency is not constrained by K deficiency. 186 Yadvinder Singh and Bijay Singh

In most irrigated areas, K input from irrigation water ranges between 10 and 50 kg ha -' per crop, which is insufficient to balance removal and leaching losses at current yield level of 5-6 t ha-'. The K content of irrigation water can vary widely from place to place and from year to year. The K concentration in irrigation water is largest in shallow-well water (5-20 mg K L-1), followed by deep-well ground water (3-10 mg K L-1), and surface water (1-5 mg K L-1). In Punjab (India), K concentration in deep-well irrigation water ranges from 0 to 275 mg K L- 1, with a man value of 6.2 -15.2 mg L (Brar, 1998). One irrigation of 7.5 cm depth will thus add about 4.5 kg K ha-'. Total numbers of irrigations needed to raise a crop of rice and wheat are 15-20 and 4-5, respectively. The irrigation water rich in K may be sufficient to meet K requirement of high-yielding crops. The K balance studies should include K input from irrigation water. Pasricha et al. (2001) reported that K content in tube well waters in the submountaneous region was lowest (0.54-14.9 mg/L) with avergae value of 4.04 mg/L, and highest level of 6.71 mgfL was found in tube well waters of souihwestern arid zone (0.64-46.4 mg/L). The central plain region of the state had an average value of 5.41 mg/L (0.87-38.1 mgIL). However, total contribution of around 80 kg K/ha though tube well waters towards K nutrition of rice-wheat system was not very significant. In southwestern region wheat 70% irrigation is through canals, contribution of K through ground water is negligible (36-42 kg K/ha).

Dobermann and Fairhurst (2000) outlined following steps in site-specific K management using QUEFTS model:

1. Estimate crop K demand for a target yield (UK). First of all define maximum yield (Ym.) based on site-specific climatic conditions. Using a relationship between plant K uptake and target yield, estimate the amount of K required to achieve the defined target yield for the selected Ymax. 2. Estimate potential indigenous K supply (IKS). The IKS can be estimated by the K omission plot technique. 3. Estimate recovery efficiency (RE) of applied K fertilizer. RE can be estimated for a particular cropping system and K application method by conducting an experiment with different fertilizer K rates when crop growth is not constrained by the supply of other nutrients.

Fertilizer K rates (FK) can be calculated as:

FK (kg K/ha)= (UK - IKS)/RE

The required fertilizer K rates depend on many factors, soil texture, availability of other nutrients, variety, yield target, straw management, addition of manure or compost, cropping intensity, and the amount of K in irrigation water. Hybrid rice always requires larger application of K (50-100 kg/ha) on most soils than inbred modern varieties. When most of the straw remains in the field or burned in-situ after combine harvesting, apply only 3 kg K/ha per ton Potassium Management in Rice-Wheat Cropping System in South Asia / 187

grain harvest. From a long-term (10 years) field experiment, Beri et al. (1995) reported that recycling of straw significantly increased both exchangeable and non-exchangeable K contents in soil over its removal from the field.

Dobermann et al. (1995) showed that relationship between rice grain yield and K uptake is scattered and nonlinear. There is a large range of K uptake (16- 50 kg K) for one ton of rough rice, which makes it difficult to estimate the K requirement for a given yield target over a large area. Total K content in grain of modern rice and wheat varieties is fairly constant between 0.25-0.33% for rice and between 0.30-0.40% for wheat. The relationship between yield and K uptake showed that the K requirement of rice in the yield range 4-8 t ha -' varied from 17 to 30 kg K ha-' of grain. Using the relationship, yield of 5-8 t ha-' would require total K uptake of 105-237 kg ha -' because K is absorbed at a rate that parallels dry matter between tillering and early grain filling, a period as short as 60 days. Thus large amounts of K must be easily available in order to meet daily K uptake rates of 1.4-3.6 kg K ha-'day- ' over that period. Similarly peak K uptake rate of wheat is also quite high. The critical level for K in rice straw at harvest is between 1.0% and 1.5%, but yields > 7 t- ha require >1.2% K in straw at harvest and >1.2% K in flag leaf at flowering. For optimum growth, the N:K ratio in straw should be between 1.1 and 1.4. To produce the maximum number of spikelets per panicle, the K content of the mature leaves should be >2% at the booting stage.

Duration of crops, its uptake rate, its rooting pattern, yield potential and conditions of growth are the factors which besides the K supplying capacity of a soil determine the actual needs for fertilizer K. Total K needs of rice or wheat is much greater than indicated by the quantities present in the crop at harvest. The K removal at the peak demand period in mid season can be 40-50% more than measured at maturity. Between flowering and maturity there are substantial losses of K due to leaching from aging leaves, leaf fall and possibly also by leakage from mature roots.

POTASSIUM BALANCE UNDER RICE-WHEAT CROPPING SYSTEM

Introduction of modern production technologies for rice and wheat with high N responsive high yielding varieties has resulted in increased annual crop demands for K by the crops. From the nutrient removal data (Table 2) it is evident that in rice-wheat system annual removal of K is quite large, while the replacement of K by fertilizer represents only a fraction of total K removal. Tandon and Sekhon (1998) found K balances in rice and wheat amounting to -141 and -61 kg K20 ha-'. Furthermore, most of the K uptake in rice and wheat crops is stored in straws, which is mostly removed from the field as animal feed and is not directly returned to the soil. Long-term studies have shown that K balance in rice wheat system is highly negative and application of recommended doses of K has only slightly improved the K balance. In a long-term experiment 188 Yadvinder Singh and Bijay Singh at Ludhiana, net negative K balance of about 250 kg K ha- 1 year- ' was observed and it decreased available K level of the soil (Table 6). There was considerable K removal from non-exchangeable K reserve of soil, which contributed about 95% towards the K nutrition of rice and wheat crops. Tiwari (1985) observed a decline in available and non-exchangeable K by 17% and 2.8% after two cropping cycles measured on 14 fields at Kanpur (Uttar Pradesh). Removal of all the straw from the fields leads to K mining at alarming rates because 80-85% of the K absorbed by rice and wheat crops is contained in the straw. The K rates applied by most farmers are lower than those used in the long-term experiments. The K balance at the farmer's fields in Haryana showed a negative K balance of 170 kg K ha-' after annual cropping of rice and wheat. The use of K in Indian Punjab is almost nil but K removal by crops is as much as of N. Consequently, the K balance is extremely negative and K depletion is steadily increasing (Figure 1). Long-term studies in Bangladesh showed that K balance in rice-wheat cropping

Table 6. Potassium balance under different rates of K application after 4 cycles of rice-wheat cropping system at Ludhiana (India) (Meelu et al., 1995) K rate Total Total K uptake Net K Depletion Contribution K applied (kg ha -1) balance of from non- (kg ha -') (kg ha-') (kg ha- ) available exchangeable Rice Wheat Total K K (%) (kg ha-') 0 0 535 348 883 -883 34 96 25 200 563 360 931 -731 28 96 50 400 548 384 932 -532 26 95 75 600 551 404 955 -355 23 94 Depletion of available K was calculated from. 0-15 cm soil layer.

1'000 o remova use balonce 600 -00 f,00 o 0

'I- 0 Z-200

6990 91192 93/91.4 89190 91/92 93/94.. 9/90 91192 9319,'

Figure 1. Nutrient use, removal and apparent balance in food grain production in Punjab, India Potassium Management in Rice- Wheat Cropping System in South Asia 189

system turned out to be negative (-118 kg K/ha) even when 83.3 kg K/ha was annually applied (Bhuiyan et a., 1993). When no fertilizer K was applied the negative K balance increased to 120 kg K/ha.

The negative K balances mean that it will be impossible to maintain the present production level and meet the future need for food for the growing population of south Asia. Results from long-term fertility experiments in India show that crop response to K application starts appearing over a period of time in soils which were initially well supplied with K (Nambiar and Ghosh, 1984). Such responses to K started appearing after 3 years in rice and 11 years in wheat at Pantnagar (Uttar Pradesh) and after 3 and 7 years respectively at Barrackpore (West Bengal). Long-term studies suggest that application of FYM and recycling of crop residues can help improve the K balance in the rice-wheat cropping system (Yadvinder-Singh and Khera, 1998). Studies on K balance help to understand the K dynamics with special reference to K build up or depletion under different levels of K management. Presently little data are available on the recovery of fertilizer K applied to rice-wheat cropping system. Long-term fate of added K will depend on soil texture (leaching) and clay mineralogy (fixation) and crop removal.

Dobberman et al. (1995) reported that application of 1250 kg K ha -' to 25 consecutive rice crops was insufficient to maintain the initial soil test values and the K balance remained negative. Therefore, the K rates, which do not equilibrate the K balance cannot show the true response of crops to K. Straw management will have a large impact on the overall K balance. Removal of crop residues for use as forage or fuel will increase depletion of K from croplands. On the other hand, returning all or most of the crop residues will reduce K removal and need for K fertilization. Lin Bao and Li Jiakang (1992) reported that on a clay soil with 98 mg exchangeable K kg-' rice yield with 75 kg K20 ha-' over NP treatment was merely o.52 t ha-' because K balance remained negative, but the yield response to K over NP increased to 1.58 t ha- , when additional organic manure was applied, which helped to achieve a positive K balance (Table 7).

Table 7. Effect of long-term (1981-1990) application of K on rice yields and soil K status on a clay soil with initial available K content of 98 mg kg - '. (Lin Bao and Li Jiakang, 1992) Treatment Grain yield Soil K K balance (t ha-') (mg kg-') (kg K 20 ha') Check 2.95 44 -881 NP 4.06 43 -841 NPK 4.58 55 -552 NPK + Organic manure 5.64 88 +533 190 Yadvinder Singh and Bijay Singh

FUTURE RESEARCH NEEDS

The soil moisture regimes in rice-wheat system show tremendous variation but effects of such moisture changes on K availability and crop responses have not received much attention. Research is needed to clarify processes of fixation and release of K during drying and wetting cycles, and extent of impeded K diffusion in the rhizosphere of rice and its effect on K uptake at very high yield levels. A better understanding is needed of the processes affecting long-term fate of fertilizer K in irrigated rice-wheat system, including more information about the influence of wetting and drying cycles on the recovery and leaching of K (Dobermann et al., 1998). Research may be initiated to predict the time taken for soils currently well supplied with K to become deficient in K.

Applied research must provide the tools necessary for practical use of long- term strategies for K management based on nutrient balance concept. Tools such as the resin capsule, models for estimating crop nutrient requirements based on interactions of N and K and models for predicting the long-term fate of added K fertilizers should be fully developed for rice-wheat system. They may provide a basis for introducing farm or field-specific nutrient management approaches. System approach in research on nutrient management in rice-wheat system must be encouraged. There is a need to develop improved nutrient management practices that will enhance fertilizer use efficiency, reduces nutrient losses and increase benefit to farmers.

Dynamic soil test methods assaying the K supplying power of soils under rice- wheat system should be developed. A integrated approach to K fertilizer recommendation may be developed based on site factors, laboratory analysis (texture, exchangeable and non-exchangeable) and data from weather records, soil survey (clay mineralogy, soil depth), probable yield and crop response, and processed by computer models that would generate a fertilizer recommendation derived almost entirely from site-specific data.

Recycling of crop residues and other organic inputs influence nutrient supplying capacity of the soil. We need an improved understanding of how crop residue management affects nutrient cycling in the subsequent wheat crop and in the soil nutrient pools. This will facilitate the development of budgets to balance nutrient removal with nutrient application at different yield targets which seems necessary in sustainable, high yielding, rice-wheat production system. Long-term field experiments on well-characterized sites should be initiated and carefully monitored for changes in soil fertility and crop productivity.

REFERENCES Abedin Mian, M.J., H.P. Blume, Z.H. Bhuiyan, and M. Eaqub. (1991). Water and nutrient dynamics of a paddy soil of Bangladesh. Zeitschrift far Pflanzenernaehr und Bodenkunde 154: 93-99. Potassium Management in Rice-Wheat Cropping System in South Asia 191

Azad, A.S., Bijay-Singh, and Yadvinder-Singh. (1993). Response of wheat to graded doses of N, P and K in soils testing low, medium and high with respect to P and K in Gurdaspur district of Punjab. Journal of Potassium Research 9: 266-270. BBS 1992. Statistical Year Book of Bangladesh, 1990-91. Bangladesh Bureau of Statistics, Dhaka, Bangladesh. Beaton, J.D., Hasegawa, M., Xie Jiang-Chang, Keng, J.C. and Halstead, E.H. (1992). Influence of intensive long term fertilization on properties of paddy soils and sustainable yields. In: Proceedings of InternationalSymposium on Paddy Soils. Nanjing, China. September 15-19, 1992. pp. 252-271. Beri, V., B.S. Sidhu, G.S. Bahl and A.K. Bhat (1995). Nitrogen and phosphorus transformations as affected by crop residue management practices and their influence on crop yields. Soil Use Management 11: 51-54. Bhargava, P.N., H.C. Jain, and A.K. Bhatia. (1985). Response of rice and wheat to potassium. Journal of Potassium Research 1: 45-61. Bhuiyan, A.M., M. Badaruddin, N.U. Ahmed, and M.A. Razzaque. (1993). Rice- wheat system research in Bangladesh: A review. Wheat Research Center, Bangladesh Agricultural Research Institute, Dinajpur, Bangladesh. 96 pp. Brar, J.S. (1998). Fertility status of soils of Punjab and contribution of ground water towards plant nutrition. In: Balanced Fertilization in Punjab Agriculture, eds. M.S. Brar and S.K. Bansal, Ludhiana, India: Department of Soils, Punjab Agricultural University; Basel, Switzerland: International Potash Institute; Gurgaon, India: Potash Research Institute of India Pp. 10- 19. Dobermann, A., K.G. Cassman, C.P. Mamaril, and J.E. Sheehy. (1998). Management of phosphorus, potassium, and sulfur in intensive, irrigated lowland rice. Field Crops Research 56: 113-138. Dobermann, A. and Fairhurst, T. (2000). Rice: Nutrient disorders and nutrient management. Potash and Phosphate Institute (PPI) and Potash and Phosphate Institute of Canada (PPIC). 191 pp. Dobermann, A., P.C. Sta. Cruz, and K.G. Cassman. (1995). Potassium balance and soil potassium supplying power in intensive, irrigated rice ecosystems. In Potassium in Asia- Balanced Fertilization to Increase and Sustain Agricultural Production. Basel, Switzerland: International Potash Institute, pp. 199-234. Driessen, P.M. (1986). Nutrient demand and fertilizer requirements. In Modelling of Agricultural Production: Weather, Soils and Crops, eds. H. van Keulen and J. Wolf, Wageningen, The Netherlands: Pudoc, pp. 182-202. Grewal, K.S. and Mehta, S.C. (1996). Response to potassium in some field crops in Haryana. In: Proc. PPICIHAU Workshopon use of potassium in Haryana agriculture. Hisar, India. December 16, 1996. pp. 68-73. 192 Yadvinder Singh and Bijay Singh

Hegde, D.M.and A. Sarkar (1992). Yield trends in rice-wheat system in different agro-ecological regions. In: Rice-Wheat Cropping System, eds. R.K. Pandey, B.S. Dwivedi and A.K. Sharma, PDCSR Modipuram, India, pp. 15-31. Islam, A. (1995). Review of soil fertility research in Bangladesh. In Improving Soil Management for Intensive Cropping in the Tropics and Sub-tropics, eds. M.S. Hussain, S.M. Imamul Huq, M. Anwar Iqbal, and T.H. Khan, Dhaka, Bangladesh: Bangladesh Agriculture Research Council, pp. 1-18. Kanwar, J.S. and Mudahar (1986). Fertilizer Sulphur and Food Production. Martinus Nijhoff/ Dr Junk Publishers. Dodrecht, The Netherlands, 247 pp. Kawaguchi, K. and K. Kyuma. (1977). Paddy Soils in Tropical Asia. Their Material Nature and Fertility. Honululu: The University Press of Hawaii. 258 pp. Kemmler, G. (1980). Potassium deficiency in the soils of the tropics as a constraint to food production. In Priorities for Alleviating Soil-Related Constraints to Food Production in the Tropics. Los Banos, Philippines: International Rice Research Institute, pp. 253-275. Kolar, J.S. and H.S. Grewal. (1989). Response of rice to potassium. International Rice Research Newsletter 14(3): 33. Komal-Singh, Bansal, S.K. and Moindeen. (2001). Leaching losses of potassium as influenced by accompanying onion. journal of Potassium Research. 17: (in press) Krauss, A. (1998). Long-term field trials an indispensable tool to monitor soil fertility. In: Balanced Fertilization in Punjab Agriculture, eds. M.S. Brar and S.K. Bansal, Ludhiana, India: Department of Soils, Punjab Agricultural University; Basel, Switzerland: International Potash Institute; Gurgaon, India: Potash Research Institute of India. pp. 34-48. Lin, Bao and Li, Jiakang (1992). Some results of long-term fertility trials in sustainable rice farming in China. In: Proc. Intern. Symp. on paddy soils. Nanjing, China. September 15-19, 1992. pp. 274-280. Meelu, O.P., Yadvinder-Singh, Bijay-Singh and A.L. Bhandari. (1995). Response of potassium application in rice-wheat rotation. In: Use of Potassium in Punjab Agriculture, eds. G. Dev and P.S. Sidhu, Gurgaon, India: Potash and Phosphate Institute of Canada-India Programme, pp. 94-98. Meelu, O.P., Yadvinder-Singh, M.S. Maskina, Bijay-Singh, and C.S. Khind. (1992). Balanced fertilization with NPK and organic manures in rice. In Balance Fertiliser Use for Increasing Foodgrains Production in Northern States, Gurgaon, India: Potash and Phosphate Institute of Canada - India Programme, pp. 63-74. Nambiar, K.K.M. and A.B. Ghosh. (1984). Highlights of Research on Long-term Fertilizer Experiments in India (1971-82). New Delhi, India: Indian Potassium Management in Rice-Wheat Cropping System in South Asia 193

Agricultural Research Institute. 189 pp. Pasricha, N.S., Sharma, B.D., Arora, C.L., and Sidhu, P.S. (2001). Potassium distribution in the soil and ground waters of Punjab. Journal of Potassium Research. 17: (in press). PDCSR. (1990). Annual Report. Modipuram, India: Project Directorate Cropping System Research. 396 pp. Prasad, B.L. and J. Prasad. (1992). Availability and critical limits of potassium in rice and calcareous soils (Calciorthents). Oryza 29: 310-316. Rana, D.S., P.S. Deol, K.N. Sharma, Bijay Singh, A.L. Bhandari and J.S. Sodhi (1985). Interaction effect of native soil fertility and fertilizer application on yield of paddy and wheat. Journal of Research (PAU) 20: 431- 436. Randhawa, N.S., and H.L.S. Tandon. (1992). Advances in soil fertility and fertiliser use research in India. FeriliserNews 26(3): 11-26. Regmi, A.P. (1994). Long-term effects of organic amendments and mineral fertilizers on soil fertility in a rice-wheat cropping system in Nepal. M.Sc. Thesis, Los Banos, Philippines: University of Philippines. 142 pp. Saunders, D.A. (1990). Report of an On-farm Survey-Dinajpur District: Farmer's Practicesand Problems, and their Implications, Monograph No. 6, Nashipur, Bangladesh: BARI Wheat Reserach Centre. 39 pp. Sekhon, G.S. (1995). Characterization of K availability in paddy soils - present status and future requirements. In Potassium in Asia - Balanced Fertilization to Increase and Sustain Agricultural Production, Basel, Switzerland: International Potash Institute. pp 115-133. Sharma, A.N. and R. Prasad. (1980). Nutrient removal (NPK) in rice-wheat rotation. Fertiliser News 25(10): 34-36, 44. Sharma, K.N., J.S. Brar, M.L. Kapur, O.P. Meelu, and D.S. Rana. (1978). Potassium soil test values and response of wheat, bajra and gram to fertilizer K. Indian Journal of Agronomy 23: 10-13. Singh, B. and A.L. Bhandari. (1995). Response of cereals to applied potassium. In: Use of Potassium in Punjab Agriculture, eds. G. Dev and P.S. Sidhu, Gurgaon, India: Potash and Phosphate Institute of Canada- India Programme, pp. 58-68. Singh, K.N., and M. Singh. (1987). Effect of levels and methods of potash application on the uptake of K by dwarf wheat varieties. Mysore Journal of Agricultural Science 21: 18-26. Singh, M., and V. Singh. (1992). Balanced fertilisation with NPK for increasing wheat production. In Balance Fertiliser Use for Increasing Foodgrains Production in Northern States,Gurgaon, India: Potash and Phosphate Institute of Canada - India Programme, pp. 75-84. 194 Yadvinder Singh and Bijay Singh

Swarup, A., and K.N. Singh. (1989). Effect of 12 years of rice-wheat cropping sequence and fertilizer use on soil properties and crop yields in sodic soils. Field Crops Research 21: 277-287. Tandon, H.L.S. and G.S. Sekhon. (1988). Potassium Research and Agricultural Production in India. Fertiliser Development and Consultation Organization, New Delhi. 144 pp. Tiwari, K.N. (1985). Changes in potassium status of alluvial soils under intensive cropping. Fertiliser News 30(9): 17-24. Tiwari, K.N., B.S. Dwivedi, and A. Subba Rao. (1992). Potassium management in rice-wheat system. In: Rice-Wheat Cropping System, eds. R.K. Pandey, B.S. Dwivedi and. A.K. Sharma, Modipuram, India: Project Directorate Cropping System Research, pp. 93-114. Tiwari, K.N., G. Dev, D.N. Sharma and U.V. Singh. (1998). Maximising yield of a rice-wheat sequence in recently reclaimed saline-sodic soils. Better Crops International 12(2): 9-11. Yadav, R.L., S.R. Singh, K. Prasad, B.S. Dwivedi, R.K. Batta, A.K. Singh, N.G. Patil, and S.K. Chaudhary. (2000). Management of irrigated ecosystem. In: Natural Resource Management for Agricultural Production in India, eds. J.S.P. Yadav and G.B. Singh, New Delhi, India: Indian Society of Soil Science, pp. 775-870. Yadvinder-Singh and Bijay-Singh (2001) Efficient management of primary nutrients in the rice-wheat system. in: The Rice-Wheat Cropping System of South Asia: Efficient Production Management (ed: Palit Kataki), Food Products Press, an imprint of The Haworth Press, Inc., 2001, pp. 23-86. (Also published in Journal of Crop Production 4: 23-86). Yadvinder-Singh, and T.S. Khera. (1998). Balanced fertilization in rice-wheat cropping system. In: Balanced Fertilizationin Punjab Agriculture, eds. M.S. Brar and S.K. Bansal, Ludhiana, India: Department of Soils, Punjab Agricultural University; Basel, Switzerland: International Potash Institute; Gurgaon, India: Potash Research Institute of India, pp. 74-87. Potassium Nutrition Management for Improving Yield and Processing Quality of Potato

J.P. SINGH, S.!'. TREHAN AND R.C. SHARMA* ,-tulr/Potato Resca&h Station, Jlandhar-144003 PIZjah)

ABSTRACT

Pot assiuin fertili/ation inproves the yield and tuber size of potato. It improves the processing quality of tubers by minimizing the enzy ttc browning during peeling and cutti n of fresh tubers and discolouration of products like chips and trench fries during trying. Decrease in phenols. orthohydric phenols, free amino acids and tyrosine due to K fertilization isresponsibe lot imuprovemntC in processing quality. Increase ini crude and soluble proteins, starch and ascorbic acid due it K application improves the nutritive quality of tubers. Direct application of potassiun to potato is essential- Both early as well as late crop of potatoes need to be fertilized with equal rates of potassiuin. Opti mal dose of fertilization varied from 86 to 132 kg K/ha depending upon soil, variety and agroclimratic conditions in different parts of India. While, the likely responses %aiied from 3.4 to 6.7 t/ha of potato tubers. Depletion of soil K under intensive potato based cropping systens for prolonged periods restlted in) severe negative balance of potassium in soils to the detriment of crop yields. Maintenance K fertilization to crops other than potato in the cropping systems was advocated as insurance against possible decline i yield of crops in the long run. Iigh efficiency of mttive soil K (10514 ) to that of fertilizer K to potato further justifies maintenance of soil K at a high level in potato based cropping systeins. Utility of various agrotechniqtues illpotassium nutrition Managelent viz. sources of potassiuin. placement methods, amendments, interactions, split and toliar applications has been reviewed and discussed along with role, requirement, deficiency synptons and critical limits in soils and plant for potato. Role of- potassium in irost draught and disease tolerance in potato and economics of fertilization is highlighted

INTRODUCTION

Potato is less efficien user of potassium than other crops (Trehan and Claassen, 1998, 2000). As such potato invariably responds to potassium application in various kinds of soil and agrocli matic conditions in wshich it is grown. Potassium does not enter into any organic ligand with plant ConstItuents. Nevertheless, it has tremendous role in nutrition ol potato plant. It is implicated 195 196Ite Si'igh.,o £P lhihand N...Slwnnu directl .r indirctl 5 in eiea li phvsi l oical and biochiemical proces'es in potato plant. It has impotlu rTole in tuwer Yield toatinon, veytrlalive groth and ntainienattce of cell stIucre, thUs resistaniC aeaflt drotehL"It, fiost ind diseiics and pests Role and reqi ement of' potassium InI improving tihe icd and pltcessine qualhir otpollo clop co ini different reioIsl otIndia is precented hele,

Role of Potassiui

Potasiii!i increases heal cxpansion particularly at early stagc of growth and extcids leaf aire duration bI deljvint senescence towards matutiy (Figure 1). It aids in translocation of photosvntates iromIi leaf to tubers. Thus it incrases both the rate and duratil of tiber bulkin_. The Increase in tuber Vicld is. manly throuli incieased itber size and not the ILumber)(Grewal anid Sinllb 1980 Trel an uf at 2001).

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ligurc I , n i .P/ I Mlu!d Int* I t "vciojut.7t K I ti'S/. c/ha tplo t,. fdl;ce "' th <'ar'wl/ic/c £!,r

Ycrce: (IPIit>Ri r PR.I potai> csCrI)M C[i 'a .iz CC, lieidat Jhilnihsar, Punjab. ] 08)I

Deficiency s1 mptoms

In potato dtci ency simnpitoms of potassium coincide \%khi tuerisation and rapid tuber bulking phase lDeficient potato plants assume a dark bluish green colour compared to healthv yellowish ereen colour of normal plants (Figure 2). Lnder severe deficiency bronzing, scorching of lca'es and necrosis of leaf margins I'murn.,w Nrnll.., Manac"m r,. lmpmtoug Keld jand Pnein... alliyla ofi?; 197

I[t it QRII to. wl X takes place at later stages ol growh (Figure 3 and 4). Inefficient utilization of soluble N compounds and thus their accamulation is implicated in development of necrotic leaf spots and margins in leaves ot K deficient potato plant.

Deficiency limits in soil and plants

Alluvial soils having less than i16 mkg K tNIOAc-K) were classified as deficient for potato (Singh and (3rxvaI. 1985). In alluvial soils of Patna, average response to applied K vva, 9. 1. 4.3 and 0 6 1/ha when soil test value of am monit nMacetate extractable K v as 55. 131 and 177 rng kg :(Table ). In the acidic hill soil average response to applied K was 6.4, 3.9 and 1 8 t/ha when soil test values of aminonium acetate extractable K ,vax 140, 182 and 212 mg ku iGreval et al-. 1991), 191~~~ ./. T1izh /1.P'hamdi T R.C Shur'a

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it' PFLl (CPR] P )I,I~r 0Pr e hxc/rrnrt l~d i ialtrrrikpr. iro/zrb 19M8) Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 199

Table 1. Potato response (i/ha) to potassium in relation to soil test values at Patna (Bihar). - 1) Levels of K (kg/ha) Soil Test Values of NH 4OAc-K (mg kg 55 131 177 50 6.0 2.6 0.0 100 9.8 5.1 0.4 150 9.3 4.5 0.0 200 11.2 4.9 2.0 Mean 9.1 4.3 0.6 Source: Singh and Grewal (1985)

Plant tests measuring concentration of K in tissues indicate the supply from the soil medium. However, the concentration rapidly changes during the growth period due to several factors limiting its utility and reliability as an index for detecting deficiencies under field conditions. In alluvial soils leaflet K concentration of 3.62% at 50 days after planting was classified as deficient whereas concentrations ranging from 3.8-5.0% as adequate (Singh, 1987a, b). The concentration of K is highly variable with crop age and even cultivars (Figure 5).

Requirement for potato production

A mature crop of potato removes on an average 3.82 kg K per ton of tuber yield (Singh and Grewal, 1995). This value is fairly constant, as shown by the relationship between levels of applied K, total K uptake and K uptake per ton of tuber produced (Figure 6). Obviously the removal and, therefore, the requirement for fertilizer K depends on realizable tuber yield target as a function of the level of technology and management at farm, variety, soil and agro- climatic conditions. A normal crop of potato (30-40 tlha) removes about 110- 170 kg K/ha from the soil. Maximum accumulation of K takes place between 30 to 60 days of planting in the plains and 65 to 85 days in hills (Grewal and Trehan, 1993). Therefore, a ready supply of K from soil is required during early stages of growth of the fast growing potato crop. Most of the light textured potato growing soils are poor in fertility unable to match the rate of supply of K to the demand by the potato plant during early stages of growth (Grewal et al. 1991). Therefore, external supply of K through fertilizers and manures is essential.

Response to K fertilization

The potato is grown over the length and breadth of the country wherever conditions are favourable in about 1.2 million ha. However, 80% of the area 200 J.P. Singh, S.F Trehan and R.C. Sharma

KUFRI JYOTI

.4 TH LEAF. BLADE 4 TH PETIOLE

4.5 o-o r z-0-990 9 0-.o r=:-0.993 --- r=-.987 r:-0.999

41 w s r' IV It cl

zZ IV,, -c 6O U 1,5 3

0 30 45 60 0 30 45 60 CROP AGE (DAYS AFTER PLANTING)

KUFRI CHANDRAMUKHI

4 TH LEAF BLADE 4 TN PETIOLE

4.5 o-o r:-0.982 9 o-o r -0.996 .-- r :-0.982 r :-0.999 t4f

z ,

oTc , Icl 4, _J I U "1.5 3 030 45 60 0 30 45 60 CROP AGE (DAS AFTER PLANTING)

Figure 5. Relation ship between K concentration in leaf tissues of potato and crop age. Source. (Trehan and Grewal, 1994) under potato is confined to Indo-Gangetic plains extending from Punjab to West Bengal. In all 7 potatoes growing zones have been identified as follows:

1. North-Western plains (Punjab, Haryana, northern parts of Rajasthan) Potassin Nutrition Management for Improving Yield and Processing Quality of Potato 201

35 1140 10

* Tuber yield _ 33 0 Total K uptake 130, 8 0 j:A K uptake/t tuber 30

"-J uC

m 29- 110

_J 0C 27- 100 . 2 "1

25 ' ' 90 0 0 21 42 63 84 105 APPLIED K (kg/ha)

Figure 6. Relationship between tuber yield and K uptake in potato. Source: (Singh e al., 1995)

2. Western and Central Gangetic plains (Western UP, MP, Chhattisgarh and Rajasthan) 3. Eastern Gangetic plains (Eastern UP, Bihar, Jharkhand, West Benagal and Orissa) 4. Plateau region (Maharashtra, Gujarat and Karnataka) 5. North-Western hills (J & K, HP and Uttarakhand) 6. North-Eastern hills (Assam, Meghalaya, Arunachal Pradesh, Sikkim and Tripura) 7. Nilgiri hills (Tamil Nadu)

The optimum dosages of K fertilization to potato and likely response in different zones have been summarized in Table 2. Potatoes growing alluvial soils in Indo-Gangetic plains are mostly coarse in texture, low in organic carbon and neutral to alkaline in pH. In North-Western plains the mean optimum 202 J.P Singh. S.F. Trehan and R.C. Sharma

Table 2. Fertilizerpotassium needs of potato crop in different potato growing zones of India Location Optimum Likely References dose response (kg/ha) (q/ha) 1. North-western plains Jalandhar 104 32 (Singh et. al., 1996) Jalandhar 97 47 (Singh & Grewal,1995) Jalandhar 99 92 (Trehan & Sharma, 1998) Mean 100 57 2. Western and Central Gangetic plains Pantnagar 120 51 (Singh & Raghav, 2000) New Delhi 100 26 (Lal & Arora, 1993) Chhindwara 84 42 (Nandekar et al., 1991) Babugarh 84 31 (Grewal et al., 1984) Modipuram 112 32 (Upadhay & Grewal, 1985) Modipuram 84 23 (Sharma et al., 1984) Mean 97 34 3. Eastern Gangetic plains Patna 138 76 (Singh & Grewal, 1985) Patna 80 74 (Singh & Grewal, 1983) Patna 126 66 (Sharma et al., 1984) Varanasi 166 86 (Singh & Singh, 1995) Faizabad 149 35 '(Singh et al., 1997) Mean 132 67 4. Plateau region Banglore 104 62 (Lalitha et al., 1997) Rajgurunagar 84 10 (Grewal et al., 1984) Mean 94 36 5. North western hills Fagu 75 75 (Verma & Grewal, 1983) Shimla 79 61 (Grewal, 1985) Shimla 149 83 (Sood & Sharma, 1985) Lahul 42 36 (Sharma & Sharma, 1989) Mean 86 64 6. North eastern hills Shillong 100 54 (Sharma & Singh, 1988) Shillong 120 47 (Ram & Prasad, 1985) Mean 110 64 7. Nilgiri hills Ootakamund 96 38 (Grewal, 1985) Pnnaszh, . Xuafh,"M'Iu'uu ... , Improdagv held ....Prcssn Quality o'au; 233

requirement is 100 kg K/ha with likely response of 5.7 t/ha (Table 2). Corresponding lalues in We stein and Cental gangetic plains is Q7 kv, K/ha wfilh likely xesponse of 3.4 tha. In Eastern (jan getic plains requirementl of K is highest to the extent of 132 kg K/ha vilh likely response of 6,? Uha

In plateau region potato is gro. n in Black Cotton and Red soils mostly as rainfed crop. The mean optimum requirement in these soils is 94 kg K/ha wilh likely iespone of 3.6 I/ha (Table 2).

Potato grow inc acidic hill soils are characterized by high organic carbon and low pll. In North-Western hills mean opti mum reuuiretment is 86 kg K/ha with likely responmse of 6.4 rI a Table 2). Corresponding values for North Eastern hills is I10 kg K/ha 'iuh likely response of 5.0 t/ha. In Nilgiri hills optimum (lose is 96 kg K/ha with likely response ot 3.8 i/ha.

Increase in luber yield is nainly through the increase in yield and proportion of large size tubers at the cost of mnedium and small size tubers (Figure 7). In alluvial soils, both autumn and springs crops oesponded to direct as well as residual effect ot K fertilization (SingIh ef at., 2000), The response to direct effect in auuin and sphrig potatoes was L,6 and 1.2 times more, respectively, than the residual effect (Singh et al., 2000). Therelore, direct application ot polassium to polato is essential.

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*240.+19.

F igtire 7. 1 l,, <.*& th m~e RI111 PR po~w 111llm nt ii ,rm t t 11r'i aiandtta , 'nvi, j4.9)) 204 J.P Sin vih SRVlw, vin, R.. XA,,rh(

Ferilizalion with K at equal rate, to both erly as well as Late crop of polatoes wNas necessary CFable 3). Cost cuting by reducing polasstiull hetili.ation to early or immaturely harvested crop is ruled oal (Singh "t 01., 1996). Because, of the titemendous role of K in earls velctative growth and bulking of tubers.

Ta hle 3. oI/ir'p*arfsijroi/i at ion oan tuhber yied fq/ha ) I oh/on lai hale'socd cyopv of potwao Ku,'iBad iaoh larvesting Dates Level (if K 1kg/ha) (a>of planting) 0 75 F 10 50 IMa 70 235 262 269 273 260 85 335 354 358 367 353 I00 366 3 4 408 405 393 Mean 312 337 34 5 348 CD, 033) Dates = 15: K = 11; Dales x K = NS Sore: (Singh et id., 1996)

Agroteehniques and efficiency of potassium fertilization

Efficiency of fertilizer potassium is low compared to nitrogen. The mean apparent recovery of applied K to potato is 36£. fehc mean itilizalion efficiency of K absorbed from fertilizer was 49 % of that of native soil K sources Sini'zh and Grewal 1995). Various agrotechniques has e been employed Io improve tihe efficiency of fertilizer K to potato. These are reviewed here in brief.

Sources of potassium fertilizers

la alluvial soils of Puniab. the muriate of potash (MOP) and sulphate of potash (SOP) were equal l effective (Singh et ai, 1996). The SOP had an edge over MOP in alluvial soils of Banaras, llttar Pradesh (Ramaiah at aL, 1987). Schoenite (KSO + MgSO) was as effective as MOP in alluvial soils of Delhi (Gre ail alnd Trehan. 1993) and Laterite soils of Tamil Nadu (Maiy and Arora. 1980). Application of SOP nilay be preferred in sulphur deficient soils while that of schoenite in magnesium deficient soils. The benefit to cost rat io of that of MOP is better than SOP rGrewal and Trehan. 1993).

Organic siources of potassium

Faria ard manure @ of 30-50 t/ha met the K needs of potato and raised the tuber vield potential to higher levels compared to fertilizer K (Grewal and Tie han, 1993). This was attributed to the presence of additional secondary and micro nutrients in I armyard manure (FYM). Lower dosages of FYM (15 i/ha) met 50% of K needs of potato. Green manuring of dhai ncha and sunhemp reduced thre K Potassiumn Nutrition Management for Improving Yield and Processing Quality of Potato 205

fertilizer requirement of potatoes to the extent of 30-38 kg K/ha (Sharma and Sharma, 1990).

Placement methods

Response of potato to K application was not influenced by the band placement (below or above or along seed tuber) or broadcasting in alluvial soils under irrigated conditions (Singh and Grewal, 1995). In the acidic hill soils, where potato is grown under rainfed conditions, band placement of K along with seed tubers was found superior to broadcast (Grewal and Sharma, 1980). Similarly, in the acidic sandy loam soil of Banglore double band placement was superior to broadcast in increasing the tuber yield and uptake of K by the tubers (Krishnappa, 1990).

Amendment with organic manures

Amendment of potassic fertilizers with farmyard manure did not improve the efficiency of the fertilizer K in terms of tuber yield of potato (Singh and Grewal, 1995).

Foliar application

Foliar application of K by spraying 2% KCI solution in the standing crop at 50 days after planting increased the tuber yield by 4.3 tlha but could not supplant soil application (Trehan and Sharma, 1998). While, foliar application was not beneficial over the soil application in West Bengal (Dasmahapatra et al., 1984). Therefore. foliar application could be resorted to in case of severe deficiency visible in standing crop with limited benefits. To avoid scorching of foliage due to salts and chloride toxicity, spraying has to be done in the morning hours only and the period between 11-15 hrs must be avoided for spraying purposes (Trehan and Sharma, 1998).

Split application

In light textured loamy sand, soil split application of K (half at planting + half 30 days after planting increased the tuber yield by 6 % compared to basal application (Singh and Grewal, 1995). Normally basal application is preferred.

Interactions

Strong interaction between nitrogen and potassium fertilization on tuber yield is reported. Increasing levels of N alone decreased the K concentration in plant inducing hidden hunger for potassium (Sharma and Arora, 1987). Therefore, K requirement of potato increased with increase in rate of N application (Sharma

I * 206 J.l. Singh. S.P Trehan and R.C. Sharma

et at., 1984; Singh, 1986; Sharma and Atora, 1987). The dosages of fertilizer N and K are thus interdependent (Table 4).

Table 4. Effect of nitrogen and potassium interaction on tuber yield (qiha) of potato (Kufri Chandramukhi) at Patna, Bihar Levels of K Levels of N (kg/ha) (kg/ha) 0 50 100 150 200 250 Mean 0 154 212 218 253 262 258 226 67 177 263 304 300 314 334 282 134 186 258 304 338 365 379 304 Mean 172 244 275 295 314 313 C.D. (5%) N = 20 ; K = 15; N x K = 37 Source: (Singh, 1986)

Maintenance fertilization of potassium

Application of P and K to only potato crop in the potato based cropping systems was recommended during the eighties (Grewal and Sharma, 1981; Sharma et al., 1983). Because succeeding cereals and other crops failed to respond to direct application of P and K fertilizers. The residuals of K applied to potato fully or partially met the requirement of succeeding crops (Prasad et al, 1981; Mandal et al. 1981).

However, long term experiments have shown that in intensive cropping systems (200-300%) the removal from soil was far in excess of applied K resulting in severe negative balance of K in the soil to the detriment of crop yields (Sharma and Singh, 1989; Singh, et al., 1997, 2001; Singh, et al., 2000; Roy et al., 2000). The rice-potato-wheat cropping system suffered the most from negative balance (Figure 8). The negative balance of K in the soil was responsible to a large extent for decline in the yield of crops and rendered potato based cropping systems unsustainable in the long run (Singh et al., 2001). The reason for the phenomenon is not far to seek. The efficiency of native soil K is 105% more than the fertilizer K (Singh and Grewal, 1995). These observations clearly advocate towards maintenance fertilization of K to other crops as well to maintain the soil potassium in potato based cropping systems as insurance against possible decline in yield of crops in the long run.

Recent studies have also shown that enhanced fertilization including K to other crops as well in the potato based cropping systems maximized the production potential and profitability (Guar and Pandey, 1994; Kushwah and Grewal, 1995; Sharma and Goydani, 1999; Sood et al., 1999;). This could be attributed to depletion of soil K in potato growing soils over the period 1980 to 2000 due to intensive cropping. Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 207

0"P-W-R 0 P-W-M 1i P-P-M E P-P-M-W-GM

0--

E -1000 -2000

S-3000

S-4000 -5000 K

Figure 8. Mean balance of potassium in soil after 17 years (1970-87) in different cropping systems. Potato-Wheat (spring)-Rice (P-W-R). Potato-Wheat (spring).Maize (P-W-M), Potato- Potato-Maize (P-P-M) and Potato-Potato-Wheat (winter)- Green Manure (P-P-M-W- GM). Source: (Singh eial, 2001)

Tuber quality

Beneficial effects of potassium fertilization on both physical and chemical tuber quality are far more than few adverse effects. It promotes shining and provides lustrous physical appearance to the tubers. Increasing levels of K application decreased the undesirable enzymic browning of potatoes (Joshi et al., 1982; Verma el al. 1983; Joshi et al., 1992). It also reduces the contents of phenols, orthodihydric phenols (ODP) and tyrosine which are implicated in the enzymic browning as well as unacceptable discolouration of the processed products on frying (Joshi et al., 1992; Singh et al., 1996). Increasing levels of K fertilization linearly increased the lipid content in tubers (Joshi et al., 1982; Verma et al., 1983). Potassium increased the nutritive quality of tubers by increasing the soluble as well as the crude protein content of potato tubers (Singh et al., 1996; Lalitha et al., 1997) and ascorbic acid content (Mondy and Munshi, 1993). Potassium application increased the starch content in tubers in potassium deficient soils (Lalitha et al., 1997). Low phenols and free amino acids is a desirable character promoted by K application (Singh et al., 1996).

Some adverse effects on tuber quality has also been reported. Potassium application decreased the drymatter in tubers, the decrease was more with muriate than sulphate of potash (Joshi et al., 1982). However, the decrease in dry matter was not significant in alluvial soils (Table 5). Potassium increased the reducing 0o

Table 5. Effect of sources and levels of potassium on biochemical properties of potato tubers Main effects Tuber Starch Redu- Sucrose Total Soluble Free Phenols Ortho- dry (%) cing sugars proteins amino hydric matter sugars acids phenols

(mg/100 g fresh tuber)- Sources MOP 19.05 14.1 378 194 573 961 67.2 43.5 10.5 SOP 19.30 14.1 438 213 651 998 61.5 41.5 8.9 C.D. (5%) NS NS 3 7 7 11 1.8 0.4 0.3 Levels of K (kg/ha) 0 19.40 14.3 320 250 570 956 76.0 46.3 12.7 50 19.40 14.3 381 207 588 1015 68.8 43.3 10.3 100 19.21 14.0 488 185 673 987 61.8 40.7 9.0 150 18.76 13.9 445 173 617 988 50.8 39.7 6.8 C.D.(5%) NS NS 4 10 10 15 2.5 0.5 0.4 Source: (Singh et al., 1996) Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 209 sugar content in tubers which is implicated in colouration of processed products on frying (Table 5).

Processing quality and storage behavior

Potassium improves the processing quality of potato tubers in three ways. Large grade tubers promoted by K fertilization reduce peeling losses considerably. Secondly, use of costly chemical to avoid enzymic browning by the processing industry during peeling and cutting operations is eliminated to a large extent due to K fertilization which minimizes the enzymic browning of tubers as discussed above. Thirdly, it minimizes the discolouration of processed products during frying. The colour intensity of chips and french fries depend on relative amounts of reducing sugars and free amino acids in fresh tubers. These react at frying temperatures to give colouration in fried chips. Balanced application of NPK produced low content of reducing sugars with least amount of free amino acids to give acceptable colour of fried chips compared to unbalanced applications of N or NP or NK (Singh et al., 1995).

Application of 150 kg K/ha reduced the weight loss and sprouting in tubers during storage by 22 and 9%, respectively over the no K treatment (Table 6). The two sources of potassium were not different about storage behavior.

Table 6. Effect of sources and levels of potassium on storage behavior of potato tubers Main effects Weight loss (%) Sprouting Total rottage Weeks of storage (%) (%) i 14 Sources MOP 9.4 18.4 8.9 7.2 SOP 8.7 17.4 10.0 6.3 C.D. (5%) NS NS NS NS Levels of K (kg/ha) 0 9.4 20.4 8.5 7.1 50 9.1 17.9 11.0 7.1 100 9.4 17.4 10.7 7.9 150 8.3 15.9 7.7 4.8 C.D. (5%) NS 3.6 2.3 NS Source: (Singh et al., 1996)

Resistance against draught

Potassium application increased the water use efficiency from 64 kg tubers/ mm of water without K application to 79 kg tubers/mm of water at 150 kg K/ 210 J.P. Singh. S.P Trehan and R.C Sharma ha (Banerjee and Saha, 1983). However, the consumptive use of water was not influenced by the potassium application.

Resistance against frost

Increasing levels of available soil K linearly reduced the extent of frost damage and increased the tuber yield in potato (Grewal & Singh, 1980).

Resistance against diseases

Potassium application imparted resistance in potato plant against late blight disease in hills (Sharma et al, 1999).

Economics of potassium fertilization

The benefit:cost ratio of potassium fertilization at the current rates of fertilizer prices is Rs. 2.85 (Singh and Grewal, 1996).

Conclusions/Summary

Potato crop invariably responds to potassium application in terms of improved tuber yield, and processing and nutritive quality. At higher dosages, it also improves the keeping quality of tubers in country stores. Direct application of potassium to potato is essential for maximum benefit. Basal application is the preferred mode of fertilization, but split application may be beneficial in light textured soils. In alluvial soils band placement of K fertilizer was better than broadcasting. However, in hills and plateau region particularly with rainfed crop band placement was better. Fertilization with potassium was highly cost effective. In the intensive potato based cropping systems all the crops in the system need potassium fertilization particularly in alluvial and hill soils to maintain soil K to sustain the productivity of the cropping systems in the long run.

REFERENCES Banerjee, N.C. and Saha, S.K. (1983). Effect of different levels of irrigation and potassium on growth and yield of potatoes. South Indian Horticulture 33: 153-157. Dasmahapatra, A.N, Mondal, S.S. and Pandit, B.C. (1984). Response to methods of potassium application on the yield of potato in W. Bengal Gangetic plains. Journal Indian Potato Association 11: 130-133. Gaur, P.C. and Pandey, S.K. (1994). 20 Years of Potato Research All India Coordinated Potato Improvement Project. Central Potato Research Institute, Shimla, Technical Bulletin No. 43. pp 23-24. Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 211

Grewal, J.S. (1985). Nutritional requirements of potato. Paper read at Golden Jubilee Celebrations of CPRI, Shimla. Grewal, J.S. and Sharma, R.C. (1980). Fertilizer needs of potato. Fertilizer News 25(9): 49-59. Grewal, J.S. and Sharma, R.C. (1981). Fertilizer use in potato based cropping system in India. Fertilizer News 26(9): 33-43. Grewal, J.S. and Singh, S.N. (1980). Effect of K nutrition on frost damage and yield of potato on alluvial soils of Punjab. Plant and Soil 57: 105-110. Grewal, J.S and Trehan, S.P. (1993). Phosphorus and potassium nutrition of potato. In Advances in Horticulture (Eds. K.L. Chadha and J.S. Grewal). Malhotra Publisishing House, New Delhi. Vol 7: 261-297. Grewal, J.S., Sud, K.C. and Sharma, R.C. (1991). Soil and Plant Tests for Potato. Central Potato Research Institute, Shimla. Technical Bulletin No. 29, pp 8. Grewal, j.S., Trehan, S.P. and Sharma. R.C. (1991). Phosphorus and potassium nutrition of potato. Central Potato Research Institute, Shimla. Technical Bulletin 31: pp 10. Grewal, J.S., Singh, A.K., Akhade, M.N., Singh, K. and Singh, B.N. (1984). Response of potato to graded doses of nitrogen, phosphorus and potassium on alluvial and black soils. Journal Indian Potato Association 11: 20-25. Joshi, K.C., Grewal, S.S., Misra, J.B. and Verma. S.C. (1982). Discolouration of potato tubers in relation to K fertilization. In Potato in Developing Countries (Eds. B.B. Nagaich et al.) Indian Potato Association, CPRI. Shimla. pp. 265-269. Joshi, K.C., Mishra, J.B., Bist, B.S. and Verma, S.C. (1992). Effects of potassium fertilizers on the enzymic browning and the contents of phenolic compounds in potato tubers. Journal Potassium Research 8: 247-254. Krishnappa, K.S. (1990). Studies on the levels and their methods of application of potassium to potato in sandy loam soil. Journal Indian Potato Association 17: 20-23. Kushwah, V.S. and Grewal, J.S (1995). Fertilizer requirement of rice grown after potato in potato-rice rotation. Journal Indian Potato Association 22(3&4): 92-94 Lal, S.S. and Arora, P.N. (1983). Response of potato cultivars to phosphatic and potassic fertilizers and their residual effect on cowpea. Journal Indian Potato Association 20: 245-248. Lalitha, B.S., Sharanappa and Hunsigi, G. (1997). Balance sheet of available potassium and sulphur as influenced by K and S application in seed tuber and true potato seed raised crop. JournalIndian Potato Association 24: 171- 173. 212 J.P Singh, S.P. Trehan and R.C. Sharma

Maity. K. and Arora, P.N. (1980). Effect of varieties, levels and sources of K on the yield , dry matter and grade of potato tuber. Indian Journal Agronomy 25: 390-397. Mandal, A.K.. Roy, A.B. and Pal, H. (1981). Fertilizer use injute based cropping systems in different agro-climatic zones. Fertilizer News, 26(9): 45-50. Mondy, N.I. and Munshi, C.B. (1993). Effect of type of potassium fertilizer on enzymatic discoloration and phenolic, ascorbic acid and lipid contents of potatoes. Journal Agricultural and Food Chemistry 41: 849-852. Nandekar. D.N., Sharma, T.R., Sharma, R.C. and Sawarkar, S.D. (1991). Fertilizer requirements of potato cv. Kufri Badshah in Madhya Pradesh. Journal Indian Potato Association 18: 178-179. Prasad, R.N., Ram, P., Barooah, R.C. and Ram, M. (1981). Soil fertility management in North-Eastern hill region. ICAR Research Complex for NEH region, Shillong, Technical Bulletin No. 9: pp. 3 0 Ram, P. and Prasad, R.N. (1985). Response of potato to potash at different levels of nitrogen in an Alfisol of the central plateau of the Khasi hills of Meghalaya. Journal Indian Society Soil Science 33: 935-937. Ramaiah, N.V., Shukla, D.N., Sreenivasaraju, M. Gopal and Singh, B. (1987). Effect of source and levels of potassium on growth and tuber yield of potato varieties. Andhra Agriculture Journal 34: 355-356. Roy, S.K., Sharma, R.C. and Trehan S.P. (2000). Integrated nutrient management by using farmyard manure and fertilizers in potato-sunflower-paddy rotation in the Punjab. Journal of Agricultural Science, Cambridge (in press) Sharma, I.P., Roy, K., Tiwari, R. and Verma, U.K. (1983). Response to phosphorus, potassium and farmyard manure in multiple cropping with potato. Indian Journal Agricultural Research 17: 25-29. Sharma, R.C. and Sharma, H.C. (1990). Fertilizer phosphorus and potassium equivalents of some green manures for potatoes in alluvial soils of Punjab. Tropical Agriculture 67: 74-76. Sharma, R.C., Upadhayay, N.C., Singh, K and Sharma, A.K.. (1984). Studies on nitrogen-potassium and potassium-magnesium interaction in potato production. Journal Indian Potato Association 11: 48-53. Sharma, R.C., Sood, M.C., Patricia, 1. Khan, M.A. and Bansal, S.K. 1999. Nitrogen and potassium interaction on the tuber yield and soil parameter at Shimla. Global Conference on Potato, New Delhi, Indian Potato Association. pp 134 (Abstracts) Sharma, S.P. and Sharma, H.L. (1989). Response of potato (Solanum tuberosum L.) to nitrogen, phosphorus and potassium fertilization in dry temperate high hills of Himachal Pradesh. Indian Journal Agricultural Sciences 59: 679-81. Potassh., Nutrition Management for Iproving Yield and Processing Quality of Potato 213

Sharma, T.R. and Goydani, B.M. (1999). Production potential of potato based cropping system and its fertilizer economy. Journal Indian potato Association 26(3&4): 107-110 Sharma, U.C. and Arora, B.R. (1987). Effect of applied nitrogen on phosphorus and potassium concentration in potato plant (Solanunt tuberosum L.). Indian Journal Plant Physiology 30: 314-316. Sharma U.C. and Singh, K. (1988). Response of potato to N, P and K in acidic hill soil of Meghalaya. Journal Indian Potato Association 15: 40-44. Sharma, U.C. and Singh, K. (1989). Nutrient balance sheet and economics of three potato based cropping systems in acidic soils. Journal Indian Society Soil Science 37: 754-758. Singh. D., Singh, T. and Verma, S.K. (1997). Response of potato to nitrogen and potassium application under Faizabad conditions. Journal Indian Potato Association 24: 40-43. Singh, J.P. (1986). Optimizing fertilizer rates of nitrogen and potassium for potato in plains of Bihar. Journal Indian Potato Association 13: 57-62 Singh, J.P. (1987a). Role of phosphorus and potassium content of leaf in maximizing potato yield. Indian Journal Agricultural Sciences. 57: 565- 566. Singh, 1P. (1987b). Leaf analysis for balanced nutrition of potato. Journal Indian Potato Association 14: 88-91. Singh, J.P. and Grewal, J.S. (1983). Direct effect of phosphorus and potassium fertilizers and farmyard manure on potato and their residual effect on cheena and maize. Journal Indian Potato Association 10: 16-23. Singh, J.P. and Grewal, J.S. (1985). Potassium and nitrogen requirements for potato in Indo-Gangetic alluvial plains of varying fertility. Journal Potassium Research. 1: 197-204. Singh, J.P. and Grewal, J.S. (1995). Requirement of potassium to potato crop and effect of some agrotechniques on yield and fertilizer use efficiency. Journal Potassium research 11: 160-165 Singh, J.P. and Grewal, J.S. (1996). Economics of potassium fertilization and some agrotechniques in potato crop production. Journal Potassium Research 12: 93-95. Singh, J.P., Marwaha, R.S. and Srivastava, O.P. (1995). Processing and nutritive qualities of potato tubers as affected by fertilizer nutrients and sulphur application. Journal Indian Potato Association 22: 32-37. Singh, J.P., Marwaha, R.S. and Grewal J.S. (1996). Effect of sources and levels of potassium on potato yield , quality and storage behavior. Journal Indian Potato Association 23: 153-156 214 J.P. Singh, S.P. Trehan and R.C. Sharma

Singh, J.P., Trehan, S.P. and R.C. Sharma (1997). Crop residue management for sustaining the soil fertility and productivity of potato based cropping systems in Punjab. Journal Indian Potato Association 24: 85-99. Singh, J.P., Lal, S.S. and R.C. Sharma (2001). Productivity and sustainability of potato based cropping systems with reference to fertilizer management in North-western plains of India. Proceedings Global Conference on Potato. Indian Potato Association, Shimla (in press) Singh, M., Singh, J.P., Sharma, R.C., Lal, S.S., Singh, A.K., Singh, P., Singh, R.P., Govindakrishnan, P.M. and Saini, S.S. (2000). Long term effect of fertilization and manuring on productivity of some potato based cropping systems in Punjab. Journal Indian Potato Association 27: 69-76. Singh, N.P. and Raghav, M. (2000). Response of potato to nitrogen and potassium fertilization under U.P. Tarai conditions. Journal Indian Potato Association 27: 47-48. Singh, V.N. and Singh, S.P. (1995). Effect of levels and methods of potassium application on vegetative growth and yield of potato cv. Kufri Badshah. Journal Indian Potato Association 22: 118-121. Sood, M.C. and Sharma, R.C. (1985). Effect of pine needle mulch on tuber yield and fertilizer economy of potato in shimla hill soils. Journal Indian Society Soil Science 33: 141-44. Sood, M.C., Sharma, R.C. and Khan, M.A. (1999). Improvement of potato productivity through potato-garlic system in Shimla hills. Indian Farming 49(9): 29-30. Trehan, S.P., Claassan, N. (1998). External K requirement of young plants of potato, sugar beet and wheat in flowing solution culture resulting from different internal requirements and uptake efficiency. Potato Research 43: 229-237. Trehan, S.P. and Claassen, N. (2000). Potassium uptake efficiency of potato and wheat in relation to growth in flowing solution culture. Potato Research 43: 9-18. Trehan, S.P. and Grewal, J.S. (1994). A rapid tissue testing methodology for optimum potassium fertilization of potato grown under subtropical. short- day conditions. Fertilizer Research 38: 223-231. Trhehan, S.P. & Sharma, R.C. (1998). Soil and foliar application of potassium for increasing its efficiency in potato. Journal Indian Potato Association 25: 42-45. Trehan, S.P., Roy, S.K. and Sharma, R.C. (2001). Potato variety differences in nutrient deficiency symptoms and responses to NPK. Better Crops International 15: 18-21. Upadhay, N.C. and Grewal, J.S. (1985). Effects of phosphorus and potassium Potassium Nutrition Management for Improving Yield and Processing Quality of Potato 215

fertilizers and farmyard manure on potato-wheat rotation in an alluvial soil of western Uttar Pradesh. Journal Indian Potato Association 12: 63-69. Verma, R.S. and Grewal, J.S. (1983). Response and economics of nitrogen, phosphorus, potassium fertilization of potato in acidic brown hill soils. Journal Indian Potato Association 10: 89-94. Verma, S.C., Joshi, K.C., Misra, J.B., Grewal, S.S. and Sharma, T.R. (1983). Effect of potassium supply on the quality of tubers of Indian Potato varieties. Conf. Papers 8"h Trienial Conf. European Potato Association of Potato Research. Munich, Germany. pp 138-139 (Abstracts). Potassium Nutrition of Sugarcane in Relation to Yield, Quality and Abiotic Stress Tolerance

R.S DWIVEDI Indian Institute of Sugarcane Research Raebareili Road, Lucknow-226002

ABSTRACT

Sugarcane depletes potassium heavily in the range of 150-720 K/ha to yield 100-250 t cane/ha. It requires 1.5-3.0 kg potassium per ton of cane production. Sugarcane response to added K when soil has less than100 kg exchangeable K/ha and LTM leaf blade and sheath has less than 0.85% and 0.95% K respectively at 90 days of plant growth. The ratoon and plant cane respond to 130 and 117 kg cane respectively to per kg of added potassium. The solar energy harvesting efficiency and sucrose yield is increased by 10 to 20 % due to potassium application on K deficient soils. Hidden hunger of K, though not reported earlier has been detected using EDTA-Osmoticum test. Further studies are required in this direction.

The physiological and biochemical disorders created under aboitic stresses are obviated by the accumulation of organometallo-osmoticums like potassium-malate, potassium-citrate and potassium-oxalate etc. in plants. Application of K augments the synthesis of natural organic osmoticum like sugar, C3 and C4 acids, betaine etc. and favours the accumulation of proline and abscisic acid involved in withstanding protein denaturation under stress conditions. Application of K helps to regulate stomatal movement and control water loss through osmoregulation. However, under saline and alKaline conditions adequuate K competes with Na, maintain low Na/K ratio and induces tolerance through stabilising chemiosmotic potential and arganometallo-complexes in plants. Further studies might prove the involvement of potassium in organic complex constitution and thereby imparting abiotic stress tolerance.

Sugarcane is heavy depleter of K and it removes 150-720 kg K/ha to yield 100-250 t cane/ha (Dwivedi, 1999, Hussain, 1982, Lakshmikanthan, 1973). The Indian soils supporting tropical crop like Sugarcane ,groundnut etc are relatively rich in potassium and the exchangeable potassium ranges between 150 and 1500 kg/ha (Hunsigi and Srivastava 1981, Dwivedi 1989). However due to high intensity of cropping the available potassium is depleting fast and crops are 217 218 R.S. Dwivedi responding significantly to added potassium (Dwivedi et al., 1997 and Dwivedi 2000)

The average productivity of Sugarcane at national level is 71 t/ha. However in tropical and subtropical areas, the average productivity is 65 and 70 t/ha respectively. To meet the sugar requirement of burgeoning population by 2005, the national cane and sugar productivity has to be raised to 100t/ha and lit/ha respectively. Hence to achieve it, the management practices including potassium nutrition have to be improved

Secondly, because of long span of crop growth, Sugarcane is subjected to water deficit, water logging and temperature stress at one or the other stage of its growth. The salt stress is an additional problem, which deters the Sugarcane productivity. The stresses infringe on larger area of Sugarcane crop and reduce cane and sucrose productivity and production significantly (Tablel) (Dwivedil995).

Potassium induces tolerance to abiotic stress by altering morpho-physiological attributes (Dwivedi 1997and 1999) and thereby impede the decline in yield and quality of Sugarcane (Dwivedi 2000, Dwivedi and Srivastava 2001). In present paper the information on yield and quality of Sugarcane under normal and abiotic stress have been discussed. The prospects of using potassium in improving morpho-physiological and biochemical process and mechanism of potassium mediated abiotic stress tolerance in raising overall productivity/production of sucrose; energy and cane at national level are discussed.

Table 1. Spread of abiotic and biotic stress and degrees of losses in cane and sucrose production and yield in Sugarcane (After Dwivedi 1995) Stress Spread Cane (% loss) Sucrose (% loss) (% area) Production Yield/ha Production Yield/ha Abiotic Drought 63-65 15-20 20-40 12-20 18-45 Flood 10-30 5-20 5-15 8-25 10-30 Salt Stress 20-25 10-20 20-30 15-30 25-60 Low temperature 1-2 2-4 3-5 4-8 5-10 Mineral Deficiency 20-40 24-45 25-50 28-48 30-55 Biotic Weeds Everywhere 10-15 15-20 10-15 15-20 Diseases Everywhere 2-5 2-5 3-8 5-10 Pests Everywhere 2-5 2-5 3-6 3-6 Potassium Nutrition of Sugarcane in Relation to )ielt Quality and Abiotie Stress Tolerance 219

Potassium Requirement

Potassium appears to be essential for Sugarcane growth and yield because it absorbs much more amount of potassium than the added K 20 to the field (Anonymous 1989-90, Dwivedi 1999, and Dwivedi and Srivastava 2001). The Sugarcane crop yielding 100-250ttha cane has been reported to remove 150-720 kg K20/ha (Lakshmi Kanthan 1973, Hussain 1982, Dwivedi 1999). This means that for every tonne of cane production 1.5-3.0 kg K is essential. Removal of potassium by Sugarcane varies with soils type, mineralogy etc. (Table 2). Under Maharashtra conditions a tonne of Sugarcane crop removes 3.5 kg K2 0/ha (Zende et al., 1972). Sundra and Subramanian (1989) reported that for every tonne of cane production 2.84 kg K20 is required.

The requirement of potassium for Sugarcane is estimated to be twice that of Nitrogen and three times that of phosphorus. However these values vary with agroclimatic conditions as a result of which a huge variation in potassium requirement have been recorded in different States of India.

Table 2. Nutrient removal by Sugarcane (Anonymous 1989-90) States Variety Nutrient Removed kg/tonne

N P 20 5 K20 Andhra Pradesh C0419 0.67 0.30 1.34 Maharashtra C0740 1.22 0.79 1.55 Bihar B070 3.08 0.26 3.15

K Supply by Soil

LiKe other essential elements and crops, the soil and plant test correlation ship in case of potassium and Sugarcane is not very sound. Potassium status of Indian Soils supporting Sugarcane crop has been reported to be medium (Srivastava and Hunsigi 1978). The Nitric Acid extraction was found to be better by these workers for predicting potassium-supplying power of soil than NH 4O AC extraction. They further found that exchangeable K was poor index of potassium availability to long duration crop liKe Sugarcane or continuous system of cropping like Plant Sugarcane-Ratoon Sugarcane. Hunsigi and Srivastava(1981) suggested that a portion of none exchangeable but plant available K termed as "Step Potassium" need to be included (Table 3) for better prediction of potassium supplying power of soil to Sugarcane. Hence, extraction in conc. H2SO4 or extraction in boiling IN HNO 3 to obtain "Step Potassium" are the better measure of potassium availability to Sugarcane. However till today, the reliable techniques to predict exchangeable or available potassium to plant are not available and need to be developed to meet potassium requirement under fast nutrient depleting cropping system. 220 R.S. Dwivedi

Table 3. Available potassium in soil and methods of extraction:- Soil categories Exchangeable Exch. K in Non-Exch. Step K K in NH 4 OAc, conc. H2SO 4 K in boiling (mg/kg soil) pH = 7 (mg/kg soil) IN HNO 3 (mg/kg soil) (mg/kg soil) 1.Responsive 150 300 400 300 2. Marginal 150-300 300-500 400-600 300-600 3. Non-responsive 7300 7500 7600 600 (sufficient) I

It is only the potassium present in soil in water soluble and exchangeable forms that are readily available to plant, whereas, the potassium available in non-exchangeable form in the soil is considered to be slowly available over long period of time. The relative abundance of these forms of K is governed by the dynamic equilibrium of K in soil as shown below:

Non-Exchangeable K ! Exchangeable K = Water soluble K Lattice Potassium (Inert Potassium)

Several edaphic, atmospheric and management factors control this equilibrium and thereby availability of potassium to plants.

Non-exchangeable potassium in soil is however, 5-10 times more abundant than the exchangeable K. Since, the uptake of K by plant is much more faster than the release of K from non-exchangeable to exchangeable form, the need to supplement K through fertilizer becomes imperative with a view to have high yield and quality. Considering this, the following critical limit for available K in soil has been fixed (Table 4).

Table 4. Critical limits of avatilable K in soils (The values are based on soils of U.P. which share 49-51 % of area of Sugarcane in India) Soil Category Available Potassium Response (kg/ha) (% fall in yield) Low Potassium <100 >30 Medium Potassium 100-250 10-25 High Potassium >250 0 - <10

Critical limits of Potassium in Plant tissues for higher Physiological efficiency

Sugarcane is most endergonic C4 crop with highest solar energy harvesting efficiency of 0.801-1.22% among cultivated crops on annual basis (Dwivedi 1994). Such efficiency is achieved when tissues have sufficient inorganic nutrient Potassium Nutrition of Sugarcane in Relation to ield, Quality and Abiotic Stress Tolerance 221 content. Potassium is one among them, the concentration of which in healthy plants has been reported to range between 1.15 and 1.85% in second leaf blade from top i.e. LTM(last transverse marked) leaf (fully developed leaf usually third from spindle) and 1.75-2.65% in its leaf sheath. The critical value of K in Sugarcane could be as follow:

1. 0.9% in second leaf blade and 1.4% in its leaf sheath at 90 days of plant growth (formative phase) 2. 0.6% in second leaf and 0.7% in its leaf sheath at 150 days of growth (grand growth phase).

Considering the critical limit of K in second leaf blade and sheath and related depression in yield as reported by Rama Rao and Sekhon (1989), a trial was conducted by author at Coimbatore (T.N.), Lucknow (U.P.), Pune (Maharashtra), Pusa (Bihar) and Karnal (Haryana) representing different agroclimatic conditions, with a view to examine the deviations in tissue potassium in second leaf from top which is usually considered as LTM (Last transverse marked) leaf, the most physiologically active one in plant. The tissue concentration and corresponding depressions in yield were similar with little deviations at different locations. The average values of all the five locations are mentioned in Table 5.

Table 5. Critical limits of Potassium in LTM leaf of Sugarcane at formative phase (90 days growth) Recommended leaf/portion Potassium % in dry matter S SD MD D Second leaf (LTM) blade 1.15-1.86 0.95-1.14 0.85-0.95 <0.85 Second leaf (LTM) sheath 1.75-2.65 1.45-1.74 0.95-1.44 <0.95 S - Sufficiency, Maximum yield to less than 10% reduction; SD - Slightly deficient (10-20% yield reduction; MD - Moderate deficiency (20-40% reduction); D - Deficiency (>40%yield reduction).

Hidden hunger of Potassium (Biologically active Potassium)

. Hidden hunger of potassium has not been reported so for in the literature probably because it is not a constituent of any organic substance at molecular level. However, potassium has been reported to be essential for regulating metabolic activity and plant growth. For regulating the activity of more than 60 enzymes, the presence of adequate amount of K has been reported to be inevitable. Besides this, its active association with ATP-ase activity, stomatal movement and abscissic acid accumulation, induction of drought and temperature tolerance, signal transduction for drought resistance, impairing photosynthesis, carbohydrate 222 R.S. Dwivedi accumulation and proteins synthesis etc. compel every one to think about its involvement in plant metabolism not in elemental form only but also as organometallo complex form. Recently, it has been noted that potassium is the constituent of EDTA-osmoticum (EDTA-O) which regulates drought tolerance process in Sugarcane(Dwivedi et al., 1992, 1997; Dwivedi and Srivastava 1993, Dwivedi 2000). Detailed studies on EDTA-O as revealed that less potassium responsive genotypes have high potassium in EDTA-O as compared to high responsive genotypes. Drought tolerant genotypes showed high potassium content in EDTA-O (Table 6). However, no significant difference in elemental K in leaf tissues were noted among tested ten genotypes (Table 6). This clearly reveals that K in EDTA-O gives an idea of biologically active K in plant tissues (Dwivedi and Srivastava 2001). The measurement of EDTA-O fraction of K can predict K hunger in absence of apparent deficiency symptoms and decline in elemental K in plant tissues right at early stage of growth. This inturn can recommend K application, which can save plants from hunger, poor growth and yield decline.

Table 6. EDTA-Osmoticum (EDTA-O) as diagnostic test for detecting hidden hunger of Potassium and Zinc in Sugarcane genotypes under irrigated conditions. Genotypes EDTA-O Constituents Total elemental % Response (mg g-' of EDTA-O content in (rise in cane dry wt leaves yield over of control) leaves) Zn K Zn K (ppb) (ppm) (ppm) (%) ZnSOI K20 (12.5 (40 kg/ha) kg/ha) Cos 8118(T) 1880 5.6 41 19 1.35 4.0 6.0 LG9001(T) 2220 8.4 48 20 1.26 3.7 8.9 C01148(T) 2100 7.6 44 19 1.22 7.2 8.8 COJ64(S) 1110 1.2 26 18 1.13 18.6 29.1 COLK8001(S) 1100 1.6 28 21 1.12 16.2 25.2 C0419(S) 1080 1.4 26 22 1.16 17.2 24.1 COLK8901(S) 1040 1.0 22 21 1.13 16.6 22.7 S.Sponteneum(T) 2660 9.2 64 18 1.13 3.7 5.8 E. arundanceus(T) 2550 8.5 52 20 1.02 4.5 8.8 Schlorastachya Sp(T) 1860 7.5 50 22 1.25 5.7 8.6 CDat 5% level 12.1 120 3.12 NS NS - - T and S :Tolerant and Sensitive to drought respectively. Potassiun Nutrition of Sugarane in Relation to ield Quality and Abiotic Stes Tolerance 223

Apparent potassium hunger/deficiency

The causes for appearance of K deficiency in plants are mainly low K in plant tissues and soil. When soil has less than 100 kg , K20/ha and LTM (last transverse marked) leaves blade and sheath have less than 0.85 and 0.95 % K respectively at 90 days of plant growth, the deficiency symptoms appear. The K deficiency symptoms are also visible at 110 days growth, when the LTM leaf blade and sheath contain 0.6 % and 0.7% K respectively. Soil subjected to excessive liming (competition with K uptake) and excessive rain fall (leaching losses of K from soils specially from light textured ones) cause K deficiency in plants. The characteristic symptoms of K deficiency are as follow:

Gradual loss of the green colour of older blade. Small numerous yellow spots, which turn brown later on, and tissues die at border and tip portion of the leaf blade. Bottom older leaves may be entirely brown, rusty "fired". Upper surface of midrib show reddish discolouration. Less growth and tillering, stalk slender with shorter internodes.

Responses of Potassium on Sugarcane i) Cane yield: In the past starting from 1912-1981, the sugarcane crop failed to respond to added potassium. The interaction effects e.g. N x P, N x K and N x P x K were also not found significant at Shahajahanpur. (UPCSR, 1983). However due to depletion of potassium because of exhaustive cropping, the response of added potassium on cane yield was found significant. (UPCSR, 1989-90, 1991-92) (Table 7). The response of added potassium on Sugarcane in all India Co- ordinated projects was found to be dependent on soil type. Sugarcane responded maximum on flat land followed by upland, recent alluvial and lowland in the decreasing order (Table 8). However the application of K in soil with medium availability of potassium (232 kg/ha) did not respond.

Experiments conducted at IISR, Lucknow revealed that application of potassium responded significantly to C01148 genotypes of sugarcane on soil having pH 8.0, available N 150 kg/ha and exchangeable potassium 182 kg/ha. The per kg of applied potassium yielded 117 and 130 kg cane in plant cane and second ratoon respectively (Table 9) (Jafri et al., 1988)

Table 7. Effect of applied potassium on yield (t/ha) of Sugarcane at Shahjahanpur (UPCSR, 1989-90 to 1991-92) Year Potassium (Kg/ha) CD at 5% Control 41.5 83.0 124.5 166.0 1989-90 72.2 75.6 78.0 81.2 87.6 0.03 1990-91 74.3 77.7 79.5 80.4 82.4 NS 1991-92 67.1 75.7 78.5 81.6 84.7 4.04 response (kg cane/kg K) - 207 142 116 106 - 224 R.S. Dwivedi

Table 8. Response of Sugarcane to K application on different soil types (Mehrotra et al., 1972) Soil types Texture No. of Cane yield (tlha) at Response trails (kg cane/ N210P140 N210P14oK58 kg added K) Recent alluvial Sand 81 53.45 55.86 40 Flat land Loam 143 61.12 64.31 51 Upland Sandy Loam 303 66.98 69.54 44 Lowland Clay loam 62 51.47 53.52 35

Table 9. Effect of soil applied Potassium on yield (t/ha) of Sugarcane at Lucknow (Jafri et al., 1988) Crop Control Soil applied Potassium (kg/ha) CD at 5% 63.34 124.6 Plant Crop (1986) 35.7 43.0 42.6 1.2 First ratoon (1987) 35.4 41.1 43.5 NS Second ratoon (1988) 28.1 36.2 38.5 5.4 ii) Yield Attributes: At Indian Institute of Sugarcane Research, Lucknow (India), the effect of potassium on yield attributes of sugarcane was examined by the author and the results are presented in table 10. Application of 30 kg K20/ha was found to augment cane girth, cane height, no. of millable canes and cane yield significantly both under normal and water deficit conditions. However, under drought conditions the value of all the yield attributes, in general were found to be lower than normal conditions.

Table 10. Effect of Potassium on yield attributes of Sugarcane under water deficit conditions (Dwivedi and Srivastava 1996).

K20 levels Water deficit Cane girth Cane height No. of Cane (kg/ha) levels (cm) (cm) millable yield (-MPa cane (tlha) soilw) (000/ha) 0 0.03 2.52 193.4 65.3 69.4 30 0.03 2.94 219.0 68.8 82.3 90 0.03 2.62 220.3 62.8 69.1 0 0.65 2.54 186.7 60.1 61.6 30 0.65 2.74 210.4 65.2 69.5 90 0.65 2.40 207.2 60.4 69.1 CD at 5% (K x soil i) 0.114 1.78 3.62 7.46 iii) Energy Balance: Sugarcane is highly endergonic plant. The solar energy harvesting efficiency of Sugarcane and energy balance starting from crop Potassium Nutrition of Sugarcane in Relation to Yield. Quality and Abiotic Stress Tolerance 225 cultivation to crystallization of sugar or gur formation were examined in light of potassium nutrition by the author. Data in Table 11 very clearly reveal that the energy content per unit of dry matter in different parts was raised significantly due to potassium. The rise in energy harvest is therefore, but natural since, the total biomass/cane yield increased due to potassium nutrition. Further, while working out energy balance of crop cultivation and sugar crystallization or gur formation, it was recorded that potassium augmented energy harvest and total gain in energy due to potassium nutrition (table 12) (Dwivedi 1994).

Table 11. Effect of potassium on solar energy harvesting efficiency and energy balance startingfrom crop cultivation to sucrose crystallization/gur formation.

Particulars N 5oPoKo N 150P6oK30 Energy harvesting efficiency % 0.801-1.221 0.812-1.324 Energy (GJ/ha/yr) 1. Energy required in crop production 42.88 43.06 2. Fuel required in Sugar crystallization 176.00 176.88 3. Total 218.88 219.94 4. Solar energy harvested by crop 739.68 762.21 5. Energy Balance (gain) 520.82 542.27 K * = Exchangeable K in soil = 170 K20/ha (After Dwivedi 1994)

The amount of energy harvested by Sugarcane crop is sufficient to meet the energy required for boiling juice and sugar crystallization. After meeting this energy, 520.82 GJ/ha energy saving has been reported in sugarcane (Table 11) (Dwivedi 1994). Further it has been observed that the addition of potassium to sugarcane enhances solar energy harvest and results in net gain of 542.27 GJ/ ha energy. The rise in energy saving might be mainly due to increase in biomass production and enrichment of energy per unit wt. vis-A-vis accumulation of high energy organic substances in plants (Dwivedi 1994 and Dwivedi and Srivastava 1996, Dwivedi 1989).

Potassium improves stress endurance by accumulating more energy in plants and plant parts. The catabolic processes (respiration, sucrose inversion etc.) because of rich organic substances last long and plant sustain its vital activity and survival during stress period. iii. Sucrose: Effect of potassium on quality of juice was not found significant in a permanent trial (1912-1981) at UPCSR, Sahjahanpur. However due to exhaustive cropping, the significant effect of sucrose recovery was noted at several places. At PAU, Ludhiana the balanced fertilizer resulted significantly higher cane yield and CCS% (commercial cane sugar) (Kapur and Bishnoi, 1998) (Table 12). The juice extraction % and pol and brix of juice was found to be raised significantly under drought condition due to potassium application 226 R.S. Dwivedi

Table 12. Effect of balancedfertilizer application on cane yield and quality of Sugarcane (Kapur and Bishnoi 1998) Treatment Plant Crop Ratoon Crop Yield (t/ha) CCS (%) Yield (t/ha) CCS (%)

N150 67.3 12.1 52.5 12.5 N15o+P6o 76.4 12.9 65.3 13.0 Nl50+P6o+K6o 78.6 13.5 67.6 13.4 N150+P6o+K 60+FYM 84.9 13.2 72.4 13.2 LSD (P - 0.05) for cane yield : 5.2 and for CCS : 0.36 (NB- In ratoon crop 337 kg N/ha was applied instead of N150)

(Table 13) (Dwivedi 1994). The effect of potassium on sucrose recovery was pronounced under water deficit conditions. Dwivedi et al. (1997) reported significant rise in sucrose % under sole and intercropping system of Sugarcane applied with 60 kg K20/ha (Tables 13 and 14). However, at adequate soil potassium level (230 kg/ha) application of potassium could not raise sucrose recovery (Dwivedi and Srivastava 1993)

Table 13. Effect of Potassium on juice quality of Sugarcane K20 levels Soil water Cane juice Brix (%) Pol (%) (kg/ha) levels extraction juice (-MPa soil W) (M) 0 0.03 59.60 20.25 17.62 30 0.03 62.20 21.05 18.11 90 0.03 62.50 21.35 18.57 0 0.65 58.00 20.00 17.78 30 0.65 62.70 20.25 19.26 90 0.65 62.3 21.00 20.21 CD at 50% (KX soil W) 1.16 NS 0.80

Table 14. Effect of potassium applications on sucrose (%k fresh cane wt.) in Sugarcane-groundnut inter cropping system under water deficit conditions. At IISR, Lucknow. (Dwivedi et al., 1993). Potassium Water deficit stress Water deficit stress (kg K20/ha) (-MPa soil W) (-MPa soil q) 0.35 1 0.65 0.35 1 0.650 (Sole cropping) (lntercropping) 0 9.01 8.21 9.12 8.31 60 10.01 9.02 9.82 9.24 CD at 5% for (K x Soil) 0.561 Potassium Nutrition of Sugarcane in Relation to ield Quality and Abiotic Stress Tolerance 227

iv) Calorific value: The calorific values of different parts of Sugarcane is raised under potassium nutrition. Dwivedi et al. (1994) reported improvement in energy harvest due to potassium application. In fact, potassium has been found to improve the quality of crops hence the rise in energy values due to enhancement in biomass synthesis (Carbohydrate/sucrose, protein and phospholipid) is quite feasible.

v) Effect of Potassium on Enzyme activity: Acid invertase and Nitrate reductase (NR). The effect of potassium on acid invertase and NR activity has been found to be encouraging. Potassium reduces the activity of Acid invertase and thereby result high sucrose accumulation (Table 15). It is well known that low acid invertase enzyme cause less inversion of sucrose and thereby more sucrose accumulation (Dwivedi and Srivastava 1994, Dwivedi 1999, Dwivedi 2000). The significant rise in sucrose accumulation due to potassium application under water logged (WL) conditions over control water logged condition therefore appears to be quite legitimate. Secondly, potassium has been reported to accelerate aerial root, and floating root growth and improves their anatomical features and release of root exudates (Dwivedi et al., 1994, Dwivedi 1999). Consequently balanced redox potential in soil and oxygen supply to plant are regulated as a result of which crop yield is not much impeded and cane yield is raised over control under water logged conditions (Table 15).

Table 15. Effect of Potassium application (60 kg K0/ha) on cane and CCs yield, and acid invertase activity (pu mol sucrose hydrolysed/min/mg protein) in Sugarcanegenotypes under water logged (WL) conditions. Genotypes Treatment Cane yield(t/ha) CCS(t/ha) Invertase activity CO 1148 W.L 36 2.9 22.2 K+WL 42 3.2 16.2 B091 W.L 42 3.9 12.7 K+WL 48 4.4 8.6 COS8118 W.L 46 4.0 10.4 K+WL 51 5.0 7.8 COJ-64 W.L 22 1.8 17.7 K+WL 27 2.5 14.4 COLK8001 W.L 38 2.8 15.6 K+WL 44 3.4 11.2 CDat 5% 1 4.8 0.32 2.6

Nitrate reductase (NR) activity was found to be higher in Sugarcane genotypes possessing high K/Na ratio under sodic conditions (Table 22). The activity dropped significantly at low K/Na ratio. Higher NR activity might be one of the reasons for balanced nitrate assimilation vis-A-vis protein synthesis, division of cells and thereby higher tillering, and millable cane and least reduction in cane yield under sodicity conditions (Table 22). Potassium competes with Na under 228 R.S. Dwivedi

sodic conditions and thereby reduces Na injury, protein Co-ogulation and finally falls in crop growth and yield (Table 22).

Potassium Nutrition in relation to Abiotic Stress Tolerance in Sugarcane:

Sugarcane is certainly exposed to abiotic stresses at one or other stage of crop growth because of its long growth span usually ranging between 10 and 18 months. Drought, water logging, low & high temperature singly or in combination impede crop growth and cause significant loss in cane and sucrose productivity. Salt stress and mineral nutrient disorders are edaphic impediments that depress crop yield drastically (Table 1). However, the applications of potassium under these stresses obviate injuries and help in reducing significant loss in yield

(Dwivedi 1999; 2000). The losses in yield and quality due to abiotic stresses and mechanism of action of K in inducing abiotic stress tolerance are discussed here.

Potassium acts as osmoticum

Unlike other essential elements e.g. N, P, S, Mg, Fe etc. which regulate plant growth and metabolism by constituting enzyme, protein and organic substances, the evidences of K as constituent of organic substances are little or absent. Recently, Dwivedi et al. (1992, 1997), Dwivedi (2000), and Dwivedi and Srivastava (1993, 2001) reported that K is constituent of EDTA-Osmoticum which regulates drought tolerance process is Sugarcane. Thus the essentiality of K has been found to be indispensable in biophysical process, activation of biochemical reactions, chemi-osmotic energy regulation, osmoticum synthesis and organometallo-osm ticum formation which imparts tolerance in plant against stress conditions. Dwivedi (1999) gave an illustrated view on K as an osmoticum to withstand abiotic stress (Figure 1). Potassium itself is an inorganic osmoticum and makes a poor thermosensitive layer on leave and avoid temperature stress injury. It antagonizes Na injuries directly and also by forming organometallo complex osmoticum. The bound water is found more in K treated shoot as compared to control.

In Na dominated salinity, the chemi-osmoticum energy regulation through ATP-ase is done by K (Dwivedi, 1999). However, in enzymes, proteins and organic substances, the evidences for K as the constituent of organic substances are little/absent. Despite this, the essentiality of K has been found to be indispensable in biophysical processes, activation of biochemical reaction, chemi- osmotic energy regulation, osmoticum synthesis and organometallo-osmoticum formation (Dwivedi et al., 1992) (Figure 1) specially to obviate the injuries of stress environment. In present paper, the current status of K as regulator for organic and organometallo-osoticum synthesis and their accumulation to combat with water deficit, water logging, salinity, ion toxicity and temperature stress are briefly discussed. Potassium Nutrition of Sugarcane in Relation to ield, Quality and Abiotic Stress Tolerance 229

ORGANOMETALLO- ORGANO- OSMOTICUM OSMOTICUM

CHEMI-OSMOTIC POOR THERMAL ENERGY K SENSITIVITY REGULATION

ORGANOMETALLO- INORGANIC COMPLEX/ANTAGONISM OSMOTICUM

Figure I. Potassium as an osmoticum for abiotic stress tolerance(Dwivedi 1999)

Water deficit Stress

Water deficit stress injury/tolerance is a complex phenomenon. Potassium is involved in regulating water deficit tolerance in plant not only, by improving turgidity, cell and tissue expansion, root growth and stomatal movement but specially by the synthesis of organic osmoticum like sugars, C2, C3, C4 acid, a few amino acids, organometallo complexes and starch regulating energy supply, balancing H* efflux, Na, Ca, Mg, B and Zn content and providing less thermal sensitive layer on leaf and tissue surfaces (Dwivedi 1999).The same are illustrated here.

i) Organometallo-osmoticum: Water stress resistance in studies conducted by Dwivedi et al. (1986,1988,1989,1992,1993,1997) have revealed that the drop in the pH of EDTA-Osmoticum are associated with drought resistance. The EDTA- Osmoticum has been found to contain organic acids, sugar, K, Zn and Ca (Table 16). The most interesting part is that K and total organic acid in EDTA-Osmoticum is very much higher in tolerant genotypes whereas, these are low in sensitive genotypes. This indicates that the organometallo complex formation by K besides that of other elements, might be functioning as osmoticum and imparting drought resistance. Potassium-malate complex formation and II* extrusion in osmotic adjustment is well Known (Zeiger et al., 1977).

Potassium, oxalate or oxalic acid form K complex because of presence of both in tri-acid-osmoticum. This is used to delineate water logging resistant genotypes of Sugarcane which appears to be an important organometallo-complex to withstand water logging induced drought (Dwivedi et al., 1992 and also see water logging part of this chapter). Accumulation of potassium-oxalate in C2 plant under water stress to retain water by closing stomata in the day is feasible. This is regulated because under water deficit stress K-malate complex formation might become less active as a result of which oxidation of malate and the production of oxaloacetate and vice-versa add thereby carboxylation is impeded (Osmod, 1978). 230 R.S. Dwivedi

Table 16. Constituent of EDTA Osmoticum(EDTA-O) imparting resistance to drought in Sugarcane Genotypes EDTA-O % drop Reduction Constitutents analysed content in pH in cane in EDTA-O (gg organic of yield at acid/g dry EDTA -0.76 TS/RS Zn Ca K wt. of leaves) extract MPaW ppb ppm ppm 1. Saccharum (R) 2200 6.67 15.7 21.6 8.5 100 145 Spontaneum 2 Saccharum spp. Complex genotypes (cultivated) Co 1148 (R) 200 3097 34.8 13.6 7.5 68 128 LG 9001 (R) 2050 4.02 26.8 16.2 8.0 78 138 Coj 64 (S) 1100 1.22 53.3 8.5 3.2 42 72 Co 419 (S) 900 0.85 62.5 7.2 3.5 32 67 Control-EDTA pH 4.72 Dwivedi et al., 1988 and Dwivedi et al., 1992; TS-Total sugar; RS-Reducing sugar; R-Resistant & S-sensitive to drought. ii) Organic Osmoticum: CO2 assimilation is enhanced by potassium. Consequently sugar synthesis and thereby the synthesis of other osmoticum like organic acids, certain aminoacids, proteins, betaine etc, is regulated. Accumulation of proline, betaine and C4 organic acid have been found under water stress condition because of metabolis imbalaces specially when K content declines (Dwivedi 1979; Dwivedi, et al., 1986). iii) Chemi-osmotic Energy regulation: Dwivedi and Srivastava (1993) recorded rise in solar energy harvest in Sugarcane due to K application under drought conditions (Table 17). As the chemiosmotic energy regulation controls CO2

Table 17. Effect of potassium on solar energy harvesting efficiency of Sugarcane and groundnut under drought condition (adapted from Dwivedi et al., 1989 and Dwivedi and Srivastava 1993) Treatment Dry Biomass Total energy Energy yield harvest efficiency (t/ha) (106 Kcal/ha) (%) G.nut S.cane G.nut S.cane G.nut S.cane Normal KO 6.68 412.72 40.17 143 1.217 1.461 (-0.034 Mpa) K30 7.77 460.20 48.26 167 1.421 1.652 Drought KO 4.26 310.20 26.27 102 0.862 1.210 (-0.76 MPal K30 5.22 361.50 25.47 122 1.101 1.326 Potassium Nutrition of Sugarcane in. Relation to Yield, Quality and Abiotic Stress Tolerance 231

fixation, 02 release, partitioning of photosynthesis in different parts, the impact of K on energetics of Sugarcane has been worked out in detail by these workers.

Mitchells Chemi-Osmotic hypothesis of ATP generation is augmented due to K and thereby regulate energy supply to plant during stress. Higher content of K in tissues vis-a-vis application of K has been found to raise ATP molecule synthesis in chloroplast. (Pfluger and Mengel, 1972). Dwivedi(2000) recorded significant rise in energy value in different part of Sugarcane due to K application.

Temperature Sensitivity

Most of all the plants grow well at moderate temperature ranging between 20'C and 30'C except temperate vegetation. However, the spectacular rise in temperature above 35°C and fall below 20'C is of frequent occurrence in sub- tropical regions. Similarly rise in temperature above 35 0 C commonly occurs in tropical, arid and semiarid environments. Hence a threat to the survival of plants is created under such circumstances. Low temperature reduces respiration and the K uptake. The release of K and other nutrients from soil is also affected due to temperature. Consequently, poor K content in tissues does not support plants to withstand low temperature injuries. Application of K in such soil and on such plants help to obviate cold condition disorders (Nelson, 1978, Dwivedi 1999).

It has been observed that Sugarcane genotypes accumulating more K and silica withstand frost injuries better than that of less accumulating genotypes (Table 18). It appears that K perhaps form organometallo complex with silica, which provides poor thermal sensitive layer on leaves and in and around tissues. This might reduce fast conduction or convection of heat and thereby further reduces temperature injuries in cytoplasm (Dwivedi 1999).

Table 18. Leaf constituents, pot % juice and cane yield at Kashipur (U.P., India) under low temperature (20C-30°C) for 4 months after grand growth phase. Varieties Potassium (%) Silica (%) Pol (%) Cane yield (t/ha) Co 1148 (Tolerant) 1.86 1.12 16.1 65.2 Co 419 (Sensitive) 1.02 0.82 14.2 51.6 CDat 5% level 0.72 0.27 1.02 2.11 Dwivedi (1999)

The drop in pH, titrable acidity, decline in sucrose of Sugarcane juice and increase in gum content were found to be associated with low temperature sensitive genotypes (Kanwar et al., 1977 and Irvin and Degendra, 1985. Hence higher concentration of K might regulate metabolic activity of plants at low temperature and thereby impart endurance. 232 R.S. Dwivedi

Dwivedi and Srivastava (1993) and Dwivedi(1999) reported that potassium silicate which form complex with wax, Ca, Na and cellulose etc. in primary and secondry wall of epidermal cells become more viscous (solidify) by utilizing low temperature. Consequently the level of latent heat of injury is not touched and protoplasm is saved. Similarly high temperature (45°C) is utilized in loosing the aforesaid organometallo complex layer vis-'t-vis in reducing viscosity. Thus latent heat of injury is not touched and plant is saved from high temperature stress (Figure 2). Wang et al. (1955) noted that adequate application of K reduces winter Killing by raising sugar and starch, soluble protein and bound water in lucern. This type of observations were noted by Dwivedi (1993) in which 2% KH2PO4 sprayed crop faced 10% frost injury, recorded 15.6 pol % juice due to high bound water(8.8%) as against corresponding value of 50, 13.1 and 5.2 in control (Table 19).

Water logging stress

Oxygen tension followed by accumulation of CO 2, inorganic and organic substances, salinization(only on saline coastal areas), ethylene production etc.

SODICITY (>I'H9) AGGRAVATES TEMP. SENSITIVITY

EPIDERMAL CELLS LOWTEMR _R (<5° C) WAX

0811±SiO-1 2 nH 2 0 CE MAMY VIS COSITY 2+N+ LL YWA SOLIDIFY LOSES LL Jt OOR~P THERMALCONDU CT IVITY WAX LATENTHEAT LEA I HSHYD POINT- ST +S 2 UNTOUCHEDLITLC MOBMOLE C 2 \ XYL CO Ca No+SUGARS B ND ESTERS WALL NEUTRALISE HEAT POOR THERMAL CONDUCTIVITY cU EFF ECT fl.TI '1' CYTOPLASM BVCOE Cu LOOSENINGLAYER5 OF SECONDRY WALL LAYERLAR HIGH TMP PRIMARY WALL S450C) POTASSIUM SILICATE REDUCED TEMP IN JURY TEMPERATURE TOLERNCE IN"SUARCANE

Figure 2. After Dwivedi & Srivastava, 1993 Potassium Nutrition of Sugarcane in Relation to ield. Quality and Abiotic Stress Tolerance 233

Table 19. Effect of foliar spray of K on frost injury (drying of top leaves) pol %juice and bound water content (water retained in leaves (%), during drying at 50'C) in Sugarcane (Co1158) at Kashipur (U.P.) Treatments Frost injury Pol % Ratio of Bound Water (%) juice TS/RS in leaves (% dwt) No Spray (control) 50 13.1 18.4 5.2 Water Spray 40 14.2 20.7 6.5 2% KH 2 PO 4 Spray 10 15.6 22.6 8.8 CDat 5% level - 0.72 1.2 1.06

are the main disorders under water logged conditions. This causes the death of root and shoots if anoxia (very low oxygen environment) is prolonged. The redox potential and pH of soil decline. This might be balanced through release of root exudates and aerial root growth.

CO 2 released by rhizosphere is dissolved in water and causes pH drop of water logged soil (Mengel, 1978). C0 2+H20 -- H + HCO 3. Dwivedi et al. (1991) found marKed drop in redox potential and pH of water logged soil in Sugarcane cropping. Further studies have shown that external application of K in water-logged soil decreases rhizosphere pH with a drop in redox potential (Table 20) and thereby accrue better crop growth. Higher H+ ion concentration releases KI from soil minerals located in rhizosphere. However, under water logged conditions plant growth and K uptaKe is affected adversely. Distinct drop in rhizosphere pH has been reported due to form of fertilizer supply. Nitrate supply results, in a net release of OH-- or NH 4CO 3/HCO 3 whereas, NH4-N leads to a substantial drop in pH (Kirkby, 1969). Application of K reduces drop in pH of sugarcane rhizosphere soil as observed by Dwivedi et al. (1991). K helps in raising root exudates pH and thereby checK the dropping tendency of rhizosphere pH (Dwivedi and Srivastava 1996). Besides this, what are the other mechanism through which K application checKs the drop in water logged rhizosphere soil pH in Sugarcane croppiig needs further studies.

Table 20. Chages in soil pH, redox potential, pH of root exudate under water logged conditions with (60 kg K0/ha) without (control) potassium application in sugarcane cropping (Adopted from Dwivedi et al., 1991) Soil conditions and Soil pH Soil redox Potential Aerial root treatment (mm/hos) exudates pH Normal Control 7.89 -0.82 - Added K 7.89 -0.84 - Water logged Control 7.68 -0.20 7.30 Added K 7.78 -0.38 7.91 234 R.S. Dwivedi

Accumulation of the triacid osmoticum (extracted from the leaves by 0.005 N acetic acid, oxalic acid and HCI mixed in 2:1:1 proportion) in sugarcane genotypes under water logged conditions depends upon degree of their resistance. The tolerant varieties show more than 30% rise, moderately 11:29% and sensitive less than 10% rise respectively (Dwivedi et al., 1991) (Table 21). The osmoticum has been found to contain sugars, zinc, K etc. and their contents varies with genotypes. Rise in TAO content has shown rise in K and Zn content. Zinc or K form complex with organic substance perhaps to antagonize toxins produced in tissues due to oxygen tension and impart tolerance. Potassium mediated mechanism of water logging resistance is presented in Figure 3. However detailed studies are required to understand it.

Table 21. Triacid osmnoticum(TA) content and its constituents in resistant and sensitive genotype of Sugarcane under water logged conditions Varieties TAO Ratio of Zinc K (ug/g dry leaves) 'TS/RS (ppm) (ppm) COS 8118 (Tolerant) 1197 (48.8) 24.83 4.2 122 CoC671 (Sensitive) 1056 (7.3) 9.72 3.2 85 CD at 5% 22.05 0.87 4.6 (Dwivedi et al., 1991). Values in parenthesis-per cent increase over normal, T- Total, R- Reducing, S-Sugar

POTASSIUM MEDIATED MECHANISM OF WATER-LOGGING RESISTANCE IN SUGARCANE'

i I AUNOD+T CMIE T C 4 4 P140-411 PH OZ1 .'S

I A O T ¢ 1Ce.XU A I - TA ~

Roots ~MOAXMc t: I o AERIALO T T l *00 WD OJ t I TA. -A rw oE _- - - OOTF -

Figur H.rLAr-e ci a. -993

A -O------_- -"-I-. a.lSl!alBtel --t-_------

Figure 3. After Dwivedi el al.. 1993 Table 22. Variation in chemi-osmoticum and K contents, K/Na ratio, nitrate reductase activity (NR)(p mot NO/gf. w/h), acid invertase activity (Al) (p mol sucrose hydrolyzed/min/mg protein), calorific content, millable cane, pol (%) juice and per cent reduction in cane and sucrose yield in different genotypes of Sugarcane on sodic soil (pH 9.6, ESP52.3)(Dwivedi and Srivastava 1992) Genotype K(%) in K/Na Chemi Al NR Calorific Millable Pol % Reduction " LTM ratio osmoticum acticity activity values in cane (%) in yield (gg/gdw) stem (000/ha) juice _" (cal/gdw) cane sucrose COS767 (T) 2.7 2.7 2001 21.70 260 4001 66.54 16.68 20 28 C0740 (T) 2.6 3.2 2016 22.42 392 4160 54.50 14.21 25 30 UP-5 (T) 2.1 1.6 1800 23.22 220 3996 61.27 13.92 35 35 15" COJ64 (S) 0.9 0.4 1290 49.25 139 3690 39.50 13.42 78 81 C01148 (M) 1.2 0.6 1400 30.72 190 3868 62.00 13.92 52 58 COLK8001 ( 1.0 0.5 1400 31.66 180 3912 75.72 14.94 58 60 CD at 5% 0.37 - 8.1 2.3 10.2 12.7 7.2 0.35 7.1 5.2 236 R.S. Dwivedi

Salt Stress

The injuries of salinity and alkalinity are related with K through antagonistic and Na substitution process, maintaining osmotic potential, augmenting the synthesis of organic or organamatallo complexes, inactivation of excess Na, Cl, water SO4, HCO 3 and CO3 and thereby regulating chemi-osmotic potential and balance in cell and entire plants (Green-way and Munn, 1980; Dwivedi, 1979). Potassium forms complex with organic anions e.g. oxalic acid, citric and malic acid, aspartic acid, and proteins etc and might act as osmoticum and buffering substances in regulating metabolic reactions under stress conditions including salinity and drought. Dwivedi and Srivastava (1992) recorded accumulation of significantly higher chemi-osmoticum in the leaves of Sugarcane genotype possessing high K/Na ratio (Table 22). This ultimately regulated balanced enzyme activity crop growth and thereby low reduction in cane and sucrose yield in tolerant varieties under sodicity stress.

Perusal of data in Table 22 reveal that sodicity tolerant genotypes grow well by accumulating high energy and chemi-osmoticum in the tissues vis-ii-vis enhancing osmoticum energy regulation system. These genotypes have high K/ Na ratio than sensitive/moderately tolerant genotypes. Correspondingly, the acid invertase activity declines and little reduction in sucrose yield is resulted in tolerant genotypes. Similarly nitrate reductase activity was higher in tolerant varieties, which might have accelerated tillering and thereby impeded yield reduction under salt stress (Table 22). Tissues K/Na ratio regulated chemi- osmoticum energy regulation to withstand sodicity injury need further studies.

References Anonymous (1975-90) Annual report of all India co-ordinated Agronomy Research Project (ICAR). Anonymous 1989-90- Fertilizer statistics F.A.I. New Delhi. Dwivedi, R., Snehi and Srivastava, K.K. 1993. Scenario of research on physiology and biochemistry of sugarcane in "Sugarcane research and Development in sub-tropics" (ed G.B. Singh and O.K. Sinha) IISR, ICAR, Lucknow India pp. 143-190. Dwivedi, R., Snehi, Srivastava, K.K., Solomon, S. 1988 Rapid test for drought resistance in Sugarcane. Sugarcane (Spring suppl.), 31-32. Dwivedi, R., Snehi, Srivastava, K.K., Nigam, M. and Ram, M. 1992 EDTA Osmoticum : A heritable prognostic. Trait to detect drought resistance potential in Sugarcane genotypes. Proceedings of lSSCT. Bankok 21: 11-15. Dwivedi, R., Snehi, Srivastava, K.K., Nigam, M and Ram, M. 1991. Studies on the mechanism of water logging resistance in Sugarcane genotypes; Proceedings of InternationalConference of Plant Physiology. Banaras Hindu Potassium Nutrition of Sugarcane in Relation to Yield. Quality and Abiotic Stress Tolerance 237

University India pp. 301-306. Dwivedi, R., Snehi, Bal, A.R., Qadar, A. and Joshi, Y.C. 1982. Studies on salt resistant characters in graminoid alkali halophytes. India Journal of Plant Physiology. 25: 231-236. Dwivedi, R.S. and Srivastava, K.K. 2001 EDTA- Osmoticum as a diagnostic test for detecting hidden hunger of Potassium and Zinc in Sugarcane T h ISPP, held at Canada, 21-27 July, pp. 7-23 Dwivedi, R.S, Misra Y and Srivastava K.K. 1997 Effects of Potassium on EDTA- osmoticum, Nitrate reductose activity and productivity of groundnut- Sugarcane intercropping under water deficit conditions In (Eds.T. Ando et al) Plant Nutrition for sustainable food production and environment. pp. 93-94. Kluwar Academic Publishers, Japan. Dwivedi R.S. and Srivastava, K.K. 1992 Developing criteria for selecting sugarcane genotypes resistant to salt stress. Final Report. IISR (ICAR) Lucknow pp. 29. Dwivedi, R.S. and Sugarcane K.K. 1996. Developing criteria for selecting Sugarcane genotypes resistant to water logging. Final Report IISR (ICA), Lucknow pp. 42. Dwivedi, R.S. and Sugarcane K.K. 1996a Physiological characteristics of sugarcane for water deficit resistance. Final Report IISR (ICAR), Lucknow pp. 72. Dwivedi, R.S. 2000 Physiology of Sugarcane in (Ed Shahi, H.N. et al) 50 years of Sugarcane Research in India, IISR (ICAR) Lucknow pp. 75-110. Dwivedi R.S. 1995 Constraints in cane productivity in (Eds G.B. Singh and U.S. Shukla): Sugarcane production constraints, IISR, Lucknow pp. 105-109. Dwivedi, R.S. 1999 Role of Potassium as an organometello-osmoticum in raising abiotic stress tolerance. In (eds. Tiwari K.N. and S.C. Mudgal), Use of Potassium in UP agriculture. UPCAR, Lucknow. pp. 120-129 Dwivedi R.S. 1994. Sugarcane :an ideal energy crop with potential for obviating the green house effect. Agri & Equip International (World crops) 45(1 1&12), 102-106. Dwivedi R.S. 1994, (Hindi Translation) Ganne Men Poshak Tatwa Avom, Urbarak Prabandh. IPI Switerzerland. p. 108 Dwivedi R.S. 1988 Mineral Nutrition of groundnut. Metropolitan Book Co. New Delhi 110002 (India) pp. 135. Dwivedi, R., Snehi, 1989. Potassium nutrition in relation to energy partitioning and solar energy harvesting efficiency of groundnut. Oleaginex. 44: 413- 417. Dwivedi, R., Snehi, 1979. Salt stress - Plant physiology. A decade of Research. 238 R.S. Dwivedi

CSSRI, Karnal. pp. 141-168. Dwivedi, R.S. 1992. Potassium as an organometallo-osmoticum to induce abiotic stress resistance in plants. Int. Symp.on K research, Akbar Hotel, New Delhi, India. pp: 51-52. Epstein, E. 1969. Mineral metabolism of halophytes, British Ecology Society Symposium 9: 345-355. Greenway H. and Munn, R. 1980. Mechanism of salt tolerance in halophytes. Annual Revision Plant Physiology. 31: 149-190. Hunsigi, G 1977. Kinetics of soil Potassium during continuous cropping with Sugarcane. Ph.D. thesis, Kanpur University, U.P. (India) Hunsigi 0. and Srivastava, S.C.1981. Some measures of Potassium availability to Sugarcane. Fertilizer News 26(6): 35-38. Hussain, S.A. 1989 Blue Prints for maximizing yields of Sugarcane, Sind Sugar Corp. Ltd. Beaumont Road, Karachi, Pakistan pp. 43. Irvin, I.E. and legendre B.L.1985. Resistance of Sugarcane varieties to deterioration following Freezing. Sugarcane (March/April): 1-4. Jafri, S.M.H. Singh T. and Ghosh, A.K. 1988. Ann Repotr. IISR Lucknow pp. 27-28. Kanwar, RS., Singh, Q. and Batta, S.K. 1977. Studies on ripening under low temperature condition in north India. Sugar Journal. 79: 340-346. Krikkby, E.A. 1969. Ion uptake and ionic balance in plant in relation to the form of N nutrition. 1. J.H.Rorison Ecological aspect of mineral nutrition of plant: British Ecology Socicety Symposium No. 9, 215-235. Kapur, M.L. and Bishnoi 1998. Balance fertilizer for Sugarcane. In Balanced Fertilizer in Punjab Agriculture. (Eds. N.S. Pasricha et al.) PAU Ludhiana. Lakshmikanthan M 1973, Technology in Sugarcane growing. Andhra Pradesh Agri. Univ. Hydrabad, Andhra Pradesh. Mehrotra, C.L.,Tiwari and Pawar, P.S.(1979) Effect of soil types on response of Sugarcane to NPK in UP. Fertilizer News 17(2): 43-47 Mengel, K and Kirkby, E.A. 1982. Principles of plant nutrition, Intern. Pot. Inst. Switzerland. p. 655. Mengel, K. 1978. Potassium dynamics in rhizoshpere and Potassium uptake by roots. Potassium in soil and crops (ed. G.S. Sekhon) Pot. Res. Institute of India New Delhi, India, pp. 127-146. Nelson W.L. 1978. Influence of Potassium on tolerance of Stress. Potassium in soil and crop (ed. G.S. Sekhon), PRII, New Delhi (India) pp. 203-222. Osmand, C.B. 1978. Crassulacean acid metabolism: A curiosity in context Annual Potassium Nutrition of Sugarcane in Relation to Held Quality and Abiotic Stress Tolerance 239

Review of Plant Physiology 29: 379-414. Pflunger, R and Mengel, K. 1972, The photosynthetic activity of chloroplast obtained from plants with different Potassium nutrition. Plant and Soil 36: 417-425. Rama Rao, Nand Sekhon, G.S. 1989. Critical Potassium levels in selected crops. Sugarcane PRII special publications PRII, Gurgaon, Haryana (India,). pp. 60-65. Salisbury, F.B. and Ross, C.W. 1986, Plant Physiology CBS Publishers New Delhi, India. p. 540. Sundra B and Subramanian, S (1989) Nutrient uptake in short duration Sugarcane based sequential cropping. fertilizers 34(10): 21-26. Srivastava, S.C. and Hunsigi, G 1978, Argonomic and economic evalution of Sugarcane to Potassium In (Ed. Sekhon G.S.) Potassium in soil and crops. PRII New Delhi pp. 327-338. UPCSR 1983. Seventy years of Sugarcane research (1912-1981), UPCSR. Sahajahanpur, UP. UPCSR 1989-1990 & 199-92. Ann. Report AICRP on Sugarcane, Sajahanpur Centre, UPCSR, Sahajahanpur, UP Wang, L.C., Attoc, O.i. and Trang E. 1955. Effect of time and fertility levels on the chemical composition of alfalfa. Argonomy Journal. 45: 3-5. Waisel Y1972. Biology of halophytes, Academic press, New York. pp. 395. Zeiger, E.W. Woody and P. Hepler 1977. Light sensitive membrane potentials in onion guard cells. Nature 270: 270-271 Zende, G.K. (1972) Effect of Season and management practices on the uptake of nutrients by different variety of Sugarcane proc 24' h convention, DSTA, Pune. pp. 73-89. Potassium Fertility in Cotton Growing Soils of India and its Influence on Yield and Quality of Cotton

M.S. BRAR Department of Soils, Punjab Agricultural University, Ludhiana - 141 004

ABSTRACT

Cotton growing area in India is divided into three zones, North, Central and Southern Zone. Soils of Northern zone are alluvial, light textured, low in organic carbon with illite as predominant clay mineral. Soils of the Central zone and Southern zone are primarily black, alluvial and red, with high content of clay and calcium carbon. Black (vertic) soils have Montmorillonite/Smeclite as predominant clay mineral whereas red soils have kaolinite as the dominant clay mineral. Normally solution and non- exchangeable potassium is more in alluvial illitic soils whereas exchangeable K is more in vertic smectitic soils.

Earlier studies conducted on low yielding and long duration varieties showed no response to potassium application. However, the response to potassium application is increasing over the period of time. Response of cotton to application of potassium has been found to be site specific and year specific. Short duration high yield varieties are more responsive to K application than long duration varieties. Non-exchangeable potassium plays a significant role in the nutrition of cotton. Cotton productivity can be sustained by the use of balanced fertilization. The potassium application has been found to increase both yield and quality of cotton crop. Basal application of potassium is better than other methods and there is no additional advantage of split application. Generally soils of northern zone are more responsive to potassium application as compared to soils of other two zones.

Key words: Potassium Fertility, Cotton Yield, and Cotton Quality.

Cotton with its indeterminate growth habit, producing vegetative and reproductive organs simultaneously over a longer period of time, is structurally and physiologically more complex than most of the other field crops (Venugopalan and Pandarikakshudu, 1998). Although it is not very exhaustive crop, nutritional stress and imbalances affect vegetative and reproductive metabolism and ultimately limit seed cotton yield as well as fibre and seed quality. It is a long duration (135 to 270 days), deep rooted and drought tolerance crop. It grows well in alluvial, medium to deep black and red soils with pH ranging from 6.0 241 242 M.S. Brar

to 8.5. Good cotton production requires adequate moisture, good supply of nutrients and warm climate. In India, it is grown as rainfed crop on 70 per cent of the total area. Cotton production in India has witnessed several remarkable achievements since independence. Spectacular increase in production has been possible due to increase in area during early period, followed by increase in productivity (yield ha -') due to introduction of improved varieties and hybrids and improved irrigation, soil, fertilizer and other agronomic practices.

Potassium is an essential major nutrient element, which plays an important role in photosynthesis, water balances and balance between mono and divalent cations (Balaguru and Khanna, 1982), translocation of carbohydrates and resistance against pests and diseases. Role of potassium in the nutrition of crop plants is well known. Potassium application not only increase the yield but also the quality parameters of the cotton. The response of cotton to applied K depends upon both mineralogical make-up of the soil as well as the available and reserve K status of the soil.

Soil Characteristics and potassium fertility of Cotton growing areas

The cotton growing areas in India is broadly divided into three major zones (Fig. 1). North zone comprising states of Punjab, Haryana, Northern Rajasthan and Western UP, have 18% of the total area under cotton and contribute 23% to the total production. These are alluvial, sierozem and sandy soils. Alluvial (entisols and inceptisols) are deep soils with texture ranging from sandy loam to clay loam. In low rainfall areas sandy to loamy sand (aridisols) are common. These are calcareous and alkaline (Table 1). Permeability and retention of water is fairly good. Illite is the dominant clay mineral. Productivity of cotton in this zone is fairly high due to irrigation facilities.

Central zone, -comprising Madhya Pradesh, Gujarat and Maharashtra constitutes 60% of the cotton area with 47% of production. The soils are primarily black, alluvial and red. Cotton is primarily grown as a rainfed crop. Black (vertisols) soils are medium to deep with high clay content (30%) and clay plus silt upto 80 %. Montmorillonite is the dominant clay mineral. The pH normally varies from 7.0 to 8.5 and contains high amounts of free CaCO3 . These are high in CEC and moisture holding capacity and low in water permeability. Red soils (alfisols) are found in parts of Northern and Central Gujarat. They are sandy loam to loam in texture with pH varying from 6.5 to 7.5. Kaolinite is the dominant clay mineral in these soils.

Southern zone with states of Andhra Pradesh, Karnataka and Tamil Nadu contributes 30% to the production from 22% of the area. The soils occurring in this zone are black (vertisols), red (alfisols), alluvial (entisols) and to a less extent laterite (oxisols). This tract comes under both irrigated and rain fed agriculture. K Fertility in Cotton Growing Soils of India & its Influence on Yield and Quality of Cotton 243

JAMMU &k

• HIMACHAL APRADSH

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RAJAST1IAPORADESR4UTTA HIy LAND AGA-FUMAN BAR ORFGMHF.A PUM

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EARUADENS. ZONE SEASTERN ARSOREUM ZONE

Figure 1. Cotton growing zones in India (after Kairon and Venugopalan. 1999) Table 1. Soil characteristicsand potassium status of cotton growing soils in Punjab, Northern Zone Depth Clay PH OC CaCO 3 CEC EC Exchangeable Cations Potassim content WS: Exch: (cm) (%) (1:2) (%) (%) (me/ (dSm - ') (me/100g) (mg kg- 1) Exch Non- 100 g) ratio exch Ca+Mg Na K WS Exch Non- ratio exch

Jodhpur Ramana series, Bathinda, Punjab Cotton - Wheat 0-18 9.0 8.1 0.09 3.0 5.6 0.18 5.2 0.12 0.17 38.1 171.0 725.8 1 : 4.5 1: 4.2 18-52 9.1 8.1 0.08 3.2 6.9 0.18 6.1 0.14 0.12 28.8 150.5 798.3 1: 5.2 1: 5.3 52-77 12.6 8.1 0.05 4.1 6.7 0.19 6.5 0.12 o.12 23.4 113.7 789.0 1: 4.8 1: 6.9 77-97 13.8 8.1 0.09 3.9 6.7 0.21 6.5 0.24 0.13 21.0 115.0 819.0 1 : 5.5 1: 7.1 97-118 14.2 8.2 0.07 4.1 6.7 0.20 6.5 0.15 0.15 17.8 111.2 789.0 1: 6.3 1 : 7.1 118-146 16.4 8.2 0.06 8.5 6.7 0.20 6.1 0.15 0.15 19.9 115.6 789.0 1: 5.8 1 51 Gahri Bhagi series, Bathinda, Punjab, Cotton - Wheat 0-18 18.6 7.9 0.22 0.6 7.8 0.25 7.1 0.07 0.53 42.0 138.6 1447.0 1: 3.3 1 : 10.4 18-46 25.5 8.1 0.18 1.0 8.7 0.25 8.1 0.10 0.55 35.0 127.0 1357.0 1: 3.6 1; 10.7 46-72 24.2 8.2 0.17 1.3 9.7 0.25 9.3 0.21 0.25 30.2 114.5 1323.8 1: 3.8 1: 11.5 72-99 26.4 8.1 0.14 1.6 9.7 0.30 9.2 0.21 0.21 27.7 117.5 1458.0 1: 4.2 1: 12.4 99-132 25.0 8.2 0.17 2.3 9.6 0.35 9.2 0.19 0.21 21.5 109.8 1513.6 1: 5.1 1 :13.8 132-158 27.0 8.2 0.10 6.9 8.3 0.30 8.1 0.21 0.15 15.7 85.9 1496.6 1: 5.5 1 : 17.4 Source: Sekhon, 1993 K Fertility in Cotton Growing Soils of India & its Influence on ield and Quality of Cotton 245

Comparison of soils in tables 1 and 2 showed there is a considerable variation in the amount of water soluble K as a proportion of exchangeable K in different soils. Soils of north zone have higher proportion of water soluble to exchangeable K than those of southern zone. Water-soluble K is a function of the K saturation of CEC (Brar et al., 1986 and Suba Rao and Sekhon 1990). The values of exchangeable K are high in vertic soils of Southern zone, whereas those of non- exchangeable K are high in alluvial soils of northern zone. The relations worked out by Sekhon el al. (1992) also showed that at a given level of non-exchangeable K, exchangeable K is low in illitic alluvial soils as compared to smectitic vertisols. The response of cotton to the application of potassium in addition to absolute values of each form will also depend upon the replenishment (equilibrium) from one form to another. Ghosh and Hassan, 1980, classified the soils of cotton growing areas in medium to high category of available potassium.

Response of cotton to applied potassium in different zones

Judicious use of fertilizer is very important component of cotton production technology. Elaborate experiments to study the response of cotton to potassium applied singly and in combination with N and P have been initiated through out the country in 1962-63. In Northern Zone the experiments were conducted at Abohar, Ludhiana, Faridkot, Jalandhar (Punjab), Raya (UP), Sriganganagar (Rajasthan), Hissar and Sirsa (Haryana). Available K20 of these soils ranged from 210 to 400 kg ha-'. The response to K application was erratic. The yield, normally increased with K application, but the response was location and year specific. Generally, the response to K application increased over the period of time. Earlier experiments conducted in Central zone at Indore, Khandwa, Khergone, Akola, Achalpur, Sirgupa, Rahuri, Surat, Parbhani, Dharwad and Amravati on soils with available K ranging from 220 to 760 kg ha-' showed no response to K application (Singh 1978). Patel and Raj (1993) and Patel el al. (1993) reported non significant response to K application from the experiments conducted at Anand and at dry farming research centre, Targhadia in Semi arid Saurashtra region. However, the ECF trials of 1981-82 (29) and 1981-85 (69) conducted in Vadodara district showed a significant response to K application.

In Southern Zone also the earlier work on low yielding varieties of cotton showed no favourable effect of K application on the yield of this crop (Panse 1945, Dastur 1946, Nanjundaya, 1956). Reason reported for no response was the addition of FYM to the cotton which contains potassium. No response to applied K on yield or quality of fibre was observed at Coimbatore (Sreedharan and Mariakulandai 1968), Srivilliputtur, Paryakulam and Coimbatore (Singh, 1978). Balasubramaniam et al. (1968) conducted an experiment at ARS, Aliyarnagar under irrigated conditions during 1963-65 and observed response to K application. The positive effect of potassium on the seed cotton yield (6.8 kg seed cotton kg- ' K) has been reported at Baptala (Rao et al., 1980), 3.6 kg per kg at Nagpur (Mudholkar 1984) and 4.3 kg per kg at Vadodra (Patel and Raj, 1993). Table 2. Soil characteristicsand potassium status of cotton growing soils in Karnataka, Southern Zone Depth Clay PH EC OC CaCO 3 CEC Exchangeable Cations Potassim content WS: Exch: (cm) - (%) (1:2.5) ) (%) (%)MdSm (C mol(p+) kg (mg kg-') Exch Non- ratio exch Ca+Mg Na K WS Exch Non- ratio exch Zone II. Aikur, Gulberga, Karnatka Cotton-Sunflower-Greengram 0-15 50.4 8.3 0.67 0.50 5.6 55.7 53.3 1.04 0.60 16.7 236 685 1:14.1 1:2.9 15-30 50.9 8.3 0.69 0.46 5.6 57.4 52.2 4.82 0.57 15.2 224 742 1:14.7 1:2.3 13-60 54.0 8.4 0.80 0.30 6.8 59.4 54.6 5.09 0.58 15.8 215 768 1:13.6 1:3.6 60-100 54.0 8.3 0.82 0.25 8.9 60.2 51.6 8.87 0.49 16.0 192 704 1:12.0 1:3.7 Zone II. Rampur, Raichur, Karnatka Cotton-Jowar-Sunflower 0-15 57.2 8.5 1.00 0.46 9.0 52.3 48.0 2.29 0.55 14.5 216 771 1:14.9 1:3.8 15-30 59.0 8.5 1.20 0.40 6.8 52.5 47.5 4.85 0.39 13.7 152 795 1:11.1 1:5.2 30-60 60.3 8.5 1.25 0.31 11.3 53.1 51.2 2.25 0.36 13.0 140 762 1:10.8 1:5.4 60-100 61.0 8.5 1.30 0.28 8.9 53.9 48.3 4.85 0.34 12.7 133 676 1:10.5 1:5.2 Zone VIII, Bailhongal, Belgaum, Karnatka, Cotton-Jowar-Green gram 0-15 52.4 8.3 0.20 0.53 5.9 50.5 47.4 2.95 0.52 15.3 203 765 1:13.3 1:3.8 15-45 48.7 8.3 0.24 0.48 6.7 48.7 47.6 1.18 0.42 14.0 164 600 1:11.7 1:3.7 45-60 51.9 8.4 0.29 0.40 6.5 51.3 49.9 1.20 0.44 13.7 163 687 1:11.9 1:4.2 60-100 52.5 8.4 0.30 0.31 6.9 53.9 50.4 3.01 0.39 10.8 154 526 1:14.2 1:3.4 Zone VIII. ARS, Dharwad, Dharwad, Cotton-Cotton-Cotton 0-15 57.0 7.9 0.27 0.63 3.9 56.0 54.7 2.82 0.56 12.1 210 581 1:17.3 1:2.8 15-45 58.7 8.2 0.28 0.53 4.2 57.6 55.1 2.09 0.48 11.3 190 600 1:16.8 1:3.2 45-60 60.7 8.2 0.25 0.48 4.8 58.6 56.4 2.85 0.47 11.1 185 498 1:16.7 1:2.7 60-100 60.8 8.3 0.30 0.40 3.8 59.0 56.4 3.06 0.45 10.5 175 503 1:16.7 1:2.8 Table 2. (Contd.)

Depth Clay PH EC OC CaCO 3 CEC Exchangeable Cations Potassim content WS: Exch: (cm) (%) (1:2.5) (dSm - ') (%) (%) (C mol(p+) kg (mg kg-') Exch Non- ratio exch Ca+Mg Na K WS Exch Non- ratio exch Zone VIII. ARS, Dharwad, Cotton-Jowar-Cotton 0-15 56.3 8.1 0.32 0.61 4.0 56.3 54.9 2.04 0.15 12.0 200 502 1:16.7 1:2.5 15-30 56.9 8.2 0.31 0.55 4.3 56.6 55.9 1095 0.47 11.5 185 510 1:16.1 1:2.8 30-60 59.9 8.2 0.35 0.50 4.8 57.8 55.4 2.09 0.46 10.2 180 466 1:17.6 1:2.6 , 60-100 60.0 8.2 0.30 0.47 4.0 58.0 54.9 4.18 0.44 8.0 172 472 1:21.5 1:2.7 Zone VIII. ARS, Dharwad, Cotton-Groundnut-Cotton 0-15 56.8 8.0 0.29 0.64 3.8 56.5 54.4 2.08 0.49 12.2 207 482 1:17.0 1:2.3 1:3.1 15-30 57.9 8.2 0.35 0.54 4.0 58.4 56.6 1.95 0.43 11.0 168 520 1:15.3 445 1:17.4 1:2.7 30-60 59.8 8.3 0.30 0.50 4.1 59.0 54.3 4.01 0.42 9.5 165 60-100 59.8 8.3 0.36 0.45 3.9 60.0 52.3 8.02 0.42 8.0 164 462 1:20.5 1:2.8 Zone V II. ARS, Dharwad, Cotton-Jowar-Groundnut 0-15 58.0 8.1 0.28 0.62 3.8 55.7 53.4 2.84 0.52 12.2 203 522 1:16.3 1:2.5 15-30 59.6 8.2 0.29 0.55 4.0 55.8 54.9 1.09 0.44 11.1 173 540 1:15.6 1:3.1 30-60 60.4 8.2 0.31 0.45 4.8 56.8 55.4 1.04 0.44 10.6 172 585 1:16.2 1:3.4 &, 60-100 60.9 8.2 0.31 0.42 4.0 58.0 53.8 5.15 0.42 8.5 165 498 1:19.4 1:3.0 Source: Hirekurabar et al., (2000)

N 248 M.S. Brar

From a field experiment conducted at Cotton Research Station, Sirsa (Haryana) on a sandy loam soil with low organic carbon (0.34%) and medium available potassium (248 kg K20 ha-'), Kumar and Madan (1987) reported that potassium application increased the seed cotton yield significantly over the comrol (Table 3).

Table 3. Effect of applied K on the yield and yield contributing parameters Treatments No. of No. of Seed Weight GOT Yield K-conc. - (kg K20 bolls seed index per boll (q ha ') in leaves ha'1 plant - ' boll (g) at flowering 0 14.6 22.8 6.3 2.4 31.2 13.2 1.85 30 16.9 24.2 6.6 2.5 31.3 14.3 1.92 60 17.7 24.1 6.7 2.6 32.0 14.5 1.96 90 18.5 24.3 6.6 2.5 31.4 14.8 1.90 CD 5% 2.6 NS 0.2 NS NS 1.0 0.04 Source: Kumar and Madan, 1987

In a green house study on Samana, Fatehpur and Tulewal soils, K-deficiency symptoms were observed on soils testing less than 36 mg K kg -', whereas significant increase in yield with K application was observed on soils testing less than 50 mg K kg - ' (Brar et al., 1987). Potassium application increased the total number of flowers, number of bolls, boll weight and hence seed-cotton yield (Brar and Dhillon 1998). The cumulative flowering rate ceased at much early stage in K deficient soils, whereas it continued increasing for much longer period under proper K supply (Dhanwinder-Singh et al., 1991).

Method and time of application

The experiments conducted to determine the mode and time of K application revealed the superiority of basal dressing over the other methods. The results of the field experiments conducted at six locations on coarse textured, low OC soils with available K varying from 30.8 to 75.0 mg K kg showed that significant response to K application were observed on soils with less than 50 mg K kg - ' available K and less than 2.0% K saturation (Dhanwinder-Singh et al. 1990). The - highest yield was obtained with the application of 120 kg K20 ha ', however 90 per cent of this yield can be achieved with the application of only 30 kg K20 ha - ' (Table 4). Similar types of experiments were conducted at PAU, Cotton- Research Farm at Ludhiana and Abhoar on soils testing 74 and 116 kg K20 - - ha ', respectively (Brar et al., 1994). The highest level of 240 kg K20 ha ' was applied to rule out the possible effect of soil K fixation. Potassium application increased the cotton yield at both locations during all the 4 years. Application K Fertility in Cotton Growing Soils of India & its Influence on ield and Quality of Cotton 249 .

Table 4. Effect of applied K on seed cotton yield (q ha-') at cultivators' fields in Ludhiana district Treatments Experimental Sites Mean - (kg K 2O ha ') 1 II 111 IV V VI 0 16.9 29.3 26.1 30.5 12.1 25.0 23.3 30S 21.2 34.2 27.3 32.9 12.2 21.5 24.9 60S 24.6 34.4 28.5 34.1 13.9 22.6 26.4 120S 23.3 34.5 33.7 37.2 11.3 25.0 27.3 180S 22.7 35.0 39.3 31.5 11.4 24.3 27.4 30F 21.1 33.7 32.1 32.9 11.3 20.7 25.3 60F 18.8 33.7 29.4 34.5 11.1 22.2 25.0 120F 19.9 34.9 30.7 37.1 9.9 22.1 25.8 60S + 60F 19.5 35.2 32.2 35.7 15.4 22.4 26.7 120S + 60F 21.6 36.5 32.1 32.6 15.5 21.6 26.7 C.D. 1.7 3.8 6.4 4.3 NS NS Av.K (mg kg-') 46.7 30.8 35.0 51.9 75.0 55.5 Source: Dhanwinder-Singh et al., 1990, S=K applied at sowing, F= K applied at flowering

- of 120 kg K20 ha ' resulted in increase of 361 (19%) and 268 (12%) kg seed cotton ha -' at Ludhiana and Abohar, respectively. At a price of Rs. 2/- per kg K20 and Rs. 7/- per kg seed cotton the cost to benefit ratio at Ludhiana and Abohar was 1:10 and 1:8, respectively, indicating that even on soils medium in available K, its application is profitable. Yield trend over the years showed that the yields were higher in years when season was dry compared to wet season during flowering and fruiting. There was no additional advantage of split application (singh 1978, Dhanwinder-Singh et al., 1990, Brar et al., 1994,).

Differential response to K application by different cultivars

The high yielding cultivar of American cotton exhibited differential response to applied K. High yielding short duration LH 900 was most responsive cultivar while high yielding long duration F 286 was least responsive. Seed cotton yield, response ratio and net profit decreased in the order of LH 900> F 505 > LH 886 > F 414 and F 286 (Table 5). The highest response of K by high yielding short duration variety LH 900 was due to high demand for K per unit time which the soil was unable to meet. Gopalaswamy et al., (1974) conducted experiments from 1969 to 1972, on MCU 3 and MCU S varieties of cotton and observed differential response of two varieties to potassium application. While response to K application was observed in MCU3 and not in MCU5. 250 M.S. Brar

Table 5. Seed cotton yield, response ratio and profitability at different levels of applied K - Applied K20 (kg ha ) F 286 F4 LH 886 F 505 LH 900 Seed Cotton Yield (q ha -') 0 14.2 12.2 13.9 16.6 20.9 30 16.1 14.2 16.1 19.2 24.0 60 16.7 15.0 17.0 20.0 25.1 90 17.4 15.9 17.9 21.9 26.5 CD 2.18 1.6 1.5 2.8 2.9 Response ratio 30 6.3 6.5 7.3 8.8 10.5 60 4.2 4.7 5.2 5.7 7.1 90 3.6 4.1 4.4 5.9 6.3 Net profitability (Rs ha - ') 30 1415 1460 1685 2081 4790 60 1660 1930 2200 2506 3262 90 1995 2445 2715 3876 4200 Source: Milap Chand and Kapoor (1995)

Potassium uptake is closely related to growth rate. The potassium uptake by cotton proceeds more rapidly than dry matter production. The cotton in humid area absorbed 30% of the total K by the time only 11% of the total dry matter had accumulated (Olsen and Bledsoe 1942). The data in Fig. 2 showed that

110 a UP TAKE oDRY MATTER / 10000

90 1o 8000 o .2 70 " 6000 r j,50 , w,

4000 a- 30 - t/

2000 0 10

0 40 80 120 160 DAYS AFTER PLANTING

Figure 2. K uptake and dry mailer accumulation (after Kamprath and Welch, 1968) K Fertility in Cotton Growing Soils of India & is Influence on Yield and Quality of Cotton 251

maximum uptake of K takes place only in 30 to 40 days during the total growing period. Different type of response of cotton to K status of the soil and to K feritlizer under different growing conditions is expected. Under suitable (better soil, water and pest management) conditions for early and rapid flowering with reduced shedding of bolls, there is a heavy demand for K over a very short period during which K release from soil may be too slow. Under such situations external supply of K will be more useful and crop will respond more to applied K. Contrary to this, if this period is extended demand for K will be slow and also extended over a longer period, crop may not responds to K application.

Contribution of Non-exchangeable K towards K nutrition

Non-exchangeable K plays a significant role in nutrition of cotton. Dhanwinder-Singh et al. (1990) reported that on two soils having almost similar amount of available K (57.9 and 55.8 mg kg-') but different amount of non- exchangeable K (500 and 1075 mg kg-') behave differently to potassium application (Table 6). The cotton responded significantly to K application on soils with less amount of non-exchangeable K as compared to high non- exchangeable K soils. This again signifies the role of non-exchangeable K in potassium nutrition of cotton on illitic alluvial soils of northern zone.

Table 6. Effect of applied K on seed cotton yield (q ha-') on two soils with similar amount of available and different amount of non-exchangeable K. Rate of applied K Yield of seed cotton (q ha-') (kg K20 ha-') Site I Site If (Non-exch.K, (Non-exch.K, 500 mg kg-') 1075 mg kg-') 0 30.5 25.0 30 32.9 21.5 60 34.1 22.6 120 37.2 25.0 180 31.2 24.0 Available K (mg kg-') 57.9 55.8 HNO 3 soluble K (mg kg-') 500.0 1075.0 Source: Dhanwinder-Singh et al, 1990.

Contribution of sub surface potassium

Cotton is a deep rooted crop and the response to application of K also depended upon K distribution in surface and sub-surface soil. In soils testing more in available K in the surface and less K in sub surface soil, a substantial 252 M.S. Brar response to K indicated the significance of sub soil potassium nutrition of cotton (Sekhon, 1993). The response to K application also depended upon the profile distribution of K. On the soils of Gahri Bhagi series where surface soils contain less K as compared to Jodhpur Ramana soils, the response to K application was higher (Brar et al., 2000).

Potassium Response in relation to yield levels

Response to K application and rate of applied K depends upon the yield level of seed cotton (Brar et al., 2000). The results of the experiment conducted on Gahri Bhagi soil series, showed that at location where overall yields were low, response was obtained up to 30 kg K20 ha-' only, however, at high yielding site the 30 kg K20 ha-' rate was insufficient to meet the crop requirement and - thus the response was obtained at 60 kg K2 0 ha ' or higher rates of applied potassium.

Ineraction with other nutrients

Potassium application was more effective at the high NP rates than that at lower rates (Tomar et al., 1986). Application of combination of 120 kg N, 60 kg P20, and 60 kg K2 0 gave highest yields and the highest net return. Chakravorty and Singh (1979) reported highest weight of 100 cotton seeds in the presence of K application along with nitrogen. Singh et al. (1974) reported a non-significant interaction effect of NPK on cotton yield.

The application of 30, 60 and 90 kg K20 ha-' attwo levels of nitrogen (45 and 90 kg N ha-' increased significantly the seed cotton yield over control (Milap Chand and Kapoor 1995). Average response (kg seed cotton/kg K20) of - 6.9, 4.7 and 4.0 was obtained at 30, 60 and 90 kg K2 0 ha '. In another experiment testing medium in available K (135 kg ha-'), the response of cotton to selected combination of N (25, 50, 75 and 100 kg ha-') and K (0, 25 and 50 kg K20 ha- ') was studied for 5 years (1987-1991). The response of cotton to applied K at lower levels of applied N was small and its magnitude increased with increasing rates of applied N upto 75 kg N ha-. There was adverse effect of N applicaton beyond 75 kg K20 ha-' (Milap Chand et al., 1996).The adverse effect to some extent was mitigated by the higher level of K application.

The seed cotton yield was significantly increased (Table 7) by the combined application of 50 kg ha-' N and K at targhadia and 80 kg ha-1 of P and K at Junagarh (Patel et al., 1993).Farm trials conducted during 1980-81 to 83-84 on 39 farmers' fields in Bhavnagar district clearly indicated the favourable effect of applied K on seed cotton yield (Table 8) over the application of N and P. K Fertility in Cotton Growing Soils of India & its Influence on Yield and Quality of Cotton 253

Table 7. Effect of NxK and PxK interaction on yield of seed cotton (kg ha-') K (kg ha-') N kg ha' K (kg ha -') Phosphorus (kg ha-') 0 50 0 50 0 551 661 0 962 942 50 560 772 80 940 1023 CD 5% 76 33 Source: Patel et al., 1993

Table 8. Response (kg ha -') of cotton to fertilizers under rainfed conditions in Bhavanagar district Years No.of trials Average Yield Increase in yield due to K20 over in control (kg ha-') N6oP6o NoP6o 1980-81 6 1084 47 -32 1981-82 18 934 230 212 1982-83 10 466 96 29 1983-84 5 964 184 96 Total/mean 39 841 161 113 Source: Patel et al., 1993

Economics of K fertilization

- The application of 30, 60 and 90 kg K20 ha ' gave additional yield of 110, 130 and 160 kg ha - ' of seed cotton over the control. Other yield attributing characters like number of bolls per plant and seed index increased significantly with K application. Economic analysis of data (Table 9) suggested that application - of K20 at the rate of 30 kg K20 ha ' gave a net profit of Rs. 875 ha-' which does not change with further increase in K levels. Benefit to cost ratio of 3.9 was also maximum at 30 kg dose.

Table 9. Mean seed cotton yield and economics of K fertilization Treatment Average Increase in Value of Cost of Net Benefit) kg K20 ha - ' yield yield over additional fertilizer profit cost kg ha' control yield (Rs. ha -') ratio kg hac-

0 1320 - - - - - 30 1430 110 1100 225 875 3.9 60 1452 132 1320 450 870 1.9 90 1476 156 1560 675 885 1.3 Source: Kumar, 1997 254 M.S. Brar

Highest yield of seed cotton and highest profit was obtained at the combination of 75 kg and 50 kg K level, however, response ratio was maximum at 75kg N and 25 kg K level. There was only direct effect of K application on seed cotton yield and no residual or cumulative effect was observed (Table 10).

Table 10. Response of seed cotton (kg ha-), response ratio and profitability at different combinations of applied N and K in cotton - - Applied Applied K20 (kg ha ') Response ratio Net profit (Rs. ha ') N at K level (kg ha-') 0 25 50 25 50 0 25 50

25 1639 1695 - 2.2 - - 300 - 50 1720 1808 1869 3.5 3.0 646 1258 1607 75 1829 1937 2027 4.3 4.0 1565 2372 3004 100 - 1900 1977 - 3.1 - 1568 2073 Milap-Chand et al., 1996

Balanced fertilizaton and cotton yield

In experiments on farmers fields during 1969-80, application of N, NP and NPK increased the seed cotton yield by 44, 91 and 112%, respectively over unfertilized under irrigated conditions (Randhawa and Tandon, 1982). The balanced fertilization increased the yield of seed cotton (Table 11). There was progressive increase in seed cotton yield with increase in levels of combinations of NPK fertilizers (Patel et al., 1996).

Table 11. Effect of balanced fertilization on yield of seed cotton under rainfed conditions in Gujarat Treatments Seed cotton yield (kg ha - l) N P K 1975 1976-77 1977-78 Pooled 0 0 0 766 375 930 690 60 30 30 1512 683 1005 1067 120 60 60 2225 923 1187 1445 180 90 60 2722 1299 1415 1812 CD 5% 257 143 157 195 0 0 0 658 464 786 636 40 20 20 829 540 957 775 80 40 40 1049 519 1053 874 120 60 60 1187 579 1155 974 CD 5% 90 61 150 61 1 Source: Patel et al., 1996 K Fertility in Cotton Growing Soils of India & its Influence on Yield and Quality of Cotton 255

Nutrient application rate is site specific and varied with the soil test value, nutrient removal pattern and targetted yield. Nutrients are generally removed by cotton in the ratio of 3 : 1 3 (Bhat, 1996) and fertilizer application is recommended in the ratio of 2 1 : 1 or 3 : I :I (Mannikar et al., 1988). Recent study from intensive cotton growing area of Andhra Prasesh, revealed that the farmers applied super optimal doses of N and P while the K application was less than 20% of the recommended dose (Haffis et al., 1997).

Long term fertilizers conducted under rainfed conditions at CICR Nagapur (Kairon and Venugopalan, 1999) has reinforced the need for balanced application of NPK to prevent the decline in long term yield trends (Fig. 3).

1600.

1400 x

1200- £ ' 'a 1000 A

:800 0 0 02 0.0-"." NO PO KO • -. €_"'" 4-- 0--0 N60 W 60 x 0o-.- N60K25 .... -*.--AN 6 0 P 13 0- 0. -- .. . N60P13K25

200A A 0 I I I I I

1986. 1988 1990 1992 1994 1996

Year Figure 3. Long term effect of N, P and K in different combinations on seed cotton yield

Yield trend analysis (Fig. 4) of selected treatments indicated a negative slope under unbalanced fertilizer treatments and positive slope under balanced NPK and NPK FYM application. The data further revealed that yields with NPK and NPK + FYM application were at par during first 8 years of study and differences started in 9th year onward, indicating the long term benefits of balanced fertilizer application alongwith FYM on sustainability of cotton productivity.

Nutrient utilization efficiency was lowest in control plots and increased under balanced fertilization both under low and higher levels of applications (Venugopalan and Pandarikakshudu, 1998). 256 M.S. Brar

2500

- 2000

1500 ••

W. K 100 " 6

0 87 88 S9 90 91 92 93 94 95 96 97 YEAR No e----*-- N90P20K36 x----x N45P20K36+ 7.5T FYMIA---No P0 K0

Figure 4. Long term cotton yield trend in selected treatments

Effect on quality parameters

Role of potassium in improving fibre properties - fineness, strength, maturity and uniformity ratio has been well documented (Helkaiah et al., 1981, Shanmugham and Bhat, 1991 and Mannikar, 1993). The quality parameters like fineness and maturity of fibre were greatly influenced with the application of potassium (table 12). Increasing the dose of K application increased the fibre weight per unit length (Grarimetric millitex), maturity coefficient and tenacity at 1/8" gauge (Kumar and Madan 1987). Applied K significantly increased the harvest index and ginning out turn (GOT) in cotton (Milap Chand and Kapoor 1993).

Table 12. Quality characteristicsof cotton as affected by potassium application Treatments 2.5% Span Fineness Maturity Bundle strength (kg K20 ha-') length (mm) gravimetric coefficient tenacity (millitex) (g tex -') 0 21.00 148.2 0.71 22.5 30 21.00 151.7 0.72 22.9 60 20.60 154.7 0.74 23.0 90 20.42 158.0 0.74 23.1 CD 5% NS 2.6 0.015 NS Source: Kumar & Madan, 1987 K Fertility in Cotton Growing Soils of India & its Influence on Yeld and Quality of Cotton 257

Cropping System and response to potassium application:

Cotton-Jowar (2 year rotation) is the predominant cropping system followed in rainfed cotton on vertisol. Long-term experiment was initiated at CICR, Nagpur on a medium vertisol with clay 46%, pH 8.1, OC 0.41% and available K 550 kg ha'. Different levels of NPK were applied. Three cropping systems followed were: Monocropping, G.hirsutum (Cl), Monocropping, G. arboreum (C2) and G. hirsutum - cotton rotation (C3). The results in Table 13 showed that although jowar is considered as an exhaustive crop, cotton-jowar rotation was equally sustainable. About 400 kg seed cotton was continuously harvested from control. There was significant response to P and non-significant response to K application. Highest yields were obtained with the application of 45 kg N + 20 kg P + 30 kg K + 7.5 t FYM per ha. Working under different cropping systems, Singh et al. (2000) reported that jowar is the most exhaustive crop for K uptake. which removes almost 3 times K than that of cotton.

Table 13. Yield of cotton under different cropping systems and levels of applied nutrients Treatments Mean seed cotton yield Nutrient Harvest (kg ha-1 ) utilization index (1986-87 to 1995-96) efficiency N P K CI C2 C3 N (C1) P (CI) (CI) 0 0 0 431 467 489 11.6 52.5 27.6 60 0 0 647 703 780 11.7 54.5 27.1 60 13 0 882 1011 898 12.3 54.2 32.7 60 13 25 939 1059 978 14.9 818 29.8 90 0 0 615 872 720 12.6 60.8 29.1 90 20 0 1034 1136 1105 12.9 67.0 33.5 90 20 38 1083 1187 1114 14.1 72.8 34.7 45 20 25 1291 1374 1337 15.5 73.3 31.0 + 7.5 t FYM CD5% 128 111 Source: Venugopalan and Pundarikakshudu, 1998.

REFERENCES

Balaguru, T. and Khanna, S.S. (1982). Sodium substituting for potassium nutrition of cotton crop. Journal Indian Society Soil Science 30: 170-175. Balasubramaniam, K.M., Jayaraman, N. and Nagarathnam, A.K. (1968). Fertilizer Requirements of cotton in Parambikulam-Aliyar Project area. Madras Agricultural Journal. 5: 211-215. 258 M.S. Brar

Bhat J.G. (1996). Cotton Physiology. Indian Society Cotton Improvement, Mumbai pp 258. Brar, A.S., Brar, M.S., Thind, R.S. and Singh, T.H. (1994). Effect of potassium application on the yield potential of hirsutum cotton. Journal Indian Society Cotton Improvement. 19: 48-53. Brat, M.S., Brat, A.S., Takkar, P.N. and Singh, T.H. (1987). Effect of potassium supply on its concentration in plant and on yield parameters of American Cotton (G.hirsutum L). Journal Potassium Research. 3: 149-154. Brar, M.S., Brat, J.S. and Sekhon, G.S. (2000). Potassium status and response of cotton to applied potassium in calcareous soils of Punjab pp 73-77, GAU- PRII-IPI National Symposium on Balanced Nutrition of Groundnut and other Field Crops Grown on Calcareous Soils of India, held at GAU, Junagarh, Sept. 19-22, 2000. Brat, M.S. and Dhillon, N.S. (1998). Balanced fertilization for higher yields of cotton in Punjab pp. 105-118. In Brar M.S. and Bansal, S.K. (eds) Balanced Fertilization in Punjab Agriculture, PAU, IPI and PRII. Brar, M.S., Suba Rao, A. and Sekhon, G.S. (1986). Solution, exchangeable and non-exchangeable potassium in five soil series from the alluvial soil region of Northern India. Soil Science. 142: 229-234 Chakravorty, S.C. and Singh, S. (1979). Effect of fertilizers (NPK) on the seed weight, protein content and oil composition of cotton seed. Indian Agriculturist 23: 165-171. Dastur, R.H. (1946). Periodical partial failure of American cotton, their causes and remedies. Scientific monograph No. 2. 1.C.C.C. Bombay. Dastur, R.H. (1959). Cotton Monograph. No. 3. I.C.C.C. Bombay. Dhanwinder-Singh, Brat, M.S. and Brat, A.S. (1991). Response to K application and its critical levels for American cotton. Journal Indian Society Soil Science 39: 494-499. Dhanwinder-Singh, Brar, M.S. and Brar, A.S. (1990). Effect of potassium fertilization on yield and K concentration of cotton in coarse textured soils of Punjab. Journal Potassium Research. 6: 162-171. Ghosh, A.B. and Hassan, R.(1980). Potassium fertility status of soils of India. Fertilizer News 25: 19-24. Gopalaswamy, N. Purushothaman, S. and Palaniswamy, K.M. (1974). Effect of nitrogen and potassium on the yield of cotton in the parambikulam Aliyar Project Ayacut. Indian Journal Agricultural Research. 8: 169-172. Haffis, S., Reddy, Y.V.R., Rao, C.A.R. and Katyal, J.C. (1997). Economic evaluation of fertilizer use for different crops by farmers under different situations. Fertilizer News. 42: 107-122. K Fertility in Cotton Growing Soils of India & its Influence on held and Quality of Cotton 259

Helkiah, I. Muthuswamy, P., Chandramohan, Q.J. Ramanathan, K.M. and Krishnanmoorthy, K.K. (1981). Response of cotton to potash application in combination with nitrogen under irrigated conditions. Madras agriculture Journal. 68: 82-85. Hirekurabar, B.M., Satayanarayana, T., Sarangamath, P.A. and Manjunathaiah H.M. (2000). Forms of potassium and their distribution in soils under cotton- based cropping system in Karnataka. Journal Indian Society Soil Science. 48: 604-608. Kairon, M.S. and Venugopalan, MV. (1999). Nutrient Management Research in Cotton - Achievements under All India Coordinated Cotton Improvement Project. Fertilizer News. 44: 137-144. Kumar, V. and Madan, V.K. (1987). Effect of potassium on yield and fibre quality of cotton (G.hirsutum L). Cotton Development 16: 49-50. Mannikar, N.D.(1993). Fertilizer Management in cotton pp. 26-46. In Tandon H.L.S.(eds) Fertilizer management in commercial crops. FDCO, New Delhi. Mannikar, N.D., Bonde, W.C. and Pundarikakshudu, R.(1988). Journal Indian Society Cotton Improvement. 13: 93-108. Milap-Chand and Kapoor, M.L. (1995). Response of cotton and sugarcane to applied potassium in Punjab pp 73-88. In G. Dev and P.S. Sidhu (eds) Use of potassium in Punjab Agriculture. PPIC (India Programme), Gurgaon. Milap-Chand, Brar, B.S., Dhillon, N. and Gill, M.P.S. (1996). Response of cotton to applied K at different N levels in a cotton-wheat cropping system on a Typic Ustochrept in Punjab. Journal Potassium Research. 12: 370-375. Mudholkar, N.J. 1984. CICR, Ann. Rep. (1983-84) pp 20-22. Nanjundaya, C. (1956). Effect of manurial treatments on the yield, fibre properties and spinning value of cotton. Technological Research on cotton in India. I.C.C.C. Bombay. Pansa, V.G. (1945). A note on the cotton manuring trials in India. Second Conference on Cotton growing problems. I.C.C.C. Bombay. Patel, B.K and Raj, M.F. (1993). Response of crops to fertilizer potassium in middle Gujarat semi-arid region pp 117-127. In Patel et al.(eds) Potassium in Gujarat Agriculture GAU, Dantiwada Campus, Sardar Krush Nagar. Patel, J.C., Patel, B.S., Malavia, D.P., Shobhana, H.K. and Khanpara, D.D. (1993). Response of crops to fertilizer potassium in Semi arid Saurashtra region pp. 81-93. In M.S. Patel et al.(eds) Potassium in Gujarat Agriculture GAU, Dantiwada Campus, Sardar Krushi Nagar. Patel, P.G., Patel, U.G., Vashi, R.G. and Patel, D.M. (1996). Bulletin on Fertilizer research in cotton in Gujarat pp. 235. Main Cotton Research Station, GAU, Surat-395007, Gujarat 260 M.S. Brar

Rao, D.V.M., Reddy, O.C.V. and Narasimham, R.L. (1980). Note on the effect of higher level of potassium on yield and its attributes in cotton. Indian Journal Agricultral Sciencs 50: 639.-642. Randhawa, N.S. and Tandon, H.L.S. (1982). Advances in soil fertility and fertilizer use research in India. Fertilizer News 27: 11-26 Sanmugham. K. and Bhat, J.G. (1991). J.Indian Soc. Cotton Imp. 16: 31-35. Sekhon, G.S. (1993). Contribution of sub-soil potassium to the potassium nutrition of cotton. Third Annual Report of the Project under Emeritus Scientists Scheme, Department of Soils, PAU, Ludhiana pp. 1-27. Sekhon, G.S., Brar, M.S. and Suba Rao, A. (1992). Potassium in some benchmark soils of India. Gurgaon, Haryana-122001, India Potash Research Insitute of India. Singh-Chokhey (1978). Agronomic and economic evaluation of cotton responses to potash fertilizer. pp. 339-346. In G.S. Sekhon (edt.) Potassium in soils and crops. Potash Research institute of India, Gurgaon. Singh, J., Venugopalan, M.V. and Mannikar, N.D. (2000). Soil fertility and crop productivity changes due to cotton based cropping systems under rainfed conditions. Journal Indian Society Soil Science 48: 282-287. Singh, R., Singh, K.. Kairon, M.S. and Singh, S. (1974). Effect of NPK on cotton in the Punjab and Haryana states. Journal Research. Punjab Agriculture University. 11: 4-8. Sreedharan, C. and Mariakulandai, A. (1968). Effect of Potash on cotton. Agriculture Research Journal, Kerala. 6: 1-4. Suba Rao A. and Sekhon G.S. (1990). Watesoluble, exchangeable and non- exchangeable potassium in six soil series from tropical India. Journal Agricultural Sciences (Camb) 114: 127-131 Tomar, N.K., Sharma, J.C. and Chahal, R.S. (1986). Evaluation of fertilizer needs of cotton. Journal Indian Society Cotton Improvement 11: 21-25. Venugopalan, M.V. and Pundarikakshudu, R. (1998). Long-term fertilizer experiment in cotton based cropping system in rainfed vertisols pp. 283- 291. In A. Swarup, D. Damodar Reddy and R.N. Prasad (eds). Proceedings of a National Workshop on Long-term Soil Fertility Management through Integrated Plant Nutrient Supply. ISSS, Bhopal, India. Role of Potassium Fertilization in Improving Productivity of Pulse Crops

MASOOD ALI AND CH.SRINIVASA RAO Indian Institute of Pulses Research, Kanpur-208024, U.P.

ABSTRACT

Pulses in India are grown mostly on marginal and sub-marginal lands without proper inputs such as fertilizers. Despite larger K requirements of pulses and continued mining of soil K, it is rarely applied to these crops. Many field experiments showed the benefits of K application on yield increase of various pulse crops. Potassium supply also improved the biological nitrogen fixation and protein content of the pulse grain. However, information available on K nutrition of pulse crops is meagre. This paper deals with effects of K on yield and quality of pulses, relation of management factors with crop productivity, economics of K fertilization as well as future research needs.

Key words: Potassium, pulse growing agro-ecologicalregions, soil K status, yield and quality responses, economics and K recommendations.

INTRODUCTION

Besides being an indispensable component of vegetarian diet, pulse crops play a vital role in sustaining the long term productivity of our soil resources. Chickpea, pigeonpea, urdbean, mungbean, lentil, pea, rajmash and lathyrus are most important pulse crops grown in India. Pulses occupied an area of 20.17 m ha in 1949-50 and 24.07 m ha in 1998-99. The corresponding production of pulses increased from 8.16 mt to 14.80 mt, raising the productivity !evels from 405 kg ha (1949-50) to 622 kg ha (1998-98). The level of production has to increase further to meet nutritional requirement of growing population. The slow pace of pulse production compared to population growth has led to progressive decline in the availability of pulses per capita per day from 60.79 in 1951 to 36.9 g in 1998 (Ali and Siva Kumar, 2000). As per the recommendation of the National Commission on Agriculture (1976), 70 g pulses are required for standard balanced diet. To meet this requirement, it is estimated that by 2020 AD the pulse requirement in India will be about 30 million tones. Among various strategies to improve the pulse productivity in India, management practices play an important role. Several reports indicated that better management options contribute substantially in achieving this target of pulse production. 261 262 Masood Ali and Ch. Srinivasa Rao

The productivity of all the pulse crops is, by and large, low due to cultivation of these crops on marginal and sub-marginal land with low inputs. Among production inputs, fertilizer application plays a key role in enhancing productivity levels. However, fertilizer recommendation practices for pulse crops have been paid less attention thus often resulting in lower productivity. Pulse crops are able to fix atmospheric nitrogen, consequently, the major part of the N requirements is met by N fixation. Phosphorus fertilization also being given importance now a days and its recommendation for pulse crops is made in most of the states. Whereas, potassium application is almost neglected resulting in imbalanced nutrient supply and lower crop yields. Moreover, under intensive cropping systems, huge removal of K by different crops has led to progressive depletion of soil's reserve K.

About 60 enzymes involving in photosynthesis, metabolism of carbohydrates and protein are reported to be activated by potassium. It involves in water utilization, N fixation and its utilization, plant resistance against pests, diseases and adverse environmental conditions such as drought, salinity and sodicity and crop quality. Potassium removals of crops are almost similar to N removal. Potassium requirements of pulse crops extend up to 50 kg per tonne of grain yield (Tondon. 1988). Individual crops such as chickpea and pigeonpea remove to the extent of 50 and 43 kg K per tonne of produce, respectively.

PULSE GROWING AGRO-ECOLOGICAL REGIONS AND K STATUS

Information on K status in different agro-ecological regions of India is summarized in Table 1. The major pulse growing states are Madhya Pradesh, Uttar Pradesh, Maharastra, Rajasthan, Karnataka, Andhra Pradesh, Bihar, etc. Different soil types exist in these agro-ecological regions such as alluvial, medium and deep black soils, red and literitic soils (Subba Rao and Srinivasa Rao, 1996). Potassium status of these soils varies depending upon soil type, parent material, texture and management practices. In general, black soils with smectite as a dominant clay mineral, higher clay and CEC showed high levels of exchangeable K and medium to high nonexchangeable K content. Light textural alluvial soils with higher contents of K-rich mica are medium in exchangeable and high in nonexchangeable K content. Red and lateritic soils with kaolinite as a dominant clay mineral and light texture showed low levels of exchangeable as well as nonexchangeable K content (Table 1).

Some forms of available K in important benchmark soil series representing pulse growing region (Table 2) indicate that readily available forms viz., CaCI2 K, citric acid extractable K, NH4 OAc K and 6 N H 2SO 4 K were at higher levels in black soils representing M.P., Gujarat and Tamil Nadu followed by alluvial soils of Rajasthan, U.P.and Bihar and lower levels K were observed in red soils of A.P. and Karnataka (Srinivasa Rao et at., 2000b). Potassium fixation capacity of these soils ranged form 5 to 40 per cent (Srinivasa Rao et al., 2000a). Potassium Role of Potassium Fertilization in Improving Productivity of Pulse Crops 263

Table 1. Potassium status in different pulse growing agroecological regions of India Agroecological region and Climate/Soil Exch. Non-exch. states covered K K Region 4 U.P., Rajasthan, Hot semi-arid M-H H Gujarat, M.P. a-Alluvial Region 5 Rajasthan, Gujarat, Hot semi-arid M.P. medium-deep black H M-H Region 6 Maharastra, Hot semi-arid H M-H Karnataka, A.P. Medium-deep black Region 7 A.P. Hot semi-arid L-H L-M Red and black Region 8 Tamil Nadu, Hot semi-arid M L Karnataka, A.P. Red loamy Region 9 U.P., Uttaranchal, Hot sub-humid M M-H Bihar alluvial Region 10 M.P. Hot sub-humid H M-H black Region II M.P. Maharastra Hot sub-humid H M-H Red & Yellow Region 12 Jarkhand, M.P., Hot sub-humid L-M L Chattisgadh Red & Latoritic, black Region 13 Orissa, Jarkhand, Hot sub-humid M-H L-H Chattisgadh Alluvial M: Medium; H: High; L: Low Subba Rao and Srinivasa Rao (1996)

Table 2. Some available forms of K in important benchmark soil series representing pulse growing regions of India Soil series/Location Forms of K (m/kg) K CaC 2 Citric NH4OAc 6N fixation acid H2S0 4 (%) Black soils Kamlikheri, Indore, M.P. 22 37 151 136 32 Pithvajal Amreli, Gujarat 31 45 191 187 24 Noyyal, Coimbatore, T.N. 87 122 515 600 22 Alluvial Soils Masitawali, Ganganagar, Rajasthan 41 66 156 349 20 Rurha, Kanpur, U.P. 15 30 48 197 40 Jagdishpur, Muzaffarpur, Bihar 22 24 32 164 23 Red soils Kodad, Nalgonda, A.P. 19 27 61 78 30 Vijayapura, Banglore, Karnataka 12 10 19 22 5 Srinivasa Rao et al. (2000a, 2000 b) 264 Masood Ali and Ch. Srinivasa Rao release studies of these soils indicated that despite large reserves of K in alluvial soils of U.P., Bihar and Rajasthan, the rate of K release is much slower as compared to black soils. Hence under intensive cropping with high-yielding short duration pulse genotypes, the soil K supply may not match with K demand by crop. Therefore, application of K to pulse crops particularly in light textured acidic alluvial soils is essential to sustain higher productivity. Similarly K application is essential on red and lateritic soils as these soils possess low levels of soil K status as well as its buffering capacity (Sriniviasa Rao et al., 1998). Rate of K absorption by pigeonpea over a period of time (Figure 1) shows that the maximum K absorption during 80 to 140 days (Narasimhachary, 1980). When soils arc low to medium in K such as light textured alluvial, red and lateritic soils, pulse crops need K fertilization specially to meet the K absorption rates during these critical stages of crop growth.

30

25

20 15 E

.0 S 0 ___ 0

0-40 40-80 80-120 120-140 140-180 Period (days) Figure 1. Potassium absorption rate in pigeonpea

RESPONSE TO K APPLICATION

Pattern and extent of pulse crops response to fertilizer potassium varied depending upon yield levels, soil K status, genotypes and supply of other inputs like irrigation and nutrients. Application of 25 kg K ha- ' enhanced the chickpea, pea and lentil grain yields by 21.4, 25.1 and 23.8 per cent respectively on Typic ustochrepts of Kanpur (Tiwari and Nigam, 1985). With 50 kg K ha - ', the respective increases were 22.9, 37.4 and 32.1 per cent (Figure 2). They reported that responses to K were more in legumes compared to cereal and oil seed crops. This could be due to well branched root system of cereal crops which can exploit soil potassium more efficiently than legumes, this stimulates the pulse crop to respond well to applied K. Srinivasa Rao et al. (1999) reported that cereals deplete more soil K whereas legumes depend more an applied K for their K needs. Role of Potassium Fertilization in Improving Productivity of Pulse Crops 265

40 35[M_ i-2kg K/ha [

SD25 20 -- 0..

15 >- 0 ..... ,j .

Chickpea Pea Lentil Figure 2. Effect of different levels of K on per cent yield increase of different pulse crops on alluvial soils

Studies conducted under All India Coordinated Research Project on MULLaRP also indicated the significant grain yield increase in lentil at Ludhiana, Pantnagar and Ranchi (AICRP on MULLaRP Annual Report 1999-2000). Effect of K application along with rhizobium culture on grain yield of different pulse crops (Figure 3) indicated that substantial grain yield increase due to K application. The yield increases were considerably higher with rhizobium inoculation as compared to without culture (Tiwari and Tiwari, 1999).

2.5

1.5

0.5

Chickpea Pea Lentil Urdbean Mungbean Figure 3. Effect of potassium application on grain yield of different pulse crops 266 Masood Ali and Ch. Srinivasa Rao

In field trials conducted on calcareous alluvial soils of Muzaffarpur district of Bihar, lentil responded significantly at all the three levels of K application - (Table 3) in both the years. The maximum lentil grain yield of 1930 kg ha ' was obtained with 40, 80 and 40 kg of N, P205 and K20 respectively (Singh et al., 1992).

Table 3. Effect of potassium on grain yield (kg ha-')of pigeonpea and lentil on calcareous alluvial soil in Muzaffarpur district of Bihar Treatments Pigeonpea Lentil (kg ha - ') 1986-87 1987-88 1986-87 1987-88 Control 1075 1155 743 700 N2oP40K o 1488 1630 1039 1335 N2oP4oK2o 1535 1760 1163 1435 N3oP6oKo 1640 1885 1307 1640 175 N30P60K30 1710 1895 1617 N40P8QKQ 1908 2175 1629 1835 N 4oP8OK40 2003 2310 1884 1930 CD (5%) 98 158 128 85 Singh et al. (1992)

In a number of field trials conducted in different districts of U.P., Yadav et - al. (1993) reported that application of potassium at 20 kg K20 ha recorded a - 1 - mean yield increase of 95.3 kg ha over 20 kg N and 40 kg P,0 5 ha ' in case of chickpea (Table 4). There was an average increase of 4 kg grain kg- ' K applied at 20 kg K,O ha'. The response of lentil to K were higher (3-16 kg ha- ') and in case of pigeonpea and pea response to K was 14 and 7 kg grain - - kg ' K20, respectively at 20 kg K 2 0 ha '. An average increase of 5 kg grain kg- another ' K20 applied to chickpea is reported in northern states of India. In experiment conducted on different soils varying in fertility class indicated the significant grain yield of chickpea on both the soils types (Tiwari, 1991). In

Table 4. Response of pulses (kg ha - ') to K on cultivators fields under rainfed condition. Crops No. of trials Mean response to K (kg ha -') at

N20P 40 K 20 N30P 66 K30 N40PsoK40 Over Over Over Ko P20P4oK0 N30P60 K0 N40P80 Chickpea 205 95 72 24 Urdbean 105 77 20 42 Lentil 90 112 85 73 Pigeonpea 69 163 29 59 Pea 15 148 87 81 Mungbean 14 30 29 - Yadav et al. (1993) RAtic to ttts~iut Fe rouit'ni in hnprmp o ci i of P.tt Cp 267 field studies on sandy loam soil of Varanasi Singh et al (1994) reported that yield increase with IS kg N + 40 kg P2O ha was 39,8 per cent whereas superimposing 20 kg KO increased the yield by 63.4 per cent s its maximum oi 3038 kg ha ;.

Application of 60 kg K ha significantly increased the grain yield, grain protein, nitrogen and K uptake of frenchbean on alluvial soils of Varanasi. On lateritic soils of Dapoli, Maharashtra, grain yields of cowpea improved significantly up to 50 kg K2O ha ' (Jamadagni and Birari, 1994). In green house studies, Siugh ti t/. (1997) reported the significant increase in growth and prodcltion efficiency of lentil idue to K fertilization in agro-climatic zones of Himachal Pradesh.

Response to K vs Genotypes

In general, improved high yielding varieties are expected to respond to K application appreciably because of their larger K requirements during critical growth stages. Response of two genotypes of pegionpea viz., S-5 and UPAS-120 to K application was evaluated in 37 cultivators trials (AICARP 1976) indicated thai UPAS-120 showed 28 per cent yield increase where as S-5 showed 16 per cent response to 20 kg K application over 20 and 40 kg N and PO, respectively (Figure 4).

1400 O0 S-5 1200 UPAS-120 7: 1000

800 '600[ ". 400 200 L 0 Iff_ .. N20P4oKo N2oP4oK20o

Figure 4, Differentrat respitse of pigeonpea geoiype tio K appliion

Response to K vs Irrigation

In an interaction study between K fertilization and irrigation levels at Aligarh, pigeonpea showed the variable crop response to K application at different levels of irrigation (Figure 5). In no irrigation plots (rainfed), crop responded significantly up to 75 kg ha' where as with two and three irrigations the response was only up to 50 kg K ha , However, irrigation resulted significantly higher yields at each K level (PRII Project Report, 1989). 268 Masaod Ali and Ch. Srinivasa Rao

E0 KO EM K25 . 18H0 K50 M K75 16! [ K1 00

14 12 110 t - 2 8 iL I

o 4 ... 2 MTa No Two Three Noot Irrigations Figure 5. Responr e ef iftgronpea to K applicatn on at differtnt levels of irrigation

Interaction with Other Nutrients

Potassium plays an important role in ensuring efficient utilization of N. It also improves N fixation efficiency of the plant. Since N comes foremost in the farmers fertilization program, the NxK interaction assumes significance in pulse production. Practically very little information is available on effect of nutrient interactions in pulse crops (Randhawa eraL 1979), Few reports indicated the positive effect of nutrient interactions on yield levels of pulse crops. In peas, application of K and Zn significantly increased their content, uptake and yield levels (Figure 6). However, application of K alone decreased Zn concentration and increased K uptake. The K:Zn ratio increased with K and decreased with Zn addition (Vinay Singh r al,. 1992). In field studies with urdbean on calcareous soils of Bihar (available KO: 117 kg ha-'; hot-water extractable B: 0,37 mg kg-'), effect of B and K were additive in a year when grain yields were 0.9

0 oKOi DK30I K60 K120

45C

0 2,5 5 10 Zn level (mg/kg) Figure 6. Response of pea to K appicv atn at different Ietcli of Zn on :piP Uskgtiptsantnnt Role of Potassium Feridido n t impror Ptod.oaI.': of Pulte Crop 269

t ha>, but there was a significant B and K interaction in one year when the yields were some what higher at 1.2 t ha > (Sakail i al- 1988) (Figure 7). On the other hand, antagonistic effect of K on Ca was reported in chickpea, pea and lentil by Tiwari and Nigam (t985).

1400 ~1200 1000

C 600 400 200 0 Control K B K+B Figure 7. Effie, t of K and B on grain ield ,I n.nlbean

Effect of Crop Season

It is a common observation that crop responses to fertilizers are higher in post-monsoon (rabi, dry) season than in the monsoon season. Pulses being dry land crops are expected to respond well to potassium as K plays an important role in water relations and water use efficiency and it is known to make the plant tolerant against extreme dry and wet conditions, Based on thousands of field experiments (Tandon, 1988), it was indicated that urdbean and mungbean responded positively to K application in rabi season compared to kharif season (Figure 8).

4.5

E-Khanf 3.5 C3Rabib

25.. ..

. 1.5

D0 5 X.

Urdbean Muraan Figure S. Effci of r rop ,ason on resplunie of urdbran an~d rou~ngbeanI to K application ija]rrietrs" field 270 M A.Iand Ch SrIdvai'a ao

N Fixation

Optimum supply of K increased significamly the riizombium nodulation and N fixation. The number of nodules per plant with applied K at 40 kg KO ha increased from 39.1 to 42.6 in chickpea, 38.4 to 46.8 in pea, 10.3 to 14.8 in lentil, 48.0 to 55.5 in urdbean and from 35.2 to 46.8 in munghean. Effect of applied K alongwith rhizobium species inoculation was further beneficial in increasing the effective nodule number in all the pulse crops (Tiwari and Tiwari, 1999). Similarly, dry weight of nodules, N content and leghaemoglobin contents of nodules significantly increased with K application. Leghaemoglobin content of the nodules of chickpea, pea, lentil, urdbean and mungbean increased by 14, 19, 13, 10 and 9 per cent due to K application (Figure 9). Increase in rhizobium nodulation with K was also reported by Tiwari (1991) and Prasad (1990).

450 r ___ .400I... I. : No K :140 kg K20/ha! "350

300 gus

20 HB...

......

Chickpea Pea Lentil

Figure 9. Eff t K onlt'g ha nitt, bn rooletn: , no4,e1 t di// rert pt, rcrop

Quality of Pulse Crops

Potassium is quite often associated with crop quality. The results of the experiments conducted on farmers* fields with several rainy season and winter season pulse crops under varying doses of K indicated that in all the pulse crops, the protein content of grain improved considerably (Table 5j (Tiwari, 1986). Sugar and starch content of the grain also increased at 90 kg ha' K application. In another study conducted on lentil at BHU, Varanasi, crude protein content of grain increased from 21.2 to 21.9 per cent (Table 6; Singh and Badhoria, 1985), Increased protein harvest of french bean was reported up to 60 kg K ha> application (Singh ei at., 1995). Role of Potassium Fertilization in Improving Productivity of Pulse Crops 271

Table 5. Effect of K on protein content (%) of different pulse crops - Crop K20 (kg ha ') 0 30 60 90 Chickpea 19.59 19.75 20.13 20.89 Pea 21.00 21.70 22.05 21.84 Lentil 26.12 26.40 27.00 27.12 Urdbean 24.30 24.40 24.70 24.30 Mungbean 23.40 24.00 24.12 24.05 Pigeonpea 20.60 21.40 21.79 21.68 Tiwari (1986)

Table 6. Effect of potassium on yield and quality of lentil on alluvial soil at Varanasi Parameters Level of K Mean

KO K, K 2 K 3 Root dry weight (g/pot) 1.90 2.57 2.38 2.27 2.28 Nodule dry weight (mg/pot) 97 103 108 103 103 Straw yield (g/pot) 6.73 9.52 8.98 8.73 8.49 Grain yield (g/pot) 6.22 8.27 7.32 7.88 7.42 Crude protein (%) 21.2 22.7 240 21.9 22.5 Singh and Badhoria (1985)

Pests and Diseases

Application of potassium appears to induce crop resistance to pests and diseases by causing accumulation of defensive phenolics, making plant tissue less succulent and reinforcing definite cellular regions so as to act as barriers to the invading pests (Vaithilingam and Baskaran, 1985). Effect of K on Aphanomyces root-rot in peas under different moisture conditions (Figure 10) indicates that disease rating was considerably low with K application both in normal and water logged conditions (Wade, 1955). Potassium application reduced damage due to Phytophthora blight in pigeonpea and increased the yields. The percentage plants killed due to blight was reduced from 63.5 to 51.6 due to K application (Pal and Grewal, 1976). Investigations with mungbean and cowpea in the green house showed that the incidence of seedling rot due to Rhizoctonia solani was less in soil treated with N+K or P+K as compared with N and P alone (Kataria and Grover, 1987). Among the sources of K, the disease incidence was lowest with potassium sulphate, followed by potassium chlorite and potassium nitrate. Tests with a mungbean to Cercospora leaf-spot revealed that in the absence of K application, incidence of leaf spot increased with increasing level of N applied. The per cent incidence was 74 per cent in plots receiving N+P and 58 per cent in plots receiving N+P+K (Sivaprakasam, 1983). 272 Miood Ali and Ch. Srinivasa Rao

3.5 03 2.5 n: 2 S1.5

05.5

0 Normal Water logged Moisture Condition Figure 10, Effect of K on aphantnres root-rot in peas with different moisture conditions

Changes in Soil K under Pulse-based Cropping Systems

In a 2-year field study conducted on an acidic sandy loam soil of Ranchi under rainfed conditions involving cereal-pulse and cereal-cereal intercropping systems, potassium balance was negative in all the fertilizer treatments (Table 7; Srivastava and Srivastava, 1997). It indicated the need of a re-assessment of K recommendations to match the K requirements of component crops in acidic red loam soils of Jharkhand. Effect of continuous application of K on different forms of K under pulse based cropping systems on K deficient calcareous soils at Samastipur, Bihar (Table 8) showed that cropping without K resulted in the reduction of both exchangeable and nonexchangeable K in soil (Prasad 1993) under urd-barley as well as ragi-lentil systems. Application of 40 kg K20 increased K uptake from 12.8 to 24 kg K ha - in urdbean and from 48.2 to 54.3 kg K hat' in lentil.

Table 7. Potassium balance (kg ha - ) under pigeonpea based cropping systems Intercropping system Treatmert

Control 100% to both 50% to both Pigeonpea + groundnut -176 -132 -132 Pigeonpea + mungbean -178 -145 -148 Pigeonpea + urdbean -176 -141 -146 Pigeonpea + soybean -182 -145 -149 Pigeonpea + rice -183 -151 -154 Pigeonpea + fingermillet -185 -155 -159 Srivastava and Srivastava (1997) Role of Potassium Fertilization in Improving Productivity of Pulse Crops 273

Table 8. Effect of continuous application of K on different forms of K under pulse based cropping systems in K deficient calcareous soils ((kg/ha) K20 applied Cropping system

(kg ha -') Urd - Barley Ragi - Lentil Ex K Nonex K Ex K Nonex K

0 39.4 1152 31.6 1053 40 49.0 1167 44.0 1215 80 56.4 1349 57.7 1373 Mean 48.2 1222 44.4 1214 CD (5%) 1.9 3.9 1.9 3.9

ECONOMICS

Additional profit by application of different doses of K in various pulse - crops is presented in Table 9. At 20 kg K20 ha ' application, the highest additional returns were obtained in pigeonpea followed by pea, chickpea, lentil and urdbean (Yadav et al., 1993). The additional gain per rupee invested was also highest in pigeaonpea (16.95) followed by pea (15.3), chickpea (9.47) and lowest was in urdbean (7.5) at 20 kg K20 ha'. At 30 kg ha', the additional gain per rupee was - , 5.28 in pea, 4.3 in chickpea and 4 Rs. in lentil. Even at 40 kg K20 ha the gain per rupee invested varied from 0.30 in chickpea to 3.46 Rs. in pea. In another study, addition of 20 kg K20 ha - over recommended N and P gave additional return of Rs 672 ha - ' in case of lentil. Further, it is very interesting to note that still higher return due to K application was obtained at higher levels of NP - application. Application of 40 kg K20 ha ' added with 40 kg N and 80 kg P20 5 ha - ' gave an additional net return of Rs 3600 ha'. Similarly in case of pigeonpea, - application of 30 kg K20 ha' gave additional return of Rs 700 ha ' whereas addition of 40 kg K20 ha' at 40 kg N and 60 kg P20 5 gave economic returns of Rs 2740 ha- ' (Singh et al., 1992).

Table 9. Additional profit (Rs ha- ') by application of different doses of K - Crops kg K20 ha ' 20 30 40

Chickpea 431(9.47) 294(4.30) 39.0(0.30) Urdbean 341(7.50) 320(0.46) 119(1.31) Lentil 401(8.82) 273(4.00) 200(2.20) Pigeonpea 770(16.95) 77(1.13) 205(2.25) Pea 695(15.3) 367(5.28) 314(3.46) Figures in parenthesis indicate the gain (Rs. Rs - ' invested) on K Source: Yadav et al. (1993) 274 Masood Ali and Ch. Srinivasa Rao

RECOMMENDATIONS Inclusion of potassium in nutrient management schedule of pulse crops is not common in many states. However, because of field level response of pulse crops to K application and soil K depletion under intensive cereal-pulse cropping systems, importance of K fertilization is being realized in recent years. Based on soil test value and yield level of different pulse crops, K recommendations have been made for different pulse crops in several states. Some of the K prescription for different targeted yields of pigeon pea on black soils of Maharashtra and red and lateritic soils of Karnataka is presented in Table 10 (Patil and Patil, 2001 and Verabhadraiah et al., 2001). The recommendations were at higher levels in case of black soils as compared to red and lateritic soils due to lower recovery of added K in case of black soils. Similarly, Puri and Gorantiwar (2001) and Prasad et al. (2001) gave the K prescription for 20 q ha - 1 targeted chickpea yield on black soil of Madhya Pradesh and calcareous alluvial soils of Bihar (Table 11). Table 10. Potassium prescriptionfor different targeted yield of pigeonpea on different soils. Maharashtra-black soils Karnataka-red and lateritic soils (Yield target 16 q ha - ') (Yield target 8 q ha - ') Soil test K K prescription Soil test K K prescription - - - - (kg ha ') (kg K2 0 ha ') (kg ha ') (kg K20 ha ') 200 67 10 21 300 50 15 20 400 33 20 18 500 16 25 17 600 30 14 700 35 13 800 - 40 12 45 10 1 50 9 Source: Patil and Patil (2001) and Verabhadraiah et al. (2001) Table 11. Potassium prescriptionfor 20 q ha - ' targetted yield of chickpea on different soils Black soil (M.P.) 20 q ha - ' Calcareous alluvial (Bihar) 20q ha - ' Soil test K K prescription Soil test K K prescription (kg - - ha ') (kg K 20 ha ') (kg ha-') (kg K20 ha-') 200 61 50 74 250 52 75 59 300 44 100 43 350 35 125 28 400 27 150 12 450 18 175 - 500 10 200 550 Source: Puri and Gorantiwar (2001) & Prasad et al. (2001) Role of Potassium Fertilization in Improving productivity of Pulse Crops 275

CONCLUSIONS

* Soils of pulse growing agro-ecological regions of India vary widely in their K supplying capacity. Light textured alluvial soils, red and lateritic soils and shallow black soils with low levels of available K need K supplementation for enhanced productivity of pulse crop.

* Potassium removal of various pulse crops extends up to 50 kg ha' whereas K application is not common to any pulse crop grown in India. Based on a number of field studies, it can be suggested that application of 20-40 kg K20 ha' is beneficial for higher pulse yields.

* Potassium supply often associated with improved protein content of pulse grain, higher N fixation and high water use efficiency. Reduction in pest and disease infestation in presence of optimum K supply also contributes in improved pulse yields.

FUTURE LINE OF WORK

Very few reports are available on K effects on pulse production in India and there is a lot of scope to take up studies on K nutrition of pulses. Some of the research areas are indicated below

* Characterization of soil K in different pulse-growing agro-ecological regions

* Working out K needs of pulses in cropping systems on different soil types and its critical limits

* Interaction of K with other nutrients and management factors

* Residual effects of K in various cereal-pulse cropping systems

* Contribution of pulse residues/litter towards K status of soil and its uptake by succeeding cereal crops

* Potassium effects on drought tolerance of various pulse crops

* Role of K in pest and disease management

REFERENCES

Ali, M. and Siva Kumar (2000). Problems and prospects of pulses research in India. Indian Farming 11: 4-13. 276 Masood Ali and Ch. Srinivasa Rao

Annual Report (1999-2000). All India Coordinated Research Project on MULLaRP (Rabi), Indian Institute of Pulses Researh, Kanpur. Anonymous (1972-73 to 1978-79). Annual progress report of the All Indian Coordinated Agronomic Research Project. Indian Council of Agricultural Research, New Delhi. Jamadagni, B.M. and Birari, S.P. (1994). Yield response of cowpea to varying levels of potassium and phosphorus on lateritic soils of Konkan region. Journal of Potassium Research 10(2): 192-195. Kataria, H.R. and Grover, R.K. (1997). Influenced of soil factors, fertilizers and manures on pathogenicity of Rhizoctonia solani on Vigna. Plant and Soil 103: 57-66. Narasimhachary, P. (1980). Studies on uptake of major nutrients N, P and K by red gram variety in relation to yield, grain and protein content. M.Sc. Thesis, Acharya N.G. Ranga Agricultural University, A.P. Pal, M. and Grewal, J.S. (1976). Effect of NPK fertilizers on the photophthora blight of pigeonpea. Indian Journal of Agricultural Sciences 46(1): 32-35. Patil, A.S. and Patil, J.D. (2001). Fertilizer and integrated nutrient recommendations based fertilizer equations for the state of Maharastra. In: Subba Rao, A. and Srivastava, S. (Eds.) Soil Test Based Fertilizer Recommedations for Targeted Yields of Crops. Proceedings of the National Seminar on Soil Testing for Balanced and Integrated Use of Fertilizers and Manures, Indian Institute of Soil Science, Bhopal. pp. 133-143. Potash Research Institute of India Sponsored Project, Aligarh Muslim University, Aligarh, Progress Report, 1989. Prasad, B. (1993). Transformation, availability, and relative responses of crops to applied K under various cropping systems in calcareous soil. Journal of Potassium Research 9(2): 145-153. Prasad, B., Prasad, R. and Prasad, J. (2001). Fertilizer recommendations for the states of Bihar and Jharkhand. In: Subba Rao, A. and Srivastava, S. (Eds.) Soil Test Based Fertilizer Recommedations for Targeted Yields of Crops. Proceedings of the National Seminar on Soil Testing for Balanced and Integrated Use of Fertilizers and Manures, Indian Institute of Soil Science, Bhopal. pp. 168-203. Prasad, N.N. (1990). PRII Annual Report 1989-90. Puri, G. and Gorantiwar, S.M. (2001). Improved fertilizer recommendations for the crops of M.P. In: Subba Rao, A. and Srivastava, S. (Eds.) Soil Test Based Fertilizer Recommedations for Targeted Yields of Crops. Proceedings of the National Seminar on Soil Testing for Balanced and Integrated Use of Fertilizers and Manures, Indian Institute of Soil Science, Bhopal. pp. 144- 160. Role of Potassium Fertilization in Improving productivity of Pulse Crops 277

Randhawa, N.S., Deb, D.L., Takkar, P.N. and Pasricha, N.S. 1979. Potassium interaction with micro nutrients. Bull. Indian Society of Soil Science 12: 58- 72. Sakal, R., Singh, A.P. and Verma, M.K. 1988. Effect of boron application on blackgram and chickpea production in calcareous soil. Fertilizer News 33(2):27-30. Singh, A.K., Sharma, H.M. and Roy Sharma, R.P. (1992). Response of rabi pigeonpea and lentil to graded levels of NPK on farmers' field. Journal of Potassium Research 8(2): 152-157. Singh, A.K., Singh, K., Singh, U.N. Raju, M.S. and Sing, J.P. (1995). Effect of potassium, zinc and iron on yield, protein harvest and nutrient uptake in fenchbean (Phaseolus vulgaris L.) Journal of Potassium Research 11(1): 75-80. Singh, J., Sharma, H.L., Singh, A., Singh, R. and Singh, A. (1997). Effect of potassium application on growth and production efficiency of lentil in different agro-climatic zones of H.P. Journal of Potassium Research 13(l): 68-73. Singh, O.N., Singh, R.S. and Singh, J.P. (1994). Supplementing fertilizer potassium to chickpea. Journal of Potassium Research 10(1): 83-85. Singh, R.S. and Prasad, K. (1996). Direct and residual effects of phosphorus and potassium in rice-gram cropping system. Journal of Research (BAU) 8(2): 111-114. Sivaprakasam, K. (1983). Influence of NPK on Cercospora leaf spot incidence of mungbean. Pulse Crops News Letter 3: 52-53. Srinivasa Rao, Ch., Bansal, S.K., Subba Rao, A. and Takkar, P.N. (1998). Potassium desorption kinetics of major benchmark soil series of India. Journal of the Indian Society of Soil Science 46(3): 357-362. Srinivasa Rao, Ch., Rupa, T.R., Subba Rao, and Bansal, S.K. (2000a). Potassium fixation characteristics of major benchmark soils of India. Journal of the Indian Society of Soil Science 48: 220-228. Srinivasa Rao, Ch., Subba Rao, A. and Bansal, S.K. (2000b). Relationship of some forms of potassium with neutral normal ammonium acetate extractable K in mineralogically different benchmark soil series of India. Journal of the Indian Society of Soil Science 48: 27-32. Srinivasa Rao, Ch., Subba Rao, A., Srivastava, S. and Singh, S.P. (1999). Crop response, uptake and use efficiency of potassium in berseem and sudangrass on a Typic Haplustert. Journal of Potassium Research. 15(1-4): 113-118. Srivastava, G.P and Srivastava, V.C. (1997). Fertilizer management in pigeonpea based intercropping system: III Effect on nutrient removal. Journal of Research 9(l): 43-47. 278 Masood Ali and Ch. Srinivasa Rao

Subba Rao, A. and Srinivasa Rao, Ch. (1996). Potassium status and crop response to potassium on the soils of agro-ecological regions of India. IPI Research Topics No.20, International Potash Institute, Basel, Switzerland. pp. 1-57. Tandon, H.L.S. (1988). Potassium Research and Agricultural Production in India. FDCO, New Delhi. Tiwari, K.N. (1986). Potassium in soils, crops and fertilizers, Annual Report of the PRII sponsored Research Project. Tiwari, K.N. (1991). Potassium in soils and crop response to K application in U.P. Annual Report, PRII, Gurgaon. Tiwari, K.N. and Nigam, V. (1985). Crop response to potassium fertilization in soils of Uttar Pradesh. Journal of Potassium Research (1): 62-71. Tiwari, V.N. and Tiwari, K.N. (1999). Role of potassium in biological nitrogen fixation. In: Use of potassium in U.P. Agriculture (Eds Tiwari, K.N. and Modgal, S.C.). pp. 79-87. Vaithlingam, C. and Baskaran, P. (1985). Induced resistance to insect pests in rice with enhanced K application. In: PRII Research Review Series No. 3, 43-51. Veerabhadraiah, A.M., Thippeswamy, Narasimha Reddy, RN. and Siddaramappa, R. (2001). Status of soil testing and fertilizer recommendations in Karnataka. In: Subba Rao, A. and Srivastava, S. (Eds.) Soil Test Based Fertilizer Recommedations for Targeted Yields of Crops. Proceedings of the National Seminar on Soil Testing for Balanced and Integrated Use of Fertilizers and Manures, Indian Institute of Soil Science, Bhopal. pp. 238-266. Vinay Singh, Bahera, T.D., Singh, A.? and Mehta, V.S. (1992). Effect of graded doses of potassium and zinc on yield and their uptake by pea. Journal of Potassium Research 8(2): 144-147. Wade, G.C. (1955). Aphanomyces root rot of peas. The effect of a potassic fertilizer on the severity of the disease in a K deficient soil. Journal of Australian Insitute of Agricultural Sciences 21: 260-263. Yadav, D.S., Alok Kumar and Singh, V.K. (1993). Response of different crops to potassium on cultivators' fields in UP under irrigated and rainfed conditions. Journal of Potassium Reseach 9(3): 253-26!. Potassium Nutrition Management for Yield and Quality of Citrus in India

A.K. SRIVASTAVA AND SHYAM SINGH National Research Centre for Citrus, Amnravati Road, Nagpur-440010, Maharashtra

1. INTRODUCTION

Besides nitrogen and phosphorus, potassium is one of the indispensable nutrients in the nutrition of citrus trees and for the regular and larger scale production of high quality fruit. Potassium seems to serve some metabolic functions in growth and cell division of younger tissues, besides growth and imparting frost resistance. In addition to its role in metabolic process, potassium regulates the water economy of the trees and greatly increases citrus yield, not in number but in size of fruit (Rosselet et al., 1963; Dass and Srivastava, 1997; Srivastava, 1999b; Srivastava et al., 2001). The extreme mobility of potassium within plant is responsible largely for failure to associate it with specific functions. A method of assessing soil buffer power is needed, which accounts for all the K that is available during growth. It is also important that the relative mobility of K in solution and exchange phases and the response of root systems to soil K levels are established. The rate at which K is depleted at the root surface has important implications for potential uptake rates. Numerous field experiments on citrus in California prior to 1940; showed no clear benefit from potassium fertilization (Vaile, 1922; Booth, 1930; Parker and Batchelor, 1942). On the contrary, realisation for adequate K supply for quality citrus fruits is of comparatively recent advent in India, since citrus has been cultivated without supplemental K over the years. These experiments, however, did demonstrate a need for nitrogen and showed that a programme of half the N from manures and half from chemical salts was consistent with high production. This programme became widely used and thus resulted in K addition through the manure applications.

Potassium nutrition definitely plays a part in a quest for better quality citrus fruits and time to time advances would necessitate integration and application of all the information gleaned from various studies. During average peak reproductive life span of Nagpur mandarin orchards (10-13 years) under hot sub-humid tropical climate of central India, potassium is removed to the tune of 350-455 kg ha-' considering 277 plants ha- 1 spaced at 6 m x 6 m apart considering the annual productivity of 7 tons ha-' (Srivastava and Singh, 1999a). Removal of potassium by a kg of fresh mandarin fruits is 5 g. In the background of the current cultural practices, amount of K added to the orchard comes to only 99- 122 kg ha-', indicating the collossal gap between the K removed and aded to Nagpur mandarin crop. Similar condition exists more or less uniformly in nearly 279 280 A.K. Srivastava and Shyam Singh all-major citrus belts in India. Emerging through variables, influencing various qualitative and quantitative aspects of citrus, there are multiple interrelationships between the rhizosphere microflora, potassium nutritional status of plant and potassium availability. Using nutrient solution culture, it was found that the K nutritional status influences microbial activity on roots via its effect on plants metabolism and root exudation. Low K supply increases the quantity of readily decomposable organic compounds released from roots. Potassium nutrition, hence, affects the quantity and quality of low molecular compounds in roots and root exudates, ahd the composition of the rhizosphere microflora and microbial transformation in the root activity (Trolldenier, 1987). The problem of thoroughly evaluating the potassium status and tree conditions setting in motion the corrective steps and maintaining nutrition so as to ensure optimum yield with quality citrus is not a simple problem unless the dynamic soil-plant relationship is properly conceptualized and understood with utmost efficiency.

2. POTASSIUM AND CITRUS METABOLISM

Potassium is required by most plants in amounts greater than any other nutrient. The functions of potassium are many besides drought tolerance (Saxena, 1985). It is known to be required for cell structure, carbon assimilation, photosynthesis, protein synthesis, starch formation, translocation of protein and sugars, the water balance in plants, normal root development and many other life processes (Bhandal and Malik, 1988; Inque and Shi, 1992). Zekri (1995) listed many functions of K for several basic physiological functions such as formation of sugars and starch, synthesis of proteins, normal cell division and growth, and neutralization of organic acids, besides its involvement in more than 60 enzymatic reaction regulating carbon dioxide supply by control of stomatal opening and improving efficiency of sugar use.

3. DIAGNOSTICS OF K NUTRITION

Much researches have been carried out in the past 50 years to develop and improve diagnostic criteria without desired success for the evaluation of nutrient status and fertilizer management. The diagnostic tools of nutrient management such as leaf analysis (Kohli et al., 1993; Srivastava et al., 1994; Srivastava et al., 1995; Kohli and Srivastava, 1997; Srivastava and Singh, 1997; Kohli et al., 1998; Srivastava et al., 2000; Srivastava, 2001a;), soil analysis (Srivastava et al., 1997a; 1997b; 1997c; Srivastava and Kohli, 1997a; 1997b; Srivastava and Singh, 1999; Srivastava and Singh, 2001a; 2001b; 2001c; Srivastava, 2001b), juice analysis (Moss and Higgins. 1978; Gallasch et al., 1984) and biochemical markers (Bar-Akiva, 1965; Fridovich, 1986; Miller et al., 1993; Devi et al., 1996) have all been under continuous critical scrutiny, test and recurrent use. It is abundantly clear that no one of these alone provides complete information except combined use of leaf and soil analysis which has gained some distinction. Potassium Nutrition Management for Yield and Quality of Citrus in India 281

3.1 Symptoms of Potassium Deficiency

The most distinctive thing about citrus nutrition is the large number of nutrient deficiencies that have appeared under intensive cultivation. The visual deficiency symptoms of K have been recognized both under field and artificial studies. The deficiency of K is sometimes imparted on fruit also especially with reference to fruit size. In some cases, a combination of deficiencies, excesses or both may mask typical symptoms of a single element and make positive visual identification more difficult. Under these conditions, the identification based on visual symptomology must be subjected to verification through leaf analysis. The deficiency symptom can appear any time of year and there is usually some urgency to identify them and take corrective action, if current season standing crop is to be saved. The normal standard nutrient contents are irrelevant, since they apply only to leaves of specified type and age. The cause of symptoms must, therefore, be sought by comparing the composition of the affected leaves with other leaves identical in age, position, variety, rootstock etc., but without symptoms. An investigator should analyse the affected leaves and healthy ones from the following categories of trees : trees with affected leaves on which a proportion of healthy leaves will almost invariably be present, healthy trees on the same plot and healthy trees on an unaffected plot of the same soil type, variety etc.

Early potash deficiency symptoms are stunted growth, sparse foliage and somewhat bronzed and lustreless appearance of leaves. With more acute deficiency of potash, the leaves wrinkle and twist and only weak new lateral shoots emerge (Jones and Smith, 1964). Because of lack of mechanical strength, these shoots have a tendency to be S shaped. No distinctive or uniform leaf patterns have been noted though, yellowing, yellow spots, markings or stipplings are commonly observed. The marginal discoloration and burn, so commonly noted in several temperate fruits and mango, are conspicuously absent in citrus (Krishnamurthy and Randhawa, 1959). Smith (1966) while investigating K deficiency symptoms in citrus described as fading of chlorophyll starts as blotches in distal half of leaf, blotches pale yellow at first but deepen to bronze, as they spread and coalesce, leaf tips may turn brown. Old leaves unusually persistent in contrast to calcium, which they may resemble otherwise, foliage drab, tree excessively droughty, fruits greatly reduced in size but of good quality. Dhingra and Kanwar (1963) reported that total K20 status of soils bearing chlorotic plants was higher than that of healthy soil, which may also induce chlorosis.

Symptoms of potassium deficiency on orange, lemon and grapefruit are observed as yellow to yellow-bronze chlorotic patterns develop on older leaves, along with a cork-screw type of curling towards the lower leaf surface, particularly on the lemon. Similar leaf curling often occurs on healthy lemon trees, but the leaves do not become chlorotic. The intensity of the curling and chlorosis on lemon leaves increases as the severity of the deficiency increases. Potassium deficient orange and grapefruit trees usually do not exhibit this particular kind of leaf curl (Embleton et al., 1974c). On orange and grapefruit, the chlorosis develops primarily on leaves behind fruit and may not be easily recognised even 282 A.K. Srivastava and Shyan Singh when the deficiency is severe. The symptoms on lemon are more conspicuous, allowing comparatively easier visual diagnosis. Visual diagnosis should, as far as possible, be confirmed by leaf analysis.

Malavolta (1994) recently found abnormality, variegated chlorosis (amarelinho) associated with low leaf K in Brazil. According to Zekri (1995), under low K fertilization, deficiency symptoms develop in late summer and fall on the recently matured spring flush leaves. When K is low, the general leaf pattern begins with a yellowing of tips and margins. The yellow area then gets broader. Necrotic areas and spotting can develop on the leaves. Symptoms first appear in the older leaves because of K tendency to concentrate in the rapidly growing tissues. Potassium deficiency causes a slowing down in growth, small leaves, fine branches, compact tree appearance, an increase in susceptibility to drought and cold, reduction in fruit size, very thin peel of smooth texture, pre- mature shedding of fruit and lower acid levels in the fruit.

3.2 Biochemical Markers for K Deficiency

The use of biochemical markers aided K nutritional diagnosis is still under- exploited despite the fact that various markers put forward from time to time have the potential to serve as a one of the reliable diagnostic tools of nutrition management. The studies in the past have revealed a number of biochemical markers as an index of nutrient deficiency (Table 1). These studies hold a great promise under Indian conditions to identify K nutritional constraint. One of the clear cut advantages associated with use of biochemical markers over rest of the available tools, is the capacity to facilitate an early detection about the genesis of any nutrient deficiency. Such an ability is extremly lacking in other diagnostic tools available to researchers. Wide use of biochemical markers aided nutritional constraint analysis and subsiquent managenent, would probably lead to bridge up one of the major lacunae in today's citrus nutritional research.

Table 1. Biochemical markers suggested for identifing K deficiency Deficiency aided markers Source Reduced accumulation of soluble nitrogen compounds Forshey (1968) Reduced accumulation of soluble carbohydrate Chapman (1968) Reduced diasterase activity Krishnamurthi & Randhawa (1959) Reduced activity of pyruvate kinase Besford (1978) Reduced activity of acid invertase Schaffer et al.(1987 ); Huber (1989); Lavon et al. (1995) Increased arginine accumulation Haggag et al. (1995) Increased lysine & histidine accumulation Lavon et al.(1999) Arginine Nageswara Rao et al. (1981) L-arginine carboxylase Smith (1963; 1965; 1970) Potassium Nutrition Management for Yield and Quality of Citrus in India 283

3.3 Leaf Analysis

Leaf or foliar analysis has come into widespread use not only as aid in interpreting the results of research and confirming the visual symptomology, but as a means of detecting the early stages of, or trends towards nutritional deficiencies, excesses and imbalances in plants and, thus helping to guide soil fertility and management practices. The analysis properly done, provides a valuable tool to refine the citrus nutrition programme. It will become very important as growers fine-tune programmes to eliminate wasteful excess and keep costs to a reasonable level. By analysing the mineral content of leaves from a tree, one can actually determine what quantities of various nutrients are in the plant. By comparing these quantities with established guidelines, one can quickly see if too little, too much, or the proper amounts of fertilizers are being applied. Fertilizer rates can then be adjusted to bring the levels of minerals determined by leaf analysis to optimum levels. Interpretation of leaf analysis is based on the premise that there is a significant biological relationship between the elemental content of the plant and plant growth (Ulrich, 1952). Obviously, records which have accumulated over a period of years, are worth a great deal, since the actual cause and effect relationships between leaf analysis, fertilizer applied and fruit production can be nicely correlated. Krantz et al. (1948) outlined the principal objectives of leaf analysis :

* Determination of nutrient supplying power of the soil

* Determination of effect of treatment on nutrient supply in the plant

* Relationship between the nutrient status of the plant and crop performance as an aid in predicting fertilizer requirements

* Laying the foundation for approaching new problems or for surveying unknown regions to determine the site of experimentation

In recent years, the increased use of commercial leaf analysis has provided a method to detect the relatively small percentage of citrus orchards that might benefit from applications. Leaf analysis is the most useful diagnostic procedure for determining K status (Dass and Srivastava, 1997), while soil analysis is helpful in an understanding of the response or lack of response to K application (Srivastava and Singh, 1998a). Steyn (1959; 1961) suggested that small or large differences in final leaf analysis values could result from i. number of leaves, ii. number of trees or plants sampled, iii. Time of day for sampling, iv. metabolic activity with loss of dry weight between the time of sampling and drying, v. leaf cleaning technique, vi. temperature and time of over drying, vii. period and temperature of storage of ground samples, and viii. method of grinding (contamination factor). 284 A.K. Srivastava and Shyam Singh

3.3.1 Leaf sampling technique for K diagnosis

The leaf analysis intregates the effect of many variables like soil and climate, which can be used to a great advantage: The past studies have shown a large variation in K concentration of leaves due to difference in age of leaves, position of leaves on a shoot and leaf sample size (Srivastava, 1999b). Bhargava and Chadha (1988) also earlier reported leaf sampling guide for various fruit crop.

Leaf sampling age for Nagpur mandarin: The leaf sampling technique was developed under three major soil types viz., Typic Haplustert, Typic Ustochrept and Typic Ustorthent.

Soil type 1 (Typic Haplustert): The studies were carried out in three soil types viz., Typic Haplustert, Typic Ustochrept and Typic Ustorthent. The leaf samples were collected at monthly interval during entire growth, considering the strong positional effect of leaf on nutrient status (Srivastava et al., 1997a; 1997b), the leaves were collected from mid-point of the shoots. The maximum K in leaf accumulated in the first 2 months in the first year and 2 months in the second year which followed the stable period of 6 to 8 month leaf age. Thereafter, the concentration of K followed decreasing trend upto 12 months of leaf age. While, the reduction of leaf K with increasing age of leaf thereafter its stability period was also due to its translocation to developing fruits. It was invariably observed in all three soil types that K required for the fruit development accumulated during first 3-4 months of leaf age in all three soil types before the ripening season coincided with the period of major K loss in leaves. The best time for leaf sampling was obtained when leaves are 6 to 8 months old.

Soil type H (Typic Ustochrept): Seasonal variation in leaf K showed three distinct portions, first portion witnessed maximum accumulation of K, second portion having minimum variation during 5 to 7 month of leaf age and third portion having regular lowering trend towards the end of season. The 5 to 7 month old leaves were found ideal for leaf sampling.

Soil type III (Typic Ustorthent): The concentration of K was stabilised when leaves were 5 to 7 month old. The maximum absorption of K took place in the first 3-4 months which later on followed the stationary period and thereafter continued reduction in K content till the end of the season. The best time for leaf sampling was observed during 5 to 7 month of leaf age.

Summarising the above observations the suitable peroid of leaf sampling was observed at 6-8 months of leaf age in Arabia flush (February bloom) in Typic Haplustert soil type (Srivastava et al., 1994; 1997a; Kohli et al., 1997) and 5-7 months Mrig flush (July bloom) in Typic Ustochrept (Srivastava and Singh, 1998b; Srivastava and Singh, 1999a; 1999b) and Typic Ustorthent soil type (Huchche et al., 1997; Srivastava and Singh, 1999a; 1999b and Srivastava et al., 1999a; 1999b; 1999c; 1999d). Potassium Nutrition Management for Yield and Quality of Citrus in India 285

Leaf sampling age for Acid lime: The studies were carried out in three soil types viz., Typic Haplustert, Typic Ustochrept and Typic Ustorthent. The leaf samples were collected at monthly interval and analysed.

-Soil type I (Typic Haplustert): The leaf K concentration reached to a maximum of 1.04% in October and thereafter no distinct variation was observed between 0.71 to 0.64% during November to February. The ideal time for leaf sampling in-acid lime was recorded during 3 to 5 month of leaf age.

Soil type H (Typic Ustochrept): The stable concentration of K in leaf was observed to 3-5 month of leaf age and thereafter, the magnitude of K variation was much higher. The observations in both the soil types suggested an ideal time for leaf sampling is when leaves were 3-5 months old. (Kohli and Srivastava, 1997; Srivastava and Singh, 1998a; 1998b). Earlier studies suggested leaf sampling of 4.0-7.5 (Chahill et al., 1991) and 3.0-5.0 month old leaves (Singh et al., 1990) using middle leaf from non-fruiting terminals. Gururani and Singh (1983) recommended the use of spring flush leaves in kinnow mandarin under Tarai conditions for leaf sampling from nutritional diagnosis point of view.

Leaf sampling position for Nagpur mandarin: A total of 800 non-fruiting shoots were tagged covering 20 healthy trees in a Typic Haplustert soil having nearly uniform growth. An appraisal of nutrient composition of leaves collected at positions of 2nd, 3rd and 4th leaf on a shoot indicated statistically non- significant variation in the concentration of K. Leaf sampling position for Acid lime:No significant variation in K status was observed at all the three 2nd, 3rd and 4th leaf positions are equally effecti(,e in representing the nutrient status of tree or orchard as a whole (Table 2). Singh et al. (1997) observed no difference in leaf K status between fruiting and non-fruiting terminals in khasi mandarin.

Table 2. Leaf potassium content (%) of Nagpur mandarin (6-8 month old leaves) and Acid lime (3.5 month old leaves) leaves collected from 2nd, 3rd and 4th leaf position from non-fruiting terminals Potassium 2nd leaf CD 3rd leaf CD 4th leaf CD (age in (P= (age in (P= (age in (P= months 0.05) months 0.05) months 0.05) 6th 7th 8th 6th 7th 8th 6th 7th 8th Nagpur mandarin (1994-95) 0.84 0.87 0.82 NS 0.83 0.77 0.83 NS 0.89 0.86 0.88 NS 1995-96 1.28 1.10 1.11 NS 1.24 1.21 1.23 NS 1.20 1.27 1.17 NS Acid lime (1994-95) 1.10 1.10 1.09 NS 1.20 1.11 1.28 NS 1.24 1.21 1.02 NS 1995-96 0.89 0.92 0.98 NS 0.96 0.92 NS 1.16 1.21 1.18 NS 'Source: Kohli el al. (1998); Srivastava and Singh (1998b) 286 A.K. Srivastava and Shyarn Singh

Leaf sample size: The statistically non-significant variation in leaf K was observed in 6 to 8th month old leaves considering the leaf sample size varying from 30 to 70 leaves covering 2 to 10% trees (Srivastava et al., 1996). These minimum variations in leaf nutrient composition indicated that leaf sample size as low as 30 leaves covering 2% trees was equally effective for foliar analysis as much as 70 leaves covering even 10% trees (Table 3).

Table 3. Leaf potassium content in relation to leaf sample size in 6 to 8 month old leaves collected from non-fruiting terminals of Nagpur mandarin Leaf samling Leaf sample size covering peroid 2% trees 6% trees 10% trees No. of leaves No. of leaves No. of leaves 30 50 70 30 50 70 30 50 70 6th month 1.23 1.23 1.21 1.21 1.25 1.10 1.18 1.04 1.20 7th month 1.10 1.10 1.06 1.01 1.10 1.10 1.03 1.02 1.08 8th month 1.16 1.27 1.20 1.31 1.29 1.16 1.20 1.18 1.18 CD (P=O.05) NS NS NS NS NS NS NS NS NS Source: Srivastava and Singh (1998a; 1998b)

Leaf K standards: This is really unfortunate that Indian Citrus Industry claimed to be nearly 100 years old, does not have single leaf nutritient standard having applicability under a wide range of soil and climate. However in the recent past, efforts have been made with some success (Chahill et al., 1991). Based of nutritional survey of Nagpur mandarin orchards covering 17000 ha area, leaf nutrient standards were developed for the first time in the country which envisaged optimum leaf limit as 1.18-1.56% (Kohli et al., 1997; Srivastava and Singh, 1998a; Srivastava et al., 1999a; 2000a; Kohli et al., 2000) and critical K limit as 1.35% (Kohli and Srivastava, 1997; Kohli et al., 1998; Srivastava and Singh, 1998a; Srivastava et al., 1999a). Chahill et al., (1991) under semi-arid condition of Punjab using Kinnow mandarin envisaged optimum leaf K limit of 1.57% and critical limit of 0.72%. Based on comparison between healthy and declining coorg mandarin, an optimum leaf K concentration of 1.51-1.61% was suggested (Anonymous, 1980).

3.4 Soil Analysis

The soil analysis method rests on the assumptions that roots would extract nutrients from the soil in a manner comparable to chemical soil extractants, and that there is a simple direct relation between the extractable concentration of nutrients in the soil and uptake by plants. There is simple evidence that these assumptions are not entirely justified (Jones et al., 1955). Julier (1989) while working on potassium fertilizer experiments suggested three types of responses in relation to exchangeable K level viz., an investment fertilization range, where there is normally a response to applied K, a maintenance fertilization range in Potassium Nutrition Management for Yield and Quality of Citrus in India 287

which only the more K demanding varieties respond to K fertilizer and a range of uncertainity. The interpretation of soil analysis must address following three reference points such as K saturation of the cation exchange capacity, desired level of K and compensation for crop removal. Potassium saturation of the cation exchange capacity, known as exchangable potassium percentage is widely used for diagnostic purposes.

Optimization of soil properties has recently emerged as a promising field of investigation, representing a new stage in the soil fertility in which transition is made from simple improvement of soil properties to regulation of these, aimed to bring them into an agreement with plant needs to achieve the sustained yield. The central element of such an investigation is the optimum values of given soil characteristic (Medevedev, 1990). Multivariate quadratic correlation and regression analysis (Alvarez and Correa, 1981; Kohli et al., 1998; Srivastava, et al., 2000a; Srivastava, 2001b) has been used as a reliable diagnostic tool in determining optimum standards, since it affects regression among active (explicative) variables and the supplementary ones (to be explained) according to Lebart et al. (1977). An indepth study of Nagpur mandarin orchards covering Vidharbh region of Maharashtra and Chhinwara region of Madhya Pradesh revealed an optimum limit of available K as to 228.1-232.5 mg kg-1 , respectively, consedering correlation between fruit yield and available K upto 30 cm soil depth (Srivastava and Singh, 1999a; 1999b; 2000b; 2000d; 2001a; 20001b; 2001c). No such other soil K fertility guidelines addressing differential productivity level are available for any of the commercial citrus cultivars grown in India.

3.5 Juice Analysis

As early as, 1945 Fudge claimed that foliage composition was a more sensitive measure for mineral nutrition absorption than fruit composition. While, leaf analysis for mineral content is the accepted method used as a guide for fertilizer needs, there are many objections to its use. The method must be standardised for the type of growth, time of the year and sampling procedure. It would be logical to use fruit juice analysis of these elements which greatly affect fruit quality, since the purpose of fertilization is to obtain optimum production and maintain fruit quality. Koo (1963) earlier reported from fruit analysis that more stable values of K analysis was obtained than leaf analysis due to large effect of age and season on the leaf nutrient composition. Vandercook et al. (1975) later showed that K levels in juice were less variable than leaves. Birdsall et al., (1961) obtained very low recovery of trace elements in juice supported the notion, that juice analysis would be more reproducible for macronutrient than micronutrient analysis.

The work by Ulrich (1952) suggested that for a variety of crops, fruits were insensitive indicators of plant nutritional status because the vegetative parts of plants showed more variability in nutrient status and, therefore, leaves would be a more useful indicator of fertilizer requirements. Moss and Higgins (1978) 288 A.K. Srivastava and Shyam Singh observed level of N, P and K in juice of Valencia oranges stable over harvest period and practically all of the K, 83% N and 80% of P were found in juice serum. The use of juice analysis as an aid to define fertiliser requirement has also been used. But the works done by Moss and Higgins (1978), Koo (1982) and Gallasch et al., (1984) have revealed many advantages and disadvantages regarding the use of juice analysis in evaluating the nutritional problems indicating K nutrition. The juice analysis is advantageous in terms of providing a rapid mean of assessing the nutrient status, better correlation with fruit quality parameters, easier collection of fruit samples especially where fruit juice is prepared for quality assessment and analysis involves less preparation time and standardisation of sampling procedure need not be done. However, some disadvantages are also associated, such as storage and transport of sample is more of a problem with fruits than with dried leaf samples. No juice analysis standards are available to be used as an alternative to leaf analysis and non- digested juice is limited to the analysis of N, P and K only.

4. ONTOGENY OF RELATION BETWEEN LEAF K & SOIL K FORMS

Potassium has been observed to improve the quality of citrus fruit apart from increasing post harvest storage life (Srivastava, 2001a) and is removed in largest quantity (6.4 g kg - 1 fruit) compared to N (3.0 g kg-' fruit) and P (0.7 g kg -' fruit) according to Kohli et al. (1997). Earlier Dhatt et al. (1992) observed that Kinnow mandarin under semi-arid conditions of Punjab removed a total of 96.0 kg N, 10.8 kg P and 78.9 kg K ha -' based on 40 tons ha-' normal yield. Foliar analysis is considered as one of the most reliable tools for monitoring K fertilization in citrus. It was observed that accumulation of K in leaf is partially dependent upon its availability in soil. Any depletion in a given K form is likely to shift the equilibrium in the direction to replenish it. The availability of K may further be conditioned by the demand of K at different growth stages, the information on which is not available. Such studies are highly imperative to be undertaken for maximising the response of K fertilization. In this regard twenty healthy and uniform sized 12 year old Nagpur mandarin (Citrus reticulata Blanco) trees were selected during 1995-96 at Sahuli village of Nagpur district, having hot sub-humid tropical climate. The soil was derived from basalt type of parent material and taxonomically classified as fine, montmorillonitic, hyperthermic family of calcareous Typic Haplustert.

4.1 Relationship Between Available K and Leaf K Content

Available K was observed high throughout the growing period varying from 201 at fruit set stage to 302 mg kg-' soil at colour break stage (Table 4) on the basis of critical limit of available K as 60-150 mg kg-'. Leaf K content similarly showed its high status throughout the season except towards fruit colour break stage as evaluated on the basis of critical limits i.e. 0.40 to 0.69% as low and 0.70 to 1.09% as optimum range for sweet orange using cultivars Navel and Valencia. The highest level of leaf K (1.25%) was observed at fruit set stage due Potassium Nutrition Management for Yield and Quality of Citrus in India 289 to luxury absorption of available K and heavy demand of K by new flush of shoots. At later growth stages, the concentration of K continued to drop more or less regularly to the lowest level of 0.65% on account of possible utilisation of accumulated K by the fruits developing towards colour break stage. Such an increased movement of K from leaf to maturing fruits is largely attributed to development of total soluble solids in the fruits. After the fruit set stage, 21.6% of absorbed leaf K was utilised upto fruit development stage, 11.2% upto fruit maturity stage and beyond this stage, a maximum 25.3% of absorbed K was utilised upto fruit colour break stage. These observations showed the highest demand of K during fruit maturity stage to fruit colour break stage followed by fruit set to fruit development stage. But the maximum K was accumulated much earlier than the real K demand by the crop started.

Table 4. Forms of K at critical growth stages of Nagpur mandarin Critical Forms of K (mg kg-') Growth stages Water soluble K Exchangeable K Non-exchangeable K Flowering 8.0 213.2 428.9 *(7.8-8.2) *(193.2-233.3) *(399.7-358.2) Fruit set 7.3 193.5 387.7 (1.18-1.33) (190.0-221.7) (365.6-429.0) Fruit development 11.9 260.5 632.0 (7.0-22.8) (226.0-234.1) (501.4-663.0) Colour break 7.7 220.0 694.7 (7.2-8.2) (206.0-234.1) (565.5-624.0) Harvest 13.0 289.0 672.8 (11.8-14.2) (233.3-344.8) (565.6-780.0 Source: Srivastava et al. (1997b); Srivastava and Singh (1998a) *Range

Available K content in soil was recorded highest as 302 mg kg -' at fruit colour break stage followed by 272 mg kg -' at fruit development stage and 228 mg kg -' at fruit maturity stage. Available K further showed no correlation with leaf K content at all the five critical growth stages except fruit maturity stage (Table 5). Least correlation was observed available K and leaf K. Table 5. Correlation of different forms of K with leaf K content at different growth stage of Nagpur mandarin Critical growth Water soluble Exchangeable Non-exchangeable Available Stages K vs leaf K K vs leaf K K vs leaf K K vs leaf K Flowering 0.104 0.176 0.194 0.312 Fruit sets 0.414 0.866** 0.921 0.176 Fruit development 0.310 0.218 0.281 0.346 Maturity 0.209 0.312 0.678* 0.844** Colour break 0.456 0.911** 0.224 0.112 **Significant at 1% level; *Significant at 5% level Source: Srivastava et al. (1997c); Srivastava and Singh (1998a) 290 AK. Srivastava and Shyam Singh

4.2 Variation in Soil K Forms at Different Growth Stages

The K supplying power of soil refers to actual uptake of K by plants from water soluble, exchangeable and non-exchangeable sources of K. Both, water soluble and exchangeable K, the readily available forms of K were highest at fruit colour break stage due to drop in K demand with the result released exchangeable K remained unutilised. However, the exchangeable K was recorded well above the recommended range of 90-100 mg kg -'. Comparatively high degree of co-relationship of available K with exchangeable K (r = 0.842**) than with water soluble K (r = 0.572**) showed that soil exchangeable phase played more significant role in regulating the K availability in such clayey soil having dominantly montmorillonitic mineralogy.

The water soluble and exchangeable K which constituted 1.2% and 32.8%, respectively of K supplying capacity (as a sum of water soluble plus exchangeable plus non-exchangeable K) at fruit set stage reduced to 0.83% and 23.8% respectively at fruit maturity stage. While non-exchangeable K which initially formed 66% of K supplying capacity at fruit set stage increased by another 9% constituting as much as 75% of K supplying capacity of soil at fruit maturity stage. These observations showed that crop K demand during fruit set to colour break stage is mainly fulfilled by exchangeable K followed by water soluble K.The lowest status of non-exchangeable K as 387 mg kg-' at fruit set stage and - highest of 695 mg kg ' at fruit maturity stage showed forward shift in soil K equilibrium on account of high K demand imposed by the crop and backward shift following the required K supply at fruit maturity stage. The non- exchangeable K was more strongly correlated with exchangeable K (r = 0.781**) than with water soluble K (r = 0.321). These observations showed the better reliability of exchange phase compared to soluble phase index. It was observed exchangeable potassium percentage as a good indicator of soluble K in Haplusterts and Vertic Ustochrept types of soils.

4.3 Relationship of Soil K Forms with Leaf K Content

Leaf K content at all five growth stages showed no relationship with water soluble K probably because of a small variation in water soluble K throughout the growing season (Table 5). While exchangeable K was strongly correlated with leaf K content at fruit set stage (r = 0.866**) and fruit colour break stage (r = 0.911**). The non-exchangeable K correlated significantly with leaf K content at fruit set stage (r = 0.921**) and fruit maturity stage (r = 0.678**). According to regression equation, leaf K increased at the rate of 0.02% per 10 - 1 mg kg increase in exchangeable K (leaf K = 0.52 + 0.002 exchangeable K) and 0.04% per 10 mg kg-' increase in non-exchangeable K (leaf K = 0.75 + 0.004 non exchangeable K) during the entire growing period. Potassium Nutrition Management for Yield and Quality of Citrus in India 291

5. POTASSIUM STATUS OF INDIAN CITRUS ORCHARDS

Soils of Khasi mandarin growing soils of north-west India were observed deficient in available K (14-76 kg ha-') by Prasad and Ghosh (1976). Shome and Singh (1965) observed negative correlation of leaf Ca + Mg with leaf K content (r = 0.620) irrespective of healthy and declining orchards. The leaf nutritional status of healthy mandarin orchards of Amritsar district of Punjab showed higher status of K in healthy than declining tree. The survey of fertility status of kinnow - orchards in Ferozpur district of Punjab revealed minimum 133.0 mg kg 1 and maximum 212 mg kg - ' available K in Fazlika and Nikalkhera, respectively (Dhillon and Dhatt, 1998). Oseni (1988) reported a glirect correlation of leaf K with soil K. Survey of elite acid lime orchards of Gujrat, application of fertilizers - , as 4.08, 1.08 and 1.10 kg N, P and K tree ' respectively, was sufficient to maintain high production through the above suggested N, P and K levels in leaf (Chundawat et al., 1991). The leaf K status was observed to be dependent upon concentration of Zn (Supriya and Bhattacharya, 1995). Investigation on healthy and declining mandarin orchards in the hill regions of Assam, India, by Dey and Singha (1998) showed that the foliage of plants in healthy and declining orchards of Karbi Anglong were high in K, but low in Ca and P. In Kabri Anglong, fruit yield was positively correlated with foliar K content. In the declining orchards of the North Cachar hills, low fruit yield was associated with lower concentration of available Ca in soils, lower foliar Ca content, and the lower Ca : Mg ratio. Foliar K was regulated by the ratio of K : Ca + Mg or K : Mg in soils in the North Cachar hills, and by N : Ca in Karbi Anglong. Foliar Ca was regulated by soil ratios of K : Mg in both locations. Calcium availability in soil of > 288 kg Ca ha-', and a foliar Ca : Mg ratio of > 8.70, were associated with healthy crops in the North Cachar hills. Soil parameters to the depth of 45 cm rather than the surface layer (0-15 cm) were significantly correlated with fruit yield and foliar nutrient contents. Earlier Ghosh (1978) reported low to medium status of K in Khasi mandarin orchards of north-east India. While, low leaf K status was reported in kinnow mandarin orchards of Nagpur area of Himachal Pradesh (Awasthi et al., 1984). Raina observed kinnow mandarin soils were medium to high in available K. Upadhyay and Patiram (1996) reported 57% mandarin orchards representing six major citrus belts of Sikkim with a common disorders of yellowing and mottling of leaves due to low N and high Fe and K concentrations. In another study, Patiram and Upadhyay (1997) observed no correlation of exchangeable with soil pH and organic carbon content of soil in mandarin orchards of Sikkim. Sharma and Mahajan (1990) observed deficient level of K besides N, P, Mn and Zn in kinnow mandarin orchards of Nagpur- Indora area of Himachal Pradesh. Sekhon et al. (1977) reported 10% sweet orange orchards deficient in K in Punjab and 32% orchards in high to excess range. Based on soil analysis, Dhatt (1989) observed medium level of available K in Kinnow mandarin growing soil of Hoshiarpur, parts of Jalandhar, Faridkot, Ferozpur and Bhatinda. Srivastava and Singh (1998a) observed 77.6% Nagpur mandarin orchards optimum in leaf K status in Central India when compared with standards proposed by Embleton et al. (1974b). But, 50-62% orchards were 292 AK. Srivastava and Shyam Singh

found having sub-optimum level of K when compared according to optimum leaf K limit of 1.18-1.56% as suggested earlier. But still, response of K fertilization is a common feature. Nutrient constraints analysis of sweet orange orchards of Marathwada region of Maharashtra, by Srivastava and Singh (1999) showed higher leaf K content in declining (0.62-2.25%) than healthy trees (0.60- 1.82%).

6. RESPONSE OF K FERTILIZATION

Under Indian conditions, studies on Nagpur mandarin raised on Citrus janbhiri revealed best effect of K at the rate of 400 g tree -i year -' in alkaline black - clay soil and 300 g tree-' year ' for acid lime at Akola, Maharashtra (Anon, 1989). Other studies on Kinnow mandarin on rough lemon and Jaffa sweet orange at Bhatinda (Punjab) showed better effect of K at the rate of 400 g tree -' year -1 than even N at the rate of 800 g tree -1 year -1 in calcareous alkaline loamy soil (Anon, 1987). Various recommendations of K in relation to P20 5 and K20 have emerged through All India Coordinated Research Projects on Tropical Fruits (Table 17) and other studies at various locations (Table 18). In temperate climate of Himachal Pradesh, best response of K application to Kinnow mandarin yield was observed when applied at the rate of one third of K fixing capacity of soil and maximum fruit yield was obtained with 234 g K tree-' without having any distinct effect of depth, to which K was added (Shankhayan and Bhardwaj, 1989). Later, Sharma and Chopra (1991) recommended application of K at the rate of 68 g tree-' upto 5th year of age and 136 g tree-' from 6 to 10th year, after which K fertilizer - was stabilized as 1360 g tree ' for blood red sweet orange grown in sandy loam soils in foot hills of Himachal Pradesh. In Hoshiarpur district of Punjab, where Kinnow mandarin is grown on sand and loamy soils, the deficiency of K was prominently detected. Fruit size was exceptionally small in trees with 0.68% K. The fruit weight increased from 130 to 150 g when leaf K was increased upto 1.30% with 300 g K20 tree-' application (Dhatt, 1989).

6.1 Tree Volume and Yield Response

No significant response of application of increasing levels of K20 on the change in tree volume and fruit yield was observed (Table 6). However, the maximum increase in tree volume of 5.57 m3 and 5.49 m3 was recorded during 1994-95 and 1995-96, respectively, with 200 g K20 tree-'. The different levels of K20 application showed no significant response on plant growth and fruit yield (Table 6) during 1994-95 and 1995-96. Although, the highest fruit yield of 65.3 kg tree-' during 199495 and 62.9 kg/tree during 1995-96 was recorded with 500 g and 600 g K20 tree-', respectively. Potassium Nutrition Management for Yield and Quality of Citrus in India 293

Table 6. Response of potassiumfertilization on tree volume and yield of Nagpur mandarin Treatment Tree volume (m 3) Yield (kg tree-') (g K20 tree-') 1994-95 1995-96 1994-95 1995-96 0 47.17 49.45 (2.28) 57.5 58.2 100 42.31 (4.51) 51.39 (1.94) 60.6 52.4 200 53.55 (5.57) 56.88 (5.49) 58.4 61.2 300 48.32 (4.41) 59.75 (2.87) 52.9 54.2 400 49.54 (5.34) 63.56 (3.81) 59.3 58.4 500 51.08 (2.73) 69.07 (5.51) 65.3 52.5 600 55.06 (2.88) 71.74 (2.67) 58.2 62.0 CD (P = 0.05) NS NS NS NS Source: Kohli et al. (1995;1996); Srivastava et al. (2001) Figures in paranthesis is Mean

6.2 Changes in Leaf Nutrients Status

The leaf N and K contents showed no significant effect due to application of differential doses of K20 during 1994-95 (Table 7). However, leaf K content was maximum as 1.12% with 300 g K20 treatment compared to 0.79% in the treatment where no K20 was applied. Beyond 300 g treatment, change in leaf K content followed a constant decreasing trend up to 0.83% with 600 g K20 treatment. These observations further indicated that initially the leaf K was though in optimum range but K20 application still imparted positive response on foliar K status under soil moisture content varying between 23 to 38% throughout the growing period.

Table 7. Response of potassium fertilization on leaf nutrient composition (%) of Nagpur mandarin Treatment Leaf nutrients content (%) (g K20 tree-1) 1994-95 1995-96 N P K N P K 0 2.22 0.09 0.79 2.35 0.09 0.62 100 2.63 0.06 0.80 2.56 0.06 0.65 200 2.49 0.10 0.99 2.09 0.11 0.77 300 2.41 0.09 1.12 1.94 0.08 1.00 400 2.09 0.07 0.93 2.54 0.07 0.63 500 2.49 0.07 0.87 2.49 0.07 0.66 600 2.15 0.10 0.83 2.34 0.07 0.66 CD (P=0.05) NS NS NS 0.39 NS 0.25 Source: Kohli et al. (1995); Srivastava et al. (2001) 294 A.K. Srivastava and Shyant Singh

While during 1995-96, the lowest leaf N content (1.94%) was observed with 300 g K20 application which was significantly lower than rest of the other treatments. While varying levels of K0 application responded significantly on leaf K status. The maximum leaf K content of 1.00% was observed with 300 g - K2 Otree ' which was significantly higher than rest of the treatments. These responses are in concordance with earlier findings obtained during 1994-95 (Kohli et al., 1995; Srivastava et al., 2001)

In western part of West Bengal, Ghosh (1990) observed best result with 400 g K,0 tree-' year-' in 4 year old plants of sweet lime. Under Gonicoppal conditions, Srivastava and Bopaiah (1978) recommended K20 at the rate of 680 g tree-' for Coorg mandarin. In 15 year old Khasi mandarin, Ghosh et al. (1989) observed K20 at the rate of 300g per tree per year applied annually along with 300 g N, 250 g and P205 proved best economical dose under Meghalaya conditions. Singh and Mishra (1985) reported that N : K20 applied at the rate of 500 : 250 g tree-' resulted high yield of 32-69 kg tree-' in 6 years old declining Pant lemon trees in Uttar Pradesh. The response of K application was, therefore, affected by soil available K status, leaf K content, type of rootstocks/ cultivar, form of K, time of application and soil type.

Sharma et al. (1993) worked out the optimum fertilizer requirement for sweet orange applying the principles of game theory through long term trial. The minimum and mean values of number of fruits tree -' and net returns were calculated for the different treatment combinations. Wald's criterion, i.e. choosing a strategy is repeated, and the Laplace criterion, i.e. choosing a strategy that gives maximum return on averages, were applied to results. Under Wald's criterion, the best - - treatment was 400 kg N + 200 kg K20 ha ' giving a yield of 439 fruits tree ' and a net return of Rs. 36,187.7 ha-'. Under the Laplace criterion, the best treatment was 1200 kg N + 200 kg.K 20 ha-' giving a yield of 1103 fruits tree-' and a net return of Rs. 90,894.8 ha-'. The other recommendations emerged through studies under All India Coordinated Research Projects and recommendations from various State Government Universities have been summarised (Table 8, 9, 10 and 11). A number of other studies have suggested a wide range of K dose in comparison to N and both in India and abroad (Table 12).

7. FRUIT QUALITY

A very few studies pertaining to response of K on various fruit quality paratmeters have been doucmented so far. Bharadwaj and Shankhayan (1993) observed that soil application of K (234-210 g tree-' applied in March, June and September) in 5 year old kinnow mandarin grown in acidic soil of Himachal Pradesh brought significant decrease in juice content, TSS and TSS/acid ratio and increase in acidity. Shirgure at al. (2000a) reported best response of various quality parameters viz., juice content, TSS and acidity with 500 g N + 140 g P20 5 + 70 g K20 through fertigation at 20% depletion of available water capacity. Potassium Nutrition Management for Yield and Quality of Citrus in India 295

Table 8. Fertilizer schedule for citrus cultivars in north-west India Citrus species Age Fertilizers application FYM with spacing (years) (g tree ') (kg tree')

N P20 5 K 20 Himachal Pradesh Citrus - 800 500 600 20 Jammu and Kashmir Citrus (6 x 6 m) 1-5 80 10 15 5 10 and above 800 70 125 50 Punjab citrus (6 x 6 m) 1-3 50-150 5-20 kg 4-6 200-250 25-50 kg - - 7-9 300-400 60-90 kg - - Delhi mandarin (6 x 6 m) 1 50 40 125 20 2 100 40 125 25 3 200 80 250 30 4 300 160 375 40 5 400 320 500 50 Adult 500 400 750 60 Rajasthan mandarin (6 x 6 m) 290 200 240 100 Lime/Lemon (4.5 x 6 m) 290 290 200 50

Table 9. Fertilizer schedule for citrus cultivars in south India Citrus species Age Fertilizers application FYM with spacing (years) (g tree ') (kg tree-')

N P20 5 K 20 Andhra Pradesh Acid lime (6 x 6 m) 1 375 150 200 - 2 750 300 400 - 3 1125 450 600 - 4 and above 1500 600 800 - Sweet orange & pummelo (8 x 8 m) 1 300 70 80 - 2 600 140 160 - 3 900 210 240 - 4 1200 280 320 - 5 and above 1500 350 400 - Karnataka Lime/Lemon (5 x 5 m) 242 145 242 5 Mandarins & sweet orange (6 x 6 m) 1 35 135 13 0 2 120 120 78 10 3 400 250 •400 20 5 and above 550 370 550 30 296 A.K. Srivastava and Shyam Singh

Table 10. Fertilizer schedule for citrus cultivars in east and north-east India Citrus species Age Fertilizers application FYM with spacing (years) (g tree ') (kg tree - ')

N P 20 5 K20 Bihar: Citrus (6 x 6 m) 1300 g mixtur( tree-' 10 West Bengal: Citrus (4.5 x 5 m) 1 50 50 50 10 6 400 400 500 50 Orissa: Orange (7 x 7 m) 1 90 230 90 10 2 108 275 120 250 Lime (6 x 6 m) 1 45 115 60 10 2 90 230 90 15 Mizoram: Orange & others (3 x 5 m) 2 150 120 100 10-15 3 300 240 200 10-15 4 450 350 300 10-15 7 900 720 600 10-15 Arunchal Pradesh: Lemon (5 x 5 m) 1 90 90 90 20 Mandarin (4 x 4 m) 2 150 150 200 25 Sweet orange (6 x 6 m) 3 200 200 300 30 4 250 250 500 35 5 350 350 600 40 .6 400 400 700 45 7 450 450 900 50 Assam: Lemon (3 x 3 m) 1 150 100 150 5 4 600 400 600 20 Mandarin (5 x 5 m) 2 150 120 100 - 3 300 240 200 6 750 600 500

7.1 Pre-harvest Response

An improvement in fruit weight was recorded with increasing levels of potassium application (Kohli et al., 1995; 1996). The maximum fruit weight (154 g) was registered with 500 g K20 treatment during 1994-95 (Table 13). The highest firmness of fruits (3.35 kg cm-2) was produced with 600 g K20 followed by 3.10 kg cm-2 with 300 g K20 treatment. The juice content increased from 44.0% with 0 g K20 tree-' to 54.0% with 600 g K20 tree-', which warranted a strong necessity of K fertilization to improve fruit juice content. The maximum TSS/acid ratio of 21.4 was observed upto 300 g K20 tree-' beyond which, it decreased to as low as 15.7 upto 600 g K20 tree-'. Potassium Nutrition Management for Yield and Quality of Citrus in India 297

Table 11. Fertilizer schedule for citrus cultivars in central India Citrus species Age Fertilizers application FYM with spacing (years) (g tree ') (kg tree-')

N P20 K20 Madhya Pradesh 1 100 50 50 50 Mandarin 5 300 150 150 50 6 400 200 300 50 10 & above . . .. Maharashtra Early year 100 0 0 3 Sweet orange (6x6 m) Bearing age 1000 100 200 24-30 Lime/Lemon 1 25 0 0 6 (6 x 6 m) 2 50 0 0 12 Bearing trees 800 100 200 100 Kagzi lime (6 x 6 m) 1 100 50 0 5 2 150 75 0 10 3 200 100 0 15 4 250 125 0 20 5 and above 900 400 0 25-30 Mandarin (6 x 6 m) 2 240 120 0 5 3 360 180 0 10 4 480 240 0 15 5 600 300 0 20 6-9 720 360 0 25-30 10 and above 1000 500 0 30-50 Source: Tandon (1987)

The effect of K20 application during second year (1995-96) on an average fruit weight was inconsistent (Table 13). However, maximum fruit weight of 132.3 g was observed with 600 g K20 tree- ' followed by 128.2 g with 200 g - K20 tree '. Similarly no definite pattern on fruit firmness was observed. The maximum juice content of 52.6% was observed with 600 g K O tree-' followed by 47.5% with 300 g K20 tree-'. The TSS content showed almost no change as a result of K application upto 600 g K20 tree-'. The fruit acidity was observed as 0.79% in control showed a regular increase upto 1.00% with 600 g K20 tree - '. These observations indicated that K application induced higher synthesis of acids in the fruits which could probably lead to longer on tree storage of fruits, since fruits with higher acidity will comparatively take longer time to convert its acids into sugars to reach an ideal maturity for harvesting. The above observations indicated that 300 g K20 level as its optimum dose for achieving the proper blend of sugar and acid for good quality of mandarin fruits. Mann and Sandhu (1988) earlier observed increase in fruit weight and size, peel thickness, titrable acidity and ascorbic acid content and reduction in TSS/acid ratio as a result of K fertilization. 298 AK. Srivastava and Shyam Singh

Table 12. Potassium recommendation for various citrus cultivars in India and abroadfor comparison Doses of application Source K (850 kg ha-), (410 kg ha-'), (223 kg ha-'), Page et a. (1969), Reese and Koo (750 kg ha-'), (1000 kg ha-') (1975), Du Plessis and Koen (1984), Bazelet et al. (1980) 180 kg N + 90 kg P + 180 kg K Rodriguez (1980) 500 g N +100 g P20 5 + 400 g K20 tree' Ghosh (1990) 300 g N +250 g P20 5 + 300 g K20 tree-' Ghosh et al. (1984; 1989) 125 g N + 175 g P + 100 g K tree -' Hong and Chung (1979) 160 g N + 320 g P + 480 g K tree -' Hemandez (1981) 2.72 kg N + 1.81 kg P + 0.60 kg K tree-' Reddy and Swamy (1986) 625 kg N + 525 kg K20 ha - ' Tucker et al. (1990) 600 g N + 135 g P + 285 g K tree - ' EI-Hagah et al (1983) - 750 g N + 200 g P2O 5 + 500 g K20 tree ' Ahmed et al. (1988) 400 kg N + 200 kg K20 ha' . Sharma et al. (1990) - 1500 g N + 400 g P20 5 + 750 g K20 tree ' Maatouk et al. (1988) C 500 g N + 250 g K20 tree- ' Singh and Misra (1985) - 100 kg N + 200 kg P20 5 + 300 kg K20 ha ' Goepfert et al. (1987) 475 g N + 320 g P2 05 + 355 g K20 trec' Koseoglu et al (1990) - 100 g N + 25 g P20 5 + 50 g K20 tree ' Sharma and Singh (1989) 1 250 g N + 250 g P20 5 + 500 g K20 tree- Kannan et al. (1989) 600 g N + 200 g P20 5 + 300 g K20 tree-' Jawaharlal et al. (1989) - 500 g N + 100 g P20 5 + 400 g K20 tree ' Ghosh (1990) - 240 g N + 40 g P20 5 + 100 g K20 ha ' Pedrera et al. (1988) 800 g N + 200 g P20 5 + 400 g K20 tree-' Mann and Sandhu (1988) 600 g N + 200 g P20 5 + 200 g K tree-' Kar et al (1988) (soil application) + 0.4% Cu + 0.5% Zn (Foliar spray) 1 kg N + 0.5 kg P + 0.5 kg K tree-' Gilani et al. (1989) 100 g N + 50 g P20 5 + 50 K20 tree-' Sharma and Azad (1991) 1.4 kg N + 1.08 kg P + 1.1 kg K tree-' Chundawat et al. (1991) 180 g N + 90 g P20 5 + 45 g K20 + Aubert and Vullin (1998) 800 CaO tree-' 200 kg N + 140 kg P + 210 kg K ha-' Cantarella et al. (1992) - 0.5 kg N + 0.5 kg P20 5 + 1.0 kg K20 ha' Androulakis et al. (1992) 1.02 kg N + 0.58 kg P20 5 + Liu et al. (1994) 0.55 kg K20 tree-' - 600 g N + 200 g P205 + 100 g K20 tree Kohli et al., (1997) Ram et al. (1997); Huchche et al. (1998) 800 g M + 200 g P20 5 + 100 g K20 tree- Srivastava and Singh (1998a) 420 g N + 323 g P20 5 + 355 g K20 tree-' Koseoglu et al. (1995a; 1995b) 1.5 kg urea + 0.25 kg superphosphate + Yin et al. (1998) 1.25 kg potassium chloride + 1.1 kg magne- sium sulfate + 0.10 kg zinc sulphate tree-' Potassium Nutrition Management for Yield and Quality of Citrus in India 299

Table 13. Response of potassium fertilization on fruit quality of Nagpur mandarin Treatment Fruit quality parameters (g-' K20 1994-95 1995-96 tree-') Firm- Juice Acidity TSS/ Firm- Juice TSS Acidity TSSI ness content (%) Acidity ness content (%) (%) Acidity (kg (%) (kg (%) cm- 2) cm- 2) 0 2.83 44.0 0.72 14.4 3.0 42.2 10.3 0.76 11.2 100 2.97 47.0 0.82 19.7 2.7 40.9 10.4 0.89 11.7 200 3.01 47.0 0.82 19.0 3.0 43.5 10.9 0.79 13.9 300 3.10 50.0 0.91 21.4 3.0 47.5 10.7 0.89 15.2 400 2.98 52.0 0.86 17.5 2.9 40.5 10.7 0.84 12.8 500 2.96 50.0 0.84 19.6 3.2 37.2 10.7 0.84 12.8 600 3.35 54.0 0.84 15.7 3.1 52.6 11.1 1.00 11.1 CD 0.21 2.4 0.11 1.2 NS 3.2 NS 0.10 1.8 (P=O.05) Source: Kohli et al. (1995; 1996)

7.2 Changes in Fruit Quality During Storage

7.2.1 Keeping quality

The keeping quality of fruit was studied during 1994-95 under ambient conditions upto 15 days after the harvest. The fruits from different K treated trees were kept for 10 days storage at an ambient temperatures during 1995-96 and various changes in fruit quality were observed at 5 and 10 days of storage. Minimum fruit weight loss of 7.95% was found in 300 g K20 treatment (Table 14). The maximum fruit firmness 2 of 3.24 kg/cm was found with 600 g K20 Table 14. Effect of different levels of potassium on external appearance and flavour of Nagpur mandarin fruit during ambient storage of fruits (based on scores given out of total 2 marks by sensory evaluation panel) Treatment External appearance Flavour Weight (g K20 tree-') Days of storage Days of storage loss (%) 5 10 5 10 0 2.00 1.25 1.75 1.75 25.47 100 1.75 1.50 2.25 1.50 26.80 200 1.25 1.25 1.75 1.75 22.47 300 2.25 1.25 1.25 1.75 7.95 400 1.50 1.75 1.75 1.75 21.56 500 2.75 1.50 1.75 1.25 30.52 600 2.25 1.50 1.50 1.25 24.54 CD (P=O.05) 0.71 NS NS NS 4.25 Source: Kohli et al. (1995; 1996) 300 A.K. Srivastava and Shyam Singh treatment. However, no systematic pattern in TSS/acidity ratio could be obtained when fruits were analysed after 15 days of storage.

7.2.2 External appearance and flavour

The external appearance of fruits judged through sensory evaluation was observed good to excellent with 300 g, 500 g and 600 g K20/tree and statistically on par with each other in comparison to control treatment after 5 days of storage during 1995-96 (Table 14). The external appearance of fruits reduced invariably in all the treatments after 10 days of storage. Varying doses of K application showed no effect on external appearance after 10 days of storage. The effect of varying levels of K20 application on the change in flavour was observed non- significant.

7.2.3 TSS/Acid ratio

The effect of increasing levels of K20 was significant during 1995-96 at initial stage which became nonsignificant after 5 days of storage at ambient temperature (Table 15). However, in control TSS/acid ratio of fruit reduced from 15.20 on 0 day to 12.49 and 11.57 after 5 and 10 days of storage, - respectively. While with 300 g K20 tree ' the TSS/acid ratio increase to 14.21 from initial TSS/acid ratio of 12.24 after 5 days of storage which later reduced to 13.21 after 10 days of storage. These observations indicated that with 300 g K20 tree- I which recorded highest K content of 1.00% took another 5 days to develop higher TSS/acid ratio of 14.21 amongst all the treatments. Such change in TSS/acid ratio was not observed with other K20 levels probably due to lower leaf K status.

Table 15. Effect of different levels of potassium on TSS/Acid ratio during storage at ambient conditions Treatment Days of storage (g K20 tree-') 0 5 days 10 days 0 15.20 12.49 11.57 100 11.72 13.23 13.36 200 13.92 12.65 14.97 300 12.24 14.21 13.27 400 12.85 12.95 12.63 500 12.79 1L03 11.87 600 11.09 11.97 14.63 CD (P = 0.05) 2.42 NS 1.95 Source: Kohli et al. (1995; 1996); Srivastava and Singh (1998a) Potassium Nutrition Management for Yield and Quality of Citrus in India 301

8. INTERACTION RESPONSE OF LEAF NITROGEN AND POTASSIUM

In Nagpur mandarin growing areas of central India, Srivastava et al. (1995) observed significant correlation between leaf N and K in Kalmeshwar (R = -0.54) and Katol (r = 0.621) tehsils of Nagpur district. Considering these studies, leaf N/K ratio was suggested as a better index which was later investigated in detail. A field experiment was conducted in June flush (Mrig bloom) of 1991- 92 on ten year old Nagpur mandarin at citrus orchards of Central Institute of Cotton Research, Panjri, Nagpur under sub-humid tropical climate. The soil was taxonomically classified as fine, montmorillonitic hyperthermic family of Type Haplustert. The soil had pH 7.8, EC 0.17 dms- 1, organic carbon 0.39 per cent, available N 110 kg ha-', P 23 kg ha - ' and K 218 kg ha-'. Soil application of nitrogen @ 0, 200, 400, 600 and 800 plant - ' year -' alongwith K20 @ 100 g plant-' year-' in the ratio of 0.0, 2.0, 4.0, 6.0 and 8.0 were in randomised block design with three replications. Uniform dose of P20 5 through single superphosphate @ 200 g plant - ' in two splits in August and November was also applied to each test plant. Nitrogen in form of urea was applied in three splits in the months of April, August and November, whereas, potassium application was done in the month of November through muriate potash.

8.1 Interaction of Leaf N and K

Soil application of N and K in increasing ratio from 0.0 to 8.0 though increased leaf N content from 2.10 to 2.92 per cent it reduced the leaf K content from 190 to as low as 0.90 per cent (Table 15) and thereby leaf N/K ratio was observed in increased linearly from 1.10 to 3.24. This showed the presence of strong interaction effect on increased leaf N on leaf K content due to involvement of nitrate potassium antagonism. Leaf N content was further observed to be negatively correlated with leaf K content (r = -0.881**). Linear regression analysis between leaf nitrogen and potassium further revealed that leaf potassium reduced @ 0.78 per cent per unit increase in leaf nitrogen content as evident from the regression equation: Leaf K = 3.71-0.78 Leaf N.

8.2 Effect of Leaf N/K Ratio on Vegetative Growth and Yield

Non-significant effect of increasing leaf N/K ratio on vegetative parameters such as plant height, scion girth and canopy volume were recorded (Table 16). The highest fruit yield of 487 was'observed at leaf N/K ratio of 2.49 compared to 435 at leaf N/K ratio 3.24. These findings indicated that higher leaf N/K ratio is not always associated with increase in fruit yield. Similarly drywood production was reduced from 753 g/plant at leaf N/K ratio of 1.10 to 253 g/plant at leaf N/ K ratio of 3.24. The above observations showed that balanced N and K fertilization helped in maintaining vigour of trees. 302 AK. Srivastava and Shyamn Singh

Table 16. Effect of different leaf N/K ratios on vegetative growth, fruit yield and drywood production of Nagpur mandarin Treatment leaf Canopy Number of Drywood Leaf 3 (N/K ratio) volume (m ) fruits tree-' production (g) N/K ratio 1.10 30.73 76 753 1.10 ***(1.63) 1.69 37.11 142 634 1.69 (1.07) 2.33 43.33 408 472 2.33 (5.46) 2.42 43.51 487 2.49 (4.33) 3.23 45.04 453 253 3.24 (40.75) SEm± NS 106 120 CD (P=O.05) 231 265 Source: Kohli et al. (1993); Kohli and Srivastava (1997)

The leaf N/K ratio of 2.49 was observed as optimum to obtain better fruit yield with leaf N and K was 2.42 and 0.97 per cent, respectively. Leaf N/K ratio must be maintained between 2.4 to 3.0 with leaf N higher than 2.1 and K more than 0.8 per cent in Valencia oranges.

8.3 Effect of Leaf N/K Ratio on Fruit Quality

Non-significant effects of increasing leaf N/K ratio upto 3.24 were observed on average weight of fruit, fruit length, fruit breadth and acidity (Table 17). However, juice content was recorded maximum as 45.2 per cent at leaf N/K ratio of 2.49 followed by 43.7 per cent at leaf N/K ratio of 3.24. Similarly TSS/ acidity was also observed higher as 10.2 at N/K ratio of 2.49 compared to 7.4 at N/K ratio of 3.24. It was also observed that increase in leaf N/K ratio was associated with corresponding improvement in fruit quality indices up to a limit of 2.49 only, thereafter it decreased.

Table 17. Effect of different leaf N/K ratios on fruit quality on Nagpur mandarin Treatment Av. Fruit Fruit Juice TSS Acidity TSS/ (leaf N/K Weight length breadth (%) (%) (%) acidity ratio) of fruit (g) (cm) (cm) ratio 1.10 81.1 4.4 4.5 41.1 10.7 1.4 5.7 1.69 121.5 6.0 6.1 36.8 13.7 2.3 6.1 2.33 97.3 5.6 5.8 41.8 13.7 2.0 7.4 2.42 84.4 5.2 5.6 45.2 14.2 1.7 10.2 3.23 83.7 5.3 5.6 43.7 15.0 2.1 7.4 Source: Kohli et al. (1993) Potassium Nutrition Management for Yield and Quality of Citrus in India 303

/ 9. POTASSIUM FERTIGATION

9.1 Comparison of Broadcast Fertilization with Fertigation

Comparative efficacy of nitrogen fertigation using 60%, 80% and 100% N of recommended dose with band placement of nitrogen (100% N) application using drip irrigation system in acid lime (Citrus aurantifolia Swingle) established in medium deep soil type indicated that the uptake of potash was higher in 100% K fertigation than 100% K applied through and placement using drip irrigation system. The leaf P and K content were also observed higher with K fertigation compared to band placement nitrogen using drip irrigation system. The higher concentration of leaf nitrogen content with fertigation favoured the better quality of Nagpur mandarin fruits. The fruits weight (34.4 g fruit - ') was higher with 100% N fertigation in comparison to 100% band placement of nitrogen (32.3% fruit). The juice content (49.08%) and TSS (7.63%) were higher with 80% N fertigation when compared with juice content (45.5%) and TSS (7.03%) of fruits with 100% band placement of nitrogen fertigation over conventional band placement of application in acid lime (Shirgure et al., 1998; 2000a; 2000b).

9.2 Fertigation Response at Various Irrigation Levels

Studies were carried out in Nagpur mandarin and acid lime cultivars with various irrigation based on available water capacity of soil and fertilizer levels combinations with the aim to see whether fertilizer doses can be brought down following drip irrigation. An investiagtion on 4 levels of irrigation applied at the rate of 10%, 20%, 30% and 40% moisture depletion of available water capacity along with three levels of fertilizer combinations viz., 600 g N + 200 g P20 5 + 100 g K20, 500 g N + 140 g P20 5 + 70 g K20 and 400 g N + 80 g P20 5 + 40 g K20 in Nagpur mandarin grown on Typic Ustochrept soil type showed that irrigation at 20% depletion of available water capacity of soil with N : P : K combination of 500 : 150 : 70 proved best with reference to increase in canopy volume, fruit yield and leaf nutrient composition (Table 18). While in acid lime, irrigation at 30% depletion of available water capacity with N : P : K combination of 500 : 140 : 70 provided best response on canopy volume, fruit yield and leaf nutrient composition (Shirgure et al., 1999).

10. POTASSIUM NUTRITION - AN INDIAN PERSPECTIVE

Potassium nutrition, alone or when combined suitably with other nutrients offers a promising alternative to tailor the fertility programme in such a way that maximum use efficiency of applied nutrients is ensured besides bringing a quantum improvement in yield and quality. 304 A.K. Srivastava and Shyam Singh

- Table 18. Leaf nutrient composition of Nagpur mandarin trees in relation to various treatment combinations of irrigation and fertigation Main treatment Sub- Leaf nutrient Increase TSS Acidity Irrigation treatment composition in canopy (Fertigation) (%) volume 3 N:P 2O5 :K20 N P K (I ) (%) (%) Irrigation at 600:200:100 2.31 0.16 2.02 12.60 7.93 0.62 10% depletion (34.82)* of AWC (I1) 500:140:70 2.12 0.16 1.92 10.30 7.25 0.62 (34.63) 400:80:40 2.10 0.14 1.73 11.18 7.27 0.64 (35.33) Irrigation at 600:200:100 2.28 0.18 1.98 13.97 7.95 0.66 20% depletion (39.96) of AWC(12) 500:140:70 2.42 0.20 2.12 14.30 8.12 0.59 (41.80) 400:80:40 2.20 0.18 1.88 13.45 7.97 0.64 (36.95) Irrigation at 600:200:100 2.18 0.18 1.99 13.12 7.18 0.67 30% depletion (35.90) of AWC(13) 500:140:70 2.16 0.14 1.76 12.40 8.0.3 0.64 (36.83) 400:80:40 2.16 0.13 1.68 10.9 7.03 0.64 (36.43) Irrigation at 600:200:100 2.10 0.18 2.03 10.80 7.34 0.68 40% depletion (35.81) of AWC(14) 500:140:70 2.11 0.14 1.53 11.20 7.46 0.65 (34.92) 400:80:40 2.09 0.08 1.32 10.40 7.72 0.63 (34.14) CD(P=O.05) Irrigation levels (1) 0.11 0.03 0.20 1.12 0.32 NS Fertigation levels (F) 0.06 0.02 0.12 0.21 0.12 NS Interaction I x F 0.14 0.04 0.28 1.30 0.48 NS Source: Srivastava et al. (2000a; 2000b); Shirgure et al. (2000a) *original values

10.1 Pre-harvest Considerations

* Improvement is needed in methods of determining the K status of lemon in coastal and intermediate areas. With current information, proper age of leaves Potassium Nutrition Management for Yield and Quality of Citrus in India 305

can be obtained by marking specific cycles of growth as they develop. However. this is laborious. Possibly, standards could be developed for younger leaves. In any event, further research is needed on lemon leaf sampling techniques. An additional research is needed to find means of taking advantage of beneficial effects of elevating the K level in the trees, while minimizing the adverse effects from such elevation. The leaf K guide under such conditions if developed independently for quality and yield improvements, could lead to better understanding on K nutrition. Therefore, K response versus problems of fruit yield, size and quality should not be approached in isolation.

* The role of K has to be evaluated under rich supply of available K in relation to yield and quality which would eventually reveal K nutrition might influence the ability of citrus plants to withstand stresses other than nutritional. This may in turn be compared with the response of citrus under K stressed conditions. Such an exercise would be very handy in manipulating K fertility programme for specific variety of citrus. It is not uncommon to observe that citrus plants are virtually under less than optimum supply of K, when evaluated on the basis of K concentration in leaf, despite grown under high soil available K status. Under such condition, an additional K fertilization evokes a favourable response particularly on quality. The metabolic function of K vis-6-vis crop ontogeny would reveal many of the unsolved mysteries of K nutrition.

* A model has to be developed with the data on volume and distribution of roots together with uptake pattern characteristics and data on K release combined together to predict behaviour of soil K-plant response relationship. Rational fertilizer use is one of the essential requirements for the improvement of crop productivity. Too high rates could increase costs and might result in nutrient disequilibrium to the deteriment of yield. Too low rate make it impossible to realise the full potential of the soil-cultural technique crop combination. " Exchangeable K is the most widely used as an indicator of potash requirement, though for soils rich in interlayer K with resultant high K fixing power, other methods such as extraction by HNO3 appeared more reliable predicting crop response. The soil K advisory has to be based on exchangeable K/CEC ratio instead of exchangeable K alone. In fact, not a very sharp boundary exists between exchangeable and non-exchangeable portions of soil K. However, it is difficult to draw a natural boundary and sometimes, during one growing season, crops often manage to withdraw from soils, quantities of K which are several times larger than the quantity of K originally present in so called exchangeable or available form. Two distinct problems require reorientation for future K research are : development of an independent method to measure the uptake efficiency of roots and a more reliable determination of the amount of K taken up from the interlayer positions, so that soil type specific K recommendation could be more precisely made. 306 AK. Srivastava and Shyam Singh

Apart from the fact that correlation between fertilizer rates and yield response must become less close when the yield plateau is reached. One of the most important reasons for poor K fertilizer-yield relationship seems to be enormously large and small range spatial variability of soils and plant available K. Even if the soils are grouped together according to families, groups and series, the coefficient of variation for exchangeable K would be so large that would, in turn raise some doubts on concepts attempting to improve K fertilizer efficiency by chemical analysis of extrapolations from benchmark soils. Unless porosity and soil moisture regimes are taken into consideration, the reliability of K fertilizer recommendations will be inadequate. A comprehensive strategy as outline required to be developed to obtain a more uniform response of K fertilization through a purely holistic approach (Andres, 1990) to minimize differences arising due to difference in site characteristics from one region to another.

The uptake of K is not only affected by soil factors but also by climatic factors such as soil temperature and light intensity in addition to root morphology and density under various rootstocks-scion combinations. With regular leaf analysis, the efficiency of established fertilizer schedule adopted could be properly examined and reassessed the schedule if required. One of the major difficulties associated with leaf analysis is that, often the results of the analysis become available to the grower too late to enable him to take corrective measures. Early appearance of certain polypeptides in the plants can be viewed as an early warning system for an impending K deficiency in these plants. If needed, growers would be able to detect such a deficiency themselves at an early stage of plant growth. It would leave them enough time to rectify the situation. In such a case, the crop would have ample time to respond to the rectification, so that the eventual yield would not be much affected besides safeguarding the optimum nutrition.

10.2 Post-harvest Considerations

* At present very little information is available as to how to manipulate the nutritional regime of either soil or plant suited to affect the storage ability of citrus fruits. By varying potassium and nitrogen levels, a marked difference in yield and other quality parameters could be easily observed. There could be a possibility that one group of plants having 0.7% leaf K could show a distinct difference on shelf life when compared to another group of plants containing 2.1% K. Or do plants loaded with nitrogen show a decreased shelf life compared to just optimally N fertilized plants. It seems obvious that the effect of pre-harvest nutrition on post-harvest changes, although, a little unattended area, is just as important to the consumers as pre-harvest changes are to the growers. An increase in acidity of citrus fruits (Embleton et al., 1974a; Zekri, 1995), more so in lemon compared to oranges allows the fruits to take more time to undergo colour break or attain legal maturity Potassium Nutrition Management for Yield and Quality of Citrus in India 307

for harvesting (Embleton et al., 1974b). Such a response could well be exploited in the light of improving on tree storage of fruits, which in turn could offer a better economic consideration of K nutrition. Moreover, an increased acidity in lemon is a desirable quality attribute from processing stand point of view.

It is often suspected that fertility practice can have great effects on the nutritional quality of citrus. Many evidences have shown that healthy plants growing normally are superior to stressed, stunted and deficient plants. Once the needs for normal healthy growth are met, it appears that variety and climatic conditions can influence vitamin levels to a far greater extent than manipulation in nutritional practices. The studies have shown that fruit development right from fruit set is normally a function of length of photoperiod, indicating a varied photoperiodic responses (Moss, 1969; Monselise, 1977; Southwick and Davenport, 1986). The physiological problems observed during post-harvest handling of citrus fruits, often originate during production as a result of interaction among climatic, nutritional or other cultural factors. And sometimes, the likelihood of a problem occurring is partially under genetic control.

References

Ahmed, F.F., EI-sayed, M.A. and Maatouk, M.A. (1988). Effect of nitrogen, potassium and phosphorus fertilization on yield and quality of Egyptian Balady lime trees (Citrus aurantifolia) II. Yield and fruit quality. Annals Agricultural Science (Cairo) 33(2): 1249-68. Aiyappa, K.M., Srivastava, K.C. and Muthappa, D.P. (1965). The nutritional status of seedling mandarin (Citrus reticulataBlanco) leaves in Coorg. Indian Journal of Horticulture 22: 231-37. Alverez, M. and Correa, A. (1981). The influence of morphological and nutritional characteristics on citrus production as part of the study made at the Ceiba Du Agua enterprises. Proceedings of International Society' of Citriculture Vol. 2. pp. 561-63. Andres, E. (1990). Soil fertility data banks as a tool for a site specific K recommendation. Proceedings of 22nd Colloquium of International Potash Research Institute, Soligorsk, USSR. pp. 291-10. Androulakis, I.J., Loupassaki, M.H., Beidoun, F. and Tzombanakis, I. (1992). The effect of NPK fertilizers on the yield and mineral contents of leaves of grapefruit. Proceedings of International Society of Citriculture Vol. 2, pp. 624-27. Anonymous (1980). Mandarin cultivation. Extension Bulletin 3. Citrus Experiment Station. Gonicoppal-Chethalli complex, Coorg. Indian Institute of Horticulture Research, Bangalore. 308 AK. Srivastava and Shyam Singh

Anonymous (1987). Res. Rep. All India Coordinated Research Project on Tropical fruits. College of Agriculture, Punjabrao Krishi Vidyapeeth, Nagpur 27-30. July pp. 140. Anonymous (1989). Res. Rep. All India Coord. Res. Proj. on Tropical Fruits, A.P. Agricultuaral University, 13-16 Sept. 1989, Tirupati (Andhra Pradesh), pp. 183-85. Awasthi, R.P., Singh, Gurudev and Sharma, R.C. (1984). A survey of the mineral nutrients status of mandarin orchards in Nagpur area of Himachal Pradesh. Punjab Horticulture Journal 24: 27-36. Bar Akiva, A. (1965). Pentose accumulation and peroxidase activity in manganese deficient and normal citrus leaves. Phyton 22: 131-36. Bazelet, M., Feigenbaum, S. and Bar-Akiva, A. (1980). Potassium fertilizer experiment in a Shamouti orange grove. Pamph. 220, ARO, Volcani Center, Division of Science Publication. Besford, R.T. (1978). Use of pyruvate kinase activity of leaf extract for the quantitative assessment of potassium and "magnesium status of plants. Ann. Botany 42: 317-24 Bhandal, I.S. and Malik, C.P. (1988). Potassium estimation of uptake and its role in the physiology and metabolism of flowering plants. International Revision of Cytology 110: 205-54. Bhardwaj, S.K. and Shankhayan, S.D. (1993). Influence of potassium appliation on some Nagpur mandarinquality parameters of Kinnow fruit in mid hill sub-humid zone of Himachal Pradesh. Journal of Potassium Research 9(2): 154-59. Bhargava, B.S. and Chadha, K.L. (1988). Leaf sampling guide for fruit plantation crops. FertiliserNews. 7: 21-29. Birdsall, J.J., Derse, P.H. and Telply, L.J. (1961). Nutrients in California lemons and oranges. II. Vitamin, mineral and approximate composition. Journal of American Dietetrics Association 38: 555-59. Booth, C.J. (1930). Chaffey fertilizer experiments. Chaffey Union of High School and Junior College, Bulletin 6. Brar, M.S. and Sekhon, G.S. (1987). Vertical distribution of potassium in five benchmark soil series in northern India. Journal of Indian Society of Soil Science 35: 732-35. Cantarella, H., Quaggio, J.A., Bataglia, O.C. and Van Raij, B. (1992). Response of citrus to NPK fertilization in a network of field trials in Sao Paulo State, Brazil. Proceedings of InternationalSociety of Citriculture.Vol 2, pp. 607- 12. Chahill, B.S., Dhatt, A.S. , Raghbir Singh and Dhillon, D.S. (1991). Studies on the leaf nutrient standards in Kinnow. Indian Journal of Horticulture 48: 315-20. Potassium Nutrition Management for Yield and Quality of Citrus in India 309

Chahill, B.S., Dhatt, A.S. and Raghbir Singh (1988). Standardization of foliar sampling technique in Kinnow mandarin. Punjab Horticulture Journal 28: 118-25. Chapman, H.D. (1968). Mineral nutrition of citrus, pp1 2 7 -18 9 . In: W. Reuther, L.D. Batchelor and Webber H.J. (eds.) The citrus industry. Revised ed. Vol. 2 University of California Division of Agricultural Science, Berkeley. Chundawat, B.S., Khimani, R.A. and Kikani, K.P. (1991). Nutritional survey of elite acid lime orchard in Gujarat. Indian Journal of Horticulture 48(3): 183-86. Cicala, A. and Catara, A. (1982). Potassium fertilization effects on yield, fruit quality and mineral composition of leaves of 'Tarocco' oranges. Proceedings of International Society of Citriculture Vol. 2. 618-20. Dasberg, S. (1988). Nitrogen and potassium requirement of citrus. Vol.2. Rehovot, Israel, Balaban Publishers, 625-32. Dass H.C. and Srivastava A.K. (1997). Role of potassium in citrus nutrition: A review. Journal of Potassium Research 13(1): 80-92 Devi, D.D., Srinivasan, P. S. and Balakrishnan, K. (1996). Carbonic anhydrase activity as an indicator of zinc status of Sathgudi orange. Journal of Horticulture 24(1/2): 66-68 Dey, J.K. and Singha, D.D. (1998). Nutritional satus of healthy and declining citrus (Citrus reticulata) orchards. Indian Journal of Agricultural Science 68(3): 139-43. Dhatt, A.S. (1989). Nutrient management in citrus with special reference to Kinnow. Proceedings of Citriculture in North. Western India. Punjab Agricultural University, Ludhiana (Punjab), pp. 157-69. Dhatt, A.S., Grewal, G.P.S., Chahil, B.S. and Dhillon, D. (1992). Removal of N P K by Kinnow mandarin and Umran ber. Acta Horticulture 321: 541-44. Dhillon, W.S. and. Dhatt, A.S. (1988). Nutrient status and productivity of Kinnow orchards in Ferozpur district. Punjab Horticulture Journal 28: 7-13. Dhingra, D.R. and Kanwar, J.S. (1963). Soil factors and chlorosis of citrus. Punjab Horticulture Journal 3: 54-9. Du Plessis, S.F. and Koen, T.J. (1984). Effect of nutrition on fruit size of citrus. Proceedings of International Society of Citriculture 1: 148-50. EI-Hagah, M.H., Higazi, A.M., El-Niggar, S.Z., Ahmed, S.A. and Hasan, A.M. (1983). Effect of soil and foliar fertilization on growth of Navel orange and Balady mandarin trees. Minufiya Journal of Agricultural Research. 1: 261- 79. Embleton, T.W., Jones, W.W. and. Platt, R.G. (1974a). Plant nutrition and citrus fruit quality and yield. Proceedings of Symposium on Plant Nutrition Horticulture Products Quality, Univ. of Guelph, Aug. 14, 1974, American Society of Horticulture Science pp. 48-49. 310 AK. Srivastava and Shyant Singh

Embleton, T.W., Jones, W.W. and Platt, R.G. (1974b). Lemons - leaf analysis and potassium fertilization. California Citrology 59, 155, 174. Embleton, T.W., Jones, W.W., Platt, R.G. and B.M. Burns (1974c). Potassium nutrition and deficiency in citrus. California Agriculture 28(8): 6-8. Forshey (1968). Potassium nutrition of deciduous fruits. Proceedings of Symposium Potassium in Horticulture University of California, USA. American Society of Horticulture Science 102: 546-47 Fridovich, 1. (1986). Biological effects of the superoxide radicals. Arch. Biochemistry & Biophysics 247: 1-11 Fudge, B.R. (1945). The relation of foliar and fruit analyses to the fertilizer requirement of citrus. Proceedings of Soil Science Society of Florida. 7: 60- 74. Gajbhiye, K.S., Gaikwad, S.T., Sehgal, J.L., Bhaskar, K.S. and Ratna Gupta (1990). Status of available of K and crop response in soils of sawangi watershed in Vertisol region of Vidarbha. Ann. Rep., NBSS&LUP, Nagpur. Gallasch, P.T., Dalton, G.S. and Ziersch, J. (1984). The use of juice analysis to define fertilizer requirements of citrus. Proceedings of InternationalSociety of Citriculture. Vol. 2, pp. 140-42 Ghosh, S.N. (1990). Nutritional requirement of sweet orange (Citrus sinensis Osbeck) cv. Mosambi. Haryana Journal of Horticulture Science 19(1-2): 39-44. Ghosh, S.P. (1978). Citrus industry of north-east India. Punjab Horticulture Journal 12: 13-21. Ghosh, S., A.N. Verma and S. Givind (1989). Nutritional requirement of bearing Khasi mandarin orange (Citrus reticulata Blanco) trees. Meghalaya Horticulture Journal 2: 4-11. Ghosh, S.P., Verma, A.N. and Govind, S. (1984). Nutritional requirement of bearing khasi mandarin orange (Citrus reticulata Blanco) trees. Journal of Research of Assam Agricultural University 5(1): 11-16. - Ghosh, S.P., Verma, A.N. and Sheo Govind (1989). Nutritional requirement of bearing khasi mandarin orange (Citrus reticulata Blanco) trees in Meghalaya. Horticulture Journal 2(1): 4-11. Gilani, A.H., Yusuf, Ali, Tariq, M.A. and Mohammad Faquir, C. (1989). Studies of the effect of growth regulators and chemical fertilizers on the growth and yield in kinnow mandarin. Sarhad Journal of Agriculture 5(1): 47-51. Goepfert, C.F., Saldanha, E.L.S. De and Porto, 0. De M. (1987). The response of Valencia orange (Citrus sinensis Osbeck) to fertilizer levels, average of eight harvests. Agronomia Sulriograndense 23(2): 203-15. Gururani, A.K. and Ranvir Singh (1983). Variation in mineral composition of leaves from different flushes of kinnow mandarin under Tarai conditions. Punjab Horticulture Journal 23: 141-48. Potassium Nutrition Management for Yield and Quality of Citrus in India 311

Haggag, L.F., Maksoud, M.A. and F.M. EI-Brakouky (1995). Alternate bearing of Balady mandarin as influenced by nutritional status of tree. Anals of Agricultural Sciences (Cairo) 40(2): 759-69. Hernandez, J. (1981). Effect of N, P and K on yield, fruit quality and nutritional status of "Valencia Late" orange. Proceedings of International Society of Citriculture 2: 564-66. Hong, S.B. and Chung, S.K. (1979). Effects of N P and K fertilzer levels on the growth, yield and fruit quality of satsuma trees. Research Report of Reural Development Administration in Horticulture & Agronomy Engineering. 21: 67-75. Huber, S.C. (1989). Biochemical mechanism for regulation of sucrose accumulation in leaves during photosynthesis. Plant Physiology. 91: 656-62 Huchche, A.D., Ladaniya, M.S., Lallan Ram, Kohli, R.R. and Srivastava, AK. (1998). Effect of nitrogenous fertilizers and farmyard manure on yield quality and shelf life of Nagpur mandarin. Indian Journal of Horticulture 55(2): 108-12 Huchche, A.D., Srivastava, A.K., Kohli, R.R., Lallan Ram and Dass, H.C. (1997). Diagnosis of micronutrient constraints in Nagpur mandarin orchards of Central India. National Symposium on Developments in Soil Science, NBSS&LUP Regional Centre, Calcutta, October 8-12, 1997, Abstract pp. 178 Inque,H. and Shi, X.H. (1992). Effects of nitrogen, phosphoric acid and potassium on the root growth of trifoliate orange budded with young satsuma mandarin in sand culture. Tech.Bull. Faculty of Agriculture, Kagwa University, Japan. Jawaharlal, M., Durairaj, P., Subburamu, R., Dharamraj, G. and Irulappan,1. (1989). Effect of variable dose of acid lime on growth and yield. South Indian Horticulture. Jones, W.W. and Smith, P.F. (1964). Citrus nutrient deficiencies. In:Hunger signs in crops (H.B. Sprague ed.), Judd and Detweiler Inc. Washington DC, USA. Jones, W.W., Embleton, T.W. and Johnston, J.C. (1955). Leaf analysis - a guide to fertilizer need. California Citrology. 7: 339-40. Julien, J.L. (1989). Determination des mpr,es domter'retatopm d'analyse de terre en vue dela fertilisation potassique. Science du sol 27(2): 131-44. Kannan, M., Thamburaj, S and Seemanthini, Ramdas. (1989). Studies on the manuria requirement of mandarins in Shevroy hills. South Indian Horticulture 37(4): 203-08. Kar, P.S., Roy, A. and Mitra,S.K. (1988). Effect of prunning and fertilization on rejuvenation of mandarin orange. Indian Agriculturist 32(3): 205-10. Kohli, R.R. and Srivastava, A.K. (1995). Citrus nutrition in India - Present status and future strategies. Indian Agriculture 2001, Horticulture and Forestry Vol. II (V.K. Patil ed.) 0

312 AK. Srivastava and Shyam Singh

Kohli, R.R. and Srivastava A.K. (1997). Citrus nutrition - A retrospection. Agricultural Reviews. 18(2): 128-38 Kohli, R.R., Huchche, A.D., Ram Lallan, Srivastava, A.K. and Dass, H.C. (1993). Interaction effect of leaf nitrogen and potassium on growth, yield and quality of Nagpur mandarin. Journal of Potash Research 12(1): 70-74 Kohli, R.R., Srivastava, A.K. and Huchche, A.D. (1997a). Leaf nutrient limit for optimum yield of Nagpur mandarin (Citrus reticulata Blanco). Orchard Management for Sustainable Production of Tropical Fruits, Patna, Bihar, Abstract pp. 25 Kohli, R.R., Srivastava, A.K. and Huchche, A.D. (1997b). Nutrient requirement of Nagpur mandarin in clay soils in Central India. Indian Farming 47(2): 25-27 Kohli, R.R., Srivastava, A.K. and Huchche A.D. (2000). Leaf nutrient limit for optimum yield of Nagpur mandarin (Citrus reticulata Blanco). Indian Journal of Agricultural Sciences 70(5): 100-103 Kohli, R.R., Srivastava, A.K., Huchche, A.D., Dass, H.C., Lallan Ram and Singh, Shyam (1998). Diagnosis of leaf nutrient levels for optimum productivity of Citrus reticulata Blanco grown in black clay soils under sub-humid tropical climate. Tropical Agricultural Research and Extension 1(2): 81-86 Kohli, R.R. and Srivastava, A.K. (1997). Citrus nutrition - A retrospection. Agricultural Reviews 18(2): 128-38 Kohli, R.R., Huchche, A.D., Ram Lallan, Srivastava, A.K. and Dass, H.C. (1993). Interaction effect of leaf nitrogen and potassium on growth, yield and quality of Nagpur mandarin. Journal of Potash Research 12(1): 70-74 Kohli, R.R., Srivastava, A.K. and Shivankar, V.J. (1998). Organic culture in citrus cultivation. Indian Horticulture 43(1): 12-15. Kohli, R.R., Huchche, A.D. and Srivastava, A.K. (1995). Nutrient management studies in Nagpur mandarin and acid lime. Ann. Rep. National Research Centre for Citrus, Nagpur pp. 9-26. Kohli, R.R., Huchche, A.D. and Srivastava, A.K. (1996). Nutrient management studies in Nagpur mandarin and acid lime. Annual Report. National Research Centre for Citrus, Nagpur pp. 13-28. Kohli, R.R., Huchche, A.D. and Srivastava, A.K. (1997). Nutrient management studies in Nagpur mandarin and acid lime. Annual Report. National Research Centre for Citrus, Nagpur pp. 21-34. Koo, R.C.J. (1963). Use of leaf, fruit and soil analysis in estimating potassium status of orange trees. Citrus Industry 44: 9-10, 12, 25-26. Koo, R.C.J. (1982). Use of leaf, fruit and soil analysis in estimating potassium status of orange trees. Proceedings of Florida State Horticulture Society 75: 67-72. Potassium Nutrition Management for Yield and Quality of Citrus in India 313

Koseoglu, A.T., Colakoglu, H. and Kovanci, 1. (1990). The effect of chemical fertilizers on the fruit yield of young satsumas (Citrus unshiu Marc.). Doga Turk Tarim Ve Ornacilik Dergisi 14(l): 33-44. Koseoglu, A.T., Eryuce, N. and ColaKoglu. H.C. (1995). The effects of N. P, K fertilizers on fruit yield and quality of satsuma mandarin (Citrus unshiu Marc.). Acta Horticulture 379: 89-96. Krantz, B.A., Nelson, W.L. and Burkhart, L.F. (1948). Plant tissue tests as a tool in agronomic research (K.B. Kitchen, ed.), Diagnostic Techniques for Soil and Crops, Am. Pot. Inst. Washington, DC, USA, pp. 137-56. Krishnamurthi, S. and Randhawa, G.S. (1959). Role of potassium in nutrition of fruit crops - A review. Indian Journal of Horticulture 16: 175-82. Kumar, S., Rehalia, A.S. and. Sharma, K.K (1977). NPK content in some promising citrus cultivars as influenced by rootstocks. Journal of Research of Punjab Agricultural Universit. 14(4): 431-33. Lavon, R., Goldschmidt, E.E., Salomon, R and Frank, A. (1995). Effect of potassium, magnesium, and calcium deficiencies on carbohydrate pools and metabolism in citrus leaves. Journal of American Society of Horticulture Science 120(l): 54-58. Lavon, R., Salomon, R.and Goldschmidt, E.E. (1999). Effect of potassium, Magnesium and Calcium deficiencies on nitrogen constituents and chloroplast components in citrus leaves. Journal of American Society of Horticulture Science 124(2): 158-62 Lebart, L.. Morineau, A. and Tabard, N. (1977). Techniques da ]a description sttstiique: methods et logiciels pour I analyse des grandes tableux. Paris. Dunod, pp. 320. Liu, Y.W., Lin, M.S. and Qiu. H.L. (1994). Study of fertilizer satsumas. China Citrus 23(2): 7-10. Maatouk, M.A., Ahmed. F.F. and El-sayed, M.A. (1988). Effect of nitrogen, potassium and phosphorus fertilization on yield and quality of Egyptian Balady lime trees (Citrus aurantifolia) I. Vegetative growth and chemical composition of leaves. Annals of Agricultural Science (Cairo) 33(2): 1233- 47. Malavolta, E. (1994). Leaf analysis in Brazil - present and perspectives. Proceedings of International Society of Citriculture: Volume 2. Cultural Practices, Diseases and their Control: 7th International Citrus Congress, Acireale, Italy, 8-13 March, 1992. Catania. Italy; International Society of Citriculture, pp. 570-74. Medvedev, V.V. (1990). Variability of the optimal soil density and its causes. Soviet Soil Science 22(7): 65-75. Miller, I.E., Hofman, P. J. and Berry, R. K. (1993). Physiological and nutritional responses of five citrus rootstocks to potassium. Journal of Southern African Society of Horticulture Science 3(l): 20-23 314 AK. Srivastava and Shyam Singh

Monselise, S.P. (1977). Citrus fruit development endogenous system and external regulation.Proceedingsof International Society of Citriculture 2: 664-68. Moss, G.I. and Higgins, M.L. (1978). Analysis of orange juice for mineral content as a diagnostic tool to fertilizer practice with special reference to fruit juice quality. Proceedings of International Society of Citriculture pp. 300-02 Moss, G.I. (1969). Influence of temperature and photoperiod on flower indication and inflorescence development. Horticulture Science 25(8): 946-68. Nageswara, Rao, R.C., Krishnasastry, K.S. and Uduyakumar, M. (1981). Role of potassium in proline metabolism. II. Activity of arginase in K-sufficient and K-deficient plants. Plant Science Letters 23: 335-40 Nijjar, G.S. and Singh, R. (1971). A survey of mineral nutrition status of sweet orange orchards in Amritsar district. Punjab Horticulture Journal 32: 39. Oseni, T.O. (1988). Relationship between soil properties and leaf nutrient of cleopatra mandarin seedlings. Indian Journal of Agricultural Science 58: 571-72. Page, A.L., Ganje, T.J., Embleton, T.W. and Jones, W.W. (1969). Soil factors influencing the correction of K deficiencies on citrus in California. Proceedings of I"5 International Citrus Symposium Vol. 3, pp. 1605-12. Parker, E.R. and Batchelor, L.D. (1942). Effect of fertilizers on orange yields. California Agr. Exp. Sta. Bull. 673. Patiram and Upadhyaya (1997). Calcium, magnesium and potassium status of mandarin orange (Citrus reticulata Blanco) orchards in Sikkim. Indian Journal of Agricultural Science 67(1): 44-45. Pedrera, B., Lambert, I., Oviedo, D. and Alfonso, A. (1988). Study of three rates of N application with basal P and K on Dancy mandarin in a red ferrallitic soil II. Effects on growth, fruit quality and annual yield performance. Ciencia Y Tecnica en la Agricultura, Citricos Y Otros Frutales. 11(2): 17-28. Raina, J.N. (1988). Physico-chemical properties and available micro-nutrient status in citrus growing soils of Dhaulakuan in Himachal Pradesh. Punjab Horticulture Journal 28: 1-6. Prasad, R.N. and Ghosh, S.P. (1976). Nutritional status of existing Khasi mandarin orchards of Meghalaya. Symposium of Indian Society of Soil Science, June 18-20, Hyderabad (A.P.) Ram Lallan, Kohli, R. R., Srivastava, A. K., Huchche, A. D. and Dass, H.C. (1997). Nutritional requirement of Nagpur mandarin (Citrus reticulata Blanco) grown in Vertisol in Central India. Indian Journal of Horticulture 54(2): 91-7 Reddy, P.S. and Swamy, G.S. (1986). Studies on nutritional requirement of sweet orange (Citrus sinensis Linn.) variety sathgudi. South Indian Horticulture 34(5): 288-92. Potassium Nutrition Management for Yield and Quality of Citrus in India 315

Reddy,R.V.S., Rao, M.S., Ramavatharam, N. and Reddy (1991). Chemical composition of sweet orange (Citrus sinensis Osbeck) leaves at different periods of flowering and fruit development. Indian Journal of Agricultural Science 61(3): 207-09. Reese, R.L. and Koo, R.C.J. (1975). N and K fertilization effects on leaf analysis, trees, size and yield of three major Florida orange cultivars. Journal of American Society of Horticulture Science 100: 195-98. Rodrizuez, 0. (1980). Nutricao e Adubacao dos citrus. (0. Rodriguez and F. Viegas, ed.) Citricultura Brasileira Vol. 2, pp. 385-28. Rosselet, F., Helff, K.A.W. and Langenegger W. (1963). A comparison of nitrogen sources under two cultural practices for Valencia orange trees. South African Journal of Agricultural Science 64: 701-18. Saxena, N.P. (1985). The role of potassium in drought tolerance. Potash Review. 16: 102. Schaffer, A.A., Sagee, 0, Goldschmidt, E.E. and Goren, R. (1987). Invertase and sucrose synthase activity, carbohydrate status and endogenous IAA levels during citrus leaf development. Journalof Biological Chemistry 195: 19-23. Shankhayan, S.D. and Bhardwaj, S.P. (1989). Growth and yield of kinnow plants as influenced by level time and depth of potassium application in mid hill sub-humid zone of Himachal Pradesh. Sekhon, G.S., Brar, M.S., Chaudhry, S.K. and Nijjar, G.S. (1977). Nutrient status of healthy and declining sweet orange orchards of Punjab. Proceedings of International Citrus Symposium (K.L. Chadha and R.N. Pal, ed.) pp. 9-30. Sharma, R.C. and Azad, A.S. (1991). Effect of different levels of NPK on growth, yield and quality of mandarin. Indian Journalof Horticulture48(3): 116-20. Sharma, K.L. and Chopra, S.K. (1991). Effect of nitrogen, phosphorus and potash on the growth and yield of blood red sweet orange (Citrus senensis Osbeck) growth in foot hills and valley areas of Himachal Pradesh. Punjab Horticulture Journal 31(1-4): 19-24. Sharma, S.C., Mehrotra, N.K. and Singh Harmail (1990). Components of variance for yield and quality characters in sweet orange (Citrus sinensis Osbeck) cv Jaffa. Punjab Horticulture Journal 30(1-4): 5-8. Sharma, S.C., Mehrotra, N.K., Gupta, M.R. and Harmail Singh (1993). Game theory approach to a nutritional trial on sweet orange (Citrus sinensis Osbeck) cv. Jaffa. Punjab Horticulture Journal 30(1-4): 9-12. Sharma, S.K. and Singh, Ranvir (1989). Photosynthetic characteristics and productivity in citrus. I. Effect of nutrition. Indian Journal of Horticulture 46(3): 295-02. Sharma, V.K. and Mahajan, K.K. (1990). Studies on nutrient status of mandarin orchards of Himachal Pradesh. Indian Journal of Horticulture 47: 180-85. Shirgure, P.S., Srivastava, A.K. and Singh, Shyam (1998). Response of fertigation 316 A.K. Sri'a.stala and Shan, Singh

versus band placement in acid lime. Abst. Nat. Send. on New Horizons in Production and Post-Harvest Management of Tropical and Sub-Tropical Fruits New Delhi, pp. 26- Shirgure, P.S., Srivastava, A.K. and Ram Lallan (1999). Leaf soil buildup and growth response of prebearing acid lime (Citrus aurantifrlia Swingle) as affected by N fertigation versus band placement method. Proceedings of International Symposiun of Citriculture (Hi-tech Citrus Management. S.P. Ghosh and Shyam Singh, ed. J.. pp. 551-57. Shirgure, P.S., Srivastava, A.K. and Singh Shyam (2000a). Irrigation and fertigation effect on growth, yield and quality of Nagpur mandarin (Citrs reticulata Blanco). Indian Journal of Agricultural Science 70(10): (In press). Shirgure, P.S., Srivastava. A.K. and Singh, Shyam (2000b). Irrigation and fertigation interactions in relation to Nagpur mandarin plant growth and fruit quality. Abstract of National Seminar on Hi-tech Horticulture, Bangalore, pp- 7 3 . Singh. H.P., Chadha, K.L. and Bhargava, B.S. (1990). Leaf sampling technique in acid lime (Citrus aurantifolia Swingle) for nutritional diagnosis. Indian Journal of Horticulture 47(2): 133-39. Singh, Ranvir and. Mishra, K.K (1985). Effect of varying doses of N, P. K and growth and yield of lemon. Programme Horticulture 17: 95-99. Singh, A.R., Maurya, V.N.. Pande, N.C. and Rajput, R.S. (1989). Role of potash and zinc on the biochemical parameters of kagzi lime (Citrus aurantifolia Swingle). Harayna Journal of Horticulture Science 18(1-2): 46-50. Singh. C.S.. Patiram, Ram, M. Prasad, R.N. and Chandra, A. (1997). Leaf nutrient status of fruting and non-fruiting terminals of mandarin (Citrus reticulata Blanco) orchards for diagnosis. Journal of Hill Reseerch 10(2): 158-60. Smith, P.F. (1966). Leaf analysis of citrus. Fruit Nutrition (N.F. Childers ed.), pp. 179-07. Smith, T.A. (1963). L-arginine carboxy-layse of higher plants and its relation to potassium nutrition. Phytocheni 2: 241-52. Smith, T.A. (1965). N-carbamylputrescine amidohydrolase of higher plants and its relation to potassium nutrition. Phytochein 4: 599-07. Smith, TA. (1970). Putrescine. spermidine and spermine in higher plants. Phytochemn. 9: 1479-86. Southwick, S.M. and Davenport, T.L. (1986). Characterization of water stress and low temperature effects on flower induction in citrus. Plant Physiology 81: 26-29. Srivastava, A.K. (199 9a). Soil suitability in citrus. Citriculture. (Shyam Singh, edited), National Research Centre for Citrus, Nagpur. Maharashtra, pp. 108- 19 Poa.siu, NuritionlManagement for Yield and Quality of Citrus in India 317

Srivastava, A.K. (1999b). Citrus nutrition. Citriculture. (Shyam Singh, ed), National Research Centre for Citrus. Nagpur, Maharashtra, pp. 183-93 Srivastava, A.K. (2001a).Citrus Nutrition Citrus (Shyam Singh and S.A.M.H. Naqui, ed.) International book Distributing Company, Lucknow, UP.. pp. 187-00 Srivastava, A.K. (2001b). Soil suitability for Citrus. Citrus (Shyam Singh and S.A.M. H.Naqui, ed.) International book Distributing Company, Lucknow, U.P., pp. 101-118 Srivastava, K.C. and Bopaiah, M.G. (1978): Prospectus of growing kinnow mandarin in the southern states. Punjab Horticulture Journal 18: 139-41. Srivastava. A.K., Huchche, A.D., Kohli, R.R., Ram Lallan and Dass, H.C. 9 97 (1 a). Identification of nutritional problems of Nagpur mandarin orchards of Central India. National Symposium on Citriculture, National Research Centre for Citrus, Nagpur, November 17-19, 1997, Abstract. pp. 23-4 Srivastava, A.K.. Huchche, A.D., Ram Lallan and Singh. Shyam (1999a). Critical leaf nutrients limit in relation to productivity of Citrus reticulata Blanco, cultivars Nagpur mandarin. International Symposium on Citriculture. Nagpur, November 23-27, 1999. Abstract p. 71 Srivastava. A.K.. Huchche. A.D.. Rain Lallan and Singh Shyam (2000a). Leaf nutrient diagnostic for optimum yield of Citrus reticulata Blanco cultivar Nagpur mandarin. IXth Congress of International Society of Citriculture, scheduled December 3-7, 2000 at Orlando, USA. Srivastava, A.K., Huchche. A.D., Ram Lallan and Singh, Shyam (2000b). Leaf nutrient diagnostic for optimum yield of Citrus reticulata Blanco cultivar Nagpur mandarin. 1Xth Congress of International Society of Citriculture, scheduled December 3-7, 2000 at Orlando, USA. Srivastava, A.K., Huchche, A.D., Lallan Ram and Shyam Singh (2001a) Pre- and post-harvest response of Nagpur mandarin (Citrus reticulata Blanco) to K fertilization in Typic Haplustert. Journal of Potash Research (Accepted). Srivastava. A.K. and Kohli, R.R. (1997b). Soil and climate adaptability of citrus cultivars in India. National Seminar on Orchard Management for Sustainable Production of Tropical Fruits, March 10-11, 1997, Patna, Bihar, Abstract, pp. 19 Srivastava, A.K. and Kohli, R.R. (1997c). Soil suitability criteria for citrus - An appraisal. Agricultural Reviews 18(3): 134-46. Srivastava. A.K. and Kohli, R.R. (1999). Agro-ecological approach for land use planning of citrus. Agricultural Reviews 20(l): 41-47 Srivastava, A.K., Kohli, R.R., Dass, H.C. and Ram Lallan (1993). Physico- chemical properties and fertility status of mandarin growing soils. National Seminar on Developments in Soil Science, Indian Society of Soil Science, New Delhi, Central Soil and Water Conservation Research and Training Institute, Dehradun, U.P., October 6-10, 1993 318 A.K. Srivastava and Shyarn Singh

Srivastava, A.K., Kohli, R.R., Dass, H.C., Ram Lallan and Huchche, A.D. (1995). Relationship of leaf K with N status of mandarin orchards. Indian Journal of Horticulture 52(1): 234-38. Srivastava, A.K., Kohli, R.R., Dass, H.C., Huchche, A.D. and Ram Lallan (1996). Foliar sampling technique in Nagpur mandarin (Citrus reticulata Blanco). 8th Congress of International Society of Citriculture Nelspruit, South Africa May 15-18, 1996 Ram Srivastava, A.K., Kohli, R.R., Dass, H.C., Huchche, A.D. and Lallan (1997a). Evaluation of the nutritional status of Nagpur mandarin (Citrus reticulata Blanco) by foliar sampling. Tropical Agriculture, (Trinidad) 75(l): 1-12. Srivastava, A.K., Kohli, R.R. and Huchche, A.D. (1997b). Relationship between leaf K and soil K forms at critical growth stages of Nagpur mandarin (Citrus reticulata Blanco). Journal of Indian Society of Soil Science 46(2): 245-48. Srivastava, A.K., Kohli, R.R. and Huchche, A.D. (1997c). Dynamics of potassium use and its fertilisation response on quality of Nagpur mandarin (Citrus reticulata Blanco). International Symposium on Tropical Crops Res. and Development, Kerala Agricultural University, September 9-13, 1997, Abstract Srivastava A.K., Ram Lallan, Huchche A.D., Kohli R.R. and Dass H.C. (1994). Standardisation of leaf sampling technique in Nagpur mandarin under sub- humid tropical climate. Indian Journal of Horticulture 51(1): 32-36. Srivastava A.K, Shirgure P.S. and Singh Shyam (1999b). Citrus soils - their nature and properties. Intensive Agriculture 37(13-14): 28-31. Srivastava, A.K., Shirgure, P.S. and Singh Shyam (1999c). Integrated management of nutrient and water in Nagpur mandarin (Citrus reticulata Blanco) through drip irrigation system. Annual Report (1998-99), National Research Centre for Citrus, Nagpur, Maharashtra, pp. 45-49. Srivastava, A.K., Shirgure, P.S. and Singh Shyam (2001b). Integrated management of nutrient and water in Nagpur mandarin (Citrus reticulata Blanco) through drip irrigation system. Final Report (1998-2001), National Research Centre for Citrus, Nagpur, Maharashtra, pp. 1-14. Srivastava, A.K., Shirgure, P.S. and Singh Shyam (2000a). Integrated management of nutrient and water in Nagpur mandarin (Citrus reticulata Blanco) through drip irrigation system. Annual Report (1999-2000), National Research Centre for Citrus, Nagpur, Maharashtra, pp. 42-48. Srivastava, A.K. and Singh Shyam (1997a). Soil fertility constraints of citrus orchards in India and their management. Abstract Symposium on Soil Fertility and Environment, Allahabad University, Allahabad, December 18-20, 1997. Srivastava. A.K. and Singh, Shyam (1998a). Fertilizer use efficiency in citrus. National Research Centre for Citrus, Nagpur, Maharashtra, pp. 1-66 Srivastava, A.K. and Singh, Shyam (1998b). Leaf and soil sampling techniques Potassium Nutrition Management for Yield and Quality of Citrus in India 319

in Nagpur mandarin and acid lime, Extension Folder, National Research Centre for Citrus, Nagpur, Maharashtra, pp. 1-4 Srivastava, A.K. and Singh, Shyam (1999a). Potassium Nutrition in Citrus. National Research Centre for Citrus, Nagpur, Maharashtra, pp. 1-114. Srivastava, A.K. and Singh, Shyam (1999b). Soil suitability-crop response relationship to Nagpur mandarin. International Symposium on Citriculture, Nagpur, November 23-27, 1999, Abstract pp. 40 Srivastava, A.K. and Singh, Shyam (2000a). Soil suitability criteria for evaluating the optimum productivity of Citrus reticulata Blanco, cultivar Nagpur mandarin. lXth Congress of InternationalSociety of Citriculture, December 3-7, 2000, Orlando, USA, pp. 139-140 Srivastava, A.K. and Singh, Shyam (2000b). Identification of suitable soils for optimum productivity of Nagpur mandarin (Citrus reticulata Blanco). Adhoc Final Project Report, ICAR, New Delhi, pp. 1-108 Srivastava, A.K. and Singh, Shyam (2000c). Calcium nutrition in Nagpur mandarin (Citrus reticulata Blanco) in black clay soil types. National Seminar on Developments in Soil Science - 2000. 65th Annual Convention, Indian Society of Soil Science, New Delhi, December 27-30, 2000, Abstract pp. 80 Srivastava, A.K. and Singh, Shyam (2000d). Soil fertility evaluation of Nagpur mandarin orchards in central India. National Seminar on Agriculture Scenario: Challenges and Opportunities, November 11-12, 2000, Gwalior (M.P.), Extended Summaries, pp. 31-32 Srivastava, A.K. and Singh, Shyam (2001a). Free CaCO 3 content influencing yield and quality of Nagpur mandarin (Citrus reticulata Blanco). Journal of Indian Society of Soil Science 49(1) Srivastava, A.K and Shyam Singh. (2001b). Development of optimum soil pro[perty limit in relation to fruit yield and quality of Cirus reticulataBlanco, cv Nagpur mandarin Tropical Agriculture (Accepted) Srivastava, A.K. and Shyam Singh (2001c). Soil fertility limit in relation to optimum yield of Nagpur mandarin (Citrus reticulata Blanco) Journal of Indian Society of Soil Science (Accepted) Srivastava A.K., Singh Shyam, Huchche, A.D. and Ram Lallan (2000). Yield based leaf and soil test interpretation for Nagpur mandarin in Central India. Commun. Soil Science & Plant Analogy 42 (3&4) Srivastava, A.K., Singh Shyam, Huchche, A.D. and Ram Lallan (1999b). New leaf nutrient norms for sustained productivity of Citrus reticulata Blanco cultivar Nagpur mandarin. International Conference on Managing Natural Resources for Sustainable Agricultural Production in the 21st Century, New Delhi, February 14-18, 2000, Abstract Steyn, W.J.A. (1959). Leaf analysis: Errors involved in the preparative phase Journal of Agricultre and Food Chemistry 7: 344. 320 A.K. Srivastava and Shva Singh

Steyn, W.J.A. (1961). The errors involved in sampling of citrus and pineapple plants for leaf analysis purpose. Plant Analysis and Fertilizer Problems. 3: 409-30. Supriya, Langthasa and Bhattacharya, R.K. (1995). NPK contents of Assam lemon leaf as affected by foliar zinc sprays. Annals of Agricultural Research 16(4): 493-94. Tandon, H.L.S. (1987). Fertilizer recommendations for Horticulture Crops in India. - A Guide Book. Fertilizer Development and Consultation Organization C-l10, Greater Kailash, New Delhi, India. Trolldenier, G. (1987). Rhizosphere organisms - potassium interactions with emphasis on methodology. Proceedings of 20th Colloquium International Potash Institute, Baden bei Wein/austria. pp. 283-97. Tucker, D.P.H., Davis, R.M., Wheton, T.A. and Futch, S.H. (1990). A nutritional survey of south central, south west and east coast flatwoods citrus groves. Proceedings of Flordia State Horticulture Society 103: 324-27. Upadhyay, R.C. and Patiram (1996). Nutrient status of mandarin orange (Citrus reticulata Blanco) in Sikkim. Journal of Hill Research 9(2): 375-79. Ulrich, A. (1948). Plant analysis-methods and interpretation of results. (H.B. Kitchen ed.), Diagnostic techniques for soils and crops. Annals of Potash Institute, Washington, USA, pp. 157-98. Ulrich, A. (1952). Physiological basis for assessing the nutritional requirements of plants. American Revision of Plant Physiology 3: 207-28. Vaile, R.S. (1922). Fertilizer experiments with citrus trees. California Agricultural Experiment Station Bulletin. 345. Vandercook, C.E., Price, R.L. and Harrington, C.A. (1975). Multiple automated analysis for orange juice content: Determination of total sugars, reducing sugars, total acidity, total amino acids and phenolics. Journal of Association of Officials Anal. Chemistry. 58: 482-87. Wallace, A. (1990). Nitrogen,phosphorus, potassium interactions on Valencia orange yields. Journal of Plant Nutrition 13(3-4): 357-65. Yin, Ke Lin, Li, Yin Guo, Wang, Cheng Qiu and Wnag, Shu Liang (1998). Specifically prescribed fertilization for citrus trees and the principle component of analysis of foliar Fe and Zn and other nutrient elements. Southwest Agricultural University. 20(3): 1989-92. Zekri, M. (1995). Nutritional deficiencies in citrus trees: nitrogen, phosphorus and potassium. Citrus Indus. 8: 58-60. Influence of Potassium in Balanced Fertilization on the Yield and Quality of Vegetable Crops

PRITAM K. SHARMA, S.P. DIXIT, S.K. BHARDWAJ AND S.K. SHARMA* Department of Soil Science CSK Himachal Pradesh Agricultural University Palanpur-176062, Himachal Pradesh, India

ABSTRACT

The current review highlights the role of potassium in balanced fertilization; particularly in respect of, productivity and quality parameters in summer vegetable crops (tomato, capsicum, frenchbeans, pointed guard, colocacia and turmeric) and in winter vegetable crops, (Chinese mustard, radish, pea, onion, garlic, cabbage, cauliflower, potato and sweat potato) that are, currently, being sown in different agro-ecosystems of India. By and large, these crops require potassium application ranging from 20-80 kg K 20 ha-' from external sources particularly on soils with coarse texture having low cation exchange capacity, low organic matter content and originating from parent materials other than llite and muscovite kind of minerals. Furthermore, the various aspects of vegetable crops that have been found to improve following potassium application, are: productivity per unit area, quality and thereby; the economic aspects leading to better marketability.

However, there are certain crops in summer season category such as coriander, methi, spinach and drumsticks whereas among winter category - turnip and carrot which have so much nutritional value for human consumption yet there exists a wide information gap on the role of potassium in upgrading the productivity and quality parameters of these crops in different parts of the country in varied soil climatic situations.

Also, the studies on other management skills such as the integrated use of inorganic sources of K with organics; use of amendments and mulching either individually or collectively in upgrading the productivity and quality of vegetable crops, on a sustainable basis, have not been carried out through long term experiments; which needs further research appraisals. Likewise, such studies involving of the use of potassium on quality seed production of vegetable system are also needed.

-Department of Vegetable Sciences. Y.S. Pormar University of Horticulture and Forestry. Nauni, Solan. HP, India 321 322 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and S.K. Sharma

INTRODUCTION

Potassium plays many essential roles in vegetable crops such as an activator of a number of enzymes associated with energy metabolism, nitrate reduction and sugar degradation; besides regulating the opening and closing of stomatas in leaves and uptake of water by root cells. Its participation in photosynthesis, protein syntheses, starch synthesis and translocation of sugars, is well known. All vegetable crops including root crops respond adequately to potassium, which significantly improves their quality, thereby, marketability. By and large, it has a balancing influence on the combined effects of phosphorus and nitrogen besides offering resistance to diseases and lodging in vegetable systems.

The current review details the role of potassium in different facets such as productivity and quality of vegetable systems being raised in different eco- systems under varied soil-climatic situations, in India.

TOMATO

The potassium nutrition work on tomato has been reported from many parts of the world. For example, Singh and Verma (1991) reported that potassium exhibited pronounced effect in improving the vegetative growth of tomato plant and that height and number of branches per plant with increasing levels of potassium upto 120 kg/ha (Table 1). Application of 120 kg potassium per hectare proved to be the best in this regard. However, higher dose (160 kg/ha) had slightly reducing effect on the lesser number of days required for first picking with increasing level of potassium. The early harvest might be due to earlier fruit set and development of lycopene pigment in the presence of balanced dose of potassium. They also reported that number and weight of marketable fruits per plant and average weight of fruit, significantly, increased with the addition of potassium upto 80 kg/ha and beyond this level, the difference was non- significant. Number of branches, total number of fruits and weight of fruit/plant were increased with the application of 120 kg K20/ha, which ultimately, contributed towards increase in yield/plant.

Sharma (1992) reported that tomato responded to K application fairly adequately and that the highest 1000 seed weight, germination percentage and seed yield per plant in case of tomato, were obtained significantly at 30 kg K20/ ha in the presence of 120 kg N and 60 kg P20/ha (Table 2).

Nandal et al. (1998) demonstrated that potassium application influenced the plant height and that the maximum height was recorded with 80 kg K2 0/ha (Table 3). The number of branches per plant was not influenced by K application and that higher dose of K increased the fresh and dry weight of plant significantly during both the years. The application of potassium also upgraded the translocation of photosynthates in the plant resulting in better growth (Table 4). They further Table 1. Effect of potassium on height, number of branches, days taken to picking, number and weight of marketable fruit and average fruit weight Treatments Height of plant Number of Days taken to Number of Weight of Average (cm) branches first picking marketable marketable fruit per plant fruits/plant fruits/plant (g) weight (g) 86-87 87-88 86-87 87-88 86-87 87-88 86-87 87-88 86-87 87-88 86-87 87-88

Potassium (kg/ha) 40 82.04 80.52 10.55 9.95 77.36 78.06 22.0 21.8 814 774 38.86 35.47 80 86.97 86.98 13.99 12.62 75.82 75.94 24.0 23.6 945 903 39.31 38.16 120 88.75 90.05 15.30 13.48 73.24 74.71 24.0 23.7 955 911 39.61 38.61 160 87.81 89.69 13.94 12.20 72.51 73.12 23.0 21.9 896 862 38.75 39.24 LSD (0.05) 2.40 2.45 1.02 0.90 2.76 2.54 0.9 0.5 52 11 1.31 1.82 , Singh and Verma (1991) 324 Pritan K. Sharna. S.P. Dixit. S.K. Bhanlw'aj and S.K. Sharia

Table 2., Effect of different levels of K on 1000 seed weight. germination percentage and seed yield per plant of tottato Treatments 1000 seed Germination Seed yield weight (g) percentage per plant (g) 1989 1990 Pooled 1989 1990 Pooled 1989 1990 Pooled Potassium levels (kg/ha) 30 3.8 2.9 3.4 96.7 94.0 95.6 4.6 4.1 4.3 60 3.3 2.5 2.9 94.0 90.5 92.2 3.8 3.8 3.8 LSD(0.05) 0.3 0.3 0.3 2.6 2.5 2.3 0.8 0.3 0.5 Sharma (1992)

Table 3. Effect of potassium on the growth of tomato Treatments Plant height Branches Fresh weight Dry weight (cm) per plant (g/plant) (g/plant) 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 Potassium levels (KO kg/ha) 0 58.0 68.0 11.1 10.8 434 480 155.0 170.9 40 67.1 73.6 11.8 11.2 504 537 167.6 180.0 80 80.3 79.9 11.1 11.7 550 631 175.9 194.3 120 73.8 78.5 11.4 11.5 590 654 183.1 205.0 LSD 0.05 0.7 1.7 NS NS 2 2 2.1 6.0 Nandal et al. (1998) said that the total yield increased significantly upto 80 kg KO/ha during both the years (Table 4). Likewise, the weight of fruits and early yield increased significantly upto 80 kg K20/ha.

In so far as quality parameters of tomato were concerned, it was demonstrated (Table 5) that ascorbic acid, total soluble solids, reducing and non-reducing sugars were significantly improved with increasing levels of K upto 80 kg K,O/ ha. Potassium, also, improved the colour of fruits but its application beyond 80 kg KO/ha deteriorated the quality of fruits by increasing the content of seed bocules in the fruits.

In another study, Sharma (1995) reported that the days to 50% flowering, height, number of branches per plant, number of fruits per plant, weight of fruit per plant, fruit yield, seed yield per plant and total seed yield were significantly got upgraded when K rates ranged from 30 to 60 kg K,O/ha but 30 kg/ha was found adequate as compared to 60 kg K20 ha - ' (Table 6). 'rable 4. Effect of potassiutn on the flowering and yield of tomato Treatments Days taken to Days taken to No. of flower No. of fruits Wt. of fruits Early yield Total yield 50% flowering 50% fruiting per truss per plant (g/plant) (q/ha) (q/ha) 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 " Potassium levels (kg K 20/ha) 0 53.3 55.5 59.7 62.3 3.9 4.8 27.5 584.0 597.0 73.2 67.5 174.3 181.2 190.2 40 53.2 55.3 59.9 62.1 4.1 5.0 34.5 29.1 687.0 706.0 79.9 75.1 193.0 201.3 80 53.0 54.9 59.5 61.3 4.2 5.1 38.9 31.5 823.0 886.6 89.5 84.3 212.0 222.1 120 53.1 55.6 60.1 62.4 4.1 5.1 36.0 30.8 791.0 867.0 87.0 82.2 210.8 219.7 LSD 0.05 NS NS NS NS 0.0 0.2 1.4 NS 30.0 40.0 3.4 4.2 10.4 7.3 Nandal et al. (1998)

em Table 5. Effect of potash on quality of tomato fruits Treatments Seed Boculs/fruit Ascorbic acid Total soluble Lycopene Reducing Non-reducing content (mg/1l00 g solids content sugar sugar (g/kg fruit) fruit) (%) (kg/g fruit) (g/100 g fruit) (g/100 g fruit) . 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91

Potassium levels (kg K20/ha) 0 4.5 4.5 4.7 4.3 22.2 20.5 5.0 4.9 208.1 203.9 2.4 2.5 1.1 1.1 40 4.8 4.7 4.9 4.5 23.0 21.7 5.1 5.1 212.1 206.3 2.6 2.6 1.2 1.2 80 5.1 5.9 5.1 4.7 24.2 22.7 5.3 5.3 214.7 208.3 2.7 2.7 1.3 1.3 - 120 5.0 5.0 5.0 4.6 23.9 22.4 5.4 5.3 214.7 208.3 2.7 2.8 1.3 1.3 3.3 NS 0.2 NS NS t LSD 0.05 0.1 0.1 0.1 NS 0.7 0.9 0.2 NS 1.4 Nandal et al. (1998) Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 327

Table 6. Effect of levels of potassium on certain growth characters related to seed production of tomato (Pooled data for 1989 and 1990) Treatments Days to Height No. of No. of Weight Fruit Seed Seed 50% of )ranches fruits/ of fruit/ yield yield/ yield flower- plant plant plant plant (q/ha) plant (kg/ha) ing (cm) (g) (g)

K2 0 (kg/ha) 30 36.6 213 9.6 10.4 772 255 4.7 172 60 35.8 199 8.5 9.4 723 237 4.1 147 LSD 0.05 NS 11 0.4 0.7 47 15 0.5 16 Sharma (1995)

Recently, a study by Singh et al. (2000), demonstrated that number of marketable fruits per plant and average fruit weight were, significantly, improved - by potassium application @ 150 kg K20 ha ' in almost all the eight varieties of tomatoes (Table 7) and that there was no significant differences between 150 and 187.5 kg K20 application rates in so far as these characteristics were concerned; in the sandy loam soils of Kandaghat (H.P.), India. Perhaps, kinds of varieties involved and the type of soils studied, responded differently to K application in two sets of studies.

Pujor and Marard (1997) studied the effects of K deficiency on hydroponically grown tomato at the early production stage (23 leaves, 3 trusses). Two types of K deficiency were applied; the permanent deficiency lasted for 23 days whereas the 10 days temporary deficiency was followed by a 7 days period of potassium supply resumption. Growth was assessed through non destructive measurement; permanent K deficiency resulted in growth, slowed down before visual symptoms appeared on the adult leaves (leaves 12-17), but the older leaves (next to the 1st truss), were not affected. Temporary K deficiency reduced the growth rate but after K supply resumption, the plants recovered a growth pattern, which was, similar to that of the control plants. The K of the older leaves appeared to be less mobilizable then that present in the adult leaves where the visual deficiency symptoms appeared.

In tomato plants, which had been temporarily deprived of K before being referred onto a standard nutrient solution, K uptake was faster than in the control plants. This result was found to be related to the plant's ability to recover a normal growth pattern.

Chen and Gableman (1995) evaluated one hundred tomato strains, representing widely diverse geographic areas, in a sandy zeolite culture medium for their response to both low (0.25 mm) and adequate (1.0 mm) K levels. Three types of strains deficient in K acquisitions were classified: (1) efficient strains Table 7. Effect of nitrogen, phosphorus and potassium levels on marketable fruit size and yield per plant of tomato hybrids (pooled over 2 years) Hybrid Average fruit weight (g) Number of marketable fruits per plant

Level (N:P,0 5:K,O, kg ha_) Level (N:P 205:K20. kg ha.,) D4 D, D2 D3 D4 Mean D, D 2 D 3 Mean

Meenakashi 373.7 396.7 473.9 470.2 428.6 1.50 1.57 1.78 1.77 1.66 Manisha 415.6 504.3 497.4 386.8 446.5 1.62 1.86 1.79 1.54 1.71 Menka 393.9 472.0 560.7 452.2 469.7 1.53 1.77 2.01 1.72 1.77 Solan Sagun 323.3 375.1 490.1 460.0 412.2 1.37 1.51 1.82 1.74 1.61 FT-5xEC-174023 237.0 225.3 250.5 311.1 256.0 1.14 1.11 1.18 1.34 1.19 EC-174023xEC-174041 261.2 311.2 298.8 278.5 287.4 .1.20 1.34 1.31 1.25 1.27 Rachna 78.3 133.0 116.0 105.4 108.2 0.71 0.86 0.81 0.79 0.79 Naveen (check) 285.9 409.0 332.0 355.4 345.6 1.27 1.60 1.39 1.46 1.43 Mean 296.1 353.3 375.2 352.5 1.29 1.45 1.51 1.45 CD at 5% 27.5 0.07 Hybrid (H) 19.5 0.05 H x L 55.0 0.15 Singh et al. (2000) 75 Level of N, P,0 5 K20 (kg ha-') : DI-100: :55; D2-150:112.5:82.5; D3-200:150:110: D4-250:187.5:137.5 Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 329

characterized by their ability to acquire K under low-K status with dry matter accumulations comparable to the strains grown under adequate-K supply, (2) inefficient strains that grew well under adequate-K supply but with a low capacity to acquire K at low-K stress and correspondingly with lesser dry weight production, and (3) slowly growing strains featured by low-K content in tissue and low dry matter accumulation irrespective of external K levels. The efficient slowly growing strains came mostly from south-central America, where tomato origin was domesticated. The strains from other regions, however, mostly showed inefficiency in K acquisition. Two distinct features associated with the efficiency of K acquisition were identified. One was the proliferation of root length and another was higher net K-influx rate per unit root length under low-K stress. One result suggested that mechanisms for efficient acquisition of nutrients were lost during the cultivation of plants and centres of plant origin and domestication contain valuable genetic resources for improving plant efficiency in nutrient acquisition.

Capsicum

During the field experimentation studies (1991 and 1992) on capsicum in the soils from Kandaghat (H.P.), Sharma (1995) maintained three levels of K 50, 100 and 150 kg K20 ha-', and demonstrated (Table 8 and 9) that the effect of K on days to 50% flowering was non-significant in both the years. The fruit and seed yield per plant as well as per hectare were recorded highest at 100 kg K20/ ha whereas 1000 seed weight and germination percentage were recorded highest at 150 kg K20/ha.

Table 8. Effect of potassium on seed production of capsicum Treatment Days to 50% Plant height Number of Number of (kg/ha) flowering (cm) branches/plant fruits/ plant 1991 1992 1991 1992 1991 1992 1991 1992 Potassium levels 50 50.22 57.44 68.86 63.24 5.44 5.08 4.30 3.72 100 51.00 58.33 75.97 71.15 6.42 7.53 6.50 6.10 150 49.44 58.00 69.65 65.42 6.31 5.73 4.90 4.16 LSD 0.05 NS NS 8.97 3.99 0.86 1.19 2.26 0.74 Sharma (1995)

The interaction effect of potassium x phosphorus on fruit yield, seed yield, plant height, number of branches and fruits/plant were also studied (Table 10) and the maximum values with respect to these characters, were obtained at a combination of 100 kg K20 and 75 kg P2O5Tha. Table 9. Effect of potassium on seed production of capsicum Treatment Fruit yield/ Fruit yield Seed yield/ Seed yield/ 1000 seed Germin- (kg/ha) plant (g) (t/ha) plant (g) ha (kg) wt. (g) ation (%) 1991 1992 1991 1992 1991 1992 1991 1992 1992 1992 Potassium levels 50 338.40 278.46 12.5 9.3 3.199 2.498 118.50 83.27 5.859 96.88 100 510.00 694.68 19.0 23.6 5.598 5.387 207.00 179.60 5.884 98.11 150 412.70 525.71 15.3 17.5 4.321 3.173 160.00 105.74 6.531 98.11 LSD 0.05 170.81 68.08 6.33 2.27 2.339 1.701 86.70 56.72 0.502 0.60 Sharma (1995) Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 331

Table 10. Effect of interaction between phosphorus and potassium on seed production of capsicum Treatments* Plant height Number of Number of 1000 Germi- (cm) branches/plant fruits/plant seed nation wt (g) (%) 1991 1992 1991 1992 1991 1992 1992 1992 P, K, 71.40 66.40 5.46 6.30 5.06 5.13 6.667 99.08 K2 86.40 74.06 6.86 9.60 10.00 9.47 6.150 97.66 K 3 82.40 72.20 6.60 6.73 5.03 5.47 6.236 98.66 P2 K 67.80 62.80 5.60 4.86 4.50 3.90 5.406 96.00 K2 71.10 69.93 6.26 7.00 4.60 5.40 6.030 97.66 K3 68.60 65.66 5.60 6.06 4.40 4.00 6.721 98.66 P 3 K, 67.30 57.83 5.26 4.10 3.20 2.13 5.504 65.66 K2 70.40 69.46 6.13 6.00 4.60 3.33 5.472 96.00 K 3 58.50 58.40 6.73 4.40 5.40 3.00 6.637 97.00 LSD 0.05 15.50 6.91 1.49 2.07 3.92 1.29 0.871 1.05 Sharma (1995)

*K1, K2 and K 3 are 50, 10 and 150 kg K/ha respectively

French bean

Diwedi et al. (1995) studied the effect of phosphorus and potassium fertilization on seed yield of French bean. They observed that variety Arka Komal significantly gave higher seed yield than contender mainly due to superiority in pods/plant and seed/pod (Table 11). Both varieties responded upto 50 kg K20/ha for seed yields.

Table 11. Effect of potassium application on the yield parameters of french bean (Phaseolus vulgaris, L.) (Average 1992-93 and 1993-94) Treatment Pods/plant Seed/pod Seed yield (q/ha)

K20 (kg/ha) 25 16.1 3.17 14.40 50 17.7 3.28 18.20 75 18.3 3.30 18.81 LSD 0.05 0.9 0.19 0.74 Diwedi et al. (1995)

In another experiment, Kohli et al. (1991) studied the effect of phosphorus and potassium fertilization on seed crop of french bean cultivars SVM-I and Kentucky wonder and the results revealed that the seed yield increased 332 Pritam K. Sharma. S.P. Dixit, S.K. Bhardwaj and S.K. Sharma significantly in both the cultivars during both the years under the fertilizer levels heavier 100 seed weight Plo0 K25 (Table 12). The same combination registered and better seed vigour of harvested seed. However, the fertilizers doses did not reveal consistent response towards shelling percentage and seed germination percentage over the two years.

Table 12. Effect of phosphorus and potassium fertilization on seed yield of french bean (varieties SVM-1 and Kentucky wonder) Fertility Seed yield (kg/plot of 2 x 2 m) Seed levels 1986 1987 yield (kg ha-') SVM-I Kentucky Mean SVM-I Kentucky Mean (q/ha) wonder wonder 0.95 0.75 0.85 18.65 P50 K25 0.73 0.56 0.64 0.94 0.72 0.83 18.30 P50 K50 0.74 0.53 0.64 0.62 0.92 0.72 0.82 18.03 P50 K 7 5 0.72 0.52 0.91 1.04 23.65 P10o K25 0.98 0.73 0.85 1.48 1.11 0.87 0.98 22.15 P100 K50 0.90 0.69 0.79 1.12 0.85 0.98 22.10 P100 K 7 5 0.92 0.66 0.79 0.70 0.81 17.83 P150 K25 0.73 0.51 0.62 0.92 0.85 0.70 0.77 16.93 P150 K50 0.66 0.51 0.58 0.84 0.67 0.75 16.35 P150 K 7 5 0.65 0.47 0.56 LSD Fertility 0.03 0.02 Cultivar 0.05 0.06 Fert. x cultivar NS 0.03 Kohli et al. (1991)

Pointed goard

Yadav et al. (1993) conducted experiments on this crop at experimental field of Horticultural Experiment and Training Centre, Basti, India during 1989- 90 on a sandy loam soil having pH 7.4, organic carbon 0.43% and available K, 242 kg/ha. The application of K tended to increase the size but the results were non-significant (Table 13). The increasing level of K ranging from 40-80 kg/ha brought a significant improvement in total soluble solids and specific gravity of the crop (Table 14). Increasing levels of K increased the vitamin C content of the fruits but it was non-significant. As is indicated in Table 13, K application @ 80 kg/ha increased the yield to 96.7 and 97.4 q/ha from 92.3 and 92.9 where 40 kg K was applied during 1989-90 and 1990-91, respectively. Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 333

Table 13. Effect of K on different growth parametersand yield of pointed gourd K levels Fruit Fruit No. of Weight of Yield (kg/ha) length diameter fruits/plant fruits/plant (t/ha) (cm) (cm) 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 89-90 90-91 40 5.51 5.80 3.00 3.07 81.00 91.00 2.07 2.17 9.3 9.3 80 5.61 5.86 3.05 3.14 86.00 96.00 2.17 2.29 9.7 9.7 LSD 0.05 0.08 0.05 NS NS 1.28 3.21 0.06 NS 0.08 0.15 Yadav et al. (1993)

Table 14. Effect of potassium on quality of pointed gourd Potassium levels Total soluble Specific Vitamin C (kg/ha) solids (%) gravitiy content (mg/100g) 1989-90 1990-91 1989-90 1990-91 1989-90 1990-91 40 4.06 3.99 0.77 0.78 30.12 30.38 80 4.17 4.15 0.78 0.78 30.56 30.50 CD at 5% 0.21 0.10 NS NS NS NS Yadav et al. (1993

Colocacia

Mandal et al. (1982) studied the effect of potassium on early maturing and high yielding variety of Colocasia V-14 and reported that rhizome production increased with increasing levels of potash upto 120 kg/ha (Table 15) and that the optimum level of K was 144 kg K20/ha for realizing better productivity of crop. The dry matter and carbohydrate percentage increased upto 40 kg K20/ha and eventually, it decreased in this content (Table 15). The crude protein percentage and oxalate percentage was 5.82 and 0.17 at 0 K level and it was 5.65 and 0.15 per cent at 160 kg K20/ha, respectively.

Table 15. Rhizome yield and quality constituents of colocasia as affected by different levels of K K levels Mean tuber % (kg K20/ha) yield (t/ha) DM CHO Crude protein Oxalate 0 19.8 31.4 20.6 5.82 0.17 40 21.6 32.4 20.8 5.56 0.16 80 22.5 30.6 18.4 5.65 0.16 120 24.6 31.2 18.4 5.42 0.16 160 24.5 31.6 19.4 5.65 0.15 CD at 5% 2.0 - Mandal et al. (1982) 334 Pritam K. Sharma. S.P. Didi, S.K. Bhardwaj and S.K. Sharma

WINTER VEGETABLE CROPS

Potato

Uppal et al. (1997) reported that potassium application had a significant effect on total and large sized tuber yield. They also reported that whole dose of K applied at flowering was more effective than split application of K as top dressing or foliar spray (Table 16). They further observed that specific gravity of tuber chip yield, total solids, TSS, reducing sugars, starch and protein content for chip making were better. However, chip colour and score were not affected considerably with K application @ 150 kg K2O/ha over control (Table 17).

Table 16. Effect of potassium application on potato yield (Mean of two years) Yield of potato tuber under different grades (q/ha) Treatments Large Medium Small Total yield cm) (<5->7.5 cm) (kg K20/ha) (>7.5 cm) (5-7 cm) (<5 dia dia dia dia

K, (50) 107.6 96.9 41.6 246.1 41.9 240.0 K2 (100) 94.6 103.5 59.8 238.7 K3 (150) 101.7 97.2 Control (0) 79.5 94.4 45.5 219.4 LSD (0.05) 17.9 9.0 NS 18.8 Uppal et al. (1997)

Table 17. Effect of timing of K application and withdrawal of irrigation on quality characteristics of potato tubers Treatment Total TSS Reduc- Starch Proteins Sp. Chip olour Chip yield (kg K20/ha) solids (%) ing (%) (%) gray- sugars ity Score No. (q/ha) (%)

50 23 6 0.10 71.5 9.9 1.088 65 1 77.5 100 19 6 0.10 14.0 10.1 1.081 65 1 74.3 150 19 6 0.10 15.2 9.6 1.081 65 1 76.3 Control 17.5 6.5 0.17 13.2 9.7 1.077 61 1.5 64.0 Uppal et al. (1997)

Prasad et al. (1997) studied the effect of soil moisture and potassium levels on sweet potato and reported that its yield increased significantly in the presence of mulch or a protective irrigation, compared to other treatments (Table 18) and a significant response of K was recorded upto 40 kg K2Oha. They further Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 335

reported that potassium uptake was significantly affected by K levels (Table 19) and that a significant increase in K uptake upto 60 kg P20/ha as compared to 0 and 20 kg (20/ha was also observed.

Table 18. Effect of potassium on tubers dry weight (g) per plant at different growth stages Treatments 1993-94 1994-95

(kg K2 0/ha) 60 75 90 105 120 60 75 90 105 120 0 24.5 38.0 49.8 52.9 52.9 24.9 39.9 52.7 59.2 56.7 20 25.3 39.6 54.0 55.6 55.6 28.9 40.5 59.3 60.1 61.6 40 27.0 41.5 54.4 58.3 58.5 29.6 44.6 58.1 64.1 63.7 60 27.5 42.8 54.4 59.5 59.5 29.1 45.0 58.8 64.4 64.7 80 28.1 43.6 57.0 60.4 60.4 28.8 45.8 62.5 67.5 67.5 100 27.3 42.3 55.2 59.1 59.1 29.9 44.4 58.6 65.0 64.9 CD (5%) 2.99 4.24 5.22 6.87 17.32 3.17 4.49 5.63 7.56 3.77 Prasad et al. (1997)

Table 19. Potassium uptake (kg/ha) by tuber + vines of sweet potato Treatments (kg K20/ha) 1993-94 1994-95 Mean Potassium levels 0 62.2 64.3 63.7 20 73.0 78.9 76.0 40 78.6 92.9 85.7 60 97.5 102.4 99.9 80 99.5 105.4 102.8 100 88.6 103.1 95.8 LSD 0.05 11.75 12.45 11.55 Prasad et al. (1997)

Singh (1998) reported that the highest tuber yield was obtained with the application of 120 kg K20/ha + 120 kg stockosorb/ha that maximum response of 52 kg tuber per kg K20 was at 120 kg K20/ha (Table 20).

Dubey et al. (1997) studied the effect of K on tuber yield and their storage behaviour where in they concluded that the maximum tuber yield of 31.4 t/ha was observed in treatment when K was applied @ 100 kg K20/ha. The other parameters such as number of leaflets, tubers per hill, and haulms dry yield were also higher where it was applied @ 100 kg K20/ha (Table 21). They also reported that maximum concentration and uptake of N, P and K was found in treatment where K was applied @ 100 kg K20/ha (Table 22). 336 Pritam K. Sharma, S.P. Dixi. S.K. Bhardwaj and S.K. Sharma

Table 20. Biomass, tuber yield and response of potato as influenced by different treatments Treatments Biomass Tuber yield Response (g plant- ') (t ha-') Kg tuber kg -' Kg tuber kg- ' K20 stochosorb K level (kg K20 ha-) -- KO 416.26 26.46 K60 446.63 28.26 30 - K120 493.95 32.70 52 - LSD 0.05 NS 3.32 - Stochosorb level (kg ha -1) S60 432.83 27.59 - S120 471.58 30.90 - - LSD 0.05 NS 3.36 - - K x S levels

KO S60 409.00 25.91 - 431.83 KO S120 423.50 27.02 - 225.17 K 60 S6 437.50 27.43 - 457.17 K 60 S12o 455.75 29.09 - 242.42 K120 S6 452.00 28.82 - 480.33 K120 SI2 0 535.50 36.59 - 304.92 LSD 0.05 NS 5.52 - Singh (1998)

Table 21. Effect of K application on growth, yield and storage behaviour of potato (Data pooled over two years) K level No. of No. of Tuber Haulms Spoilage % (kg K20/ha) leaflets tubers yield dry per hill at per hill (tUha) yield Numeral Weight tuberization (q/ha) stage 0 191.0 7.8 22.5 3.1 35.3 34.8 25 199.5 8.4 24.6 4.8 31.3 29.5 37 221.3 8.6 27.3 5.6 29.3 24.8 50 239.3 9.4 30.4 6.0 23.3 19.8 62 239.5 9.3 29.8 5.3 20.3 17.7 75 248.0 9.0 31.0 6.3 18.7 14.3 100 262.5 9.7 31.4 5.8 14.0 12.8 LSD 0.05 16.4 0.6 2.1 1.1 4.8 3.9 Dubey et al. (1997) Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 337

Table 22. Effect of K application on the nutrients concentration and uptake by potato (data pooled over two years) K level Tubers Haulms

(kg K20/ha) N P K N P K

Concentration (%) 0 1.75 0.15 1.81 1.79 0.13 1.69 25 1.82 0.16 1.83 1.84 0.14 1.77 37 1.86 0.16 1.85 1.88 0.16 1.81 50 1.90 0.18 1.98 1.96 0.17 1.88 62 1.92 0.19 2.00 1.96 0.17 1.88 75 1.94 0.19 2.02 1.95 0.18 1.89 100 1.97 0.20 2.04 1.98 0.19 1.91 LSD 0.05 0.03 0.01 0.05 0.03 0.01 0.04 Uptake (kg/ha) 0 78.58 6.74 81.27 55.13 4.00 51.44 25 86.65 7.88 90.15 78.02 5.94 75.05 37 101.41 8.72 100.86 94.00 8.00 90.50 50 115.51 10.93 120.27 99.96 8.67 95.88 62 114.28 11.31 119.04 101.92 8.84 97.76 75 120.40 11.79 126.36 117.32 10.80 113.40 100 123.51 12.54 127.91 107.32 10.30 103.52 LSD 0.05 5.54 1.82 6.25 8.34 1.94 10.82 Dubey et al. (1997)

Bansal and Umar (1998) conducted 10 experiments on farmers' field of Meerut, U.P., India, on a neutral soil, which had medium level of available K (65-70 ppm), the results revealed that K application as K2SO 4 resulted in a higher yield and dry matter content. The higher tuber yield was observed where 150 kg K20/ha was applied during 3 years of experimentation (Table 23). The split application of 150 kg K20/ha during 1995-96 showed significantly lower tuber yield than basal application alone. This proved futility of splitting K to a short duration crop like potato.

In variety Kufri Bahar, chips colour score was above 5 in all the K treatments during 1995-96, hence the tubers were not considered suitable for making chips. However, K application at 225 kg K20/ha, significantly, improved chips quality as indicated by a colour score of 3.2 and 4.0 during 1996-97 and 1997-98, respectively.

The economic analysis of the data revealed that the net extra profit over control at harvest was the maximum in the treatment T3, which was nearly Rs. 6500/- higher than T2 during 1995-96. 338 Pritam K. Sharma, S.P Dxit, S.K. Bhardwaj and S.K. Sharma

Table 23. Effect of K application on yield and dry matter of potato tubers Treatments Tuber yield (t/ha) Dry matter (%) (kg/ha) 1995-96 1996-67 1997-98 1995-96 1996-67 1997-98

TjNjooPiooKo 24.5 22.9 20.5 15.0 15.7 17.7 T2NjooPjooKjjo 29.9 29.4 26.8 17.2 18.1 19.5 T3NooPoK 1 5o 34.0 32.8 31.1 20.0 19.9 21.6 T4NlooK75+75 32.8 32.4 30.4 18.3 21.8 22.4 Mean 30.0 29.6 27.3 17.3 18.5 19.9 LSD 0.05 3.36 3.7 3.7 1.8 2.1 1.7

Economics of K application to potato during 1995-96 Treatments Response Net profit VCR at VCR at VCR at (kg/ha) over control (Rs/ha) harvest 2 weeks 4 weeks (t/ha)

NJ00POcoK0o 5.49 8240 5.30 5.73 7.15 N10oPooK 5 0 9.57 14819 6.12 6.66 8.33 NI00Po0K75 T5 8.44 12747 5.43 5.87 7.34 Bansal and Umar (1998) Values of tubers (Rs/kg) at harvest = 1.85; at 2 weeks 2.00 and 4 weeks = 2.50, cost of K20 (Rs/kg) = 19.17

Application of 150 kg K20/ha also proved to net highest profit during 1996- 97 and 1997-98. In terms of actual profit, 150 kg K20/ha application through SOP proved highly remunerative in potato and keeping in mind the improvement in quality characters, chips quality even at 225 kg K20/ha should be recommended to the tubers meant for processing industry.

Sharma (1992) studied the response of potato (cv. Kufri Jyoti) to potassium application in a field trial at upper Shillong and it was reported that application of K did not increase the plant height, stem height, leaf and tuber number/m 2, but increased the average weight of tubers, thereby, affecting the tuber yield (Table 24).

Sood and Grewal (1993) conducted the field experiment to evaluate the leaf-K indices for corrective potassium dose to potato at earthing up. They found positive effect of K applied at planting on K concentration in petioles whereas leaf blades showed a highly significant and positive correlation with tuber yield. They further reported that both K indices were good enough for predicting K requirement of potato at early stages for taking up corrective measurers for getting optimum potato yield in Shimla hills. Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 339

Table 24. Effect of potassium on tuber yield and potassium uptake by potato (av. data for 2 years) K (kg/ha) Tuber yield (tlha) K uptake (kg/ha) Tubers Haulms Total

0 16.7 76.4 13.0 89.4 50 22.1 94.8 17.0 111.8 100 22.8 102.4 17.2 119.6 150 22.0 101.5 18.9 120.4 200 21.9 99.4 19.0 118.4 LSD 0.05 1.6 8.7 2.2 10.4 Sharma (1992)

Lal and Sharma (1995) studied the response of potato to potassium application in mid hills of Himachal Pradesh (India) with 6 levels of K (0, 25, 50, 75, 100 and 125 kg/ha) and 2 levels of FYM (0 and 20 t/ha) and reported that the application of K increased the tuber yield, but a significant response was obtained only upto 125 kg/ha when applied in combination with FYM (Table 25).

Table 25. Effect of potassium with and without FYM on tuber yield Treatment K (kg/ha) Tuber yield (t/ha) FYM Mean 0 20

0 8.81 17.37 13.09 25 10.82 19.43 15.13 50 12.71 19.01 15.86 75 16.35 19.55 17.95 100 15.63 20.45 18.04 125 15.82 17.36 15.69 Mean 13.36 18.86 LSD 0.05 K 1.13 FYM 0.65 K x FYM 1.60 Lal and Sharma (1995)

Chinese Sarson

A field study was conducted by Sharma (1995) during the winter of 1990- 91 and 91-92 in the mountain acidic sandy loam soil in which 3 levels of potash 340 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and S.K. Sharma

30, 60 and 90 kg K20/ha; were tried in addition to other treatments in case of Chinese sarson (Table 26 and 27). It is evident that potassium nutrition could not influence the number of days taken to 50% bolting and flowering, however maximum plant height and number of branches per plant were recorded at 60 kg K20/ha which was significant over 90 kg K20/ha. Similarly, the maximum seed yield per plant, per plot and per hectare, 1000 seed weight and germination percentage was recorded at 60 kg K20/ha. The effect of interaction between P and K levels was found significant with respect to seed yield per plant and per hectare (Table 27) and the maximum values with respect to the characters were recorded at 20 kg P20 5/ha and 60 kg K20/ha which was also significant over many other treatment combination of P and K.

Table 26. Effect of potassium on seed production of Chinese sarson (Pooled data for 1990-91 and 1991-92) Treatment Days Days to Plant No. of Seed Seed 1000- Germi- (kg K20/ha) to 50% height branches yield/ yield seed nation 50% flower- (cm) per plant (q/ha) weight (%) bolting ing plant (g) (g) 30 99.49 119.21 132.28 7.35 36.89 13.66 2.95 93.88 60 99.55 118.10 135.98 8.70 43.88 16.36 3.20 95.00 90 99.31 119.10 123.99 7.23 33.90 12.55 2.80 93.72 Sed 1.15 2.40 5.23 0.59 4.29 1.58 0.16 0.73 CD at 5% NS NS 11.09 1.25 9.10 3.36 0.34 1.56 Sharma (1995)

Table 27. Effect of interaction between phosphorus and potassium levels on seed production of Chinese sarson (Pooled data for 1990-91 and 1991-92) Treatment* Seed yield per plant (g) Seed yield (q/ha) PIKI 41.73 15.40 P IK2 57.42 21.34 PIK 3 38.07 14.09 P2K 32.57 12.06 P2K2 38.78 14.37 P2K 3 35.56 13.46 P3K 36.37 13.17 P3K 2 35.15 13.01 P3K 3 28.07 10.39 SE(d) 7.43 2.75 LSD 0.05 15.77 5.84 Sharma (1995)

*Kj, K2, K3 = 30, 60 and 90 kg K20/ha P1, P2, P 3 = 20, 40 and 60 kg P 2Osha Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 341

Sharma (1997) in a study on the effect of P and K on radish seed crop, found that the effect of K application in days to 50% bolting and flowering was non-significant. Maximum plant height and number of branches/plant were recorded at 120 kg K20/ha, which was, significant over 60 kg K20/ha seed yield per plant and seed yield/ha was also recorded highest at 120 kg K20/ha and was significant over rest of K levels (Table 28). The interaction effect of P and K was significant for seed yield rate/plant as well as per hectare and maximum values with respect to these characters were obtained at treatment combination of 120 kg P20 5 and 120 kg K20/ha.

Table 28. Effect of potassium on seed production of radish (pooled data for 1993-94 and 1994-95) Treatment Plant No. of Seed yield Seed height branches per plant yield (cm) per plant (g) (q/ha)

Potassium levels (kg K20/ha) 60 118.6 8.2 18.2 7.5 120 124.6 9.2 37.4 11.3 180 121.7 8.6 26.2 9.2 LSD 0.05 1.4 0.5 1.3 0.4 Sharma (1997)

Pea

Kanaujia et al. (1997) reported that potassium had positive effect on plant height and days for maturity of peas and that the maximum values were recorded at 90 kg K20/ha (Table 29). However, no significant response was observed in case of days taken to I" flowering because of high level of K existing in the soil. The number of nodules per plant, and fresh and dry weight of nodules per plant increased with increasing levels of K and highest values were recorded at 90 kg K20/ha. A study of Table 30 showed that green pod yield was increased by K application upto 60 kg K20/ha which, may be due to either direct or indirect involvement of K in major plant processes such as photosynthesis, respiration and enzyme activation. Quality characters like shelling percentage, dry matter, protein and sugar content in green seed were significantly influenced by K level upto 60 kg K20/ha. Kanaujia et al. (1998) conducted an experiment in well drained loamy soil having neutral pH on pea and found (Table 31) that pod length, pod girth and seeds/pod were significantly increased by K level upto 60 kg K20/ha and consequently, leading to more green pod yield significantly influenced by combined application of 60 kg each of P20 5 and K20 and rhizobium inoculation gave the highest pod yield over other treatment combinations (Table 32). They revealed that N and K content in plants as well as in seeds were "a

Table 29. Effect of potassium on growth and development characters of pea cv. Lincoln Treatments Plant Days Days Number of nodules Fresh weight of nodules Dry weight of nodules (kg I 20/ha) height taken taken to per plant per plant (mg) per plant (mg) (cm) to first market- flowering able Days after sowing Days after sowing Days after sowing maturity _ 45 90 135 45 90 135 45 90 135

0 62.04 93.35 152.70 15.66 31.15 14.78 40.84 68.65 36.58 21.87 31.55 18.20 30 73.98 93.66 153.00 19.49 34.98 17.37 47.19 76.24 41.91 26.99 34.40 22.81 . 60 78.98 94.00 153.95 22.13 39.66 19.17 53.84 84.69 47.93 32.94 37.51 28.10 ~ 90 88.31- 94.68 154.65 24.64 43.75 21.46 56.82 92.63 50.23 35.39 41.62 31.58 LSD 0.05 1.29 NS 0.81 1.62 3.41 2.49 4.37 2.93 4.47 2.32 3.55 3.01 ? Kanaujia et al. (1999) Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 343

Table 30. Effect of potassium on yield and quality of pea cv. Lincoln Treatments Green Shelling Dry matter Protein Total sugar (kg K20/ha) pod yield percentage content content content (q/ha) (%) (%) (%) (M) 0 83.47 47.68 30.89 23.25 3.49 30 94.70 51.66 31.95 24.18 3.67 60 104.20 54.34 32.94 24.87 3.77 90 95.68 51.17 32.15 24.49 3.75 LSD 0.05 3.02 0.66 0.35 0.39 0.12 Kanaujia et al. (1997)

Table 31. Effect of potassium on growth and yield of pea Treatments Pod Pod Number Weight Number Green (kg K20/ha) length girth of pods/ of pods/ of seeds/ pod yield (cm) (cm) plant plant (g) pod (q/ha)

0 7.73 3.34 21.17 67.25 5.41 83.47 30 7.94 3.62 24.60 81.44 5.68 94.70 60 8.20 3.46 27.80 91.93 6.11 104.20 90 8.02 3.41 24.47 80.49 5.66 95.68 LSD 0.05 0.09 0.02 0.54 2.57 0.10 3.47 Kanaujia et al. (1998)

Table 32. Interaction effect of phosphorus,potassium and rhizobium inoculation on yield of pea (qiha)

Phosphorus (kg P20 5/ha) x Rhizobium

Treatment P0 P30 P60 P90 (kg K2/iha) RU RI R0 RI R0 RI RO RI

0 56.18 59.21 74.53 87.35 100.4 103.8 93.06 93.18 30 59.50 92.04 86.85 91.51 105.0 110.6 101.1 111.0 60 67.08 92.03 88.86 116.0 109.8 131.7 112.4 115.9 90 62.13 88.54 87.60 96.58 99.06 114.5 10.1 116.9 LSD 0.05 8.57 Kanaujia et al. (1998) higher at 90 kg K2/iha as compared to lower doses of K (Table 33). Kanaujia et al. (2000) also reported a significant increase in number of nodules/plant due to K application during 1994-95 and 1995-96 (Table 34). Table 33. Effect of potassium on NPK contents of plant and seed at maturity pea cv. Lincoln Nitrogen (%) Phosphorus (%) Potassium (%) Treatments Plant Seed Plant Seed Plant Seed--I

(kg K20/ha) 94-95 95-96 Mean 94-95 95-96 Mean 94-95 95-9 Mean 94-95 95-96 Mean 94-95 95-96 Mean 94-95 95-96 Mean

0 3.69 3.31 3.50 3.70 3.71 3.70 0.32 0.31 0.31 0.37 0.39 0.38 1.70 1.70 1.70 1.06 1.09 1.07 30 3.71 3.34 3.53 3.82 3.92 3.87 0.33 0.32 0.33 0.38 0.40 0.39 1.74 1.75 1.75 1.12 1.13 1.12 60 3.73 3.38 3.55 3.87 3.97 3.92 0.34 0.34 0.34 0.39 0.42 0.41 1.77 1.82 1.80 1.16 1.17 1.16 ~ 90 3.76 3.42 3.59 3.90 1.06 3.98 0.34 0.35 0.34 0.39 0.43 0.41 1.79 1.85 1.82 1.21 1.19 1.20

LSD 0.05 0.03 0.04 - 0.05 0.04 - NS NS - NS NS - 0.05 - 0.05 0.01 0.03 - Kanaujia et al. (1998) Q Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 345

Table 34. Effect of potassium on the number of nodules per plant of pea cv. Lincoln Treatments Number of nodules per plant (kg K20/ha) 45 DAS 90 DAS 135 DAS

1994-95 1995-96 1994-95 1995-96 1994-95 1995-96 0 15.37 15.96 31.18 31.12 12.19 17.37 30 19.28 19.71 36.24 33.73 15.60 19.15 60 22.79 21.48 40.90 38.42 17.37 20.98 90 26.02 23.27 47.03 40.48 20.10 22.83 LSD 0.05 1.35 1.89 3.37 3.45 2.66 2.32 Kanaujia et al. (2000)

Kanaujia et al. (1999) also reported that green pod yield was significantly influenced by application of P and K and rhizobium inoculation during both the years. An application of 60 kg P20 5 and K20/ha each alongwtih rhizobium inoculation gave the highest yield (12.1 and 14.2 t/ha) during 1994-95 and 95- 96 respectively (Table 35). This combination also gave maximum profit of Rs. 52,657 per hectare (Table 36). The higher levels of P and K, with and without rhizobium inoculation, showed decreasing net returns. They explained that the increase in green pod yield was probably due to active role of P and K as major nutrient in plant nutrition. Addition of these nutrients increased the rate of symbiotic N fixation and in turn, stimulated the growth of plants, thereby, having tremendous effect in giving higher yields (Table 36).

Onion

Singh and Dhankar (1989) reported that application of potash (K2 0 80 kg/ ha) alone and in combination with zinc (K20 100 kg + ZnSO 4 25 kg/ha) reduced bolting, neck thickness, increased plant growth, yield, ascorbic acid, TSS, dry matter, sugars and S content of bulbs. In a similar study, Saimbhi and Randhawa (1983) reported that out of 4 levels of K20 tested; only the levels upto 60 kg/ ha showed a significant increase in bulb weight and yield over control (Table 37). Higher levels of 90 and 120 kg/ha did not prove significantly better than 60 kg K20fha.

In another study, Singh et al. (1993) reported the use of potassium at two levels i.e. 0 and 60 kg K20fha did not affect significantly the yield and seed yield attributing characters such as plant height, number of leaves and bulb diameter.

Total yield was not affected significantly due to K application but addition of K increased the bulb yield. Singh el al. (2000) reported that the application Table 35. Interaction effect of phosphorus, potassium and rhizobiurn on the green pod yield (I ha -') of pea cv. Lincoln

Phosphorus (kg P20 5) x Rhizobium Treatment 1994-95 1995-96 P P (kg K 20 ha-') Po P30 P60 P90 PO P30 60 90 RO R, Ro R, Ro R, Ro R Ro R, R o R, Ro R, R o R,

0 5.5 5.8 7.3 8.6 9.9 10.0 8.9 8.4 5.8 6.0 7.6 8.9 10.2 10.7 9.7 10.2 30 5.4 9.2 8.8 9.0 10.0 10.7 10.0 11.0 6.5 9.2 8.5 9.0 11.0 11.4 10.2 11.2 60 6.8 9.3 8.7 12.0 10.8 12.1 11.1 11.6 6.6 9.2 9.1 11.3 11.2 14.2 11.3 11.6 90 6.0 8.6 8.7 9.1 9.1 10.4 9.5 11.3 6.4 90.73 8.8 10.3 10.7 12.5 10.6 12.1 LSD 0.05 0.9 0.81 Kanaujia et al. (1999)

Ro Without rhizobium; R = with rhizobium o - ' 2 Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 347

Table 36. Economics of the treatments Treatment Expenditure Gross income Net income (Rs ha-') (Rs ha-1) (Rs ha-' )

PoR0 Ko 37520.0 39386.0 1866.0 PoRoK30 37761.5 41650.0 3885.5 PoRoK 60 37980.5 49956.0 8975.5 PoROKgo 38199.5 43491.0 5291.5 PoR 1Ko 37842.5 41447.0 3604.5 I PoR K30 38084.0 64428.0 26344.0 POR IK60 38303.0 64421.0 26118.0 PoRIKgo 38522.0 61978.0 23456.0 P3oRoK o 38135.0 52171.0 14036.0 PzoRoK3o 38376.0 60795.0 22418.5 P3oROK 60 38595.5 62202.0 23606.5 P3oRoK9o 38814.5 61320.0 22505.5 P30RIKO 38457.5 61145.0 22687.5 R P3o IK30 38699.0 64057.0 25599.5 P3oR 1K60 38918.0 81200.0 42282.0 P3()R1Kg 39137.0 67606.0 28469.0 P6oROKo 38750.0 70280.0 31530.0 P6oR(JK3 38991.5 73500.0 34508.5 P6oRoK 6o 39210.5 76860.0 37649.5 P6oRoKqo 39429.5 69342.0 29912.5 P 6oRIKo 39072.5 72660.0 33587.5 I P60R K 30 39314.0 77420.0 38106.0 P6oR t K6o 39533.0 92190.0 52657.0 P6oR 1K go 39752.0 80150.0 40398.0 P6oRoKo 39365.0 65142.0 25777.0 P90RoK 30 39606.5 70770.0 31163.5 P9OROK6W 39825.5 78680.0 38854.5 P90RoKo 40044.5 70070.0 30025.5 PgoRKo 36687.5 65226.0 22538.5 R P9o 1K 30 39929.0 77700.0 37771.0 PgoRIK 6o 40148.0 81130.0 40982.0 P9qR IK 90 40367.0 81830.0 41462.0 Kanaujia et al. (1999) Expenditure (Rs ha-') included Rs. 37502 for fixed inputs + cost of Rhizobium @ Rs. 60/kg, cost of P20 5 @ Rs. 19.75/kg + cost of K20 @ Rs. 7.30/kg + additional labour charges as pr treatment (varied from Rs. 22.50 to 112.50). Gross income (Rs. ha - ') was calculated by yield in kg/ha (Average of two years) multiplied by Rs. 7.00 (sale rate of pods). 348 Pritam K. Sharmna, S.P. Dixit, SK. Bhardwaj and S.K. Sharma of potash @ 83 kg/ha recorded the highest weight per bulb and as a result, enhanced the bulb yield by 14.2% and 6.9% over lower levels of 41.5 and 82.5 kg K20/ha, respectively (Table 38).

Table 37. Influence of K levels on the yield and dry matter in onion K20 (kg/ha) Bulb weight TSS Dry matter Bulb yield Dry matter (g) (%) (%) (t/ha) yield (qlha) 0 45.1 12.1 11.8 17.7 20.86 30 47.4 12.0 11.7 19.9 20.30 60 48.0 12.0 11.5 21.0 24.10 90 47.9 12.0 11.7 20.5 23.98 120 47.7 12.1 11.6 20.1 23.29 LSD 0.05 2.3 NS NS 0.53 0.38 Saimbhi and Randhawa (1983)

Table 38. Response of kharif onion to K fertilization Treatments (kg K/ha) Weight per bulb (g) Bulb yield (t/ha) 41.5 43.2 9.6 62.2 46.3 10.3 83.0 49.3 11.0 LSD 0.05 0.88 0.25 Singh et al. (2000)

Singh (1998) reported that the biomass of onion, diameter of bulb and yield was significantly influenced by different treatments. The highest bulb yield of 24.67 tonnes was obtained in K3 oS,5 0. Bulb yield also increased with the application of stockosorb @ 150 kg/ha. Large size bulb of 4.79 cm was recorded

in K300So followed by K150So and K 300SI 50 (Table 39). The highest bulb weight 45.47 was recorded with the application of 300 kg K20 + 150 kg stockosorb per ha. The highest biomass of 70.53 g was observed at K30oSISo.

Garlic

Abbas et al. (1994) evaluated the effect of potassium on growth and yield of garlic, which demonstrated that garlic yield got upgraded due to an application of 60 kg K20/ha over control. A similar trend was obtained for the mean data of two years. However, during 1992-93, even 30 kg K2 0/ha was significant over control. The per cent increase in grain yield was 15.55% over control due to 60 kg K2Oha, on an average, for two years (Table 40). The plant height, clover bulb, weight of bulbs and bulb diameters also increased due to potassium application. They further reported that VCR was maximum i.e. 48.97 in 60 kg Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 349

Table 39. Biomass, bulb wt. dia of bulb, yield and response of onion as influenced by different fertiliser treatments at two irrigation levels Treatments Bioimass Bulb wt. Diameter Yield Response (g plant - ') (g) of bulb (t ha-') (kg bulb kg-' (cm) Stochosorb)

T, K150So I 51.33 35.47 4.39 14.00 T2 K150So 12 60.00 41.73 4.77 22.33 - T 3 K150 SI50 11 52.40 37.67 4.51 14.60 4.00 T4 K150 S150 12 62.27 41.60 4.64 23.27 6.26 T5 K3o0S o 11 50.60 35.07 4.23 13.27 - T 6 K 30S 0 12 67.33 44.40 4.70 23.40 - T 7 K 300SI5 0 1 56.00 37.54 4.17 14.93 11.06 T8 K300S 1 50 12 70.53 45.47 4.74 24.67 8.46 T9 KoS o 12 49.87 31.90 4.06 11.73 - LSD 0.05 13.85 9.25 0.42 4.79 Singh (1998)

Table 40. Effect of K on yield and its attributes of garlic K20 Plant Cloves/ Bulb Bulb Garlic yield kg ha-' height bulb weight diameter (t/ha) (cm) (gm) (cm) 91-92 92-93 91-92 92-93 91-92 92-93 91-92 92-93 91-92 92-93 Mean 0 24.25 20.05 25.41 18.58 12.26 11.50 10.49 9.87 9.0 7.2 8.1 30 26.50 25.16 26.92 22.58 15.83 14.08 10.90 10.88 9.4 8.1 8.7 60 27.25 26.23 29.25 24.20 16.75 15.52 11.67 11.12 10.4 8.5 9.4 90 27.25 27.34 28.67 23.50 16.92 16.25 11.25 11.50 10.5 8.8 9.6 LSD 0.05 1.93 2.71 2.54 1.70 1.23 0.92 0.58 0.98 0.94 0.81 0.88 Abbas et at. (1994)

K20/ha treated plots followed by 46.46 in case of 30 kg K20/ha treated plots. The VCR was lowest in treatment where 90 kg K20/ha was applied (Table 41).

Table 41. Economics of application of K in garlic (average of 2 years) K20 Garlic yield Response kg Cost of garlic Cost of Value/cost (kg/ha) (q/ha) bulb/kg nutrient yield (Rs/ha) fertilizer ratio VCR

0 81.35 - - - 30 87.35 20.00 12000 258.30 46.46 60 94.00 21.08 25300 516.60 48.97 90 96.26 16.57 2982 774.90 38.48 Abbas et al. (1994) Note: Cost of garlic @ 20/kg, cost of K20 @ Rs. 8.61/kg, Cost of N @ Rs. 6.38/ kg 350 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and S.K. Sharma

Cauliflower

In an investigation on alluvial loamy sand (pH 8.8) and having high soil potassium content, Randhawa and Khurana (1983) reported an increase in yield of two varieties of cauliflower (PG-26 and PG-35) due to 60 kg over 40 kg K2 0/ ha but the effect was non-significant. However, in GSB variety, there was a decrease in yield due to increase in K application (Table 42). The quality of curd was also affected by K application but it could not reach the level of significance. The effect of potassium on dry matter content, protein content and carbohydrate content of curds was also changed due to K application.

Table 42. Effect of potassium on yield and quality of cauliflower in the alluvial soils of Ludhiana (Pb.), India K levels Yield (q/ha) Quality of circles Mean of (kg/ha) @ practices three varieties GSB PG26 PG35 Mean GSB PG26 PG35 Mean GSB PG26 PG35 40 196 168 162 175 8.22 7.83 6.34 7.30 8.54 1.69 1.22 80 192 186 166 181 8.13 7.37 5.92 7.14 8.47 1.65 1.22 LSD 0.05 NS NS NS NS NS NS NS NS NS NS NS Randhawa and Khurana (1983) @ Rating based on a score card of 10 marks

In a study by Mitra et al. (1998) on cauliflower, a synergestic effect was reported between K and Mg in the crop. When Mg deficiency accentuated, the effect of low K was noticed by further lowering the biomass, concentration of chlorophyll a and b, starch, inorganic P, proteins and activities of ATPase and pyruvatekinase and stimulated the activities of acid phosphotase, peroxidase concentration of proline and non-reducing sugars. In cauliflower, low Mg enhanced, further the effects of excess K with the activity of peroxidase and concentration of proline, sugar, starch and reduction in pyruvate kinase and chlorophyll contents, thus, reflecting a synergestic role of K and Mg.

Cabbage

Sarkar et al. (1994) conducted an experiment on the response of K to cabbage in the soils of Bihar (India) in terms of days to maturity, equational diameter polar diameter, average head weight and head yield. They reported significant response of potassium application on different yield parameters and productivity of cabbage except in case of polar diameter, whose response was nonsignificant (Table 43). Further, they reported that 100 kg K 20/ha was significant over control, but was at par with 50 kg K 20/ha level in case of head weight. The application of 100 kg K20/ha, significantly, decreased/reduced the days to maturity over no K treatment. Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 351

Table 43. Effect of K on different parameters of cabbage Treatment Days to Equatorial Polar Av. head Head (kg K20/ha) maturity diameter diameter weight yield (cm) (cm) (kg) (t/ha) 0 76.12 12.66 13.25 1.073 29.98 50 71.33 14.65 13.65 1.113 40.06 100 71.79 14.79 13.58 1.237 42.41 150 72.56 15.48 13.82 1.244 43.85 200 72.54 15.70 13.93 1.348 47.36 LSD 0.05 4.15 1.34 NS 0.20 11.13 Sarkar et al. (1994)

Turmeric

Singh et al. (1998) conducted an experiment comprising of three levels of potassium to evaluate their effect on yield. quality and uptake of N, P and K in turmeric. The results revealed that application of 80 kg of potassium under low hill condition of Nagaland (India) increased the accumulation of N, P and K contents as well as curcumin content and productivity of turmeric (Table 44).

Table 44. Effect of potassium on yield and quality of turmeric Treatment Fresh Yield Curcumin Concentration of (kg K20/ha) yield of per plant content rhizomes (%) rhizomes cured (q/ha) N P K 0 316.6 43.3 5.50 0.695 0.059 0.99 40 389.3 60.0 6.24 0.827 0.072 1.40 80 394.4 64.7 6.44 0.965 0.077 1.57 LSD 0.05 46.7 2.7 0.16 0.058 0.005 0.086 Singh et al. (1998)

Sharma et al. (2001) in a study on potassium management in the presence and absence of farm yard manure for turmeric crop (Curuma longe L. var T-12) in mountain acidic lands of Western Himalayas, found that the application of potassium and FYM, individually, improved the yield of turmeric to the extent of 52 and 22 per cent with values of response yard stick, value-cost ratio and benefit-cost ratio as 53 kg turmeric/kg K20, 16:1 and 15:1, respectively (Table 45). The quality parameters of turmeric rhizomes such as protein and curcumin content showed an improvement to the tune of 19.8 and 4.6 per cent due to potassium whereas 14.87 and 5.67 per cent due to FYM application (Table 46). 352 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and S.K. Sharma

Table 45. Average effects of potassium and FYM on additional productivity (qi ha), response yard stick, value cost ratio and B/C ratio (Average 1999 and 2000)

(a) Yield in control (N0 P0 Ko) 49.57 q/ha (b) Yield in FYM' 0 60.37 q/ha (c) Additional productivity due to FYMQ over control 10.86 q/ha (d) % increase due to FYM 22.00 q/ha

(e) Yield due to 100% NPK (N6oP 30 K0 ) 61.40 q/ha

(f) Yield due to 100% NPK (N60 P30 K60 ) 93.20 q/ha (g) Additional productivity due to K60 over Ko 31.80 q/ha (h) Per cent increase due to K6o 52

(i) Response yard stick (kg rhizome per kg K20) 53 (j) Value cost ratio 16:1 (k) Benefit cost ratio 15:1 Sharma et al. (2001)

Table 46. Average effect of potassium and FYM on quality parameters of turmeric Treatment Protein Curcumin (%) (%) (a) Control (NoPoKo) 5.58 2.12 (b) FYM10 6.41 2.84 (c) Increase due to FYM10 over NoPoKo 0.83 0.12 (d) Per cent increase over control due to FYM10 14.87 5.67 (e) 100% NPKo (N6oP 30 K) 8.04 2.60

(f) 100% NPK (N60P30 K60 ) 9.63 2.72 (g) Quantitative increase due to K6 . over Ko (%) 1.59 0.12 (h) Per cent improvement due to K6o over Y. 19.8 4.60 Sharma et al. (2001)

The productivity and quality aspects of turmeric could be upgraded to or significant extent, thereby, improving its marketability and ensuring better economic returns to the livelihood of small and marginal farmers of'montain acidic lands of Western Himalayas.

EPILOGUE

It can be concluded from this review that vegetable crops grown during summer season such as coriander, methi, spinach and drumsticks and some that are growm during winter season like turnip and carrot have so much nutritional value for human consumption yet there exists a wide information gap on the role Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 353

of potassium in upgrading the productivity and quality parameters of these crops in different parts of the country in varied soil climatic situations.

Also, the studies on other management skills such as integrated use of inorganic sources of K with organics; use of amendments and mulching either individually or collectively in upgrading the productivity and quality of vegetable crops, on a sustainable basis, have not been carried out through long term experiments; which needs further research appraisals. Likewise, such studies involving in the use of potassium on quality seed production Of vegetable crops. Potassium plays significant role in the yield and quality aspect of vegetable crops. These crops have great potential for exporting as fresh vegetables to neighbouring gulf countries. Use of potassium in balanced fertilization under such situations is of paramount of importance.

REFERENCES Abbas Mohd, Saxena, R., Parmar, S.S. and Sharma, K.K. 1994. Effect of N and K on the growth and yield of garlic. Journal of Potassium Research 10(4): 338-342. Bansal, S.K. and Shahid Umar. 1998. Effect of SOP (Potassium sulphate) on yield and quality of potato. Fertilizer News 43(11): 43-46. Chen, Tianjun and Gableman, W.H. (1995). Isolation of tomato strains varying in potassium acquisition using a geolite culture systems. Plants and Soil 176: 65-70. Diwvedi, U.C., Sharma, R.C. and Sengrapta, S.K. 1995. Effect of phosphorus and potassium fertilization on seed yield of french bean (Phaseolus vulgaris L.) Vegetable Science 22(1): 36-38. Dubey, Y.P., Sankhyan, S.D. and Kaistha, B.P. 1997. Effect of K on yield and storage behaviour of potato (Solanum tubersonum L.) in Lahaul Valley of H.P. Journal of Potassium Research 13(4): 273-276. Kanaujia, S.P., Rastogi, K.B. and Sharma, S.K. 1997. Effect of phosphorus potassium and rhizobium inoculation on growth, yield and quality of pea cv. Lincoln. Vegetable Science 24(2): 91-94. Kanaujia, S.P., Rastogi, K.B., Sharma, S.K. and Raj Narayan. 1999. Response of phosphorus, potassium and rhizobium inoculation on pod yield and economics of pea (Pisum sativum) cv. Lincoln. Haryana Journal of Horticulture Science 28(1&2): 117-118. Kanaujia, S.P., Sharma and Rastogi, K.B. 1998. Effect of phosphorus, potassium and rhizobium inoculation on growth and yield of pea. American Agricultural Research. 19(2): 219-221. Kanaujia, S.P., Sharma, S.K. and Raj Narayan. 2000. Effect of phosphorus, 354 Pritant K. Sharma. S.P. Dixit. S.K. Bhardwaj and S.K. Sharma

potassium and rhizobium inoculation on mineral composition of pea. Horticulture Journal 13(2): 51-55 Kohli, U.K., Kumar Arun and Arya, P.S. 1991. Effect of phosphorus and potassium fertilization on seed crop of french bean (Phaseolus vulgaris L.) cultivars SVM-I and Ketucky wonder. Vegetable Science 18(2): 134-139. Lal Brij and Sharma, S.P. 1995. Response of potato (Solanum tubersuin) to potassium application in mid hill soils of Himachal Pradesh. Indian Journal of Agricultural Science 65(6): 433-434. Mandal, R.C., Singh, K.D. and Maina, S.B. 1982. Effect of nitrogen and potash fertilization on tuber yield and quality of colocasia. Vegetable Science 9: 82- 84. Mitra, A., Khurana, N., Nautiyal N. and Chatterjee, C. 1998. Potassium- magnesium interaction in cauliflower metabolism. Indian Journal of Horticulture 55(2): 157-163. Nandal, J.K., Vasist, R. and Pandey, U.C. 1998. Effect of P and K on growth, yield and quality of tomato. Journal of Potassium Research 14: 44-49. Prasad, U.K., Prasad, TN., Narayan, S. and Kumar, A. 1997. Effect of soil moisture regimes in sweet potato yield, potassium balance and water use efficiency. Journal of Potassium Research 13(3,4) Dec.: 283-289. Pujor, A. and Marard, P. 1997. Effects of K deficiency on tomato growth and mineral nutrition at early production stage. Plant and Soil. 189: 189-196. Radhawa, K.S. and Khurana, D.S. 1983. Effect of nitrogen, phosphorus and potassium fertilization on the yield and quality of cauliflower. Vegetable Science 10: 1-7. Saimbhi, M.S. and Randhawa, K.S. 1983. Influence of nitrogen, phosphorus and potassium on the yield and processing quality of onion bulbs. Vegetable Science 10: 73-76. Sarkar, S.K., Singh, S.P. and Jain, B.P. 1994. Response of cabbage to K and line in Bihar Plateau. Journal of Potassium Research 10(4): 398-401. Sharma, Pritam, K., Baghla, Kanika, Dixit, S.T and Bhardwaj, S.K. 2001. Preliminary studies on potassium management in turmeric as influenced by farm yard manure in mountain acidic lands of western Himalayas India. Paper accepted for presentation in international Symp. on importance of potassium on nutrient management for sustainable crop production in India, New Delhi. Dec. 3-5, 2001. Sharma, S.K. 1992. Quality of tomato seed as influenced by N, P and K nutrition. Him Journal of Agricultural Research 18 (1&2): 9, 12. Sharma, S.K. 1995. Seed production of tomato as influenced by nitrogen, phosphorus and potassium fertilization Annals of Agricultural Research 16(3): Influence of K in Balanced Fertilization on the Yield and Quality of Vegetable Crops 355

399-400. Sharma, S.K. 1995a. Effect of phosphorus and potassium fertilization on plant growth, seed yield and quality of Chinese sarson seed. Himachal Journal of Agricultural Research 21(1&2): 32-34. Sharma, S.K. 1995b. Effect of phosphorus and potassium on capsicum seed production. Indian Journal of Horticulture, 52(2): 141-145 Sharma, S.K. 1997. A note on effect of phosphorus and potassium fertilization on radish seed crop. Vegetable Science 24(2): 169. Sharma, U.C. 1992. Effect of levels of N, P and K and their interaction on yield and nutrient uptake of potato in acid soils. Journal of Indian Potato Association 19: 77-80. Singh, J. and Dhankar, B.S. 1989. Effect of nitrogen, potash and zinc on growth, yield and quality of onion. Vegetable Science 16(2): 136-144. Singh, J.P. and Singh, M.K. and Singh, R.D. 1993. Growth and yield of onion (Alliun cepa L.) bulb influenced by date of transplanting, nitrogen and potash fertilization. Vegetable Science 20(1): 14-17. Singh, Janardan. 1998. Effect of stocksorb polymers and potassium levels on potato and onion. Journal of Potassium Research 15(1-4): 78-82. Singh, K.P., Jain N.K. and Poonia, B.L. 2000. Response of kharif onion to nitrogen, phosphorus and potash on eastern plains of Rajasthan. Indain Journal of Agricultural Science 70(12): 871-872. Singh, R., Kohli, U.K. and Sharma, S.K. 2000. Effect of nitrogen, phosphorus and potassium combinations on yield of tomato hybrids. Annals of Agricultural Research 21(l): 27-31. Singh, R.P., Jain, N.K. and Poonia, B.L. 2000. Response of kharif onion to nitrogen, phosphorus and potash in eastern plains of Rajasthan. Indian Journal of Agricultural Science 70(12): 871-872. Singh, S. and Verma, S.K. 1991. Influence of potassium, zinc and boron on growth and yield of tomato (Lycopersicon esulentum) Vegetable Science 18(2): 122-129. Singh, U.B., Singh, N.P. and Swer, B. 1998. Effect of potassium and nitrogen on yield and quality of turmeric (Curcuma longa). Journal of Potassium Research 15(4): 88-92. Sud, K.C. and Grewal, J.C. 1993. Evaluation of leaf-potassium indices for application of corrective K dose to potato in Shimla hills. Indian Journalof Agricultural Science 63(2): 107-109. Uppal, H.S., Suraj Prakash, S.S. Machal and Bhupinder Kaur. 1997. Effect of time of K application and withdrawal of irrigation on yield and chip quality of potato. Journal of Potassium Research 13(4): 277-289. 356 Pritam K. Sharma, S.P. Dixit, S.K. Bhardwaj and,S.K. Sharma

Yadav, J.P., Mishra, R.S. and Mishra, H.R. 1993. Effect of various levels of nitrogen, phosphorus and potash on growth, yield and quality of pointed gourd (Trichosanthes dioica Roxb) Vegetable Science 20(2): 114-117. Potassium Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco

V. KRISHNAMURTHY, B.V. RAMAKRISHNAYYA AND K.D. SINGH Division of Crop Chemistry and Soil Science Central Tobacco Research Institute, Rajahmundry-533105

Introduction

Flue-cured Virginia (F.C.V.) tobacco is an important commercial crop grown in an area of 1.5 lakh ha by about 65,000 registered growers in Andhra Pradesh and Karnataka States with an annual production of 150 million kg of leaf fetching Rs. 1,000 corers as foreign exchange to the country. In India, flue-cured tobacco is grown on a great variety of soils ranging from light-textured sands to sandy loams of East Godavari, West Godavari and Khammam Districts (popularly known as Northern Light Soils), the red loams of Prakasam and Nellore Districts (known in tobacco circles as Southern Light Soils), heavy black cotton soils of Guntur, Krishna, East Godavari, West Godavari, Khammam, Warangal and Karimnagar Districts of Andhra Pradesh (known in tobacco trade circles as Northern and Central Black Soils),medium black soils(silt loams) of Prakasam and Nellore Districts (known as Southern Black Soils)and loamy sands and sandy loams of Mysore, Hassan, Chitradurg and Shimoga Districts of Karnataka State (known as Karnataka Light Soils), producing a wide spectrum of leaf styles catering to the varying needs of importing countries in the world.The physico- chemical properties of these soils are given in Table 1.

Flue cured (FCV) tobacco plant is remarkably sensitive to physico-chemical properties and mineralogical composition of the soil and climatic conditions under which it is grown. In general, the cured leaf produced on Northern Light Soils (NLS) and Karnataka Light Soils (KLS) is larger, bigger in size, lighter in colour and body, milder in strength, mature, pliable and elastic with high filling value, good flavour and excellent burning properties. In contrast, the Northern Black Soils (NBS) and Central Black Soils (CBS) produce leaf which is smaller, narrower and heavy-bodied, darker, immature and neutral filler. A balanced and desirable tobacco growth can only be achieved with an adequate and well-timed supply of nutrients (Tso, 1990). Among the several other factors influencing the tobacco productivity, soil fertility and fertilizer use contributes nearly to about 50 per cent of the yield and quality improvement of FCV tobacco crop.

Potassium characteristics of the soils growing tobacco in India were first determined and reported in early 70's (Ramakrishnayya, 1971, and Ramakrishnayya and Chatterjee, 1976). Using the Quantity-Intensity factors and buffering capacity in respect of potassium of the Vertisols and Alfisols in which 357 00

Table 1. Physico-chemical properties of FCV tobacco soils of India (surface soil) Agro-climatic Silt Clay Textural pH Dominent C.E.C. Exch.K Exch.Ca Exch.K/ zone/soil type (%) (%) Class* Clay mineral (cmol (p)+ (kg-') Exh.Ca Andhra Pradesh: 1. Northern Black Soil 14 50 C 8.2 Montmotilonite 48.3 0.72 45.9 0.02 (Vertisol of Rajahmundry) (D)*+ Illite 2. Northern Light Soil 5 8 S 7.2 Kaolinite (D) 4.5 0.12 3.2 0.04 (Alfisol of Devarapafli) + Illite 3. Central Black Soil 18 49 C 8.3 Montmorillonite 48.6 0.94 45.4 0.02 (Vertisol of Guntur) (D) +lllite 4. Southern Black Soil 17 28 Sil 7.8 llite (D) + 24.0 0.62 22.0 0.03 (Entisol of Nellore) Montomoiillonite 5. Southern Light Soils 6 17 SI 7.4 Kaolinite (D) 4.9 0.93 5.5 0.16 (Alfisol of Kandukur) + Beidellite Karnataka: 9.00 0.39 2.5 0.16 Z. 6. Karnataka Light Soils 4 13 Ls 5.4 Illite (D) + (Alfisol of Hunsur) + Kaolinite *S - Sandy, Ls - Loamy sand, SI - Sandy loam, Sil - Silt loam, C - Clay, *D - Dominant

P~ Potassium Nutrition Management for Improving Yeld and Quality of Flue-cured Tobacco 359 FCV tobacco has been cultivated in India, it was inferred that Vertisols have a high buffering capacity but low intensity making them good reserves for potassium but poor suppliers of potassium in comparison with calcium and magnesium. The Alfisols, on the other hand, have poor buffering capacity but high intensity of potassium. Therefore, they will be fast depleted of potassium by continuously growing crops, which are heavy feeders of potassium like tobacco. In order to test this inference, which was based on the experimental studies in laboratory, Krishnamurthy and Ramakrishnayya (1982) conducted pot studies with Vertisols and Alfisols continuously cropping them to tobacco. They found that Vertisols replenished potassium year after year while Alfisols were fast depleted of potassium when potassium application was withheld in the nutrients supplied to the crop (Krishnamurthy, 1982; Ramakrishnayya and Krishnamurthy, 1982). Simultaneously, they looked for occurrence of K-deficiency in nurseries, which were raised on Alfisols with continuous watering and low or no K-application. Since nurseries till then were raised on Vertisols and the recent transition to light soil (Alfisol) nurseries did not adequately take care of potassium nutrition, Krishnamurthy et al. (1982) found many nurseries suffering from K-deficiency, which could be corrected by K addition in time! Extending the philosophy of limited K-supplying power of Alfisols to the field crop of tobacco, Krishnamurthy and Ramakrishnayya surveyed the tobacco growing soils (particularly Alfisols) in East and West Godavari and Khammam Districts in Andhra Pradesh and looked for any K deficiency symptoms on the succeeding tobacco crop in those light soils which tested low in available K. Circumstantially, farmers had not realised the necessity of applying adequate quantities of the potassium to their Alfisol crop because their experience was till then based on Vertisol crop of tobacco which did not respond to K fertilization. Soon Krishnamurthy et al. (1983) observed many field crops of Alfisol tobacco suffering from K deficiency. They conducted several field experiments in soils with low potassium availability and established the need for adequate K application for obtaining a quantitatively and qualitatively improved crop. Their later studies were concerned with the balanced nutrition of tobacco crop with N and K and leaf positional as well as leaf segmental studies in respect of potassium concentration in the tissue which have been useful for a knowledge of potassium dynamics in tobacco soils as also the tobacco plants. Following is a detailed account of the experiments conducted, results obtained and conclusions drawn by Krishnamurthy and Ramakrishnayya and others relating to their comprehensive and exhaustive studies on potassium dynamics in Indian flue-cured tobacco soils and crop.

Importance of Potassium for FCV tobacco crop

Potash requirements of the tobacco plant are high when compared to the other agricultural plants and it is an indicator plant for K deficiency. In the production of bright cigarette tobaccos, potassium is the most important of all the plant nutrients and a liberal use of it through sulphate of potash is highly desirable for superior quality. The Vertisols under FCV tobacco cultivation in 360 V. Krishnamurthy, BY Ramakrishnayya and K.D. Singh

India, being rich in potash-bearing minerals and being put, over the years, to intensive tobacco cultivation which has high demand for K started showing up K deficiency (Krishnamurthy, 1982). The importance of potassium for tobacco plant growth, its content and availability in tobacco soils and its influence on yield and quality of flue-cured tobacco and its management in tobacco based cropping have been discussed in this paper.

Potassium is regarded as an important element of quality in tobacco crop. A high K content in cured leaves has frequently been used as a criterion of quality. Among all the mineral nutrients absorbed from the soil, K is absorbed in the highest amounts by tobacco plant indicating its importance to growth, development and maturity of the plant (Table 2). Besides its role in influencing the water relations and photosynthesis of green plants, potassium is known to improve the colour, texture, body, elasticity, and fire-holding capacity/ combustibility of the cured leaf. Potassium is also known to impart drought and disease resistance to the growing tobacco plant, besides counteracting and neutralizing the adverse effects of excess nitrogen and chlorine. A high level of potassium in leaf results in deep orange colour of the cured leaf.

Table 2. N, P K Removal from Soil by the FCV Tobacco Crop (cv: K-326) in NLS (Kg/ha)during 2000-2001 at 70 days growth Name of the Dry matter Nutrient concentration Nutrient uptake plant part yield (kg/ha) in dry matter (%) (kg/ha) N P K N P K Leaves 2466 2.12 0.30 4.25 52.5 7.4 105.0 Stalks 997 1.05 0.18 2.43 10.7 1.7 24.2 Roots 329 1.02 0.18 1.84 3.3 0.6 6.0 Inflorescence 79 4.33 0.74 4.00 3.9 0.6 3.2 Total 3871 - - - 70.4 10.3 138.4

Occurrence of K deficiency in tobacco nurseries and field crop

When the K content in green leaf falls below critical level due to short supply of K from the soil, the tobacco plant tends to exhibit characteristic symptoms of deficiency on leaf. Occurrence of K deficiency in tobacco seed beds and transplanted field crop and its effects on tobacco yield, chemical composition and quality of tobacco grown in light-textured Alfisols of East Godavari and West Godavari districts of Andhra Pradesh in India were reported by Krishnamurthy and Ramakrishnayya (1982), Krishnamurthy et al. (1982; 1983 and 1984).

The early symptoms of K deficiency are characterized by appearance of chlorotic/yellowish-puckered spots on the upper portion of the green leaf. These Potassium Nutrition Managetent for Improving Held and Qualiy of Flue-cured Tobacco 361

spots may also extend towards the basal portion of the leaf. As the deficiency becomes moderate, the yellowing and puckering nature of the spots increase. Severe necrosis, cutting of leaf margins in the upper half and tip and falling out of affected leaf portions giving a ragged appearance to it are the indications of extreme conditions of K deficiency. Where the K-deficiency is widespread, even 70 to 80% of the plants show K deficiency symptoms (Krishnamurthy et al., 1984).

When K deficiency appeared in early stages of the young, rapidly growing plants, the symptoms were pronounced in mature bottom leaves and when it appeared in more advanced stages of plant growth (at maturity or near topping), the chlorosis, yellowing, puckering and necrosis of leaf margins and tip were seen even in the top leaves. It may be noted that the symptoms of K deficiency appear on leaves long after the hunger actually occurs in the plant. Much damage to the growth and yield of the plant would have already occurred by the time, the hunger signs are noticed and it may be too late to make up the deficiency by K fertilization. It is also noticed that signs of K hunger may appear at any stage during the life of the tobacco plant, and neither its size nor its age alters the effects. Excess N fertilization aggravates K-deficiency.

Systematic Studies made In CTRI on K Nutrition Management of FCV Tobacco in Vertisols and Alfisols

The potassium characteristics of the soils growing tobacco in India were first determined and reported in early 70's (Ramakrishnayya, 1971; Ramakrishnayya and Chatterjee, 1976). Using the Quantity-Intensity factors and buffering capacity in respect of potassium of the Vertisols and Alfisols in which FCV tobacco has been cultivated in India, it was inferred that Vertisols have a high buffering capacity but low intensity making them good reserves for potassium but poor suppliers of potassium in comparison with calcium and magnesium. The Alfisols, on the other hand, have poor buffering capacity but high intensity of potassium. Therefore, they will be fast depleted of potassium by continuously growing crops, which are heavy feeders of potassium like tobacco. In order to test this inference, which was based on the experimental studies in laboratory, Krishnamurthy and Ramakrishnayya (1982) conducted pot studies with Vertisols and Alfisols continuously cropping them to tobacco. They found that Vertisols replenished potassium year after year while Alfisols were fast depleted of potassium year by year when potassium application was withheld in the nutrients supplied to the crop (Krishnamurthy, 1982; Ramakrishnayya and Krishnamurthy, 1982). Simultaneously, they looked for occurrence of K-deficiency in nurseries, which were raised on Alfisols with continuous watering and low or no K- application. Since nurseries till then were raised on Vertisols and the recent transition to light soil (Alfisol) nurseries did not adequately take care of potassium nutrition, Krishnamurthy et al. (1982) found many nurseries suffering from K- deficiency, which could be corrected by K addition in time! Extending the 362 V. Krishnamurthy, B.Y Ramakrishnayya and K.D. Singh philosophy of limited K-supplying power of Alfisols to the field crop of tobacco, Krishnamurthy and Ramakrishnayya surveyed the tobacco growing soils (particularly Alfisols) in East and West Godavari Districts in Andhra Pradesh and looked for any K deficiency symptoms of the succeeding tobacco crop in those light soils which tested low in available K.Circumstantially, farmers had not realised the necessity of applying adequate quantities of the potassium to their Alfisol crop because their experience was till then based on vertisol crop of tobacco which did not respond to K fertilization. Krishnamurthy et al. (1983) conducted several field experiments in soils with low potassium availability and established the need for adequate K application for obtaining a quantitatively and qualitatively improved crop. Their later studies were concerned with the balanced nutrition with N and K and leaf positional as well as leaf segmental studies in respect of potassium concentration in the tissue which have been useful for a knowledge of potassium dynamics in tobacco soils as also the tobacco plants. Following is a detailed account of the experiments conducted, results obtained and conclusions drawn by Krishnamurthy and Ramakrishnayya and others relating to their comprehensive and exhaustive studies on potassium dynamics in soils and in Indian flue-cured tobacco crop.

Q/I-Relations and potassium Availability Indices in fcv Tobacco Soils

The quantity factor ( K) and the intensity (ARK) proposed by Beckett (1964) are believed to give a better picture of K supplying power of a soil than available K alone. The potential buffering capacity (PBCK) combines in one parameter, the quantity and intensity factors. Studies on Q/I relations of K in fcv tobacco growing Alfisols and Vertisols of Andhra Pradesh and Karnataka by Ramakrishnayya (1971), Ramakrishnayya and Chatterjee (1976) and Srinivas (1987) revealed that the available K in labile pool in both the soil types is quite satisfactory whereas the ARK is high in Alfisols and low in Vertisols which indicated that the availability of K in contrast to Ca and Mg in soils, is high in Alfisols and low in Vertisols (Table 3). Thus, the generally low level of K in tobacco leaf grown in Vertisol which is less than 2.0% irrespective of the higher available soil K can be attributed to low ARK. However, the buffering capacity of Alfisols is many times less than that of Vertisols which accounts for the quick depletion of K from Alfisols. On the basis of pot culture studies and K-fertility evaluation of fcv tobacco soils of Andhra Pradesh ,Krishnamurthy et al. (1984) concluded that K-fertilization can be withheld for 3-5 years in case of Vertisols of CBS and NBS of A.P. The K availability is also affected by poor soil aeration, excess C0 2, soil moisture stress as encountered in Vertisols (soil compaction, hardness and severe drought as in southern rainfed Alfisols of Andhra Pradesh). Of the several extractants used for determining available K in Alfisols, neutral normal ammonium acetate was found to be the reliable index of K availability to tobacco plant (Krishnamurthy and Ramakrishnayya. 1986a). Potassium Nutrition Management for Improving held and Quality of Flue-cured Tobacco 363

Table 3. Potassium activity ratio (ARk) and PotentialBuffering Capacity (PBCk) of tobacco soils from Andhra Pradesh and Karnataka Soil Sample Depth ARk PBCk (cm) (M/Le')+10 (me/(M/L' 0 ) Andhra Pradesh Chinnaygudem 0-25 20.8 4.7 (Red soil) 25-69 23.0 6.1 Rajahmundry 0-36 1.5 123.0 (Black soil) 36-86 0.1 174.0 Guntur 0-23 1.0 135.5 (Black soil) 23-58 0.0 175.0 Lam 0-30 1.8 135.0 (Black soil) 30-58 0.2 180.0 Mangamur 0-28 1.0 135.0 (Black soil) 28-51 0.3 163.0 Karnataka Hunsur 0-23 12.5 12.9 (Red soil) 23-48 0.2 100.0 Bylakuppe 0-28 15.5 10.4 (Red soil) 28-51 11.3 11.4

Changes in Available K Status under Continuous Tobacco Cropping

To study the changes and to monitor the available K status in Alfisols and Vertisols under continuous tobacco cropping, Krishnamurthy and Ramakrishnayya had conducted a series of pot, nursery and field experiments during 1977 to 1988 with and without potash fertilizer application. Pot studies indicated that continuous cultivation of flue-cured tobacco in Alfisols without potash application led to appearance of visual symptoms of K deficiency in growing plants during second and third crop seasons in no potash treatment (control plot) of Alfisols. The initial fertility of the soils is given in Table 4.

Table 4. Mechanical analysis and initial fertility status of pot culture soils No. Place Textural Sand Slit Clay pH Available Nutrients Class % % % (1:2) OC P K (%) (kg/ha) (kg/ha) SI Katheru Clay 22.1 25.4 52.5 7.8 0.30 10.8 340 S2 Rajahmundry Sand 90.3 3.7 6.0 6.0 0.30 11.7 333 S3 Morampudi Sand 91.7 3.3 5.0 7.0 0.15 7.5 370 54 Devarapalli Sand 89.0 4.8 6.2 6.9 0.09 19.8 340 364 V Krishnamurthy, BY Ramakrishnayya and K.D. Singh

The available K content decreased to a low value of 100 kg K ha-' from the initial high value of 340 kg K ha - 1 after three successive croppings (Table 5). The Vertisol (SI) with initial available K content of 340 kg K ha-' did not show symptoms of K deficiency in control plots even after three successive crop seasons and maintained its available K status at a more or less constant level of 327 kg K ha -' (Krishnamurthy and Ramakrishnayya, 1982). The results of pot experiment showed that the Alfisols of Andhra Pradesh, unlike the heavy Vertisols, are subject to depletion of available K more quickly and release of K, if any, from reserve sources is inadequate to maintain the available K status at a level sufficient to meet the crop requirements in the absence of added potash fertilizers in Alfisols.The cured leaf yield and K content of the leaf were drastically reduced in no potash treatments in light soils(Alfisols) while they were unaffected in black soils (Table 6).

Table 5. Depletion of available K status of soils under continuous FCV tobacco cultivation without potash fertilization SI. Soil Type and Location pH Clay Initial Depletion of (1:2) Content available available K in soil (%) K (kg/ha) (K kg/ha) after 1st 2nd 3rd Crop Crop Crop seaso seaso season S1 Vertisol, Katheru 7.8 52.5 340 355 278 327 S2 Alfisol, Rajamundry 6.0 6.0 333 190 196 146 S3 Alfisol, Morampaudi 7.0 5.0 370 231 197 162 S4 Alfisol, Devarapalli 6.9 6.2 340 188 136 100

Table 6. Effect of applied K on yield (giplant) and K content of cured leaf in different soils Soil Type and Yield (g/plant) with K content (%) with Location '0' (kg 300 (kg '0' (kg 300 (kg

K20/ha) K20/ha) K20/ha) KO/ha) Vertisol of Katheru 62 81 1.48 2.20 Alfisol of Rajahmundry 49 74 0.78 3.88 Alfisol of Morampudi 58 70 0.63 3.78 Alfisol of Devarapalli 48 68 0.53 3.88

Field experiment conducted on an irrigated Alfisol of Kalavacherlawith flue- cured cultivar 16/103 in East Godavari District of Andhra Pradesh revealed that increase in levels of potash significantly increased the cured leaf yield, grade index and K content of the leaf (Krishnamurthy et al., 1989) and a combination of 50 kg N and 120 kg K20 ha -' were optimum for higher yields and better quality tobacco (Table 7). Potassium Nutrition Management for Impoving Weld and Quality of Flue-cured Tobacco 365

Table 7. Available K in Soil, Yield characters and Chemical composition of flue-cured tobacco leaf' as influenced by levels of potash at Kalavacharla, East Godavari District, A.P. K20 Available Cured Grade Chemical composition of K leaf index cured leaf - (%) (kg ha ') (kg ha-') (kg ha-') (kg ha-') Nilcotine Reducing Potassium sugars 0 110 2142 1149 2.22 10.04 2.21 60 139 2311 1327 2.17 13.85 2.82 120 157 2414 1385 2.11 11.19 3.24 180 205 2529 1340 2.11 12.14 3.50 240 276 2212 1160 1.99 11.82 3.45 300 318 2320 1275 2.02 12.85 3.43 L.S.D. (P=0.05) 103.08 202.53 N.S. N.S. N.S. 0.3523 Initial soil had pH 5.3, available K 155 (kg ha-') and clay 6.0%

- It is seen that when 40 kg N ha ' was given to the fcv tobacco in Alfisol - of West Godavari district, 80 kg K20 ha ' was found to be optimum (i.e. N: K ratio I : 2). When N dose was increased to 50 or 60 kg N ha - ' as in Kalavacharla trial, the plant's demand for K and the stress on soil K increased. Under these conditions, a potash dose of 120 kg K20 ha-' was found to be the requirement, showing the optimum ratio of nitrogen to potassium as 1:2 (Krishnamurthy et al., 1989). The irrigated kaolinitic Alfisols of East Godavari, West Godavari and Khammam districts of Andhra Pradesh are deep sands and sandy foams, acidic is soil reaction; and more than 50% of them are deficient in available K status. Hence, good response to potash application in these irrigated sandy soils is expected (Krishnamurthy et al., 1986a). With the hope of getting better plant growth and higher tobacco yields, the Northern Light Soil tobacco farmers are resorting to excessive use of nitrogen fertilizers without proper balance of K thereby aggravating the problem of K deficiency in the field crop on these sandy soils. As suggested by Krishnamurthy et al. (1989), a balanced N: K dose of 60 kg N ha-' with 120 kg K20 ha-' (i.e. I : 2) for FCV variety 16/103 will go a long way in improving the yield and quality of tobacco in Northern Light Soils and in maintaining the long-term productivity of these sandy soils. It is also observed that for high yielding exotic variety like K-326,100 kg N/ha is required for higher yields and better quality. However, omission of potash for nine successive seasons did not influence the yield or quality of FCV tobacco crop in Vertisols of Northern andCentral Black Soils of Andhra Pradesh (Reddy et al.2000).

Krishnamurthy and Ramakrishnayya (1986a) and Ramakrishnayya and Krishnamurthy (1990) reported that the potassium content in tobacco leaf was strongly and positively correlated with available K status in sandy and sandy 366 V Krishnamurthy, B.Y Ramakrishnayya and K.D. Singh loam soils. The data in Table 8 revealed a very strong positive correlation between the available K status of surface soil and K content of leaf in bottom, middle and top positions (r > 0.90), whereas the subsoil K did not show such a strong correlation with leaf K indicating that leaf K was largely dependent on available K of surface soil (Ramakrishnayya and Krishnamurthy 1990).

Table 8. Regression between soil K (X) and leaf K (Y) Leaf position Regression equation Coefficient of correlation Bottom: Y =0.4395 + 0.0142 X 0.955** Middle: Y =0.0679 + 0.0114 X 0.934** Top: Y =0.5789 + 0.0092 X 0.920** Mean: Y =0.0673 + 0.0116 X 0.954" **Significant at 1% level

Equations connecting leaf K (Y) with soil K (X) were also found to have a very good predictability as can be seen from the coefficient in Table 8. Available potassium in soil as determined by normal, neutral NH 4OAc extraction method of Chapman and Pratt (1961) has been found to be a reliable method for assessing the potassium status of tobacco soils (Ramakrishnayya and Krishnamurthy, 1990). Krishnamurthy et al. (1982) concluded that occurrence of K deficiency symptoms in Northern Light Soils, tobacco crop is a serious limiting factor in soils and tobacco crop for getting higher yields and better quality leaf. For using leaf analysis as a basis for assessing the nutritional, status of tobacco plant, and for determining the potash fertilizer recommendations for FCV tobacco crop in Northern Light Soils , Krishnamurthy and Ramakrishnayya (1993) had suggested the tentative limits of K in green leaf based on available K status of soil and appearance of visual symptoms of K deficiency (Table 9).

Table 9. Effect of available K status in Alfisols on occurrence of K deficiency Available K in soil K deficiency or K content in leaf (kg/ha) sufficiency lamina (%) Below 118 Deficient less than 2.0 118-280 Hidden hunger 2.0-2.5 Above 280 Sufficient greater than 2.5

Potassium Distribution Pattern in FCV Tobacco Plant

There is evidence to suggest that tobacco plant accumulates a reserve of potassium in the early stages of growth and it is sufficient to sustain the later phases of development. Ramakrishnayya and Krishnamurthy (1990) studied the K distribution pattern in green leaves of K deficient and K-sufficient flue-cured tobacco plants (cultivarl6/103) grown in irrigated Alfisols of Andhra Pradesh and found that K content of leaf lamina in K-deficient plants increased from bottom to the top; the bottom leaf of the K- deficient plant contained the lowest Potassium Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco 367

K (1.06%), top leaf showed 1.59% K and the middle leaf, an intermediate K content of 1.25%. When K was in sufficient quantity in the soil, the distribution of K in leaf followed normal pattern i.e. bottom leaf contained the highest K (4.30%), followed by middle leaf (3.92%) and top leaf (3.69%). Thus, the K content of leaf in K-deficient plants was generally less than 1.6% K and in K- sufficient plants K content in leaf was more than 3% (Table 10). The F-test revealed highly significant differences in K content in leaf from different stalk positions within each of the two groups of (i) healthy and (ii) K-deficient plants.

Table 10. Potassium content of leaf in healthy and K-deficient plants (t-test) in irrigated Alfisols of Andhra Pradesh. Leaf Mature Green Leaf K (%) t- t-theo- Position Range Average calculated retical Healthy Deficient Healthy Deficient Bottom 3.25-5.40 0.50-2.35 4.30 1.06 10.366" 2.34 Middle 3.00-4.55 0.75-2.50 3.92 1.25 15.000* 2.75 Top 3.10-4.40 1.05-2.55 3.69 1.54 12.954* 2.75 *Significant at 1% level.

Nitrogen and potassium distribution pattern and their relative ratios in different segments of mature green leaf of flue- cured tobacco cultivar 16/103 (Figure 4) grown in northern light soils of Andhra Pradesh was investigated by Krishnamurthy et al.(1997and 2000) who concluded that the midrib acts as a reservoir of K supply to tobacco leaf (Table 11).

Table 11. KIN Ratio in Green Tissue of Different FCV tobacco Leaf Segments Tissue segments Lamina Midrib K-Sufficient Leaf Tip 0.99 3.33 Middle 1.12 4.90 Base 1.26 6.60 K-Deficient Leaf Tip 0.21 0.36 Middle 0.20 0.42 Base 0.20 0.61

The K-concentration in lamina tissue of K-sufficient leaf ranged between 2.36 to 3.92% on dry basis and lamina tissue of K-deficient leaf, it varied between 0.62 to 0.75% K (Krishnamurthy et al., 1997)

Interaction of K with Other Nutrients and Crop Management Practices

Interactions among plant nutrients and other inputs of crop production influence crop yield and quality. Positive interactions are a bonus to the farmer 368 V.Krishnamurthy, BY Ramakrishnayya and K.D. Singh and may lead to changes in fertilizer use practices. Lundegardh (1945) emphasized the value of leaf analysis as an index of nutritional balance in corps. Shear et al. (1946) stated that leaf composition is the only valid criterion by which the nutrient status of the plant can be assessed.

K x Ca interaction

Ca content of Vertisols grown tobacco is higher (3.0%) than K content (1.0 to 1.5%) (Venkataraman and Tejwani, 1961). The results from Q/I relations of soil K by Ramakrishnayya and Chatterjee (1976) also indicated that due to higher activity of Ca and Mg in relation to K (i.e. low ARk) in Vertisols, the K content of Vertisol grown leaf is low (1.0-1.5%), while it is relatively high (2.5- 3.5%) in irrigated Alfilsol grown leaf on account of the high ARk in Alfisols. It is also noticed that even though the K content of Alfisol-grown fcv tobacco leaf is normal, calcium deficiencies have appeared in tobacco nurseries and field crop because of the inherent Ca-deficiency in sandy soils (Sannibabu el al., 1985). Krishnamurthy and Ramakrishnayya (1997) Krishnamurthy et al. (1997 and 2000) have shown that high exch. Ca*2 content in heavy Vertisols depresses the uptake of K+ by the tobacco plant due to ionic antagonism. Further, they observed that higher levels of K depresses the calcium concentration of the leaf and the leaf K/Ca ratio is always > 1.0 in FCV tobacco grown in NLS and <1.0 in Vertisol grown leaf (Table 12).

Table 12. K/Ca Ratio of FCV tobacco Soils and Cured leaf. Soil type/Location Exch. K+ and Exch. K K and Ca in Ca,2 in soil cured leaf (%) (coml. (p)+ kg-') Exch. Ca'- K Ca K/Ca Exch. Exch. ratio +2 K + Ca Northern Black Soil (Vertisol of Rajahmundry) 0.72 45.91 0.02 1.5 3.0 0.5 Northern Light Soil (Alfisol of Chinayagudem) 0.12 3.15 0.04 3.0 2.5 1.2

N x K interaction

There is a close relationship between N and K in their physiological functions and the main effect of K is to improve the efficiency of N. Increased K uptake results in increased N uptake and vice versa. Pal et al. (1966) reported from sand culture experiments that there was a significant increase in N content of FCV tobacco leaf as the level of applied K increased. Reddy (1980) reviewing the environmental factors in production of flue-cured tobacco in Karnataka, observed that although the soils are reasonably rich in available K, with increased Potassium Nutrition Management for Improving Yield and QualiY of Flue-cured Tobacco 369 levels of N, invariably K deficiency symptoms are noticed in the tobacco crop. Field experiment conducted in Northern Light Soils during 1983-84 with one dose of 50,60 and 100 kg N ha- ' in combination with 40, 80 and 120 kg K,O ha-' showed that the combination of 60 kg N and 120 kg K 20 ha-' (i.e. N: K ratio 1:2) produced higher yield and better quality tobacco (Krishnamurthy, 1985). For balanced N and K fertilizer management of flue-cured tobacco in irrigated Alfisols of West Godavari and East Godavari districts of Andhra Pradesh, Krishnamurthy et al. (1989) recommended N: K ratio of 1:2 as the ideal. Krishnamurthy and Ramakrishnayya (1992), working on N and K balance in FCV tobacco crop in irrigated Alfisols, found that a concentration of 3.0% N and 2.5 to 3.0% K in green leaf lamina of 60 day old crop was optimum for normal growth, maturity, higher yields, and better cured leaf quality (Table 13).

Excessive use of nitrogen fertilizers and inadequate addition or omission of potash in fertilizer schedule leads to potassium deficiency under light soil conditions (Krishnamurthy, 1985).

Table 13. Nitrogen and Potassium Concentration and N/K ratio in FCV tobacco leaf(cv:16/103) in Northern Light Soils of A.P. (Age of the crop: 60- 65 days) No. of Nutrient N/K Crop Condition/Symptoms leaf concentration ratio on green tobacco leaf Samples in lamina (%) in leaf Analysed N K lamina 6 High Normal Vigorous plant growth: dark 3:41 2:75 1:24 green and fully expanded (3.04-3.96) (2.54-3.05) leaves free from K deficiency 5 High Moderate Dark green leaves with 3:84 2:24 1:71 incipient symptoms of K (3.36-4.32) (2.09-2.45) hunger 16 High Low Dark green, succulent soft 4.12 1.55 2.66 tissue; leaves wilting/ (3.10-5.07) (2.59-2.78) drooping at noon; severe K deficiency symptoms on leaves. 3 Normal Normal Vigorous plant growth; fully 2.74 2.66 1.03 expanded leaves with (2.63-2.92) (2.59-2.78) normal green colotir and without K deficiency symptoms on leaves. 3 Low Normal Stunted plant growth; pale 1.89 2.82 0.67 yellow coloured leaves (1.73-2.06) (2.81-2.84) without K deficiency symptoms (Figures in parentheses represent ranges) 370 V Krishnamurthy, B.Y Ramakrishnayya and K.D. Singh

Effect of Potassium on Cured Leaf Quality

Potassium as a quality determinant of smoking tobacco has been extensively investigated and it is generally accepted that a good quality leaf contains high level of K. The results from work done in India on the effect of K on physical, chemical , burning and smoking properties of the cured FCV tobacco leaf are reviewed below.

Effect of K on physical properties of cured leaf

Cured leaf produce with high K supply is smooth and thin bodied with deep orange colour. Such leaf is pliable and resilient with mild aroma. Studies on the effect of high K supply on Alfisol grown FCV tobacco by Krishnamurthy and Ramakrishnayya (1993) revealed that when the cured leaf contained high K, the production of burnt leaf was much reduced (less than 10% blemish). In contrast, cured leaf produced with deficient K supply (the crop showed severe K deficiency symptoms) was medium to dark brown, very brittle and shattery with medium body, thin texture with necrotic leaf margins (Table 14). Such K-deficient cured leaf exhibited pungent and earthy smell and showed more than 30% blemish (i.e. burnt leaf). Cured leaf lacking in K content resulted in poor coloured, trashy leaf with limited commercial use.

Table 14. Physical and chemical quality characters of cured leaf from K- sufficient and K-deficient FCV tobacco plants Cured leaf characters K-sufficient (Healthy) K-deficient Physical Colour Medium bright Medium to dark brown Condition Pliable Brittle and shattery Body Medium to light Medium Texture Medium Thin Aroma Mild Pungent and earthy Blemish (Burnt leaf) 10% 30% Leaf Burn (Seconds) Good (5.0) Poor (1.0) Chemical Total Nitrogen (%) 1.99 4.92 Total Potassium (%) 3.39 1.45 Total sugars (%) 16.90 4.90 Nicotine (%) 3.07 3.55

Effect of K on chemical properties of the cured leaf

While studying the cured leaf characteristics of flue-cured tobacco from K- sufficient and K-deficient areas in Northern Light Soils of Andhra Pradesh, Krishnamurthy et al. (1983) observed that when the available K supply in the Potassium Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco 371 light soil was high, the K and reducing sugar contents of the leaf were high ranging from 2.55 to 3.0% K and 18.65 to 20.42%, respectively (Table 15). In contrast, when the available K supply in the light soil was low, the K and reducing sugar contents of the cured leaf were low (1.25 to 1.8% K and 7.44 to 11.89% reducing sugars).

Table 15. Soil and Cured leaf charactersfrom healthy and K-deficient fields in NLS. Soil characters Leaf characters No. of pH Organic Available Available K Reducing Samples carbon P K content sugars (%) (kg/ha) (kg/ha) (%) (%) Healthy 10 5.5-6.4 0.21-0.35 6.30-13.20 255-364 2.55-3.00 18.65-20.42 (5.9) (0.27) (8.86) (282) (2.71) (19.10) Deficient 10 5.1-6.0 0.16-0.30 4.50-9.90 65-118 1.25-1.80 7.44-11.89 1 (5.6) (0.20) (6.15) (92) (1.50) (8.34) Figures in parentheses represent average values

The positive influence of higher reducing sugar content in light soil grown leaf from high available K sites may be attributed to the known role of K in favourably influencing the photosynthesis and efficient utilization of water by the growing tobacco plant. Increase in the potassium content of leaf is generally considered to have no significant influence on the nicotine content of tobacco, since there are no known functions of K in the synthesis of nicotine. It is also noticed that when the available K supply of the soil in relation to Ca and Mg is high as in Northern Light Soils of Andhra Pradesh, K content of the cured leaf is higher and Ca and Mg contents are lower.(Krishnamurthy and Ramakrishnayya,1997 and Krishnamurthy et al.2000). On the other hand, when the K supply of the soil is low in comparison to Ca and Mg, as in heavy black soil of Andhra Pradesh, K content of cured leaf is lower and Ca and Mg contents are higher (Krishnamurthy and Ramakrishnayya 1982 and Krishnamurthy et al., 1984 b and Sannibabu et al., 1985).

Effect of K on burning properties of the cured leaf

From a sand culture experiment, Pal et al. (1966) reported that an increased K supply improved the leaf burn while increased application of chloride decreased the burn. They obtained significant correlation between K content of the cured leaf and leaf burn (r = 0.5440*). Ramakrishnayya and Krishnamurthy (1990) observed that cured leaves from K-deficient fields exhibited poor leaf burn of less than one second while those from K-sufficient healthy plants showed very good leaf burn of more than 5 seconds. 372 V Krishnamurthy, B.V Ramakrishnayya and K.D. Singh

Effect of K on smoking properties of the cured leaf

Effect on tar and nicotine contents of the smoke

Studies on the effect of different levels of applied K on the leaf K and smoke composition (Kameswara Rao et al., 1992) showed that the leaf K content can be increased by applying K fertilizers on light soils which in turn increases the leaf burn substantially culminating in the reduced TPM (Total Particulate Matter) and lower smoke nicotine. The linear regression equation computed between TPM and potassium is shown below:

Y = 34.97 - 2.60** X

Where Y = TPM in mg/cigarette; X = Percent potassium in cured leaf ** = Highly significant

Thus, increasing the K content of light soil tobacco leaf by natural agronomic practices can go a long way in production of cigarette tobacco with lower TPM and nicotine in smoke delivery and thereby making cigarette smoking less hazardous to human health.

As leaf potassium is highly significantly and negatively correlated to dry TPM (-0.761 **) and nicotine content in smoke (-0.754**) (Tso, 1977), exogenous application of potassium was tried to reduce the smoke constituents Kameswara Rao et al. (1989, 1992); (Prabhu et al., 1990 and Yamamoto et al., 1990). However, utilization of tobacco leaf and midribs with higher levels of potassium would be a better proposition to exogenous application of potassium in view of certain practical problems during cigarette manufacture. Prabhu et al. (1990) reported 15% reduction in TPM, 19% reduction in nicotine and i% reduction in carbon monoxide due to midrib inclusion (which contains high potassium) in the blend. Narashima Rao et al. (2000) concluded that the utilization of tobacco leaf with low tar potential in conjunction with increase in filling value as also the potassium content of the blend results in substantial reduction in tar, nicotine and carbon monoxide content of the cigarette smoke.

Effect of Sources and Methods of K Application

Sulphate of potash is recommended and used by the farmers. Muriate of potash as a source of potassium is discouraged as chlorides affect adversely colour, texture, flavour, taste, combustibility and the keeping quality of leaf in storage. Chilean nitrates offer some scope for use in irrigated light soils. The major differences in performances among the commonly used fertilizer K sources are due to the associated anion. Potassiun Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco 373

Soil application is the common method of K fertilization in all flue-cured tobacco growing tracts in India. In irrigated Northern Light Soils of Andhra Pradesh and Karnataka Light Soils, potash is applied in two splits by dollop method (placing the potash in 10 cm deep hole and 10 cm away from the plant on either side and closing the hole with the soil). In black soils rainfed southern red soils, potash is applied in a band in plant row plough furrow (PRPF) before planting.

SUMMARY AND CONCLUSIONS

Tobacco is an indicator plant for potassium deficiency and is a luxury consumer of K. High potassium content in cured leaves has frequently been used as a criterion of quality. Besides its role in favourably influencing the water relations and photosynthesis in growing tobacco plant, potassium is known to improve the colour, body, elasticity and fire holding capacity of the final cured leaf. It mitigates the ill effects of excess nitrogen in growing plant and counters the adverse effects of excess chloride in cured leaf.

Omission of potash in fertilizer schedule in irrigated Alfisols for nursery and field crop led to depletion of soil available potassium to less than the critical level, resulting in K deficiency in growing tobacco plants and adversely affecting the cured leaf yield and leaf burn. Therefore, application of potash to irrigated Alfisols resulted in marked increase in cured leaf yield and leaf burn. In contrast, omission of potash in Vertisols crop neither produced K deficiency in plants nor affected the cured leaf yield or quality. Hence, it is recommended to omit K to fcv tobacco crop in Vertisols of East Godavari, West Godavari, Krishna and Guntur districts of Andhra Pradesh.

Higher leaf potassium has been shown to reduce the smoke TPM (total particulate matter viz tar and nicotine contents of smoke), and hence it is possible to lower the smoke TPM and Tobacco Specific Nitosamines(TSNA) by rational potash fertilization of fcv tobacco crop and thereby making cigarette smoking safer and less hazardous to human health.

In India flue-cured tobacco growing Vertisols are calcareous and clayey with high potassium reserves and Alfisols are coarse textured with low potassium reserves. In deep Vertilsols, response of tobacco to applied potassium is absent and its omission for several seasons did not produce any adverse effect on cure leaf. Therefore, it is recommended is to omit potash in fertilizer schedule for Vertisols in Central and Northern tobacco belt of Andhra Pradesh. In Alfisols (NLS, KLS, SLS) where soil potassium status is low to medium, marked response to potassium application is observed. The omission of potassium in these soils led to visual symptoms of potassium deficiency and affected adversely the yield and quality of flue- cured tobacco. The field experiments revealed that tobacco crop requires 120 kg K20 ha-' in Alfisols of Northern Light Soils, 60 kg K20 374 V.Krishnamurthy, B.Y Ramakrishnayya and K.D. Singh

- ha ' in Southern Light Soils and 100 kg K20 ha-' in Karnataka Light Soils for producing high yields and better quality tobacco. The implications of quantity and intensity relationships in explaining the potassium dynamics in Vertisols vis-t-vis Alfisols have been discussed. Potassium distribution pattern in tobacco plant and individual leaf segments have been thoroughly investigated and concluded that the midrib in green leaf acts as a reservoir of K supply to different leaf segments. The relationship between available K in soil and leaf K has been established through regression equations and demonstrated that available K extracted with neutral normal ammonium acetate is a reliable index of K availability to tobacco plant in Alfisols and K fertilization can be made on the basis of K status of the surface soil. Higher potassium content in leaf improves colour retention and leaf-burn and reduces the TSNA content of the leaf and tar, nicotine and carbon monoxide contents of the tobacco smoke, thus making cigarette smoking safer and less hazardous to human health.

Future Lines of Work

As regular potash fertilization of FCV tobacco crop is essential for getting higher yields and superior quality tobacco Northern Light Soils, Southern Light Soil and Karnataka Light Soils (Alfisols), studies on the following aspects of K research in tobacco crop need to be initiated and strengthened. ol Long-term experiments similar to permanent manurial trials on the effect of omission/inadequate application of K on flue-cured tobacco crop in SBS, SLS and KLS may have to be initiated. ] Lack of response to added K and absence of visible deficiency symptoms on the growing tobacco plant in Vertisols inspite of low K concentration (around 1.5%) in leaf needs probing. o Mineralogy of different soils growing tobacco needs to be investigated to understand the nature and amounts of K-reserves, activity ratios and available K-content. ol Interaction of N and K Ca in different soils and their effect on cured leaf. L Studies on drought and disease resistance in relation to potash fertilization. ol Studies on K content of cured leaf in relation to TSNA and smoke deliveries of Total Particulate Matter (TPM), nicotine and carbon monoxide content.

REFERENCES Chapman, D. and Pratt, PF. (1961) Methods of analysis for soils, plants and waters. University of California, California, USA. Garner, W.W. (1946). The Production of Tobacco. The Blakiston and Company, Philadelphia, U.S.A. Potassium Nutrition Management for Improving Yield and Quality of Flue-cured Tobacco 375

Janardhan, K.V.; Janakiraman, N. and Narasimhan, S.P. (1989) Nitrogen and potassium nutrition of flue cured tobacco in transitional light soils of Karnataka. Journal of. Potassium Research. 5(4): 164-170. Kameswara Rao, B.V; Murthy, K.P.S.N; Nagabhushanam, M and Bhide, S.V. (1989). Effect of additives on tobacco smoke particulate matter and its mutagenicity. Tobacco Research. 15: 76-9. Kameswara Rao, B.V., C. Narasimha Rao and K. Nageswara Rao (1992). Effect of potassium on tar and nicotine delivery from cigarette. CORESTA Congress, Jerez De La Frontera. 11-16, October. Krishnamurthy, V. (1982) Analytical studies on fertility status of flue-cured tobacco soils of Andhra Pradesh. PhD Thesis. Andhra University, Waltair. Krishnamurthy, V. (1985) Potassium nutrition of flue-cured tobacco. Res. Topics No. 12. International Potash Institute Bern Switzerland: 44-45. Krishnamurthy, V. and Ramakrishnayya, B.V. (1882) Depletion of available potassium in light and black soils of Andhra Pradesh under continuous cropping with tobacco (Nicotina tabacum). Indian Potash Journal. 7(2): 19- 24. Krishnamurthy, V. and Ramakrishnayya, B.V. (1986a). Available potash status of northern light soils of Andhra Pradesh and occurrence of potash deficiency in tobacco. Tobacco Research. 12(1): 72-77. Krishnamurthy, V. and Ramakrishnayya, B.V. (1986b). Forms of potassium in flue-cured tobacco soils of Andhra Pradesh. Tobacco Research 12(2): 204- 207. Krishnamurthy, V.; Ramakrishnayya, B.V. and Gopalachari, N.C. (1984). Available potassium status of flue cured tobacco soils of Andhra Pradesh. Fertilizer News. 29(11): 36-39. Krihnamurthy, V.; Ramakrishnayya, By, and Kemmler, G. (1984) Potassium dynamics of tobacco soils in Andhra Pradesh state, India. Potash Review. Subject 4, 81st suite, International Potash Institute, Bern, Switzerland. Krishnamurthy, V.; Ramakrishnayya, D.V. and Murthy, K.S.N. (1988b) Fertility status of fcv tobacco soils of Mysore district in Karnataka. Indian Tobacco Journal. 20(1): 9-11. Krishnamurthy, V.; Ramakrishnayya, B.V.; Reddy, P.R.S. and Sanni Babu, M. (1983) Occurrence of potassium deficiency in the field crop of flue-cured tobacco in northern light soils of Andhra Pradesh. Indian Potash Journal. 9(3): 22-26. Krishnamurthy, V.; Reddy, P.R.S. and Ramakrishnayya, B.V (1982) Occurrence of potassium deficiency in tobacco seedlings raised on northern light soils of Andhra Pradesh. Tobacco Research. 8(1): 81-95. 376 V. Krishna.iurhy, B.V. Ramakrishnayya and K.D. Singh

Krishnamurthy, V.; Reddy, P.R.S. and Ramakrishnayya, B.V. (1983) Visual symptoms of potassium deficiencies in tobacco. Tobacco News. 6(2): 8-10. Krishnamurthy, V.; Reddy, P.R.S. and Ramakrishnayya, B.V. (1984) Observations on occurrence of severe potassium deficiency in field crop of flue-cured tobacco crop in northern light soils of Andhra Pradesh. Indian Tobacco Jouinal. 16(l): 3-4. Krishnamurthy, V; Reddy, P.R.S. and Ramakrishanyya, B.V. (1989) Nitrogen and potassium fertilizer management in irrigated sandy soils of Andhra Pradesh for quality flue-cured tobacco production. Int. Symp. Managing sandy soils, Jodhpur, Abstracts. 1: 355-359. Krishnamurthy, V; Reddy, P.R.S. and Ramakrishanyya, B.V. (1989b) Effect of potassium fertilization on number of transplants, seedling characters and K uptake by fcv tobacco seedlings in a sandy soil having low available K status. Tobacco Research. 15(2): 112-115. Krishnamurthy,V and B.V. Ramakrishnayya 1993) Effect of potassium on yield and quality of FCV tobacco.In "Plant Nutrition Effects on Production and quality of Tobacco" (Ed.G.Dev et al.) PPIC-India Programme, Gurgaon, Haryana, pp. 78-102. KRISHNAMURTHY, V AND B.V.RAMAKRISHNAYYA. (1994) Nitrogen and Potassium Balance in Flue-Cured Tobacco Grown in Irrigated Alfisols. Tobacco Research. 20(1): 71-73. Krishnamurthy, V; C.C.S.Rao and B.V.Ramakrishnayya. (1996) Chemical Quality Characteristics of Flue-Cured Tobacco as Affected by Different levels of N and K Fertilization in Irrigated Alfisols. Journal of Potassium Research. 12(4): 391-399. Krishnamurthy, V; B.V.Ramakrishnayya and N.S. Murthy. (1997) Distribution Pattern of Potassium is Different Segments of Flue-Cured Tobacco Leaf. Communications in Soil Science and Plant Analysis. 28(9&10): 665-671 (USA). Krishnamurthy, V and B.V.Ramakrishnayya. (1997). Potassium Fertility of Flue- Cured Tobacco Growing Soils of India. Journal of Potassium Research. 13(2): 159-169. Krishnamurthy, V.; and I.J.Chandra. (2001). Changes In Soil Fertility During Two Decades of FCV Tobacco Cultivation in Light Sols of West Godavari District, Andhra Pradesh. Journal of Indian Society of Soil Science. (Communicated) Krishnamurty, S.; Umamaheswararao, M. and Balagopal, K. (1972) Effect of continuous application of organic manure, inorganic fertilizers and their combination on the yield and quality of flue-cured Virginia tobacco in black cotton soils of Andhra Pradesh. Indian Journal of Agricultural Science. 42: 341-346. Potassium Nutrition Management for Improving ield and Quality of Flue-cured Tobacco 377

Lovett, W.J. (1959) Studies on metabolism of detached tobacco leaves I. Influence of potassium nutrition on the growth of tobacco and quality of cured leaf. Australian Journal of Agricultural Reseach. 10: 27-40. Lundegardh, J. (1945) Leaf analysis as a guide to soil fertility. Nature. 151: 310' 311. Mc Cants, C.B. and Woltz, W.G. (1967) Growth and mineral nutrition of tobacco. Advances in Agronomy. 19: 215-265. Muhr, G.R.; Datta, N.P.; Sankarasubrahmoney, H.; Leley, V.K. and Donahue, R.L. (1965) Soil Testing in India. U.S.A.I.D., New Delhi. Nakanishi, Y. (1999). Physical properties of leaf tobacco. In "Tobacco Production, Chemistry and Technology" (D.L. Davis and M.T. Nielsen, Eds.). Black- Well Science, London. pp. 313-19. Pal, N.L.; Bangarayya, M. and Narasimhamurthy, Y. Ch. (1966) Interrelation of potassium and chlorine supply on the bum of flue-cured tobacco. Soil Science. 102(5): 346-352. Parker, F.W.; Nelson, W.L.; Winners, Eric and Miles, I.E. (1951) The broad interpretation and application of soil test information. Agronomy Journal. 43: 105-112. Patel, G.C. (1965) Phosphate and potash manuring of flue-cured tobacco grown in black cotton soils of Andhra Pradesh; problems and progress - A review. Indian Tobacco. 15: 12-23, 25-31. Prabhu, S.R., B.V. Kameswara Rao and MurtyK.P.S.N. (1990). Reduction of particulate matter and nicotine in cigarette tobacco blends. Tobacco Research. 16: 141-2. Ramakrishnayya, BV. (1971) Physico-chemical and mineralogical studies in some Indian soils growing flue-cured tobacco with special reference to their fertility status. Ph.D. Thesis. Indian agricultural Research Institute, New Delhi. Ramakrishnayya, B.V. and Chartterjee, R.K. (1976) Q/I relations of soil potassium of some Indian soils of tobacco area. Bulletin Indian Society of Soil Science. 10: 93-98. Ramakrishnayya, B.V. and Krishnamurthy, V. (1982) Importance of potassium fertilization for nurseries and field crop of flue-cured tobacco in light soils of Andhra Pradesh. India. 12th Int. Cong. Soil Sci., New Delhi. Abstract 6, 405. Ramakrishnayya, B.V. and Hussaini, S.S. (1987). Interrelation of root-knot nematode and potash influe-cured tobacco. Indian Journal of Nematology. 17(1): 22-29. Ramakrishnayya, B.V. and Krishnamurthy, V. (1990) Distribution pattern of potassium in flue-cured tobacco leaf. Indian Journal of Plant Physiology. 33(1): 72-75. 378 V. Krishnamurthy, B.V Ramakrishnayya and K.D. Singh

Ramakrishnayya B.V. and V. Krishnamurthy (1996). Response of flue-cured tobacco to potassium fertilization.Journal of Potassium Research. 12: 305- 313. RAPER, C.D. Jr. AND Mccants, C.B. (1966) Nutrient accumulation in flue- cured tobacco. Tobacco Science. 10: 109. Reddy N.S. (1980) Environmental factors in production of flue-cured tobacco in Karnataka state. Tobacco Research. 6(1): 1-9. Reddy, P.R.S;C.C.S. Rao, C.C.S; Krishnamurthy, V; Ramakrishnayya, B.V; Murthy, K.S.N; Harishu Kumar, P; Rao,.U.M and Murthy, N.S. (2000) Effect of Omission of Phosphorus and Potassium in fertilizer schedule for flue- cured tobacco in Vertisols of Andhra Pradesh. Tobacco Research. 26(1) :31- 41. Sannibabu, M; T.Sitaramachari and Krishnamurthy, V. (1985) A note on occurrence of calcium deficiency in the field crop of white burley tobacco and in fcv tobacco nurseries grown in northern light soils of Andhra Pradesh. Tobacco News 8(4): 9-11. Shear, C.B.; Crane, H.L. and Myers, A.T. (1946) Nutritional element balance: A fundamental concept in plant nutrition. Proceedings of American Society of Horticultural Science. 47: 239-248. Srinivas,D. (1987) Studies on potassium and its influence on tobacco in light soils of East and West Godavari Districts of Andhra Pradesh. M.Sc (Ag) Thesis, APAU, Hyderabad. Tejwani, K.G. and Venkataraman, K.V. (1958) Nutritional balance in flue-cured tobacco. Soil Science. 86(6): 310-312. Tso,T.C. (1977). Simple correlation and multiple regression among leaf characteristics, smoke components and biological responses of bright tobaccos. Technical Bulletin No. 1551. USDA, Washington D.C. pp. 78-9. Venkataraman, K.V. and Tejawani, K.G. (1961) Further studies on the nutritional balance in flue-cured tobacco: Interrelationships between cations accumulated in leaves. Soil Science. 91: 324-340. Yamamoto, T., Umera, S; and Kaneko, H. (1990). Effect of exogenous potassium on the reduction in tar, nicotine and carbon monoxide deliveries in the mainstream smoke of cigarettes. Beitr. Tabakforschung Intl.14: 379-85. Potassium Nutrition Management of Oil Seed Crops

B.A. GOLAKIYA AND M.S. PATEL Department of Agricultural Chemistry and Soil Science Gujarat Agricultural University, Junagadh - 362 001 (India)

Introduction

The crops that are cultivated for the production of oils are known as oil seed crops. With ever increasing population, the demand of edible oil will remain at its highest peak. Oil seed production can effectively help not only in mitigating oil requirement of large segment of our population, but also will create millions of extra jobs and thereby will bring a dynamic socio-economic change across the world.

With the appraisal of world oil seed balance sheet (Table 1) it has been evident that almost one third (31.4%) of the total quantity of the oils were under international trade.

In the world output of 17 oil seeds (Table 2) major players are India (9.4%), China (13.1%), Brazil (10.6%), Argentina (8.3%) and USA (30.1%) contributing upto 71.5 per cent in aggregate. The oil seeds of our concern here are groundnut, castor, sesame, sunflower, safflower, soybean and linseed. Total world production of groundnut from an acreage of 24.5 m ha-' was 30 mt in the year 1998-99 with average yield of 1.3 t ha-'. China with 31.2 per cent share is the single largest groundnut producing country followed by India (26.8%), Nigeria (8.2%) and USA (5.8%). India (20.9%), USA (16.2%), China (15.4%), Argentina (14.7%) and Vietnam (10.7%) were the major exporters of shelled groundnut, togather contributing around 80 per cent of the total world exports. World production of castor seeds was 1.1 mt from 1.3 m ha with an average yield of 0.9 t ha-'. India is the largest producer (75.6%) of castor seed followed by China (16.0%). The total world production of sesame was around 2.3 mt in 1997-98 from an area of 0.3 m ha, with an average productivity of 0.36 t ha-'. India is the largest producer of sesame contributing around 31 per cent of the world production (Table 3). Though producing 24.7 mt of oil seeds annually, productivity is strikingly low in India (Table 4).

Oil seeds are cash crops. Oil extraction and post harvest processing attracts large section of producers, processors and traders all over the world. However, it requires quantity, stability and quality in the oil seeds produced. It is now recognized that large improvements in oil seed productivity may only be obtained by simultaneously improving nutrition and cultural practices, controlling pests and diseases along with growing the improved varieties. There are intricate

379 380 B.A. Golakiya and M.S. Patil

Table 1. World oil seed balance sheet (mt) Description 1998-99 Opening Stock 10.66 Production 105.30 Import 33.71 Export 33.69 Closing stock 10.87 Stock/use (%) 11.33 Singhal (1999)

Table 2. World output of 17 oil seeds (nt) Major player 1998-99 India 26.99 China PR 37.43 Brazil 30.47 Argentina 23.82 USA 86.14 Canada 10.62 Ex-USSR 9.70 East Europe 5.70 EU-15 15.78 Total 286.33 Singhal (1999)

Table 3. Share of India in World oil seed production Crop Production (%) Groundnut 26.8 Mustard 18.7 Sesame 31.0 Castor 75.6 Linseed 20.1 GAP report (2000)

Table 4. Production of oil seeds in India (1999-2000) Crop Oil' Production 2 Productivity3 (%) (mt) (kg ha-') Groundnut 44-56 9.1 1078 Mustard 37-42 6.0 667 Soybean 18-24 6.8 1126 Castor 35-58 1.0 900 Other five oilseeds 1.8 504 Total nine oilseeds 24.7 842 'Das (1997), 2Jain (2001), 3Damodaran and Hegde (1999) Potassium Nutrition Management of Oil Seed Crops 381

interactions between these factors, which combine to give large increase in yield (Covke and Gething, 1979). Possibly, the most striking and widespread interaction between oil seed production factors is that found to exist between HYV's and fertilizers (Arnon, 1979). Importance of this interaction has also been realized for groundnut (Patil et al., 2000) and mustard (Kumar, 1982; Bhola and Yadav, 1982). The requirement of potassium for normal growth and development in all living organisms is well established. Next to nitrogen and phosphorus-potassium is a limiting fertilizer element in Indian soils. The information that is available from other parts of the world indicates that whereas the application of nitrogen results in reduction of oil content, this adverse effect is corrected by the application of potassium (Bhumbla, 1978; Swami and Yadav, 1985). There are number of reports to indicate response of applied potassium on oil seed crops (Tandon, 1989; Das, 1997; Golakiya, 1999; Golakiya and Gundalia, 2000).

Present paper is an attempt to rectify the different facets of potassium nutrition management in oil seeds, viz., rate, methods, timing, genotypes, seasons, soil types, interactions of potassium with other nutrients, cropping sequences, yield targeting, DRIS norms, etc.

Critical Limits of K

Potassium requirement of oil seeds varies with the crops (Table 5). Depending upon the yield, it ranges from 2.35 kg to 9.5 kg K q for linseed and mustard,. respectively. The uptake of potassium in oil seeds viz., mustard, groundnut, soybean, sunflower, sesame and linseed was reported to be 133, 110, 101, 141, 64 and 72 kg ha-', respectively (Aulakh et al., 1985; Jain et al., 1984). It was next to nitrogen uptake by the some of the oil seed crops. The deficiency, sufficiency and higher limits of potassium varied with the crop, variety, location and soils (Table 6). Mustard and sunflower seem to be heavy feeder of potassium. The soil critical limits of exchangeable potassium for oil seeds in the different countries also varied with soil orders (Table 7). The soil critical limit of potassium in Vertic Ustochrepts of Western India was 145 kg ha-' (Fig. 1c). Similarly the critical concentration of K in the pod at 30 DAS (Fig. la) and the same in haulm at harvest (Fig. lb) was 0.9 and 0.46 per cent, respectively, to harvest 86 Bray's

Table 5. Potassium requirement of oil seeds Crop Yield (kg ha-) KR (kg q-1) Groundnut 1900 3.8 Castor 900 3.69 Mustard 1500 9.51 Soybean 2500 5.37 Sesame 1200 4.35 Linseed 1600 2.35 Subba Rao and Srivastava (2001) 382 B.A. Golakiya and M.S. Patil

Table 6. Deficiency, sufficiency and high limits (%) of potassium in oil seeds. Crop Deficient Sufficient High Reference/Remark Groundnut 0.01 0.21 to 0.68 > 1.30 Burkhart & Collins (1942) Castor 1.19 2.12 > 2.32 Moshkin (1986) Mustard 1.50-1.99 2.0 to 4.0 > 4.00 Tandon (1993) Soybean 1.26-1.70 1.71 to 2.50 > 2.51 Tandon (1993) Sunflower 2.01 2.37 >_ 3.22 Carter J.K. (1978)

Table 7. Critical limits of exchangeable potassium in soils for oil seeds. Crop Critical soil Soils Reference Ex. K status Sunflower 70-82 mg kg-' Siliceous sands of Lewis et al. (1990) SE Australia Soybean 0.14 Cmol kg- 1 Indonesian Ultisols Themon et al. (2000) 0.10 to 16 Cmol kg-' Humid tropics of Gill (1988) West Sumatra Groundnut 0.19 Cmol kg- 1 Humid tropics Cox and Urib (1992) Ultisols 145 kg K20 ha-' Vertic Ustochrepts Golakiya (1999) of Gujarat

110 Fig. lb Fig.[a I101 '100* 11W O

/ nttaT*:0.97%KMt~.k*&4%khLT

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 14 0.3 0.4 0.5 0.6 0.7 K content (%) K content (%)

F.it.ld 110 Fit.Ic

1000-

90-

-- 50 F 100 150 2W 250 00 350 LOW Medxn High Availabi K O (kg ha')

Fig. I. Critical limits of potassium in Groundnut Pa asu N.wri.. i Lanage ne of Oil Serd Cro 383 per cent yield (Golakiya, 1999a). The yield response of groundnut gradually increased with diminishing available potassium (Fig. ld). The critical leaf concentration of potassium for maximum yield in soybean was 1.2 per cent (Cox and Uribe. 1992). However. Tandon (1993) reported broad range appreciable for diverse area.

Determinants of Potassium Management in Oil seeds

Plant tissues, particularly young growing organs, are rich in potassium. Although crop needs considerable amount of potassium, potash fertilizer application does not yield crop response in each and every case. Soil properties and peculiarities of crops influence the effectiveness of potash fertilizer. About 17 major oil seeds are grown all over the world in varied soils and agro-climatic conditions. Potassium nutrition management in them varied with soil status of potassium, crop, variety, soil type, season, productivity, etc. To rectify the effects of these factors on crop response to potassium, an example of groundnut crop with database of 100 field trials is reviewed here.

Soil Productivity:

Productivity of groundnut ranges from 1000 to 6000 kg ha I in the soils of Western India. But for general assessment, 70 field trials were subdivided into low (< 1000 kg ha-'), medium (1000 - 2000 kg ha- ) and high (> 7200 kg ha>) productivity classes (Fig. 2a). Almost a dozen soils with low productivity registered yield increment upto 24 per cent under 80 kg K20 ha- over no potassium control. The yield response under medium productive soils was upto 12 per cent. We usually consider 12 per cent yield response as routine level - not attractive for the farmers. Yield response of groundnut to K under high productivity soils was to the tune of 22 per cent. Why the crop under medium productive soils skipped away from K response? Perhaps the medium productive

2 22

o> is 16 514] 0 12 1 .- Low Medium High Productivity Productivity Productivity (12 trials) (25 trials) (33 trials) Fig. 2a. Soil productivitv 384 RA Goakiyu ad MS. P11i soils are medium in fertility while low productive soils needs K due to low fertility and high productive soils need K to sustain the higher yield levels.

Season:

Groundnut in is grown during monsoon and summer. Season plays pivotal role in groundnut production (Fig. 2b). Groundnut response to graded levels of K under monsoon ranges from 12 to 15 per cent while the same under summer ranges from 13 to 24 per cent. This is because groundnut yield under summer are stable and above 1000 kg ha- due to assured irrigation. Hence the crop responds to better management practices. While monsoon groundnut is subject phenophasic drought and pest epidemics hence its yields are low and unstable (Golakiya, 1999). This is how season is an important determinant of groundnut response to K,

Monsoon 0 (37 trials)

C)

",s u m m e r 14 .6 ...

1-040 I] 80 0 120kgKO ha' Fig. 21,. Searn Genotypes:

Variety x K interaction is very valuable positive interaction, which the farmers can take advantage of by growing high yielding and other improved varieties. It was found in over 11,000 experiments on farmers fields that the addition of 60 kg KO ha- in combination with N an P resulted in HYV's producing 1.1 to 1,3 more units of seeds/kernels per unit of applied potash that locally improved tall varieties (Tandon and Kanwar, 1984). This 26 per cent increase in effectiveness of K occurred in both the seasons. Farmers of Western India are highly adaptive to new agro-techniques especially new varieties. Location specific genotypes are available. Farmers sow almost a dozen of genotypes of groundnut. be it spreading. semi spreading, erect, bold seeded or short duration. Genotypes differ in response to fertilizers, Potassium is not an exception (Fig. 2c).

The yield response of five promising genotypes to K varied from 22 to 51 per cent at 80 kg KO ha over control (Patil et al., 2000). Usually the genotypes Possmium N i .f.t wAanagemen of Oil Seed (Irops 385

GG4

JG6l- GG-5

TG-26

J-11

0 20 40 60 % yield at 80 kg KO ha over control

Fig. 2x. Ge O.tees

Table 8. Modelling rhe determinants of K nutrition management in groundnut. Determinant Productivity Modeling Soil productivity Low Y = 4,412 + 1,843 1x - 0.2529x (12 trials) R2 = 0.96 Medium Y = 12.002 + 7713x - 0.0607x 2 (25 trials) R? = 0.7504 High Y = 14.68 + 5.0527x --0.6493x (33 trials) R2 = 0.9533 Season Monsoon Y 12.676 + 1.6531x - 0,1829x: (37 trials) R- = 0.9383 Summer Y 13.024 + 4.01lx - 0.515x2 (33 trials) W = 0.8289 Available K Medium Y = 7.232 + 3.058x - 0,3993x2 (18 trials) W = 0.8966 High Y = 12.864 + 2.8897x - 0.3643x2 (52 trials) R2 = 0.9375 with broad haulm-pod ratio, long duration and bold seeded, responded more to K application. In many case the root characteristics also play major in determining yield response to nutrient application (Zizala el al, 2000). Subba Rao and Srivastava (2001) also observed wide variation in potassium requirement of mustard (Table 9) and groundnut (Table 10) genotypes. For the similar yield targets the varieties differd in their potassium requirements.

Soil available K:

Soils of Western India are adequate in available K (Golakiya and Patel, 1988). The crop under medium and high available K responded to the extent 23 386 1tA, Gclakiva and MS, tai

Table 9. Fertilizer potassium mnagement according to soil tvjus in miustard. Soil type Variety KR CS%quation Yield range (kg q-)

Mollisol Kranti 9.51 33,0 145.0 FK 2O 10-15 6.55YT-0.22STV Medium Varuna 6.69 15,0 143.0 FKO = 16 black soil 4.66T - 01J3 SK Alluvial Pusa bold 137 40.0 21.0 FKO = - 16 6.ST - 0.19 SK Subba Rao and Srivastava (2001)

Table 10. Varietal differences in potassium management in groundnut. Variety KR (kg q') Equation Yield range

JI -24 0.72 FK2O = 3.14T - 0.16 SK - 25 M-13 3.80 FKO = 3.09T - 0.25 SK20 - 20 Tirupati 1.52 FK,0 = 4,06T - 0,36 SK ~ 20 Girnar-I 2.36 FK2O = 1.84T - 0.75 SK - 25 POL 1 5.00 FKO = 8.35T - 0.65 SK-0.87 OK - 25 Subba Rao and Srivastava (2001) to 27 and 13 to 18 per cent respectively (Fig. 2d). The crop under 52 field trials with high available K soil responded to K application. The soils of Saurashtra are calcareous Vertic Ustochrepts. Though rated high in available K - the crop at 50 to 75 DAS suffers from hidden hunger of K. It was evident front the literature (Bunsa and Golakiya, 20 0 Chodvadiya et al., 2000) that the disruption occurs among the inter-relations of forms of K and its relation to K content in plant at 50 to 75 DAS (Chodvadiya et al., 2000). Hence even the high available K soil failed to cop-up with crop demand of K at 50 to 75 DAS. Therefore, the crop responded to K application in high available K soils. 20 1 0 _jkg 120 KO ha

a 10 kg K O ha

2313

Medium K High K (18 Trials) (52 Trials)

Fig. 2d. Sil available potaxssw Potassium Nutrition Management of Oil Seed Crops 387

Source, Rate, Method and Time:

As stated earlier, the most common and widely used potassium fertilizer is potassium chloride (MOP) which accounts for 99% of all potash used. It is about half as expensive as potassium sulphate (SOP). For most situation, the recommended source is MOP (60% K20) due to lower per unit cost, and the question of a choice of fertilizer is hardly discussed.

For some specific situations where the crop quality is of major importance and exclusion of excess chloride as in MOP, is needed, the use of potassium sulphate (50% K20 + 18% S) is recommended to obtain superior quality produce. Some recommendations on this aspect have been summarized by Tandon and Kemmler (1986).

Groundnut response to K is determined by the rate of K application. Several experiments wherein the crop failed to respond to K application the reason being just low (< 30 kg K20 ha-') rate of K application (Patel et al., 1993). The average (70 trials) response of groundnut to K application at 80 kg K20/ha was upto 17 per cent. Lower doses are not effective due to K fixation in soil. While high dose of the same order were deleterious due of built up to transitory salinity in already alkaline aridisols (Golakiya, 1997).

The most common recommendation for seasonal crops is to include potash in basal dressing and apply it by drilling, placement, furrow application or broadcast before sowing/transplanting. In the case of NPK complex fertilizers which account for about one-third of all potash applied in India, the potash is obviously applied as a part of the NPK application. Although application to the soils is the most common recommendation, for a number of crops, foliar spray of potash is also recommended to supplement the soil application. In such cases, potassium sulphate and occasionally potassium nitrate is recommended to avoid/ minimize leaf schorching due to Cl.

In seasonal crops, the most common recommendation is to apply the full dose of potash as a basal dressing. However, over the years, recommendations for split application of potassium have been emerging, more particularly for groundnut grown in light-textured soils in high rainfall area in order to reduce the possible leaching losses.

In India, split application of both potassium and nitrogen is recommended in the states of Andhra Pradesh, Kerala, Orissa and Uttar Pradesh. The initial potassium status of the soil is also an important factor in determining the best strategy for potash application. Adding NK granules in one or two splits in the standing crop was more advantageous than application of the entire amount of potassium as basal dose. 388 B.A. Golakiya and M.S. Patil

Interaction with other nutrients

The occurrence of interactions among plant nutrients or between nutrients and other inputs of production is a common feature of crop production. These interactions can either be positive or negative. They become increasingly important as agriculture is intensified. In practice, positive interactions are a real bonus and farmers should be guided to exploit it. Sound advice on potassium management should help farmers to realize the most from positive interactions in terms of yields, nutrient use efficiency and net return while avoiding negative interactions. Many times negative interactions occur due to lack of appreciation for balance nutrient application which is in its broad sense means taking care of all nutrient deficiencies. There is less research on interactions, involving potassium than in case of other major nutrients. The more important interactions involving potassium in oil seeds are discussed here (Table 11).

Table 11. Interaction of potassium with other nutrients in oil seeds. Crop Interaction Plant S/NS Magnitude Reference part (%) Groundnut K30 x N25 Pod S 16 Golakiya (1999a) Haulm S 21 Golakiya (1999) K60 x N50 Pod S 17 Gundalia et al. (2000) Shelling S 2 Gundalia et al. (2000) Oil S 0.5 Gundalia et al. (2000) K60 x Zns0 Pod S 27 Polara et al. (2000) K100 x Ca,,, Pod S 32 Singh (2000) Ki00 x B2 Pod S 25 Singh (2000) Sesame K60 x N60 Grain S 19 Vinay Singh et al. (1991) Linseed K44 x S35 Grain 5 38 Singh and Singh (1994) Oil 5 1.2 Singh and Singh (1994)

Potassium plays on important role in ensuing efficient utilization of nitrogen. Since nitrogen comes foremost in the farmer's fertilizer programme, the N x K interactions assumes special significance. This is perhaps the most researched interaction and also of major practical importance as well. Pod and haulm yield of groundnut increased by 17 and 21 per cent, respectively. Shelling by 2 per cent and oil by 0.5 per cent in groundnut (Golakiya, 1999; Gundalia et al., 2000). With the same interaction in sesame, seed yield increased by 19 per cent. Interestingly, the pod yield of groundnut increased upto 27and 32 per cent under K x Zn (Polara et al., 2000) interactions. Application of Zinc increased potassium content in soybean (Gupta and Gupta, 1984) in sodic soils. This perhaps indicates that Zn is a limiting nutrient in sodic soils and its application improves crop growth and nutrient uptake. Similarly, the pod yield increased upto to 23 per cent under K x B interaction. Grain yield of linseed increased upto 38 per cent under K x S interaction (Vinay Singh et al., 1991). The large quantity of N used Potassium Nutrition Management of Oil Seed Crops 389 in intensive cropping encourage crop uptake of N and K in farm deplete soil available K.

Environmental stresses

Majority of the oil seeds are rainfed, grown on marginally fertile soils. Dry spells, pest and disease epidemics are common occurrence in these corps. Potassium is well reputed for drought insulation (Rajgopal, 1985), disease (Sekhon, 1982b) and pest resistance (Table 12, 13). Effect of potassium on groundnut under water stress have been reviewed (Golakiya, 1999; Golakiya and I Patel, 1992, Golakiya, 1993). Potassium at 60 kg K20 ha- as KCI, or a 2 per cent K solution sprayed at 40 DAS increased the yield by 10 or 6 per cent, respectively (Golakiya and Patel, 1988).

Table 12. Effect of potassium and drought stress in groundnut. Dry spells Pod yield kg ha- I

Control 60 kg K20 ha-' 2% K spray Control 1957 2150 (10) 2062 (6) Single 1486 1613 (9) 1538 (4) (24) (25) (35) Double 835 1039 (24) 892 (7) (57) (52) (57) Triple 485 612 (21) 524 (8) 1 (75) (72) (75) Golakiya and Patel (1988)

Table 13. Effect of potassium on diseases and pests of oil seed crops. Crop Disease/pest *K+ Reference English name Latin name effect Groundnut Tikka leaf spot Cercospora + Bala Sundaram et al. (1976) personata Sunflower Root rot Macrophomina + Sivaprakasam et aL (1975) phaseolina Mustard Mustard aphid Lipaphis erysimi 0 Kundu & Pant (1968) Mustard Mustard aphid Lipaphis erysimi 0 Kundu & Pant (1968) Mustard Mustard aphid Lipaphis erysimi 0 Kundu & Pant (1968) Soybean Nematode Cyst nematode + Borkert et al. (1987) Stink bug Cercospora + Borkert et al. (1987) kikhchi Yellowing Cercospora + Borkert et al. (1987) kikhchi 390 B.A. Golakiya and M.S. Patil

Potassium application reduced the incidence of stem rot and sesame leaf spot significantly (Subramaniun and Balasubramanian, 1977). Potash application reduced the tikka disease of groundnut (Balasubramanian et al., 1976), leaf blight of cotton (Weir et al., 1986) and yellowing in soybean (Borkert et al., 1987). The potassium application improves resistance to environmental stresses by osmo-regulation, proline accumulation, induction of phenolics, betains, phytoalaxins an by morpho-phenological changes in plants.

Potassium and crop quality

Soybean

Soybeans are grown for both protein content (26-40%) and oil content (16- 26%) in general; an inverse relationship between the oil and protein contents of soybean seed has been observed (Appelqvist, 1977; Davidescu et al., 1977). Increased application of N, relative to P and K decreases the oil content, whereas increased application of P and K relative to N increased the soil content.

Gaydou and Arrivets (1983) determined the effect of K supplementation on oil content, protein content and yield of soybeans grown in Madagascar. When 1 K was increased from 0 to 75 kg ha- (0-90 kg of K20 ha-1), the increase in oil content was significant at the 0.05 level of probability, and the decrease in protein content was highly significant (P=0.01). Jones et al. (1977) observed that applied K increased the number of nodules, the total and individual weights of the nodules, and the number of pods per soybean plant more than P, but increases were largest when both K and P were applied.

Mustard

Forster (1977) compared the effects of N and K fertilizers on a high erucic acid producing winter mustard cultivar and three other winter cultivars low in erucic acid. With increasing K, the oil content was progressively augmented. The most dramatic effect of increasing N and K nutrition was in the production of larger numbers of seeds per plant. The increase in oil yields reflects the greater seed yields.

Under field conditions in Bangladesh, Joarder (1983) observed differences among cultivars in response to fertilizer treatments. With increasing levels of NPK, the oil content of 'Assam Local' increased from 373 to 383 g kg- 1. No significant effect by K on oil content of mustard was observed by Sheppard and Bates (1980). These investigators concluded that the Canadian soils probably contributed ample K. Potassium Nutrition Management of Oil Seed Crops 391

Sunflower

Sunflower has a high K requirement, approximately 200 kg tonne-' of seed. Devidescue et al. (1977) reporting on experiments said that a K deficiency induced by withholding K fertilizer for 27 yrs. at Versailles, France, reduced sunflower oil content from 49.5-40.9%.

In the sunflower production area of Minnesota, the sandy loam soils are generally low in K: often < 112 kg of exchangeable K ha - , and low in available N usually < 34 kg ha-. Simkins and Overdahl (1982) showed that additions of K to these sandy soils dramatically increased oil content and oil yield. The yields of seed and oil were nearly doubled when the K applied was increased from 0 to 222 kg ha-' (0-268 kg of K20 ha-'). Fertilization with K increased the size of the sunflower heads and seeds.

Groundnut

Pande et al. (1971) studied the response of groundnut to field trials on NPK on a sandy loam soil in Orissa, India. The highest level of K tested, 40 kg ha-', increased the oil content from 47.8 to 48.8 per cent. A combination of NPK (20+40+ 40 kg ha-') gave an even higher oilcontent, 49.3%. This combination of NPK also increased the protein content of groundnut from 24.9% (for the control) to 27.3%.

Bhuinya and Chowdhury (1974) stated that application of K to Brahmaputra floodplain soil in Bangladesh increased the oil content of groundnut and that the response to applied K was greater than for P. The K application, however, decreased protein content.

Senegal is the largest producer of groundnuts in Africa. Ochs and Ollagnier (1977) reported that the response of groundnuts to K is very variable in Senegal. Generally the response is small, but in some areas, K can be the most important nutrient. In experiments carried out in Senegal by the Institut de Recherches pour les Huiles et Oleagineux (IRHO), application of K decreased oil content slightly (0.5%), but an increase in pod yield of 143% made the fertilizer application cost effective. Many workers reported positive effect of potassium on the quality parameter of groundnut viz., test weight (Jana et al., 1990; Chavan and Kalara, 1983; Bhalero etal., 1993), shelling (Mishra, 1994; Ganeshmurthy and Balasubramaniyan, 1992), oil content (Shahid Umar et al., 1994; Young 1983) and protein content (Angadia et al., 1989; Kankapure et al., 1994).

The crop response

Swami and Yadav (1995) reviewed the published work on the response of oil seeds to potassium application. Out of about 600 trials, almost 60 per cent trials turned out with significant response of potassium. About 75 per cent of the 392 B.A. Golakiya and M.S. Patil trials with groundnut, sunflower and soybean registered with significant positive effect of potassium fertilization (Table 14). In sesame, about 40 per cent of the trials reported with significant response of potassium. However just 10 per cent of the trials in mustard were with significant effect. Optimum fertilizer recommendations for rainfed oil seed are recorded in Table 15. The remunerative - doses of potassium for various oil seeds varied from 20 to 40 kg K20 ha in a large number of fertilizer trials on farmer's fields with groundnut, mustard, sunflower, soybean, safflower and castor (Kulkarni et al., 1980b). The average increase in pod yield of groundnut was 3 kg per kg potash applied at 40 kg K20 ha-'. Large numbers of experimental results on response of groundnut to fertilizers have been summarized by Kanwar et al. (1983). In mustard response to potassium was significant in Bihar and Gujarat at 40 kg K20 ha-' the average response being 4.5 to 5.5 kg grain per kg K20. In sesame, there was a marginal response 1 to potassium; 6.2 kg grain per kg K20 applied at 40 kg K20 ha- . in linseed significant response to potassium was reported only from Himachal Pradesh (10.5 to 19.5 kg per kg K 20).

Table 14. Distribution of response of oil seeds to potassium application in India. Crop Total number Positive No Negative of trials response response response Groundnut 702 524 139 39 Mustard 354 28 - 326 Sesame 95 39 11 45 Soybean 426 321 82 23 Sunflower 52 38 12 02 Swami and Yadav (1995)

Table 15. Optimum fertilizer ratesfor rainfed oil seeds based on farm experiments

Crop N-P 20 5-K20 District covered kg ha-' Groundnut 30-40-30 Anantpur, Mohboobnagar (AP), Bellary, Gulbarga (Karnataka), Dhule (Maharashtra) 20-60-40 Anravati, Sangli, Nanded (Maharashtra) 20-60-30 Prakasam (AP) Mustard 30-30-20 Bharatpur (Rajasthan) 60-40-20 Alwar, Ajmer (Rajasthan) 20-40-20 Manipur (Manipur) Niger 45-15-00 Hazaribagh (Bihar), Dhenkenal (Orissa) Safflower 50-40-40 Mahboobnagar (AP), Dhenkenal, Koenjhar, Puri (Orissa) Sunflower 60-00-00 Nalgonda (AP) 60-40-40 Hazaribagh (Bihar) Castor 40-40-20 Mahboobnagar, Nalgonda (AP) Tandon (1993) Potassium Nutrition Management of Oil Seed Crops 393

Apathy of farmers towards fertilizer recommendations has remained pivotal problem of TOT (Table 16). About 60 per cent of the farmers adopted fertilizer recommendations for oil seed crops (Kiresur et at., 1995). Maximum adoption (82%) was reported with sunflower followed by sesame and mustard. Contrarily, just 24 per cent adoption of fertilizer package was observed in groundnut - the main oil seed crop.

Table 16. Adoption of fertilizer components in different oil seeds. Adoption level Groundnut Sesame Mustard Linseed Sunflower Mean Complete 24.3 73.5 71.1 38.1 82.0 60.0 Partial 71.4 25.5 20.9 60.0 20.0 38.0 Non-adoption 4.3 1.0 8.0 1.8 8.0 2.0 Kiresur et at. (1995)

Oil seed based cropping sequence

Oil seeds are a core group crops in the popular cropping sequences allover the world. Fortunately, we have results of LTFE's with balance nutrition in oil seed based cropping sequence (Table 17). Potassium has been an integral component of balance ratio in the fertilizer package for the cropping sequences. Of course, the yield increase is a time dependent variable in such trials. Groundnut yield increases by 20 to 79.8 per cent in NP vs. NPK treatments, similarly, yield of soybean, sunflower and mustard was reported to increase by 30.7, 27.2 and 20.0 per cent respectively under NPK over NP treatment. Sequential trials thus established role of K in balance nutrition over a period of time.

Table 17. Potassium management in oil seed based cropping sequence. Crop sequence % (NP vs NPK) Reference increase in yield Groundnut-wheat (12 years pooled) 45.4 24.6 Golakiya et al. (2000) Groundnut-pearl millet (3 years pooled) 26.2 24.1 Golakiya et al. (2000) G'nut-wheat-sorghum (20 years pooled) 79.83 42.63 39.10 Golakiya et al. (1998) Soybean-wheat (14 years pooled) 30.7 47.8 Kunau et al. (1990) Sunflower-soybean 27.2 26.5 Kunau et al. (1990) Mustard-sorghum 20.0 33.4 Prasad (1993) Groundnut-oat 20.0 26.7 Prasad (1993) 394 B.A. Gotakiya and M.S. Patil

Yield targeting with potassium

The variable of potassium in the yield targeting equations for nine oil seeds clearly established effectiveness of potassium to harvest maximum yields (Table 18). The yield targets range from 5 to 35 q ha-' in different crops. The required soil dose of K20 can be calculated on the base of pre-decided yield level and test value of K/K 2O.

Table 18. Yield targeted potassium nutrition management equations for oil seeds. Crop Equation Yield range

Groundnut FK20 = 3.09T - 0.20 SK 20 - 20 Castor FK20 = 3.02T - 0.10 SK - 15 Mustard FK 20 = 6.55YT - 0.22 STV 10-15 Soybean FK20 = 5.36YT - 0.58 STV 30-35 Sesame FK2O = 10.54T - 0.74 SK 20 - 10 Sunflower FK20 = 5.62T - 0.19 SK20 5 Safflower FKO = 9.87T - 0.47 SK20 5.5 Linseed FK20 = 3.06T - 0.22 SK 20 - 20 Subba Rao and Srivastava (2001)

Potassium in DRIS norms for oil seeds

A little work has been done so far on diagnosis and recommended integration system in oil seeds (Table 19). However, the DRIS norms for soybean (Hallmark et al., 1985), sunflower (Grower and Sumner, 1982) and groundnut (Dadhania et al., 2000) are quoted here to recognize the relative importance of potassium in DRIS norms for oil seeds. It is the relative proportion of K as compared to N and P in the leaves.

Table 19. DRIS norms in oil seed crops. Crop P/N N/K P/K Reference Soybean 0.14 2.69 0.18 Hallmark et al. (1985) Sunflower 0.09 3.18 0.21 Grower and Sumner (1982) Groundnut 0.08 2.35 0.18 Dadhinia et al. (2000)

Lessons from LTFE

Long Term Fertilizer Experiments (LTFEs) provide the means for studying changes in crop productivity and soil fertility under given levels of input use and management practices over a period of time. These LTFEs can predict the likely changes on farmer's field which is similarly cultivated, fertilized and cropped year after year. These provide us insights into nutrient buildups or Potassium Nutrition Management of Oil Seed Crops 395

depletions over time. One advantages of a long-term experiment is that it uncovers situations where crop response to a nutrient may be small or absent in the initial stages but becomes important after a few years of intensive cropping.

Where farmers do not apply any potassium, the crops withdraw potassium entirely from the soil reserves. Continuous cropping without potassium application results in depletion of the soil potassium with the result that even soils which were initially well supplied (high) in K, became potash deficient (Golakiya et al., 2000). Direct consequences of this are that (i) such soils lose the ability of producing high yields without supplemental K and (ii) crops start responding to potash application.

The rate at which soil potassium becomes depleted and crop responses to potassium start appearing is not the same under all conditions. It may take 1-15 year or even longer for crops intensively grown on a fixed site to respond to potash application. Sometimes, despite of a drastic fall in the laboratory-estimate of available potassium, the crops do not respond to potash (Singh and Brar, 1986). In such situations, the non-exchangeable fraction of soil potassium is able to release potassium at a fast enough rate to meet crop needs. Irrigation water high in K can also delay the onset of potassium deficiency.

The consequences of continuous cropping without potassium application are different at low yield + low input use + low level of crop management than that at moderate to high yield levels achievable in many cases by an N + P application (Table 20).

Table 20. Potassium balance (1(0 kg ha-) after two cycles of crop rotation. Cropping sequence Initial Added Total Actual Net available balance +/- Groundnut-sunflower-sesame 465 180 645 501.4 +36.4 Sesame-sunflower 465 180 645 505.2 +40.2 Soybean-safflower-sesame 465 110 575 425.5 -19.4 Cotton-groundnut 465 150 615 518.3 +53.3 Cotton-sunflower 465 180 645 441.9 -23.1 Sorghum-sunflower-groundnut 465 210 675 494.5 +34.5

Cropping without fertilizer application resulted in an average removal of 78.5 kg K20 ha-' year- (Swarup et al., 1998). This varied 4.6 fold among locations depending upon the soil type, cropping pattern and yield levels. The application of N alone led to a 57% increase in the removal of potassium by crop as compared to unfertilized plots and the N + P application brought about an average of 145% increase in K uptake. In absolute terms, greater crop growth made possible by N application in several cases enabled the crop to extract 50- 120 kg extra K20 from the sol each year. Potash removal under the optimum N + P application (over the control) exceeded 100 kg K20 ha-' year'. The highest 396 B.A. Golakiya and M.S. Patil rates of K-depletion were observed in the alluvial, black and Terai soils while the lowest rates were found in the red larns ofRanchi and Bangalore.

Conclusion

This text is a critical appraisal of potassium management in oil seeds. Oil seeds are energy rich crops grown on marginally fertile soils. Hence fertilizer package in oil seeds require a careful management of potassium. Different facets of potassium manager viz., soil status, critical limits, soil productivity, season, genotypes, source rate, metlhod and timing of the application, interactions of other nutrients and environmental stress have been reviewed across 75 research scripts. Special emphasis has been given to assess the effect of potassium management on crop quality in oil seeds. Latest concept of fertilizer manager viz., oilseed based cropping sequence on LTFE basis, yield targeting and DRIS norms in context of potassium manager have been discussed. Lesions from LTFE ventilate retrospects and prospects of the place of potassium in the fertilizer package.

References

Angadia, V.V., Sheelavantar, M.N. and Chittapur, B.M. (1989). Influence of levels of NPK and split application of nitrogen on N uptake protein and oil .contents of bunch groundnut in Vertisols under Irrigation. Karnataka Journal of Agricultural Science. 2(3): 223-225. Appelqvist, L.A. (1977). Relationship between the use of fertilizers and the production of lipids. In Fertilizer use and production of carbohydrates and lipids. Proceedings of Colloquium of InternationalPotash Institute. 13: 257- 268. Arnon, I., (1999). Fertilizer use as a lead practice in modernizing agriculture, In Potash Research - Review and Trends, pp. 451-478, IPI Switzerland. Aulakh, M.S., Sidhu, B.S., Arora, B.R. and Singh, B. (1985). Content and uptake of nutrients by pulse and oilseed crops. Indian Journal of Ecology, 12(2): 238-242. Balasundaram, C.S., Shanmugam, M., Krishnamoorthy, K.S. and Purushothaman, D. (1976). Influence of potassium nutrition on the incidence of tikka leaf spot disease of peanut (Arachis hypogaea L.), Potash Review, Sub 23 Suit 47: 1-3. Bhalero, P.D., Jadhav, P.N. and Fulzele, G.R. (1993). Response of promising groundnut genotypes to fertilizer levels during summer. Indian Journal of Agronomy 38(3): 505-507. Bhola, A.L. and Yadava, T.P. (1982). Management practices for repeseed-mustard, Potassium Nutrition Management of Oil Seed Crops 397

Indian Farming, 32: 48-50. Bhuinya, Z.H. and Chowdhury S.U. (1974). Effects of N, P, K and S on the protein and oil content of groundnut grown in Brahmaputra flood-plain soil. Indian Journal Agriculture Science 44: 751-754. Bhumbla,, D.R. (1978). Keynote address. International symposium on potassium, New Delhi. Borkert, C.M., da Costa, N.P., de B. Franca Neto, J., Sfredo, G.J., Henning, A.A. and Palhano, J.B. (1987). Potassium fertilization reduces disease and insect damage in soybeans. Better Crops International 3, 2, 3-5. Bunsa, P.B and Golakiya, B.A. (2000). Groundnut response to potassium in calcareous soil. In : Vol.11 - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 101-104. Burkhart, L. and Collins, E.R. (1942). Mineral nutrients in peanut plant growth. Soil Science Society of American Proceeding. 6: 272-280. Carter, J.R. (1978). "Sunflower Science and Technology". American Society of Agronomy. Crop Science Society of America, Modison, Wisconsin, U.S.A., pp. 113. Chavan, L.S. and Kalara, G.S. (1983). Effect of phosphorus and potassium levels under varying row spacing on yield, quality and nutrient uptake by groundnut variety TG-I under high rainfall conditions of Konkan region of Maharashtra. Indian Journal of Agriculture Research 17(1/2): 64-67. Chodvadiya, M.B., Golakiya, B.A., Polara, J.V., Marsonia, P.J. and Babaria, N.B. (2000). Quantity-intensity relationships of potassium in calcareous soils of Saurashtra. In : Vol.II - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 37-41. Cooke, G.W. and Gathing, P.A. (1979). Changing concepts on the use of potash, In Potash Research - Review and Trends, pp.361-405, Switzerland. Cox, F.R. and Uribe, E. (1992). Potassium in two humid tropical ultisol under a corn and soybean cropping system. I. Management. Agronomy Journal. 84: 480-484. Dadhania, S.M., Gundalia, J.D., Polara, J.V. and Tank, N.K. (2000). Development of Diagnosis and Recommendation Integrated System (DRIS) norms for groundnut grown on calcareous black soil. In : Vol.11 - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. III- 115. Damodaran, T. and Hegde, D.M. (1999). In oil seed situation A statistical compedium, Directorate of Oil seed Research, Rajendranagar, Hyderabad. Das, P.C. (1997). "Oil seed crop of India". Kalayani Publishers, Ludhiana. Davidescu, D., Crisan, 1. Davidescu, V and Borza, J. (1977). Relationship between 398 B.A. Golakiya and M.S. Pati

environmental conditions and oil content in sunflower and soybeans. In fertilizer use and production of carbohydrates and lipids. Proceedings Colloquium of International Potash Institute 13: 311-327. Forster, H. (1977). Influence of N and K fertilizers on the quality and yield of oil from old and new varieties of rapeseed (Brassica napus ssp. Oleifera). In Fertilizer use and production of carbohydrates and lipids. Proceedings Colloquium of International Potash Institute 13: 305-310. Gananamurthy, P. and Balasubramanian, P. (1992). Influence of phosphorus and potassium on rainfed groundnut. Indian Journal of Agronomy 57(4): 755- 757. GAP Report (2000-01). Published by Confederation of Indian Industry, pp. 47- 71. Gaydou, E.M. and Arrivets, J. (1983). Effects of phosphorus, potassium, dolomite, and nitrogen fertilization on the quality of soybean. Yields, Proteins, and lipids. Journal of Agriculture and Food Chemistry. 31: 765-769. Gill, D.W. (1988). Response of upland crops to potassium at three levels of aluminium saturation in ahumid tropics of West Sumatra. Ph.D. diss. North Carolina State University Raleigh (Diss. Abstract 88-21759). Golakiya, B.A. (1993). Drought response of groundnut :VII. Identification of the critical growth stages most susceptible to water stress. Advances in Plant Science. 6(1): 20-27. Golakiya, B.A. (1997). Annual report of GAU-PRII-IPI Project. p. 7. Golakiya, B.A. (1999). Potassium fertilization of groundnut in Saurashtra region, India. Proceedings of Workshop C organized by the International Potash Institute at the 16ti Word Congress of Soil Science, Montpellier,France, 20- 26 August 1998 pp. 57-69. Golakiya, B.A. (1999a). Water stress and nutrient management in groundnut. Proceeding of Dahlia Greidinger International Symposium on Nutrient management under salinity and water stress held at Israel Institute of Technology, Haifa, Isarel, pp. 67-80.. Golakiya, B.A. and Gundalia, J.D. (2000). Crop production constraints and their remedies in calcareous soils of Gujarat. Preceding of National Symposium on Balance Nutrition of Groundnut and Other Field crops Grown in Calcareous Soils of India held at GAU, Junagadh during 19-22 September, pp. 193-204. Golakiya, B.A. and Patel, M.S. (1988). Role of potassium in counteracting the effect of cyclic drought on groundnut. Journal of Potassium Research. 4(4): 163-167. Golakiya, B.A. and Patel, M.S. (1992). Growth dynamics and reproductive efficiency of groundnut under water stress at different phenophases. Indian Potassium Nutrition Management of Oil Seed Crops 399

Journal of Agriculture Research. 26(4): 179-186. Golakiya, B.A.; Gundalia, J.D. Bansal, S.K. and Patricia Imas (2000). Potassium nutrition management for sustaining the productivity of groundnut based cropping systems in Western India. Paper submitted in International Conference on Management Natural Resources for Sustainable Agricultural Production in the 21st Century held at New Delhi during February 14-18, 2000. Vol.2, pp. 597-98. Grove, J.H. and Sumner, M.E. (1982). Yield and leaf composition of sunflower in relation to N, P, K and lime treatments. Fertilizer research. 3: 367-378. Grower, J.H. and Sumner, M.E. (1982). Yield and leaf composition of sunflower in relation to N, P, K and lime treatments. Fertilizer News. 3: 367-378. Gundalia, J.D., Hadvani, G.J., Golakiya, B.A. and Talavia, B.P. (2000). Depletion of nutrient status during 20 years of intensive cropping in calcareous black soils (Vertic Ustochrepts). In : Vol.11 - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 47-54 Gupta, S.P. and Gupta, V.K. (1984). Influence of Zn on Ca, Mg, Na, K and P nutrition of soybean in sodic soil. Indian Journal of Ecology. 11(2): 236- 528. Hallmark, W.B., Adam,s J.F. and Morris, H.F. (1985). The sue of plant analysis to diagnose nutrients limiting soybean yield for the subsequent year. Journal of Fertilizer Industries. 2: 66-73. Jain, G.L., Sahu, M.P. and Somani, L.L. (1984). Secondary nutrient research in Rajasthan. Proc. FAI (NRC) Seminar, Jaipur, 147-174. Jain, G.L., Sahu, M.P., and Somani, L.L. (1984). Secondary nutrient research in Rajasthan proceeding FAI (NRC) seminar, Jaipur, pp. 143-174. Jain, N.K. (2001). Indian economy survey 2000-2001. Alkalanic Publication, New Delhi, p. 105. Jana, P.K., Ghatak; S., Barik, A., Biswas, B.C., Sounda, G. and Mukherjee, A.K. (1990). Response of summer groundnut to phosphorus and potassium. Indian Journal of Agronomy. 35(1-2): 137-143. Joarder, 0.1. (1983). Oil content, yield morphological response of rape (Brassica campestris L.) to irrigation and fertilizer treatment. Journal Agriculture Science (Camb.),100: 253-255. Jones, G.D., Lutz, J.A., Jr. and Smith, T.J. (1977) Effects of phosphorus and potassium on soybean nodules and seed yield. Crop Science 69: 1003-1006. Kankapura,B.T.; WarokarR.T. and Deshmukh, V.N. (1994). Effect of potassium level and it's time of application on groundnut in vertisol. Journal of MaharashtraAgricultural University. 19(1): 122-123. Kanwar, J.S. et al. (1983). Groundnut nutrition and fertilizer response in India. 400 B.A. Golakiya and M.S. Patil

ICAR, New Delhi, pp. 135. Kiresur, V., Reddy, P.S., Prasad, M.V.R. and Reddy, B.N. (1995). Economic sustainability of improved oil seed production technologies under real farm situations. Directorate of Oil seeds Research, Hyderabad, pp. 16-17. Kumar, P.R. (1982). Strategy for rapeseed-mustard production, Indian Farming, 32: 43-47. Kunau, S., Bhatnagar, V.K., Prakash Ved, Joshi, H.C. and Koranne, K.D. (1990). Yield response of soybean-wheat rotation to K application in a long term field experiment. Journal of Potassium Research. 6(2): 70-78. Kundu, G.G. and Pant, N.C. (1968). Studies on Lipaphis erysimi (Kalt.) with special reference to insect-plant relationship. III Effect of age of plants on susceptibility. Indian Journal of Entomology. 30: 169-172. Lewis, D.C., Potter, T.D. and Weckert, S.E. (1991). The effect of nitrogen, phosphorus and potassium fertilizer application on the seed yield of sunflower (Helianthus annuus L.) grown on sandy soils and the prediction of phosphorus and potassium response by soil tests. Fertilizer Research 28(2): 185-190. Mishra, C.M. (1994). Effect of fertilizer application on groundnut. Madras Agricultural Journal. 81(9): 473-475. Moshkin,, V.A. (1986). "Castor". Oxonian Press Private Limited, New Delhi, pp. 68. Ochs, R. and Ollagnier, M. (1977). The effect of fertilizers on the yield and composition of lipids in some tropical crops. In Fertilizer use and production of carbohydrates and lipids. Proceedings Colloquium of International Potash Institute 13: 269-293. Pande, D., Mishra, S. N. and Pandhi, S.C. (1971). Response of groundnut varieties to varying levels of fertility. Indian Journal of Agronomy 16: 249-250. Patel, M.S., Gundalia, J.D., Golakiya, B.A. and Hadvani, G.J. (1993). Dynamics of potassium in medium black soils of Saurashtra. Potassium in Gujarat Agriculture, pp. 32-53. Patil, M.G., Babaria, N.B., Golakiya, B.A. and Patil, P.S. (2000). Varietial differences in potassium use by groundnut. In : Vol.II - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 65-71. Patil, P.S., Babaria, N.B., Golakiya, B.A. and Patil, M.G. (2000). Varietal response of groundnut to potassium. In : Vol.II - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 72-76. Polara, K.B., Gundalia, J.D., Koria, R.G. and Bunsa, P.B. (2000). Direct and residual effect of Zn, Fe, an K in groundnut-wheat cropping system in calcareous soils. In : Vol.11 - GAU-PRII-IPI National Symposium held at Junagadh during 19-22 September, pp. 177-179. Potassium Nutrition Management of Oil Seed Crops 401

Prasad, B.,(1993). Effect continuous application of potassium on crop yield:and potassium availability under different cropping sequences in calcareous soils. Journal of Potassium Research. 9(l): 48-54. Prasad, B. (1993). Transformation, availability and relative response of crops to. applied K under various cropping systems in calcareous soil. Journal of Potassium Research. 9(2): 145-153. Rajagopal, V. (1985). Potassium and waier relations in plants. PRII Research Review Series No. 2, 5-20. Sekhon, G.S. (198 2b). some experiences in soil fertility management in India. In Trans. 121h'Int. Cong. Soil Sci., Part 5. 'Whither Soil Research', ISSS, New Delhi, 212-226. Shahid Umar, Bansal, S.K. Imas, P., Magen, H. and Umar, S. (1999): Effect of foliar fertilization of potassium off yield, quality and nutrient uptake of groundnut. Journal.of the Plant Nutrition. 22(1): 1785-1795. Sheppard, S.C., and Bates, T:E (1980) Yield and chemical composition of rape in response to N, P and K. Canadian Journal of Soil Science. 60: 153-162. Simkins, C.A. and Overdahi, C.J: (1982). Fertilizing sunflowers on sandy lands: Better Crops Plants Food 61(Spring): 1415. Singh, B. and Brar, S.P.S. (1986). Long term effects of NPK and Zn fertilization in maize-wheat rotation on'crop yields and soil characteristics. (1970-1984). Soils beptt. Bulleting. No. 12, PAU, Ludhiana, pp. 54. Singhal, V. (1999). Indian Agriculture. Indian economic data research center New Delhi, p. 285. Subba Rao, A. and Srivastava, S. (2001). Soil test based fettilizer recommendations for targeted yields of crops. Proceedings of the National Seminar on Soil Testing for Balanced and Integrated Use of Fertilizers and Manures, Indian Institute of Soil Science, Bhopal, India. pp-326. Subramanian, R. and Balasubramanian, M. (1977). Effect of potash nutrition on the incidence of stem rot, and sesamum leaf spot disease in rice. Indian Potash Journal. 2(2): 22-24. Swami, B.N. and Yadav, B.S. (1985). Potassium nutrition aspect of oil seed crops : A Review. In oil seed production and opportunities by shrivastava and Bhaskar. Published by Oxford & IBH, New Delhi, pp. 293-307. Swami, B.N. and Yadav, B.S. (1995). Potassium nutrition aspect of oil seed crops: A review. In Shrivastava and Bhaskar (Ed.) Oil seed Production Constriants and opportunities. Oxford & IBH Pub., New Delhi, pp. 295- 306. Swarup, A. Reddy D. Damodar and Prasad, R.N. (1998). Proceeding of a National Workshop on Long-Term Soil Fertility Management through integrated plant 402 B.S. Golakiya and M.S. Pati

nutrient supply. Indian Institute of Soil Science, Bhopal, India. P.335. Tandon, H.L. (1989). Fertilizer recommendations for oilseed crops, FDW, New Delhi, pp. 95. Tandon, H.L. and Kanwar, J.S. (1984). A review of fertilizer use research on sorghum in India. Res. Bull. No. 8 ICRISAT, Patancheru,'pp. 56. Tandon, H.L. and Kemmler, G. (1986). Potassium sulphate for quality crop in India. IPI, Berne, pp. 26. Tandon, H.L.S. (1993). Method of analysis of soils, plants, waters and fertilizers. Fertilizer Development and Consultation Organization, New Delhi. Vinay Singh and Surendra Singh Rathore (1994). Effect of applied potassium and sulphur on yield, oil content and their uptake by limseed. Journal of Potassium Research. 10(4): 407-410. Vinay Singh, Ram Phool Singh and Surendra Singh Rathore (1991). Effect of N and K application on oil content, nutrient uptake and productivity of sesame. Journal of Potassium Research. 7(2): 116-119. Weir B.L., Kerby T.A., Roberts B.A., Mikkelsen D.S. and Garber, R.H. (1986). Potassium deficiency syndrome of cotton. California Agriculture, 13-14, September-October (1986). Young, F.V.K. (1983). Palm kernel and coconut oils: Analytical characteristics, process technology and uses..Journalof America Oil Chemistry Society. 60: 374-379. Zizala, V.J., Golakiya, B.A and Polara, K.B. (2000). Root influx of K in the groundnut cultivars as influenced by different levels of potassium. In : Vol.!! - GAU-PRJI-IPJ National Symposium held at Junagadh during 19-22 September, pp. 93-97.