Soil and Moisture Conservation for Increasing Crop lPlrOdUlctllon in Arid Lands
J.P. GUPTA
tCAR CENTRAL ARID ZONE RESEARCH INSTITUTE JODHPUR - 342003,INDIA
OCTOBER t 983 October 1983
CAZRI Monograph No. 20
Published by the Director, Central Arid Zone Research Institute, Jodhpur. PriI1ted by MIs Cheenu Enterprise, Jodhpur, at Rajasthan Law Weekly Press, Jodhpur. Contents
Foreword Acknowledgements ii Chapter I : Introduction I Chapter 2 : Soil and Climate 2 Chapter 3 : Water conservation for crop production 3 3.1 : Water Harvesting and Recycling 3 3.2 : Subsurface Moisture Barriers 4 3.3 : Soil Amendments 9 3.4 : Soil Cultivation 15 3.5 : Mulches 16 Chapter 4 : Soil Conservation-Wind Erosion COntrol 26 4.1 : Extent of Wind Erosion 26 4.2 : Relationship with Wind Velocity 27 4.3 : Soil Fractions Susceptible to Erosion 27 4.4 : Nutrient Status of Eroded Fractions 27 4.5 : Total Nutrient Loss 28 4.6 : Control Measures 28 Chapter 5 Summary and Conclusion 35 Chapter 6 : Literature Cited 38 Foreword
Low and erratic rainfall, high evaporative demand of the atmosphere and the wind erosion are some of the physical constraints for crop production in arid lands. Efforts have been made at the CAZRI to evolve and develop techno logies like water harvesting, subsurface moisture barriers, mulches, amendments etc., for moisture conservation and wind strip cropping, use of stubbles, proper cultivation and the shelterbelts. Dr. J.P. Gupta, Scientist-3 of the Division of Soil Water-Plant Relationship, CAZRI, has studied the effect of these technologies on soil and moisture conservation in relation to crop production. These technologies have been found useful in improving soil physico-chemical environment for crop production. These techniques resulted in increased and sustained production during adverse rainfall years. Dr. Gupta has compiled the results of his ten years (1972 81) studies on these aspects and the same are presented in the monograph. It is hoped that this monograph will be useful to research and extension workers engag ed in soil and moisture conservation work fo r increasing crop production in arid lands.
Central Arid Zone Research Institute, J odhpur-342003 H.S. MANN March 31, 1982 DIRECTOR Acknowledgements
The author is highly grateful to Dr. H.S. Mann, Ex. Director. Central Arid Zone Research Institute, Jodhpur, for his able guidance, initiative, constant encourage ment and material support for the work reported in this monograph. The author is also highly indebted to Dr. K. A. Shankarnarayan, Director, Central Arid Zone Research Institute, Jodhpur. for his encouragement, interest and support in theprepa ration of this monograph. Thanks are due to Dr. A. N. Lahiri, Head, Division of Soil-Water-Plant Relationship for providing facilities and encouragement for conducting these studies. 'The author is thankful to the staff of Soil Physics and Soil Fertility Sections for providing assistance in the field work and laboratory analysis. Thanks are also due to Mrs. Bhavani Bhaskaran and Mr. Murlidhar Sharma for typing this monograph.
Central Arid Zone Research Institute, J.P. Gupta Jodhpur-342003 Scientist-3 October 1983 (Soil Physics) CHAPTER 1
Introduction
Two major problems of plant produc importance because of the increase in tion in arid areas of western Rajasthan, human and animal pressure on the land are scarcity of water and high evapora and a squeeze in agricultural land tive demand of the atmosphere. These because of increasing urbanization. factors coupled with sandy soils having Therefore, there is an urgent need to con poor moisture retention and storage serve and properly mar:age the soils. characteristics and higher vulnerability to wind erosion make plant production Different techniques of moisture difficult if not impossible. This, therefore, conservation like water harvesting, sub warrants evolution and use of soil and surface moisture barriers, soil amend -moisture conservation techniques and ments, soil cultivation and the rimlches proper soil management for increasing were evolved and used for increasing and the productivity of arid lands. stAbilizing the agricultural production. 'Efforts were also made to quantify the mov ement of sand and the nutrients associated It may be emphasised here that with it. Different techniques were evolv there is very little area in the country ed and used for checking the movement which is free from the hazards of sad erosion and destruction of land as a of sand. An attempt has, therefore, been made in this monograph to describe the natural resource. It has been estimated effect of above mentioned soil manage that in India out of 306 million hectares ment and conservation technologies in of reporting area, 145 million hectares increasing plant production in arid lands are immediately in nee~ of proper man of western Rajasthan. agement and conservation measures (Anonymous, 1968). This assumes greater CHAPTER 2 Soil and Climate
Soils: Soils of western Rajasthan during monsoon season. (July-September) are, in general, of aeolian origin. These Mean annual rainfall of the region varies are generally loamy sand to sand with from 100 mm in the north-western sector 2.0-6.0% clay, 1.5-4.0% silt, 10.0-30.0% of Jaisalmer to 450 mm in the eastern coarse sand and 65.0-80.5% fine sand boundary of arid zone of Rajasthan. The underlain with a material called 'murrum' mean annual rainfall of Jodhpur, Bikaner which generally appears at one to several and Jaisalmer is 380 mm, 290 mm and metres depth. The nitrogen and organic 100 mm, respectively. Temperatures are matter status of these soils is generally low high in summer (April-June), May is the with 0.03% nitrogen and 0.21 % organic hottest month with mean maximum carbon. The pH ranges from 7.5-8.0 and Ec temperature of 42°C. Winters ar(( norma is 0.1 mmhos/cm. The moisture retention lly rainless with mild temperatures. capacity values at 0.1 bar and 15 bars January is the coldest month with mean tension range from 8.0-10.0% and 2.0- minimum temperature of 4°C in Bikaner 3.0%, respectively. These soils predomin and Jaisalmer to 10°C in Jodhpur. The antly have macro...porosity and, therefore, pan evaporation values range from 8 to there is fast movement of water into and 10 mm/day during monsoon and 5-6 mm/ through the soil. The initial infiltration day during winter. In summer, however, rate ranges from 15-30 cm/hour. Saturat pan evaporation values of 10-15 mm/day ed hydraulic conductivity is generally 5-10 are not uncommon. Relative humidity of cm/hour. The bulk density of the surface 60-80% is found during monsoon but soils is 1.5 g/cc and that of subsurface values ranging from IS to 20% are obser soil ranges from 1.5 to 1.6 g/cc. ved during winter. Mean wind velocities of ~.O, 10,0 ~nd 20.0 km/hour were found Climate: The climate is arid with to prevail at Jodhpur, Bikaner and low,. erratic and generally high intensity Jaisalmer, respectively during summer rainfall', about 90% of which is received months (April-June).
2 CHAPTER 3
Water Conservation for Crop Production
In arid areas of western Rajasthan Another most important system of as the rainfall is generally low and water harvesting is runoff collection in erratic, soil and water conservation tanks and its recycling for supplemental techniques and proper soil management irrigation. ]n India, tanks have been used can play an important role in increasing for centuries as a source of domestic water and stabilizing plant production from and water for limited irrigation. The such lands. These techniques are there amount of runoff depends upon the fore, discussed as under: amount and intensity of rainfall, the infiltration of soil, the slope and the vege 3.1 Water Harvesting and Recycling tation. The runoff water thus collected Runoff water utilization for agri can be used as life saving irrigation or cultural purposes is a common practice supplemental irrigation. Mann et at. (1980) in Israel which has inherited large reported that parts of western Rajasthan desertic areas (Bunyard, 1973). In arid und~r rocky, semi rocky or slopy areas zone of western Rajasthan also; 'khadin' with suitable treatment can generate a cultivation, 'nala' bunding, etc., for high amount of runoff. Nine years data supplemental irrigation and ground water on computed runoff have shown that recharge are the age old practices. In there was maximum runoff during surplus order to overcome the harmful effects of rainfall years with an average rainfall of droughts and increase the crop produc 700 mm. Further, higher amount of runoff tion, two types of techniques for In situ was available during the years with water harvesLng can be used depending more frequency of high intensity showers upon the availability of land, type of crop although the total rainfall was lower than and the soil depth for storing the runoff the normal. Drought years with an water. Studies conducted at C.A Z.R.1. average rainfall of less than 90 mm were showed (Anonymous, 1974) that with not found to generate any runoff. It has water harvesting in catchment to culti also been found that soils with poor vated area ratio of 0.5, there was one to infiltration rate and as high as 9% slope two times more production potential generate more runoff than the soil s with than over flat lands. With this technique, 5% slope. Moderately fine soils were higher production of such crops found to give more runoff than the sandy as . pearlmillet, grcengram, cowpeas, soils having the comparable slopes. Runoff sorghum and sesamum was obtained than water collected from the catchments could the flat lands. be stored in cement-concrete tanks of
3 appropriate sizes with more depth so that down to the barrier and then across to evaporative surface is reduced. Runoff its edge. When the drainage of free water water thus collected can be utilized for ceases a low tension water is retained growing short duration and low water over the surface of the barrier. Fig. 1 requiring crops like gram, mustard, etc. shows 24 mm of percolation loss from H can also be used as a life saving irriga the soil profile with barrier while it was tion during drought periods of the crops 120 mm from the profile without barrier. grown in the Kharif season. This shows that there was about five times more perco!ation loss from soil profile 3.2 Subsurface Moisture Barriers without barrier. In this way the moisture A large area of western Rajasthan retention capacity of the sand soil could is occupied with sandy soils. These soils be doubled without affecting its good inspite of having some of tIte good qualities. However, this was a potential characteristics like high infiltrability, value which could be achieved by the more aeration, self mulching, etc., their placement of 2 mm thick barrier and with productivity is severely affected by poor the application of heavy irrigation. water retention and storage characteris tics. High percolation rates of these 2'OOmm ?O()~ j soils further aggravate the problem by ~ allowing heavy leaching losses of nutrients resulting in low fertility of soil. I =~~~~~t~~ 60cm _-,-,"_:::_-:_-_-_:, Such soils can be made productive by ~~t~~ffi~Y th~ use of subsurface moisture barriers. ~::~:--:.:=:: ::_ It has been found (Gupta and Aggarwal, 1:,::·::::·c-·::':~~_--;;;.;;.- 2mm nllC! ---- 1978, 1980) that the placement of asphalt ,"Sf'HALT LAYER - ~-;;;- - l as moisture barrier at 60 em soil depth iii. 2 mm thickness improves moisture and nitrogen retention capacity WI T!1 ASPHALT WITHOUT ASPHALt BARRIER BARRIER of the soil and increases crop production. Other materials like bentonite clay and Fig. 1. Moisture distribution in normal and modified soil with asphalt barrier. pond sediments were, also tried as subsurface moisture barriers. It was Oi) Water depletion: Water depletion found that the placement of barriers like from a soil depends upon the climatic bentonite clay and pond sediments at factors, the hydraulic and thermal char 60 cm depth in 5 mm thickness was acteristics of soil and the type of vegeta '60-70% and 50-60% effective in retaining, tion it supports. In a bare soil without the total rainfall in the root zone, respec vegetation, it is mainly governed by the tively. Water characteristics of soil as hydraulic and thermal gradients operating affected by asphalt moisture barrier are in the soil. Higher rate of water depletion discussed as follows. was observed from a soil without barrier (i) Water retention capacity: After a up to eight days after irrigation beyond heavy rain or irrigation, water percolates which the rate of depletion was higher
4 0;>0 ,., ILl ~ .::> o ~ 15 elY ._l 0 15 > >- III 10 cr \ ILl \ I- \ , ~ , , 't. ~ \. >', J ~
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5
E E
,!, , , . , I \ "- .. '\, \ 200 r,\ / \ ~ '---' , E ,, 150 E 100 j « u. u. 20 50 ~ a. o
Fig. 2. Soil water variations in normal and asphalt barrier profiles during growing season of P~arlmi1let. in barriercd -soil. Higher depldion rate contained 20-30 mm more moisture than from a normal soil during early period the normal soil. The differences in moist· after irrigation was probably due to the ure retention in 1977 were less than in processes of evapuration and drainage 1976 because of less rainfall received operating in the soil. Cumulative evapora during 1977. Though it was well distri tion during 30 days period after irrigation buted during the season there was hardly from barriered soil was 3-5 111m higher an event of rainfall which appreciably than the normal soil, showing thereby, increased the moisture storage of the that in a barrie red soil additional stored barriered profile. water remained mostly conserved due to 3.2.2 Effect on Nitrogen Consenation and self mulching properties of the sand. Use by Pearlmillet Nevertheless evap0t:ation loss from a bar riered soil can be checked hy the use of The placement of asphalt barrier mulches or manipulation of plant popula resulted in an increase in the retention of tion. mineral nitrogen in soil (Table I). There (a) Use of mulches: In sand soils mul was an increase in N03-N in all the three ches do not find much use in conserving depths of soil with asphalt barrier, show soil moisture be,ause of the self mulching ing thereby, reduction in leaching losses properties of sand. However, during of nitrogen. On an average, there was early period after rainfall or irrigation, 66% increase in nitrogen retention coupling of mulches with AMOBAR in soil with ari asphalt barrier than in (AMOCO, 1971) may be us::ful in check soil without such a barrier at low nitrogen ing evaporation. levels. At medium and high nitrogen (b) Manipulation in plant p(lpulatiol1 : levels, however, the retention of nitrogen in soil with a barrier was 89 and 50%, Unproductive evaporation loss of conser respectively. The higher availability ved water from the barriered soils can be of nitrogen and moisture in plots with checked by manipUlating plant popUlation. barrier led to higher concentration of Marginal increase in plant population can convert unproductive 105s due to evapo nitrogen in the grain. The total uptake ration to productive loss as ET. of nitrogen by the plants increased with increase in nitrogen levels. The mean 3.2.1 Moisture Storage al'!d its Variations as Influenced by AMOBAR crop response to N-fertilizer with barrier The moisture status of batriered was found to be 75, 34 and 19% soil was found to be higher than the more than the control at low, medium normal soil (Fig. 2). However, the variat- and high levels of nitrogen, respectively. . ions were more in 15-60 em than in 0-15 em This could be due to reduced leaching depth. In 0-15 em depth, barriered soils ~nd better utilization of the nitrogen when were found to contain 2-4% more the moisture content of the soil was moisture than normal soils while in 15-60 higher. Therefore, it appears that even em depth it was 2-10% more. Profile with a low dose of fertilizer an asphalt moisture storage of barriered soil was barrier can be quite effective in increasing generally higher and on an average, it the crop production in sandy soils.
6 Table 1. Mineral nitrogen in soil and nitrogen composition of pearlmjJ]ei as influenced by asphalt barrier Nitrogen Mineral nitrogen Total levels in 0-15 cm depth Nitrogen% nitrogen (kg/ha) (N03 +NH4) N N03-N Grain Straw uptake (ppm) (kgjha) 1976 No barrier 4(l 16.8 6,7 0.89 0.42 10.5 80 26.8 12.3 1.42 0.46 22.1 120 33.6 14.5 1.51 0.43 48.2 Asphalt barrier 40 25.8 11.2 1.20 0.55 22.0 80 49.5 26.0 1.63 0.54 35.2 120 56.0 19.0 1.99 0.54 51.8 1977 No barrier 40 20.2 7.8 1.21 0.36 30.4 80 30.6 13.4 1.34 0.33 38.5 120 45.7 16.8 1.44 0.57 72.4 Asphalt barrier 40 35.6 19.0 1.21 0.35 42.6 80 58.4 30.6 1.34 0.33 52.0 120 61.5 25.4 1.55 0.41 94.8
3.2.3 Effect on Water Use and Crop Produc and 3). Interaction between sUlJsurface tion moisture barriers and nitrogen. levels Higher grain and straw yields of produced 50-60% increase in grain yield pearlmillet were achieved with asphalt under both low and medium levels of subsurface moisture barrier (Tables 2 nitrogen. With high levels of nitrogen
Table 2. Effect of significant interaction between barrier and levels of nitrogen (N) on the grain yield (qjha) of pearlmiHet for the year 1976 Nitrogen levels No Asphalt N mean (kg Njha) barrier barrier ± 0.4
40 5.5 a* 9.0 b 7.2 a 80 8.5 b 12.3 c 10.4 b 120 20.8 c 17.0 d 18.9 c Barrier mean ± 0.3 11.6 a 12.7 b * Marginal means ;lnd means in the body of Table followed by the same letter do not differ significantly at the 5% level of probability by the L.S.D. test.
7 Table 3. Effect of an asphalt barrier and levels of nitrogen (N) on' 'yields of pearl millet. Interaction term was not significant
Treatment Grain yield Straw yield (q/ha) (q/ha) 1977 1976 1977
± 1.5 ± 2.3 ± 0.9 No barrier 22.0 a 24.7 a 39.6 a Asphalt barrier 30.7 b* 27.3 a 54.2 b kg N/ha ± 1.9 ± 2.9 ± 1.2 40 19.4 a 16.9 a 36.7 a 80 22.5 b 24.9 b 45.6 b 120 37.2 c 36.1 c 58.4 c
.. Means in 'a column under a given treatment followed by the same letter do not differ significantly at the 5% level of probability by the L.S.D. test.
also an asphalt barrier produced a higher 1976. With medium and high levels of grain yield during 1977 but, during nitrogen, extra water failed to . produce 1976, a reduction was observed. This an increase in the yield of grain. At low might have been due to a combination nitrogen levels, however, the water con of excessive nitrogen and water. On an served was used efficiently. Thus, soils average, however, the production of with barriers gave a higher yield with pearlmillet with barrier was 40-60% low levels of nitrogen than did a soil higher than without a barrier. Water was without barriers and with a medium used .less efficiently in 1976 than in 1977 level of nitrogen. The use of an asphalt (Table 4) because poor yields resulted barrier, therefore, economised the use of from a heavy infestation of ergot during water as well as of nitrogen.
Table 4. Water use efficiency (kg grain/mm/ha) as affected by the use of asphalt subsurface barrier and nitrogen levels
Nitrogen i976 1977 levels No Asphalt No Asphalt (kg/ha) barrier barrier barrier barrier 40 3.12 3.19 7.50 8.27 (177)*. _ (282) (200) (290) 80 4.67 4A6 9.13 8.74 (182) (276) (208) (274) 120 11.06 5.99 15.20 14.41 (188) (284) (210) (295) "Figures in parenthesis indicate the water (mm) used by the crop.
8 3.2.4 Scope of Subsurface Moisture Barriers applicatiqn of asphalt moisture barrier is The preceding facts adequately possible 'provided a machine similar to demonstrate the usefulness of subsurface the one. developed by International barriers as a means of increasing the Harvester Company of United States is moisture storage and nutrient con designed and developed in the country. servation in the root zone and, thereby Until such time subsurface barrier of increasing the productivity of sandy soils. asphalt or bentonite clay seems to be Nevertheless, there are several specific feasible on small scale localized place requirements which must be taken into ment for growing vegetables and fruit consideration before any planning for creepers. field scale use of the barriers. These are (iv) The cost of barrier placement as follows: with the AMOBAR machine has been (i) Under the present day techno worked out as $ 700 to 800/ha, which economic conditions, it seems that sub the manufacturers claim can be recovered surface barriers are not for all types of in less than four years. With multiple soils, for all farmers and for all crops. It cropping practice in the U.S., this initial has particular promise on sand and sandy cost is paid back even in less than 2 soils known for their poor moisture years. The barrier if placed lasts for more retention and self mulching properties, than 15 years. Inspite of this merit, the in high cash crops like vegetables, sugar machine may be expensive for an indivi beet, ground nut, oil seeds, etc. dual farmer, but certainly can be purch (ii) [t seems to have special signi ased and used on cooperative basis. ficance under rainfed rather than under irrigated conditions. Its use under latter 3.3 Soil Amendments conditions may be limited to the area where good quality water is available. Amendments are widely used these Under irrigation with saline water it can days to change physical properties of lead to an accuqlUlation of saIts in the soils so til at they are more suitable for soil profile over the surface of the barrier. plant growth. They range from chemicals Accumulation of saIts in the root zone can like gypsum and selected fertilizers to severely limit the crop growth. Further bulky materials such as porous minerals, these salts can come up to the surface in organic peats and wood shavings. The the evaporative process, which cannot be need for physical amendments is being felt easily leached or flushed down below the more in arid areas where organic matter root zone because of the restricted per levels are generally low and soil structure meability of the barrier. is very weak. in western Rajasthan (iii) Excavation technique for barr where the availability of organic matter ier placement apart from being cumber is low and the peat is not available, pond some and causing disturbance to the soil sediments available from widely scattered involves high cost and labour and so can ponds could be utilized for increasing be used over a limited area. Extensive their productivity (Gupta et al.• 1979;
9 Gupta and Aggarwal, 1980; Aggarwal Water used by the crop also increased et at., 1980). but water-use efficiency was found 3,3.1 Use of Pond Sediments maximum at 76 tonnesjha. Total and The results of field trials show that the mineralized nitrogen status of the soil application of pond sediments by mixing increased with pond sediments applica upto 30-40 cm soil depth increased the silt tion. There was further increase in and clay content of soil which in turn nitrogen status of soil after the harvest increased the moisture retention at 0.3 of the crop, showing thereby, enrichment bar tension and also the available water due to legume cultivation. Application of content of soil (Table 5). The infiltration pond sediments also increased the nitrogen concentration in the grain of green gram rate decreased with the addition of pond and nitrogen uptake by the plant. sediments. Consequently, deep-percola With the addition of 76 tonnes/ha, how tion losses were checked and the moisture ever, the nitrogen uptake was maxi retention capacity of the soil increased. mum (83.4 kg/ha), which was about Wind stable aggregates greater than 2 mm 60% more than that of the control plots. increased with the application of pond sediments. It also increased the total 3.3.2 Use of Farmyard Manure nitrogen, mineral nitrogen and organic Farmyard manure, since a long time, carbon content of soil. has been known to maintain soil produc The grain and straw yields of tivity but the use of chemical fertilizers, pearl millet increased with the addition particularly nitrogen, is becoming more of pond sediments (Table 6). The general and more common for attaining higher response was up to 76 tonnes/ha, at which yields. Low organic matter levels of the the gr~in yield increased by 40-50% Over soil creates poor physical conditions the control; beyond this level there was which seriously affect seedling emergence, either a marginal increase or some growth and yield of crops (Gupta et aT., decrease. Water use by the crop gene 1982). The studies were, therefore, con rally increased with the application of ducted to find out a suitable combination pond sediments. Water-me efficiency, of urea and farmyard manure for favour however, was maximum at 76 tonnes/ha. able physico-chemical environment for Application of pond sediments increased higher crop production.The results of field the nitrogen content of the soil. The favo trials show that with increase in applica- urable hydro-physical conditions produc tion of farmyard manure and decrease in ed by the use of pond sediments increas urea, there was decrease in bulk density I ed the nitrogen availability and uptake of soil, an increase in moisture retention by plants. The maximum nitrogen uptake . at 0.1 bar tension and decrease in saturat was, however, observed at 76 tonnes/ha. ed hydraulic conductivity (Table 8). There The grain yield of green gram was were, however, little differences in mois also found to increase with the use of . ture retention at 15 bars tension. This, pond' sediments, the maximum being therefore, increased the available water 21.5 q/ha at 76 tonnesfha (Table 7). capacity of the soil. Increase in addition
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With this combination there was 30% increase The application of exfoliated vermi in mean grain and straw yields of pearl culite in soil significantly increased the millet over farmyard manure alone or yield of lady's finger crop (Table 9). The nearly equal with urea alone. This optimum yield. however, was achieved could be due to improvement in physico with 20 t/ha level beyond which either n~ chemical environment of soil. significant increase or some decrease was recorded. Integration of grass mulch with 3.3.3 Use of Ex:foliated Vermiculite exfoliated vermiculite was not found u[eful Vermiculite is a micaceous mineral in increasing the crop production. This that exfoliates when heated or subjected to was probably because exfoliated vermi certain chemical reactions. It is a hydra culite itself acted as mulch. Its appli ted magnesium-aluminium-iron silicate. cation at 20 t/ha level increased the Exfoliated vermiculite consists of accor average production of lady's finger crop dion like granules containing millions of by 40-60% more than the control without minute air layers, to which vermiculite vermiculite. The yields were observed to OWes its high insulation value and light be generally higher in the year 1980 than weight. 1t is inert to organic solvents 1979. This was because of the application and does not decompose in water. of 50 mm of irrigation water during 1980 The application of exfoliated vermi when there was a severe drought. culite to the soil was found to increase There were no significant differences in the moisture retention at 0.1 bar tension. water use of the crop from 60 cm profile There was, however, not much difference with vermiculite application. Though in moisture retention at 15 bars. This, the cumulative water use was nearly equal therefore, increased the available water in treated and untreated plots, the deple capacity of the treated soils (Table 9). tion rate throughout the growth period The use of exfoliated vermiculite decrea of the crop was higher with vermiculite sed the bulk density and saturated application (Fig. 3) particularly at 20 t/ha hydraulk conductivity of the soil. The levd. showing thereby, the faster utiliza reduction in hydraulic conductivity was tion by plants grown in the treated plots. found to be more significant. It was about There was, thus, higher water-use effi 25% at 20 t/ha level and 50% at 40 tfha. ciency of the crop with vermiculite It also reduced the maximum soil tem- application. 13 OOO\tr)t'--V1 r---~('f')Nlr'I ...... N('!")V'700:T N ~~;:;~ M C"')~('()rr1 \0 0\ N ' a8 N IrlOOOO .:: 00 ~~~~~ ~ -NV)1r) 1rl'l)\ON """"""or; 00 ~ .g r..: .~ 0\ -au o OJ ~~~~~ u .,...... c:: OJ * ...eo ...... OJ \0 8 OJ .... '"o ....0- o +~ U c:: 0 ~ .2 E i.Ll ~ ... E"B 8 ~ o 0 Z c:: 14 200 ,E 16 a 11.1 ." ;:) 120 a: IlJ ~ ~ 80 z ...... NO VERMICLH.1TE 20T/ha . ~ ....~ - 40 2 3 .. 6 7 6 9 10 II IZ WEEKS A FTER SOWING Fig. 3. Effect of the application of exfoliated vermiculite on cumulative water use from 60 em soil profile. 3.4 Soil Cultivation further lowered the crop weed competi tion and the bulk density of the soil yet Sandy soils with poor organic either did not increase the production or matter status generally get compacted increased it marginally. This could be and thus seriously affect the growth and due to the damage caused to the roots as yield of crops. Wimer (1946) reported is reflected in poor growth and weight of favourable responses to post - planting roots. A comparison of uncultivated cultivation because of killing of weeds (weeds removed with weedicide) and once which compete with main crop for light, cultivated plots showed that even in the water and nutrients. The results of two absence of weeds, cultivation was found years of field trials show that in un useful in increasing average yields from cultivated plots weed removal with 9.5 to 1}.8 q/ha. This was probably due weedicide (atrazine @ 1 kg/ha of a.i.) to more proliferation and better growth reduced crop weed competition and of roots and better utilization of water significantly increased the yield of pearl and nutrients for higher crop production millet crop (Table 10). Soil cultivations (Gupta and Gupta, 1981). Higher water also reduced crop weed competition. One use of the value of 267 mm in 1977 and cultivation after 20 days of emergence 3]0 mm in 1978 was observed in plots reduced the dry matter production of where.weeds competed with crop. This weeds from 17.2 to 0.6 q/ha, lowered the led to reduction in water use efficiency of bUlk density of soil and thus increased the crop. There was no significant diffe the average crop production from 3.4 to rence in water use of crop under other 11.8 q/ha. More cultivations, though, treatments. Water use efficiency was 15 higher with one cultivation. More cultiva crop production. The use of mulches tions, however, did not increase the have been reported to favourably modify water use efficiency substantially. the hydro thermal regimes of .soil for Nutrients uptake by grain and straw crop produdion (Van Wijk el al., 1959; increased with increase in cultivation Moodyet al., 1963; Prihar et al., 19.77; level. However, the differences were not Gupta, 1978, 1980, t 982). Before discus significant at higher levels. Nitrogen, sing the effects of mulches, the moisture phosphorus ~nd potassium uptake by and thermal regimes of the soil are the crop in uncultivated (weeds removed discussed. with weedicide) and cultivated plots (i) Moisture regime of soil: During were significantly higher than where the rainy season (July-August) of the year weeds competed with the crop. As much 1977-78, soil moisture storage below 10 as 20.6 kgjha nitrogen, 2.0 kgjha phos cin depth was maximum and ranged from phorus and 21 kg/ha potassium was 5 to 7%. From September to January removed by the weeds during the growth there was moisture depletion from top 60 period of the crop, leading thereby, to em profile only. There was, however, no reduction in uptake by the crop. change in the profile moisture content Depth of post emergence cultiva below 60 cm depth. From 'February to tion has been found to influence soil June, there was fast elongation of drying properties and root growth (Table 11). front and depth of dry layer (less than Cultivation upto 10 cm depth was found I % moisture) was .40 cm, Lower layers, in to give the maximum grain yield of general, were found to contain 2 to 4% 10.8 qJha which was about 50% more moisture. As there was little capillarity in than the control without cultivation and this soil, so the moisture loss was proba ne&rly equal to 5 cm depth of cultivation. bly in vapour phase due to the prevalence Deeper depths of cultivation were found of vapour pressure gradients. to reduce the grain and straw yield of Moisture regime of soil with native the crop. This seems to be due to the grass vegetation was generally lower than damage caused to the roots. Maximum the bare soil without vegetation. This was nitrogen uptake in grain and straw was due to the moisture utilization by the observed with 10 em cultivation depth native grass vegetation. while maximum phosphorus' and potas (ii) Thermal regime of soil: Day sium uptake was observed with 5 cm time soil temperature (measured at 2 depth of cultivation. At this cultivation P.M.) was found to continuously rise depth there was 25% increase in uptake from January to June (Fig. 4). However, of nitrogen while it was 50% in ,case it was maximum at all depths during June. of phosphorus and potassium. During July there was a considerable fall 3.5 Mulches in soil temperatures because of the cool D~ci~cy cl wa~ ud hl~ ing caused by rainfall. There was a rise the~mal regimes of soil are the two most in temperature during September and important factors which adversely affect October after which the soil temperatures 16 on 0 00 00 3 on .,.; ,....; cO 0 C'I <"I f-< "" '" .,.~ ... N on 00 on .,.; 0\ "..: on ;:,tVi C'I C'I C'I C'I .;d ... <"I on 0 <"I.,.; 0 N .,.; -i- -; <"10 00 on ~jO ...0 cO r..: f-< .... ,.., C'I 0 \0 0 CIS ~ t- "¢ .,.; ..c 0..'::: N .0 .,.; --tlIl c;- ~ t- G) "¢ on 0"\ ~ \: \0 0 CIS .,.; ._, p. (is on on -i- -..... ::l 1° 'i:: "¢ ~ .!:! 00 ... -; '-': 0\ -i- 'S .._. "..: C'I 0\ G) ..... p. "'5 0 ...... d f-< 0 -_g G) 0 f-< ~\ ~ .... P. N cci ::s Zr; r..: -0 ...... rn - I'l .!:! .;I'l !:: "¢ CX! ~ ::l ...... ,.;"" .... I'l 0 00 ...... 't:I =CIS 't:I ... G)_ OJ .;::' 2~8 ..... ",G)8 t- t- t- oo 3: ~'-' t- t- t- =0 G) c .;::0 ~ G) ,.., \0 N CIS .~ CIS N ""! rJl :>->..c .,.; -i- .,.; .... ;i .~ N N N C'I :; CIS~~-- 0 .... V'i ....0 ..cp. G) •d't:l__ ..cCIS \0 00 00 ..... 't:I - f'! r; CIS..,-- .:; .:; "..: \-010- c:r t- ...... o o »'-' .... - 0 :;:;- ~ 0 ~ ...0.,8 = 8- on 0 on ...: ..c~"" 0 .... 0 ~·~5 00 -G) ..,- '-' ..j ::0 CIS 03 f-< 17 Air SCM Do.' Sa .. 10" - !~~_~~_~ lIS .... • I'hout ~ • __ _ 3Oc", ~ - --- 50c. 5 eM D""III ----- C1ft • $oj "qrto e .n,h 50c," tlVil cO"lr [ JOe.. 52 == 48 46 44 42 P 40 ... 30 36 II:~ ...~ :)4 ,1-0_. 32 g 30 ,. 26 24 22 / 20 " ~~~.-~.--r--~~--II--r-~--~~ .JAN, FEB. WAR APR. MA'it JUk .IUL: AUG SEP. OCT 111)\1 DEC Fig. 4. Seasonal variations il'J soil temperature. continuously decreased. Maximum soil downward thermal gradients while during tcmpf{rature in the top 5 cm depth in winter months upward thermal gradients summer was much higher than the lower' were 0bserved particularly from depths depths. It'decreased up to' 30 cm depth below 30 cm (Gupta, 1981) . . beyond which there was not much change. In winter, however, lower layers below (iii) Heat fluxes: A high variabi 30 cm were warmer than the surface. lity in day time heat fluxes was observed Mean maximum temperature of a bare from week to week (Fig. 5). From 1st to soil at 5 cm depth, in general, was 1- to 15th week there were more positive heat 2°C higher than the soil with vegetative fluxes than the negative ones, showing cover except during July when there was thereby, more heat gains in 0 to 20 cm a fall in temperature of a bare soil. Dur and 20 to 50 cm soil depths under vege in-g summer months higher day time tation. This might be due to more temperature in surface 5 cm depth led to conservation of heat energy in soil under 18 _-_-..:-:.- 9 ~ £ ~ ~ ~ ~ g 0 Q 2 ~ i ~ g -. maw 1111 "'" .... ""H ...... :1 II:». xn', aiM 1_ ...Jl lIII1~lYl. I." I. ,. I~ z. II" & !': S 0 ...~ u ,. ~ .. ~ ~ ,_ :r t :;:'" ill ,. ~ 7 fi •i .. _, "c is .. .. 2 .. . -_ • ~ jz~ .:- . '" fz ~ -,,:.-_:..--;;:::-..,.-~ I,:. o j N :;;. -..: ~1-oSI .;.->:' iii ~ ~ ~ ~ ~ 2 gOg 2 ~ ~ ~ ~ g 19 1Il0~ 6D'H not JINM. ~ ~ ~ ~ 2 ~ 0 g 2 ~ ~ ~ : ~ ~IIIU 'D~ 01 ...... I ~ •• 111:1 II'. .n, ... .1.'IJM .. .. ,- . ('~~ f-' III J. In,.:I "~~H vegetation. At lower depths, below 50 cm, _._ IlULCJt however, the bare soil waS found to have - NO MULCH higher positive heat fluxes possibly beca 2 !! eM use of more conduction of heat to lower depths by moisture present in bare soil. From 16th to 25th week period (summer months), there were mostly positive day time heat fluxes in 0 to 20 cm depth lead ing to gain in heat energy in both bare and soil with vegetative cover. During 25th to 35th week, that is monsoon period, ... II ;-:. III 9 positive and negative fluxes were foun,d 0 7 to operate. During dry periods there was 2 gain in heat while during wet or cloudy periods there was loss in heat. Lower ; I;l~ '" I!I ern depths under grass cover were found to ... 1 ... 8 store heat while bare soil lost most of the ::I ~ &5 ..J heat energy stored during summer parti o 14 :> 30 CIII cularly after very heavy rain shower. i¥ During post-monsoon period there was 10 again some gain in heat energy but during • winter months (40th to 50th week), nega 14 4 '" " ~ 4 '" 4 ~ 4 '" 4 ~h~ 2 !I " !! 6 7 Ooy. tive heat fluxes were found to operate, showing thereby, heat loss from the soil Fig. 6. Diurnal variations in soil moisture profile. The heat loss, however, was more as affected by mulches. from a bare soil than the soil with vege tative cover, indicaing thereby, that the movement of moisture under the influence vegetation acted as insulated blanket of thermal gradients. Throughout the which conserved heat in the soil. period of study (28th June to 6th July) highest moisture status of soil was obser 3.5.1 t:lfect of Mulches on "Hydro-thermal ved in mulched plots and lowest in Environment a.'1d Pearlmillet Production . unmulcned plots. During this period total (i) Effect un summer crop moisture loss from the mulched plots was Soil moisture variations: Fig. 6 shows about 2 mm less than the unmulched diurnal moisture oscillations occurring plots. in soil with and without mulches. These Soil temperature and seedling emer oscillations were more predominant !n gence:Mean maximum temperature at Scm surface 15 em depth below which these depth of mulched plot was about 8°C were of very low magnitude. In surface lower than un mulched plot (Table 12). layers up to IS em, soil moisture status Maximum temperature in mulched plots was. higher at 0400 hours while it was generally ranged from 37-45°C while it lower at 1400 hours, showing thereby, the ranged from 38-54°C in unmulched plots. 20 .... H ~,\' ~ .. ~ H \, (II }~ i !: IX /..''/ ~ ,I 10 zr 2 /(. 11.1 if) .... IL '\ 11.1 .. , II) ' 01 ,'\ "\ CD ~I .... ,,; , i.I Q) "" , or: !OJ u ~} "3 6 //' .... Q) "0 ~~,'\ R 0 ;::> !OJ »)' "0 ., en " l (II .... '{ c( 0 I) \. \ a 8 ~ (';3' "co , \ ... \ '" If) (ij , (II ... \ ...8 " .. 0 Q) "' .Q "', ~ H I:-< , I r.: \.k !! ... !liJ &II \\ ~ ~ ~ !! :I• ..J cr ~ ... ..I •:t X II) 0 t\I C ... II) C[ ~ 11.1 II) . ~ .... ~ C[ ., z 0 ~ C[ 0 = CL. Cl) III u , y Ia , i /'1" 6 ., • I I ,/~ " /~ "~ 0 ,( i.. If) "\ "'" ., .>" 'b N l~ 0 II) 0 II) (\I .,. !OJ ,., 21 :). 3~nJ.y,,31d"3J. ,'tot Table 12. Effect of grass mulch application on soil temperature, moisture loss and seedling emergence Mean Temperature Moisture Seedling Treatment soil temperature range at 5 em loss emergence at 5 COl depth depth (mm) (%) ("C) CC) Max. Min. Max. Min. No mulch 48.6 29.4 38-54 25-35 17.0 63 Grass mulch 40.3 29.8 37-45 26-35 14.7 70 There were, however, no differences in (Fig. 8). However, there were no signifi minimum temperature of mulched and cant differences in moisture status of soil un mulched plots. Rapid loss of moisture under grass and straw mulches. Higher coupled with higher temperatures of moisture status of soil under mulches was unmulched plots reduced the emergence due to reduction in evaporation and weed of seedlings (Gupta and Gupta, 19~2). population. Maximum dry.matter produ ction of 3.8 q/ha of weeds was obtained (ii) Effect on kharif crop from soil without mulch while it ranged Soil temperature: Polyethylene mulch from 0.2 to 1.2 q/ha in mulched plots was found to raise the temperature of (Table 13), showing thereby, reduced soil at 10 em depth by 1 to 3°e, while crop weed competition for moisture in organic mulches like grass and straw mulched plots. This seems to be an im lowered it by 1 to 6T (Fig. 7). There portant factor for higher crop yields in were, however, no significant differences mulched plots. in soil temperature under grass and straw mulChes. Soil temperature generally ranged from 30 to 35°e during the growth '~ ... --.. POLytTHYLIH' 130 period of the crop. Higher production 120 - llUIS obt~ined from ,soil under polyethylene { -- BAJIIA ITII_ mulch showed that soil temperature up to 38°C was not a critical factor for the growth of pearlmillet crop. It rather helped in improving growth and yield of i the crop (Gupt~ and Gupta, 1982). L IO! '. ~ Soil moisture: The soil under polye- 10 :S thylene mulch was found to contain 5 to it o,:-l.-~--:---:-~:--A---r---&':~"""""ri~ ~ ~ ... M :s Ie 35 mm and under organic mulches 5 to II!PTIIID£II OCT "'Tlt - ~5 mm·more moisture than the control without mulches during the year 1978 Fig. 8. Moisture regime of soil under mulches. 22 Table 13. Effect of mulches on weed growth, water use and yield of pearlmillet Water use Grain Straw Weed Water efficiency Treatments yield yield production use (grains, (qjha) (qjha) ( q/ha) (mm) kgjmm/ha) Polyethylene 15.5 38.1 0.25 289 5.37 Grass 8.9 27.6 0.92 286 3.11 Straw 7.2 25.1 1.23 276 2.61 Control 6.0 24.9 3.77 294 2.04 L.S.D. (0.05) 0.98 10.12 Crop yield: Mulches increased the 3.5.2 Effect on Hydro-thermal Environment grain and straw production of pearlmillet and Legume Production (Table 13). No wide variations in water use of the crop under different treatments Soil temperature: Wide variations were observed. However, it was higher in soil temperature ranging from 36 in control plots without mulch. Water to 44°C in unmulched and 32 to 41°C use efficiency of crop was maximum with in mulched plots were observed during polyethylene mulch followed by grass, the growth period of the green gram straw and the control without mulch (Fig. 9). With increase in rate of grass (Bansal et al., 1971; Gupta, 1980). Maxi mulch application there was decrease in mum water use efficiency with polyethy mean maximum weekly soil temperature lene was due to its imperviousness to with maximum reduction at 12 tlha level. vapours and the moisture, thus, con Grass mulch application at 6 tlha level served, was completely utilized for in on an average reduced the mean maxi creasing crop production. mum weekly temperature by 2 to rc CONTROL ... ------.. MULCH 3 t 1;'0 .. - .. _-.-~ 61/ he' 45 .... 0 9' I ho "".-._ . ., ... ~ ~ :;) ~ 40 I¥ 11.1 ·nIL LoI I- ." 3S (5 '1) I ! i 3 2 -~-~--~~'~_,---..-__~ __--,-_ .__ -,- __---, __ ---,---. 2 6 7 8 9 10 II WEEKS AFTER SOWI~C Fig. 9. Mean maximum weekly soil temperature as affected by different rates of mu'ch application. 23 .....00 -.0 o 00 -0\ <=> 00 -0\ o 00 .....01 -·0 en oC c ..... N .g N <'l .~ 0. 0. N t";I -:..... '5 '; 8 o 00 0\ 01r-- -0\ 00 00 N.,...., ...... ; \0 ..... 00 o N..... 24 and thus increased the root and shoot 3.5.3 Effect on Vegetable Production growth and nodulation. The application of grass mulch at Water lise and crop production: the rate of 6 tjha reduced the mean With increase in rate of grass mulch maximum temperature of soil at 10 em application there was drastic reduction depth by about 2°C while polyethylene in weed growth (Table 14). There were, mUlch did not bring about any change however, no significant differences in ET during the growth period of the crop loss from mulched and un mulched plots. (Table' 15). There was maximum ET loss Water use efficiency of the crop was, from 60 cm soil profile of a control plot therefore, higher in mulched than un without mulch (110 mm) followed by grass mulched plots. Although there was vcry mulch (106 mm) and the polyethylene little rainfall during July and August of mulch (90 mm). Grass and polyethylene 1980 and the drought conditions persisted, mulches increased the production cf there was higher plant water status and lady's finger by 15% and 46% more than dry matter production in mulched than the control without mulch, respectively. in unmulched plots. Production of green Though there were no differences in soil gram increased with mulch application temperature of control and polyethylene upto 6 tlha level beyond which yield dec mulch plots, a significant increase in crop reased. This might be due to some delay yield indicates more moisture conserva in maturity of the crop. M uleh applica tion under this mulch. This also showed tion at 6 tJha level increased the average that the temperature variations caused by production of grcengrani by 40% more grass and polyethylene mulches did not than the control without mulch. have any significant effect on the produc Though there was higher crop production tion of lady's finger crop and the during rainfall year of 1979, the crop temperature as high as 40°C was not responses to mulches were more obvious critical for the crop growth (Gupta and during a deficit year of 1980. Gupta, 1981). Table 15. Effect of mulches on ET loss and yield of lady's finger (1979) Mulches ET loss from Mean maximum Yield 60 em soil profile soil temperature (qjha) (mm) CC) No mulch 110.0 40.8 26.3 Grass 106.2 37.8 30.4 Polyethylene 90.0 40.0 38.4 25 CHAPTER 4 Soil Conservation-Wind Erosion Control Wind erosion is one of the most maximum during the period from 13th serious problems which adversely affects May to lIth June 1978 when the wind the productivity of agricultural lands in velocity ranged from 27.0 to 38.0 km/h. western Rajasthan. Studies conducted at During the period from 12th June to 26th C.A.Z.R.I. (Gupta and Aggarwal, 1978) June, though the prevailing wind velocity has shown considerable loss of soil and was maximum there was reduction in soil· nutrients from sandy plains particularly loss particularly at Bikaner due to high during summer months (April-June) when rainfall received during this period. Data high speed winds frequently blow over presented in Table 16 show a relative this region. As the soils of the region soil loss from different regions of western are more vulnerable to wind erosion, Rajasthan. There was maxiJ.llum soil loss therefore, they deserve proper manage at Bikaner followed by Chandan and ment for its control. Jodhpur. Though the soils of Bikaner and Chandan are of the same type, the 4.1 Extent of Wind Erosion decreased erosion at Chandan was due to partial stabilisation by native grass During 75 days period in summer vegetation. Minimum loss at Jodhpur (April - June) as much as 4 cm and 2 cm was due the presence of nonerodible ctmesponding to 615 t/ha and 325 t/ha soil loss was observed at Bikaner and fractions and the soil binding caused by them. Chandan, respectively. The soil loss was Tabl: 16. Relative soil loss due to wind from different regions of western Rajasthan Mean wind Soii loss (kg/ha/day) velocity Chandan Jodhpur Bikaner (km/hr) Sand'soil Loamy sand Sand soil 5 0.95 fj.26 0.47 10 7.97 1.36 120.75 15 15.62 5.09 140.44 20 76.74 15.64 273.69 25 274.48 20.05 424.75 30 1189.24 230.93 40 1776.04 1605.25 26 4.2 Relationship with Wind Velocity the Chandan soil is partially stabilised. A very close exponential relationship With increilse in wind velocity up to 15 between wind velocity and soil loss was km/h at Bikaner and 25 km/h at Chandan. observed both at Bikaner and Chandan there was only a slow increase in erosion. (Fig. I 0) Regression equations are present Beyond these velocities, however, incre ed for predicting soil Joss under different ases were much greater. Hence these wind velocities at both sites. In the case of were the critical velocities for these Bikaner, there was virtually no wind ero respective soils. Further the grain sizes sion at wind velocities of Jess than 5 km/h, of the predominant fractions ranged while at Chandan wind erosion began at from O. J 0 to 0.25 mm in diameter, there velocities above 10 km/h. This was because fore, their minimal threshold velocity ran ged from 5-15 km/h. As the percentage 150 of erodible grains above 0.1 () mm in diameter is higher at Chandan than at Bikaner. this could be another reason for a higher minimal threshold velocity for i y -0 ~~)Li! <'8)· wind erosion (Gupta el al., 1981). ,'0966·· fI,'31 4.3 Soil Fractions Susceptible to Erosion A higher percentage of particles in '00 the range 0.10 - 0.25 mm was observed in the samples of eroded soils than in the field samples collected from Bikaner and Chandan (Table 17). Particles in the size ranges 0.07 - 0.10 mm and 0.05 - 0_07 mm diameter were found to be less erosive '40 CHANDAJI since their percentages in the samples of eroded soil were generally less than in the '20 field soils. Particles less than 0.05 mm ; -0 0956(12"3,· were least eroded from the soil. As the J' -095.1·· field soils consist predominantly of .~ 80 II. !t w the higher erosive fractions; therefore they are highly susceptible to erosion. 4.4 Nutrient Status of Eroded Fractions ~ '0 With increase in fineness of soil fractions, an increase in organic matter, O~ __~J~~~~~ - __~ __~_~ nitrogen, phosphorus and potassium was o IG!'5 20 25 }(.. Xl observed. There was maximum concentra tion in fractions with grains of less than Fig. 10. Relationship between wind speed and 0.05 mm diameter. This was due to the soil eroded at two sites in western Rajasthan. fact that fine fractions contain colloidal 27 Table 17. Grain size (mm) distribution in per cent in field soil and eroded samples from two sites in western Rajasthan Site Soil description Per cent distribution of soil grain >0.25 0.10-0.25 0.07-0.10 0.05-0.07 <0.05 Bikaner Field soil 12.8 62.0 11.6 9.7 2.5 Eroded soil 12.8 69.4 8.2 9.9 0.6 Chandan Field soil 16.0 66.6 8.5 6.5 1.5 Eroded soil 14.8 73.5 5.9 5.4 0.4 materials which are extremely reactive soil having higher percentage of grains and have high cation-exchange capacities. with diameter greater than 0.10 mm. Increase of nitrogen was small but there This was due to the maximum erosion of was a considerable increase of other this fraction of soil both at Bikaner and nutrients. No significant differenct was at Chandan. observed in the nitrogen and phosphorus 4.6 Contcol Measures contents of &oil fractions having grains (i) StllbbJes mulch farming; The with diametres greater than 0 25 mm, practice of using crop residues as stubble particularly at Chandan. The nutrient mulch began in U.S.A. as early as 1910. status of the soil was, in general, higher It is one of the most significant contri at Bikaner than at Chandan: this may well butions to dry land agriculture where ,be due to a higher organic content of the wind erosion is a serious problem. In soil at Bikaner, where climatic conditions mid-west dust bowl of United States, are less severe than at Chandan. large scale mechanized' stubble mulch 4.5 Total Nutrient Loss farming is practiced as a measure of protection to the cultivated farm land Table 18 shows total nutrient losses from wind erosion. Crop residues of 2 to due to wind erosion. Loss of organic 5 m tonnesjha and pearl millet stubbles of matter at Bikaner was about three times 45 cm height were found very effective in higher than that at Chandan. Similarly, preventing the blowing of sand from loss of other macronutrients (N,P,K,S) sandy soils (Misra, 1971). While working and micronutrients (Z,Cu,Fe,Mn) was at Bikaner higher soil loss was observed two to three times higher at. Bikaner from a bare sandy plain (Table 19) than than at Chandan. This was due to grea those covered with pearlmillet stubbles ter total loss of soil at Bikaner than at showing, thereby, usefulness of stubbles Chandan. Though nutrient concentration in checking the mOVement of sand by was maximum in soil fractions with grains providing surface cover, reducing wind "having' a diameter less than O.D5 mm velocity and binding soil particles (Gupta the total nutrient loss was highest from and Aggarwal, 1980). 28 ..... \0 ..... '0 \0 N on \0 " \0 I- 00 I- ..... " M N ...... V") \D r- GO \D ..... ~ "'" :I O. 'C! ~ .,.., <:) .,.., "'"<:) <:) r- -;;-U ...... "'"on -'" V 00 " -0 M M <"'l I- M co .... r- co \0 '" 0 " U .- ~ cd oj o -- M ",,\0 .,.., IlojOJi - ..... N \0 M Q OE~ OJ.... 4l :a .,.., on 0 on .,.., on .,.., 0 8 0 tii N N ] C N N <:) 0 <:) 0 0 0 '0 0 <:) -0 -= .g v E-< (\ v E-< '" .... 0 II. I I I onI .£'" o oj~ on 0 8 0 ..... 0 .!:::e <:) 0 <:) 0 @ ~:::: 8 .... r.n~_' J! '0 tI'l tl oci .... oj OJ "0 OJ c c ~ «I :.0 00 ..I 29 Table 1-9. Sand movement from sandy fo .... '0: plain of Bikaner during 75 days .. "0 0 period. ~ '0 1 ~. ~ l! L:q -~7;~ '! Treatment Total soil loss ... 20 10 .;. i > 0 ~~ (tjha) ;:.... z a ,~ '" 10 " ~ Bare 1449 ...~ / -_ ..... /\ o'll ...... - - Stubble cover 22 ---_.. - CUMULATIVE' OCPOSITI()N e J ') ! ... ~ '".. ,- 10 ..~ ~ 0 (ii) Wind strip cropping: Strips of II 15 50 45 60 Dlb'S AFTER THE SlART 01' OBSERvA," T ION perennial grasses of Lasiurus sindiclls and Ricinus communis established at right Fig. 1I. Cumulative sand movement from typical stabilised and un stabilised angle to th~ direction of prevailing winds sand dune. reduced the impact and thesrhold velocity of wind to the minimum and thus checked Plantation of grasses and trees was found the erosion of wind and increased the to provide surface cover, bind sand production of crops grown in between particles and help in the formation of the protective strips (Misra, 1971). In soil crusts which checked the' movement another study (Gupta and Aggarwal, of sand (Gupta and Aggarwal, 1980). 1980) it has been found that a 18-20 years Bare sand dunes without vegetation, on old cover of such perennial grasses as the other hand, were found to lose Lasiurus sindicus, Cenchrlls biflorlls, as much as 37 cm of the surface sand Panicum turgidllm at Bikaner completely during 75 days period from April to June chesked the movement of sand. The (Fig. J 1). After the blowing away of grass vegetation beside providing surface 37 cm depth of the dry sand (less than cover for reducing wind velocity, helped I % moisture) the rate of blowing was in forming surface crust and binding sand generally found to decrease because of particles. This, therefore, checked the the increase in moisture content (2.0-3.0%) movement of sand. Agricultural la_nds of the unstabilised sand dunes. Moisture can, therefore, be protected with grass ?ontent ?f the unstabilised sands dunes strips and the· marginal lands, can be put was generally higher than the stabilised under complete grass cover for checking dunes (Fig. ) 2). It has also been found the movement of sand towards the pro that the sand dunes with coarser fractions ductive agricultural lands. at the surface contained higher moisture content because of the more recharge and (iii) Sand dune stabilisation: less evaporative loss. Such sand dunes, Movement of sand dunes poses a serious' therefore, should be chosen for successful threat to the productive agricultural stabilisation programme (Gupta, 1979). lands, houses, roads and water courses,' (iv) Shelter belts: Vegetation barri etc., .and, therefore, warrants stabilisation ers placed in the path of wind reduce its which can best be done with vegetation. velocity near the ground by exerting a 30 ". ~~------197~------~ ---1916 -----4 .... E --u .&:. Q. CI o (0) UnstQbjJi'&oo Sand DI,!M L E G E N o s Below 1"'0 1%- 2% 2%-3% 3%-4% .'4%-5% Above 5~ .Moisture by WDight.J ~------1915------~ -1975,--- Jul Oct Nov Dec E -u (b) Stabilisad Sgncloung Fig.tJ..MOISTURE DISTRIBUTION PATTERN IN A TYPICAL. SAND DUNE (Shrl! Fig. 12. Moisture distribution pattern in a typical sand dune of Bikaner (Shrikolayat). 31 drag on the wind and deflecting the wind stream. The effectiveness of shelterbelts in reducing wind velocity depends on many factors such as wind velocity itself, direction, shape, width, tree height and density, etc. From the eight years old , plantation of shelterbe1ts, Cassia siamea , I type shelterbelt was found to be most ,~, ~-1 effective in reducing wind velocity upto I 2 H distance (Gupta et al., 1981). The I \ .. design and tree geometry of the shelter belts used for these studies are shown in Fig. 13. Maximum soil loss was obser ved from a bare field without shelterbelt followed by sheltered field with Prosopis juliflora ,or Acacia tortilis or Cassia siamea ... .s.bDwjng tbneby tne t'ffeL~tjyent'.ss of , shelterbelts in checking soil erosion due • _><• iiif* ~ to wind (Table 20). The use of shelter I , • , - c " belts in general, brought about 50% , # '"~n~ - _;, ~ ... ..,~. reduction in wind erosion. Cassia siamea .. ... "'if • M type shelterbelt, however, was found to I . ~- be most effective in conserving soil during both the years of study. This could be ~ • ..I due to thicker branching and more leafi ness and, therefore, lesser air permeability provided by this shelterbelt. Higher amount of soil loss was. observed during the year 1980 compared to 1979 due to • I more number of windy days. Ganguli and ---, >< Kaul (1969) and Bhimaya et al. (1958) , I reported that shelterbelts when planted I .across and on the margins of agricultural ), ~.' , fields effectively protect crops and control " , ~ .. -' t o '" ~and drifting. The total nutrients loss was also found to be maximum from a ~. bare soil without shelterbelt followed by I shelterbelts with P. juliflora, A. tortilis and C. siamea showing, thereby the conservation in soil fertility by the 32 I::: ' 33 shelterbelts in general and C. siamea clods and exposes it to wind action which type shelterbelt in particular. leads to erosion. Higher percentage (42.4) Higher moisture status was obser of the clods greater than 5 mm size with ved in 0-15 em and 15-30 em layers of an average weight of 111.8 gjclod was soil protected with C. siamea than with observed in the disked field while such other shelterbelts. Residual moisture after value was lower (12.7) with an average irrigation was also higher in soil protected weight of 1.7 gJclod in the disked and with C. siamea type shelterbeIt, showing planked field (Table 21). Wind erosion thereby. less loss of moisture [rom field during the period of observation (5 days) with this type of shelterbelt. was as much as 40 tfha from the field which was thoroughly disked and planked This shows that the plantation of in contrast to a soil loss of 0.5 tfha from three lines of trees of the type Cassia the only disked field. Thus, there was Siamea-Albizzia lebbek-Cassia siamea as about 80 times reduction in wind erosion shelterbelt across wind direction can be from a field which was only· disked as helpful in reducing wind velocity, in compared to the disked and planked checking wind erosion and in delaying one. This reduction was due to more the drying of the sheltered soils. roughness provided by the soil clods (v) Tillage: Excessive tillage of (Gupta and Gupta, 1981). agricultural land when it is dry breaks 34 CHAPTER 5 Summary and Conclusion Proper soil management and con typhoides). Therefore, there is scope of servation techniques play an important the use of asphalt moisture barrier for role in increasing the productivity of arid crop production, nursery plantation and lands. Water harvesting was found to be tree establishment. an important technique in increasing Different amendments were used for water supply to the crops for higher and improving soil physical conditions, fertil sustained production during deficit rain ity status and the productivity of desert fall years. Soils underlain with impervious sandy soils. The use of pond sediments layers and having 5 to 10% slope were at the rate of 76 tonnes Iha increased the found to generate very high amount of moisture retention at 0.3 bar tension runoff particularly during high rainfall from 8.6 to 10.1 %, N from 0.028 to years or years with high intensity of 0.039% and organic carbon from 0.21 to rainfall. This water if properly collected 0.27%, resulting in 40-50% increase in and stored can be used for growing short the grain yield of pearlmillet and green duration and low water requiring crops gram with associated increase in the N and also as supplemental irrigation for uptake, water use and water-use efficiency. saving crops during the periods of drou Pond sediments, therefore, can be used ght. for improving soil physical conditions, Different materials like asphalt, fertility status of soil and the crop bentonite clay and pond sediments were production. It does not involve any ex used as subsurface moistllre barriers at penditure except the transportation and 60 em depth in 2 mm thickness for can be used wherever it is available. asphalt and 5 mm thickness for others. The use of exfoliated vermiculite These were found useful for moisture and increased t~e moisture retention at 0.1 bar nutrient conservation. The placement of tt!Dsion and decreased the bulk density asphalt as subsurface barrier led to five and saturated hydraulic conductivity of times reduction in deep percolation loss soil. Its application at the rate of 20 tina and two times increase in moisture and optimized the production of ladys finger nitrogen retention capacity of the soil. which was 40-60% more than the control With asphalt barrier, therefore, there without vermiculite. As the material was increase in moisture and nitrogen involves some cost, theref<:>re, it can be status of soil throughout the cropping profitably used for high value crops like season. This led to 40-60% increase in vegetables and also in the establishment the production of pearlmillet (Pennisetum of nursery plants and trees. 35 The contriiuous application of farm were found higher than the lower depths yard manure in association with urea leading, thereby, to downward movement showed an increase in moisture retention of heat In winter, however, the temper and decrease in bulk density and satura atures of lower layers were higher facilit ted hydraulic conductivity of soil. The ating the upward flow of heat and the combination of these two nitrogen sources vapour flux. A high variability in heat to supply 50% nitrogen from each optim fluxes with generally positive day time ized the soil environment and increased heat fluxes in summer and negative in the production of pearl millet by 30% win,ter were observed. more than with farmyard manure alone Different mulches were used for and nearly equal with urea alone. This reducing the evaporative loss of moisture can, therefore, be used for improving and lowering the thermal regime ot soil. physico-chemical environment of soil Application of grass mulch at the rate of and crop production beside economizing 6 t/ha decreased the maximum tempera the use of fertilizers. ture of soil by I to 9°C, reduced the evaporation loss and increased the seedling Post emergence cultivation of 5 cm emergence of pearlmilJet crop during the depth after 20 days of seedling emergence hot month of June. During kharif season was found to substantially reduce weed (July-September), however, the magnitude population, lower soil bulk density and of temperature reduction narrowed increase root growth and proliferation. down to I_6°C. Polyethylene mulch, on This, therefore, increased the production the contrary, raised it by 1 to 3°e. These of pearlmillet from 3.4 to 11.8 q/ha with mulches also suppressed weed growth. higher uptake of nutrients. In the improved moisture status of soil and absence ~f weeds also one post emergence thus, increased the production of pearlmi cultivation was found useful in raising the average production from 9.5 to 11.8 lIet and ladys finger crops, With increase q/ha. More cultivations, however, were in application rate of grass mulch, there not found useful in further raising the was also reduction in maximum soil tem level of crop production. The practice, perature, increase in water status of soil therefore, can be used for improving soil and plant and improvement in root physical condition,s, reducing crop-weed growth and Il'Odulation. Mulch applica competition and increasing crop yields. tion at 6 t/ha level optimized the average production of greengram which was Moisture and thermal regimes of about 40% more than the control without ~he sandy soils were quantified. Bare soil mulch. These mulches, therefore, can be without vegetation contained higher used for favourably manipulating soil moisture content than the soils with grass environment for increasing crop produc vegetation. Mean maximum temperature tion. The waste plant materials like grass, of a bare soil at 5 cm depth, in general, straw, etc., available at the farms can be w~s 1 to 2°C higher than the soil with profitably used as mulch for general field vegetative cover. Maximum soil temper crops and the polyethylene mulch can be atures at 5 cm depth during summer used for high cash crops like vegetables. 36 As much as 615 tonnes/ha and 325 and, thereby, checked erosion. Surface tonnes/ha soil loss was observed from mulches, beside providing surface cover, Bikaner and Chandan, respectively, during conserved moisture in soil and reduced 75 days period in summer (April-June). wind erosion. These techniques if adopted A high exponential correlation between can help in checking the movement of wind velocity and soil loss was observed s'and and inceasing the productivity of at both sites. Particle sizes in the range the land. 0.10-0.25 mm were observed to be more Plantation of shelterbelts of Prosopis erosive, while particles less than 0.05 mm juliflora or Cassia siamea or Acacia were least erosive. Finer fractions of torti/is generally reduced wind velocity, eroded soil were found to contain higher wind erosion and the evaporative loss contents of organic matter, nitrogen, of moisture from the protected fields. phosphorus and potassium. Total loss of However, Cassia siamea type shelterbelt macro-nutrients (N, P, K, S) and of was found to be most effective in micro-nutrients (Zn, Cu, Fe. Mn) was checking wind erosion and delaying two to three times higher at Bikancr than the drying of the soil and, therefore, at Chandan. should be planted in the fields across the wind direction. Different methods were used to check the movement of sand. Crop stubb Excessive tillage like disking and les of 30-45 cm height were found to planking of the dry soil led to the break substantially reduce the movement of age of clods and made the soil more sand. Wind strip cropping was found a vulnerable to wind erosion. A loss of 40 useful technique for checking the move tlha was observed from a disked and ment of sand. Plantation of grass or a planked soil while it was 0.5 tlha from mixture of grass and trees helped in redu only disked soil. The total nutrient loss cing wind velocity, binding soil particles was also more from the disked and plan and in forming soil crust and, thereby, ked soil as compared to only disked soil helped in checking the movement of sand. Soil cultivation should, therefore, be per Application of soil amendments like pond formed with premonsoon showers so that sediments, farmyard manure, bentonite there is formation of clods which resist clay, etc, formed wind stable aggregates the erosion of soil by wind. 37 CHAPTER 6 Literature Cited 1. Aggarwal, R.K., Gupta, J.P. and 8. Ganguli, J.K., and Kaul, R.N. 1969. Kaul, P. 1980. Nitrogen mineralisa Wind erosion control, I.C.A.R., New tion as affected by the addition of Delhi. Tech. Bull. (Agri.) 20, pp. pond sediments and bentonite clay 1-53. to a sandy soil under different mois 9. Gupta,J.P. and Aggarwal,R.K. 1978. ture regimes. I. Indian Soc. Soil Sci. Effect of asphalt subsurface barrier 28 (4): 444-449. on water characteristics and produc 2. AMOCO 1971. Productive Soil From tivity of sandy soils. Abstracts, Inter Sand. Amobar Company, 910 national symposium on Arid Zone South Michigan Avenue, Chicago, Research and Development, C.A.Z. JtIinois 60605. R.I., Jodhpur, India, pp. 70. 3. Anonymous 1968. Report of the work 10. Gupta, J.P. 1978. Evaporation from ing group for formulation of fourth a sandy soil under mulches. Anll. five year plan proposal on land and Arid ZoneJ7 (3): 287-290. water development. Min. Food Agri. Community Dev. and Coop. (Deptt. 11. Gupta, J.P., Aggarwal, R.K. and of Agri.) New Delhi. Kaul, P. 1979. Effect of the appli 4. Anonymous 1974. Annual Report. cation of pond sediments on soil C.A.Z.R.l., Jodhpur. pp. 119-121. properties and yield of pearlmillet 5. Bansal S P., Gajri, P.R. and Prihar, and green gram III arid areas of S.S. 1971. Effect of mulches on water western Rajasthan. Indian J. Agri. conservat~on, soil temperature and Sci. 49 (I!): 875-879. growth of maize (Zed mays L.) .and 12. Gupta,J.P. 1979. Some observations pearlmillet (Pennisetum typha ides ). on the periodic variations of mois Ind'an J. Agri. Sci. 41: 467-473. ture in stabilized and unstabilized 6. Bhimaya,C.P., Misra, D.K. and Das, sand dunes of the Indian desert. J. R.B. 1958. Importance of shelter Hydrology 41: 153-156. belts in arid zone farming. Proc. Farm Forestry Symposium, Indian 13. Gupta, J.P. and Aggarwal, R.K. Council of Agriculture Research, 1980. Use of an asphalt subsurface New Delhi, pp. 65-72. . barrier for improving the produc 7. Bunya~d, P. 1973. Will the desert tivity of desert sandy soils. J. Arid bloom? Ecologist 3 (9) : 334-337. Environ. 3 : 215-222. 38 14. Gupta,J.P. and Aggarwal, R.K. 1980. 21. Gupta, J.P., Rao, G.G.S.N., Gupta, Effect of asphalt subsurface mois G.N. and Ramana Rao, B.V. 1981. ture barrier on water characteristics Soil drying and wind erosion as and productivity of sand soil. Ann. affected by different types of shelter Arid Zone 19 (4). 445-450. belts planted in the desertic region of western Rajasthan, India. J. 15. Gupta, J.P. 1980. Effect of mul Arid Environ (In press). ches on moisture and thermal regimes of soil and yield of pearl 22. Gupta, J.P. and Gupta, G.N. 1981. millet. Anll. Arid Zone 19 (1 and Effect of post emergence cultivation 2) : 132-138. on weed growth, nutrient uptake and yield of pearimillet. Ann. Arid 16. Gupta, J. P. and Aggarwal, R.K. Zone 21 (4) : 241-247. 1980. Sand movement studies under different land use conditions of 23. Gupta, J.P. and Gupta, G.N. 1981. western Rajasthan. In Arid Zone Effect of the application of exfoliated Research and Developmellt. (Ed. vermiculite on soil properties and H.S. Mann) Scientific Publishers, vegetable production in arid zone Jodhpur, pp. 109-114. of western Rajasthan. Agroc/Jimica (In press). 17. Gupta, J.P. and Aggarwal, R.K. 24. Gupta. J.P., Aggarwal, R.K., Gupta, 1980. Soil physical properties and G N. and Kaul, P. 1982. Effect of nitrogen mineralization as affected continuous application of farm by the use of bentonite clay and yard manure and urea on soil pond sediments as amendments. properties and the production of Agrochimica 24 : 416. pearlmillet III western Rajasthan. IIJdian J. Agri. Sci. (In press). 18. Gupta, J.P., Aggarwal, R.K. and Raikhy, N.P. 1981. Soil erosion 25. Gupta, G.N. and Gupta, J.P. 1982. Diurnal variations in moisture and by wind from bare sandy plains III temperature of a desert soil under western Rajasthan, India. J. Arid different management practices. Environ. 4: 15-20. Archiv Fur Meteor%gie, Geophysik 19. Gupta, J.P. and Gupta, G.N. 1981. and Bioklimatologie, Austria (In A note on wind erosion from a press). cultivated field in western Rajas 26. Gupta. J.P. and Gupta, G.N. 1982. than. J. Indian Soc. Soil Sci. 29 (2): Effect of mulches on hydrothermal 278-279. environment of soil and crop pro duction in arid zone of western 20. Gupta, J.P. 1981. Some studies on Rajasthan. hydrothermal regime and day time' Abstracts, 12th Interna New heat fluxes in a desert sandy soil tional Congress of Soil Science, Delhi, India, pp. 9-10. with and without vegetation. Archiv Fur Meteorologie, Geophysik and 27. Mann, H.S., Gupta J.P., Murthy, Bioklimatologie, Austria (In press). K.N.K., Mathur, C.P. and Issac, 39 V.C. 1980. An estimation of runoff 30. Prihar, S.S., Singh, N.T. and Sandhu from some small rocky catchments B.S. 1977. Response of crops to soil of western Rajasthan and its utiliza. temperature changes induced by tion potential for crops. Indian mulching and irrigation. In Soil J. Soil Conser. 8 (I): 38-43. Physical Properties and Crop Produc 28. Misra, O.K. 1971. Agronomic tion in the Tropics., (Eds. R. Lal investigation in arid zone. Proc. and D. J. Green land) John Wiley Symposium Problems of Indian Sons, New York, pp.305-315. Arid Zone, Min. of Education, 31. van Wijk, W.R., Larson, W.1. and Government of India, New Delhi. Burrows, W.C. 1959. Soil tempera pp. 165-169. ture and early growth of corn for 29. Moody, J.E.,Jones, J.N. and Lillard, mulched and unmulched soils. Proc. J.H. 1963. Influence of straw mulch Am. Soc. Soil Sci. 23: 428-431. on soil moisture, soil temperature 32. Wimer, D.C. 1946. Why cultivate and growth of corn. Proc. Am. Soc. corn? Univ. III. College Agri. Cir. Soil Sci. 27 (6): 700-703. 597. 40 CAZRI Monograph Series No. 1 Desert Ecosystem and its Im Edited by H. S. -Mann provement, pp. 1-387 (1974). No. 2 Proceedings of Summer Institute Edited by Ishwar Prakash on Rodentology (Mimeo.), pp. 1-365 (1975). No.3 Solar Energy Utilization Re- by H. P. Garg search (Mimeo.), pp. 1-48 (1975). No.4 Rodent Pest Management by Ishwar Prakash Principles and Practices, pp. 1- 28 (1976). No. 5 White Grubs and their Manage by S. K. Pal ment, pp. 1-30 (1977). No.6 The Amazing Life in the Indian by Ishwar Prakash Desert, pp. 1-18 (1977). No. 7 Geomorphological Investiga by Surendra Singh tions of the Rajasthan desert, pp. 1-44 (1977). No. 8 Proceedings of Summer Institute Edited by K. A. Shankar on "Resource Inventory and narayan landuse planning", pp. 1-373 (1977). No.9 Land Use Classification System by Amal Kumar Sen in Indian Arid Zone, pp. 1-43 (1978). No. 10 Ecology of the Indian desert by Ishwar Prakash gerbil, Meriones hurrianae, pp. 1-88 (1981). 41 No. II Khejri (Prosopis cineraria) in Edited by H. S. Mann and the Indian desert - its role in S. K. Saxena Agroforestry, pp. 1-78 (15180). No. 12 The goat in the desert environ 'by P. K. Ghosh and M. S. ment, pp. 1-26 (1980). Khan No. 13 Hordi (Zizyphus nummularia)- Edited by H. S. Mann and A shrub of the Indian Arid Zone S. K. Saxena -its role in silvipasture, pp. 1-93 (1981). No. 14 Sheep in Rajasthan, pp. 1-38, by A.K. Sen, P.K. Ghosh. (1981). K.N. Gupta and H.C. Bohra No. 15 Water proofing of field irrigation by K. N. K. Murthy, V. C. channels in desert soils, pp. 1-23, Issac and D. N. Bohra ( 1982). No. 16 Termite pests of vegetation in by D. R. Parihar Rajasthan and their manage ment, pp. 1-31, (1981). No. 17 Water in the eeo-physiology of by P. K. Ghosh and R. K. desert sheep, pp. 1-42 (1981). Abiehandani No. 18 Ground water atlas of Rajasthan, by H. S. Mann and A. K. pp. 1-61 (1983). Sen No. 19 Agro-demograpbic Atlas of Rajas by A.K. Sen and K.N. than, pp. 1-63 (1983). Gupta 42