Evaluation of Sweet Orange (Citrus Sinensis L. Osbeck) Cv

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Evaluation of Sweet Orange (Citrus sinensis L. Osbeck) cv. Sathgudi Budded on Five Rootstocks for Differential Behavior in

Relation to Nutrient Utilization in Alﬁsol KRISHI Publications and Data Repository

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Communications in Soil Science and Plant Analysis Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/lcss20 Evaluation of Sweet Orange (Citrus sinensis L. Osbeck) cv. Sathgudi Budded on Five Rootstocks for Differential Behavior in Relation to Nutrient Utilization in Alfisol J. Kusuma Grace a , K. L. Sharma a , K. V. Seshadri b , C. Ranganayakulu a , K. V. Subramanyam a , G. Bhupal Raj a , S. H. K. Sharma a , G. Ramesh a , Pravin N. Gajbhiye a & M. Madhavi a a Central Research Institute for Dryland Agriculture, Hyderabad, India b Citrus Improvement Project, S. V. Agricultural College Farm, Tirupati, India Available online: 27 Mar 2012

To cite this article: J. Kusuma Grace, K. L. Sharma, K. V. Seshadri, C. Ranganayakulu, K. V. Subramanyam, G. Bhupal Raj, S. H. K. Sharma, G. Ramesh, Pravin N. Gajbhiye & M. Madhavi (2012): Evaluation of Sweet Orange (Citrus sinensis L. Osbeck) cv. Sathgudi Budded on Five Rootstocks for Differential Behavior in Relation to Nutrient Utilization in Alfisol, Communications in Soil Science and Plant Analysis, 43:7, 985-1014 To link to this article: http://dx.doi.org/10.1080/00103624.2012.656164

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Evaluation of Sweet Orange (Citrus sinensis L. Osbeck) cv. Sathgudi Budded on Five Rootstocks for Differential Behavior in Relation to Nutrient Utilization in Alﬁsol

J. KUSUMA GRACE,1 K. L. SHARMA,1 K. V. SESHADRI,2 C. RANGANAYAKULU,1 K. V. SUBRAMANYAM,1 G. BHUPAL RAJ,1 S. H. K. SHARMA,1 G. RAMESH,1 PRAVIN N. GAJBHIYE,1 AND M. MADHAVI1 1Central Research Institute for Dryland Agriculture, Hyderabad, India 2Citrus Improvement Project, S. V. Agricultural College Farm, Tirupati, India

The experiment was conducted to evaluate the nutrient utilization ability of sweet orange (Citrus sinensis L. Osbeck) budded on five rootstocks (viz., Sathgudi, Rangpur lime, Cleopatra mandarin, Troyer citrange, and Trifoliate orange) in Alfisols at the experimental farm of the Citrus Improvement Project, S. V. Agricultural College Farm, Tirupati, Andhra Pradesh, India. Results of the study revealed that all the five rootstocks showed differential behaviors in terms of nutrient absorption from the soil. Rootstocks exhibited significant variation in the leaf content of potassium (K), copper (Cu), manganese (Mn), and boron (B) at all the three stages of sampling. Concentrations of the following key nutrient elements significantly varied: phosphorus (P), calcium (Ca), magnesium (Mg), zinc (Zn), and Cu at stage 1; K, Ca, Mg, Zn, iron (Fe), and Mn at stage 2; and nitrogen (N), P, Zn, Fe, and B at stage 3. The performances of rootstocks in terms of relative nutrient accumulation indices (RNAIs) were in the order of Sathgudi (1.00) > Rangpur lime (0.98) > Cleopatra mandarin (0.96) > Trifoliate orange (0.76) > Troyer citrange (0.69). The present study clearly demonstrated that citrus rootstocks employed had differential nutritional behavior and different abilities to utilize plant nutrient elements. Thus, the findings of the present study and the methodology adopted can help the horticultural breeders and nutritionists choose the best /

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 rootstock scion combination having the desirable traits of nutrient utilization ability and also to plan effective fertilizer schedule programs for achieving greater yields.

Keywords Alﬁsols, correlations, efﬁciency, rootstocks, nutrient accumulation index, sweet orange

Introduction Citrus fruit occupies a prominent position among the tropical and subtropical fruits next to mango and banana, among which sweet oranges are prominent. World production of citrus fruit has experienced continuous growth in the last decades of the 20th century. Total

Received 26 October 2009; accepted 17 November 2011. Address correspondence to K. L. Sharma, Division of Resource Management, Central Research Institute for Dryland Agriculture, Santhoshnagar, P.O. Saidabad, Hyderabad 500 059, India. E-mail: [email protected]

985 986 J. K. Grace et al.

annual citrus production was estimated at more than 105 million tons during 2000–2004. Oranges constitute the bulk of citrus fruit production, accounting for more than half of global citrus production. Citrus fruits are produced all around the world, and according to estimates of the Food and Agricultural Organization, about 140 countries produce citrus fruits. However, most of the production is concentrated in certain areas. Around 70% of total citrus fruits are grown in the northern hemisphere. Predominant citrus-fruit-producing countries are Brazil, the Mediterranean countries, the United States (where citrus fruits for consumption as fresh fruit are mainly grown in California, Arizona, and Texas and most orange juice is produced in Florida), and China. These countries represent more than two thirds of global citrus fruit production. Citrus has been generally grown on rootstocks since the 1940s, and rootstock utilization in citrus production has become mandatory to solve the problems caused by soil, climates, pests, and diseases as well as to achieve greater productivity and quality (Tuzcu 1978; Toplu et al. 2008). Therefore, citrus producers almost exclusively utilize rootstocks. The rootstock performance depends on many factors such as climatic conditions, soil nutrient status, soil physical problems, nutrient availability, nutrient absorption and utilization capacity of rootstock, vigor, and resistance to diseases. Several trials have been conducted to evaluate different rootstocks, but rootstocks that are superior in one agroclimatic condi- tion may fail to perform in another (Jalikop, Ravishankar, and Srivastava 1986). Because of their diverse genotypes and differential environments, rootstocks have different abilities to utilize different elements. Even edaphoclimatic conditions and cultural practices influence the nutritional aspects of rootstocks (Sharples and Hilgeman 1972). Because the root systems of the citrus trees are developed from the rootstocks, the rootstock has direct effects on water and nutrient uptake and translocations. The effects of rootstocks on several physiological and biochemical effects causing differences in plant development, productivity, and fruit quality are well documented in several citrus species (Kaplankiran and Tuzcu 1993; Georgiou and Georgiou 1999; Kaplankiran et al. 1999; Al-Jaleel and Zekri 2003). Given that the rootstocks are of diverse genotypes, they may influence the plant nutrient status of the scions grafted on them. These effects may even change in differential environments. Further, the differential nutrient absorption and utilization behavior of citrus budded on different rootstocks may influence the total nutrient removal pattern and consequently the general fertility status of soil on which these trees grow. For this reason, it is important to determine the effects of rootstocks on fertility changes, plant nutrient status, and nutrient utilization pattern to optimize fertilization

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 programs. The prominent fertility differences of soils used in citriculture under different climatic conditions can be determined by soil and leaf analysis. Leaf tissue testing is a valuable tool to examine the tree nutrient status, particularly with respect to mobile nutrients such as nitrogen (N) and potassium (K), and for other micronutrients (Alva et al. 2006). Leaf analysis is not only important for evaluation of nutritional status of trees but also for improving the fertilizer recommendations and nutrient uptake efﬁciency (Alva and Paramasivam 1998). The long-term performance of rootstocks and their signiﬁcant effects on leaf nutrient levels have been studied for different climatic conditions across the world (Smith et al. 2004; Georgiou 2000, 2002; Storey and Treeby 2000; Marathe et al. 2004; Toplu et al. 2008). It is vital to determine the effect of rootstocks on plant nutrient status as well as the optimum rootstock/scion combinations (Toplu et al. 2008), which may be useful to optimize fertilizer programs. In the Indian subcontinent, citrus fruits are grown predominantly in Maharashtra, Andhra Pradesh, Karnataka, Madhya Pradesh, Punjab, and Assam, a total area of Nutrient Absorption Patterns of Rootstocks 987

264.5 thousand hectares with an average yield of 17.9 tons ha−1 only. The Chittoor District in Andhra Pradesh in India is one of the predominant citrus-growing regions where the citrus crop is mostly grown on Alfisol soils. Among other reasons, the production is con- strained by lack of suitable nutrient-responsive rootstock/scion combination. The present study was undertaken to evaluate the Sathgudi sweet orange budded on several rootstocks to study the influences on (i) soil fertility status and (ii) nutrient utilization pattern in terms of leaf mineral composition and relative nutrient accumulation index, and (iii) the interrelationship among the nutrients present in soil and plants in an Alfisol.

Materials and Methods To achieve these objectives, a 13-year-old root stock trial on Sathgudi sweet orange (Citrus sinensis L. Osbeck) started under the Citrus Improvement Project at S. V. Agricultural College Farm, Tirupati, Chittoor District of Andhra Pradesh, was adopted for the study. The experiment was conducted in a randomized block design with five rootstocks (treat- ments) in four replications with six trees per replication. The experimental site is located at an altitude of 182.9 m above mean sea level at 13◦ N latitude and 79◦ E longitude. Climatically, the region is semi-arid with annual rainfall of 700 to 1000 mm. The site is upland with a slope gradient of 0–1%, slight erosion, and slow runoff. Physiography of the experimental unit was plain, with moderately good drainage, ground water > 10.0 m, and no flooding. Soils were developed on granitic parent material with <3% stoniness. The five rootstocks employed for Sathgudi sweet orange (Citrus sinensis L. Osbeck) were (a) Sathgudi (Citrus sinensis Osbeck), (b) Rangpur lime (Citrus limonia Osbeck), (c) Cleopatra mandarin (Citrus reshni Tanaka), (d) Troyer citrange (Poncirus trifoliate L. Raf × Citrus sinensis L. Osbeck), and (e) Trifoliate orange (Poncirus trifoliate L. Raf). Studies were conducted on these 13-year-old trees at different intervals of time: before fertilization of the field, at 45 days after fertilization of the field, and at 135 days after fertilization of the field. The amounts of manures and fertilizers applied per tree per annum were farmyard manure (FYM) at 40 kg/tree, castor cake (N content 4.5%) at 9 kg/tree, urea (N content 46%) at 1.63 kg/tree, single superphosphate (SSP) (P2O5 content 16%) at 2.2 kg/tree, and muriate of potash (K2O content 60%) (MOP) at 0.69 kg/tree. These materials were applied to soil uniformly every year to all the rootstock basins. Initially, experimental soils were low in N (210 kg ha−1), medium in phosphorus (P; 12 kg ha−1), medium in available K (210 kg ha−1), and adequate in micronutrients.

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 The ﬁrst soil sampling was done before the fertilizer application and the second sampling was done 45 days after fertilizer application. The soils were collected in each plot near the tree basins from two depths: 0–15 cm and 15–30 cm. Six soil samples of each replication were mixed according to their respective depths and made into composite samples. For each replication, two composite samples were obtained for two depths. Weighted averages of both the depths were also computed using the bulk density values of the respective soil depths. These samples were passed through a 2-mm sieve and stored in polythene bags for further analysis. In the soils, nutrients were estimated as follows: available N by distillation with 0.032% alkaline permanganate method (Subbaiah and Asija 1956), available P by Olsen’s method (Olsen et al. 1954), available potassium (K) using ﬂame photometry (Systronic model 121; Jackson 1967), exchangeable Ca and magnesium (Mg) by ethylenediaminetetraacetic acid (EDTA) titration method (Vogel 1978), and available sulfur (S) by the turbidity method using barium chloride in a Spectronic 20 instrument at 440 nm (Piper 1950). Available boron (B) was determined colorimetrically by curcumin determinative procedure (Jackson 1976). The DTPA-extractable micronutrients [viz., zinc 988 J. K. Grace et al.

(Zn), iron (Fe), copper (Cu), and manganese (Mn)] were determined using a 1:2 soil-to- extractant ratio (Lindsay and Norvel 1978), and concentrations were measured with atomic absorption spectrophotometry (AAS). As the experiment pertained to horticultural crops (deep-rooted tree component), it was also felt essential to study a representative soil profile for its general characteristics. Hence, as an initial step, one soil profile was dug at a representative site and studied for various morphological, physical, physicochemical, and chemical characteristics. Foliar sampling was done three times during the period of experimentation. The first sampling was done in January, the second in March, and the third in July, coinciding with before fertilizer application, 45 days after fertilization, and 135 days after fertilization. While sampling, the third and the fourth leaves were collected; transported in polythene bags; washed with tap water, dilute hydrochloric acid (HCl), distilled water, and finally redistilled water; air dried for some time in the shade to exhaust the major moisture content; and finally dried in a hot air oven at 60 ± 5 ◦C. The dried samples were powdered and preserved in butter paper bags. Equal amounts of the powdered foliar samples were taken from six plants of each replication, thoroughly mixed, and composited to get one single sample per each replication. To analyze the leaf samples, 1 g of oven-dried plant samples were digested with diacid [nitric acid (HNO3) and perchloric acid (HClO4) in the ratio of 9:4]. The digested extract was diluted to 100 mL with redistilled water and filtered through Whatman no. 42 filter paper (Jackson 1967). This filtrate was used for analyzing available N, P, K, Ca, Mg, S, and micronutrients of the foliage. Nitrogen was estimated by micro-Kjeldhal method (AOAC 1970), P by vanadomolybdate method using Spectronic 20 instrument at 470 nm (Jackson 1967), Ca and Mg by titrating with 0.01 N EDTA (Vogel 1978), S by turbidometric method using Spectronic 20 instrument at 440 nm (Vogel 1978), B by curcumin procedure (Jackson, 1967), and micronutrients in a diacid extract using AAS (Vogel 1978). The leaf nutrient standards of citrus based on sampling from fruit- bearing terminals as given by Chapman (1960) were used as the standards to categorize the nutrient contents of leaves into different ranges in each rootstock.

Nutrient Accumulation Index (NAI) To compute the nutrient accumulation index (NAI), the data on leaf nutrient concentration obtained for all ﬁve rootstocks at three stages [viz., initial stage 1 (before fertilizer application), stage 2 (45 days after fertilizer application), and stage 3 (135 days after fertil- Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 izer application)] was subjected to principal component analysis (PCA) (Doran and Parkin 1994; Andrews et al. 2002) using SPSS (version 16.0; SPSS, Chicago, Ill.) and linear scoring technique (Andrews, Karlen, and Mitchell 2002). The nutrient accumulation index (NAI) was computed using the following relationship: n NAIi=1 = (Wi × Si)

where Si is the score for the subscripted key nutrient element and Wi is the weighing factor obtained from the PCA.

Statistical Analysis The data were subjected to analysis of variance (ANOVA) using a randomized block design (RBD) (Snedecor, Cochran, and Cox 1989) in a standard Drysoft design package. Nutrient Absorption Patterns of Rootstocks 989

Pearson’s correlation coefﬁcients were obtained using SPSS ver. 16. The PCA was adopted to compute the nutrient accumulation indices (NAI) using the SPSS ver. 9.

Results and Discussion

General Soil Proﬁle Characteristics

The experimental soil profile had four horizons (viz., A2,B1,B1t, and B2t) with depths of 0–40 cm, 40–88 cm, 88–100 cm, and 100–150+ cm, respectively. The color of the soil was yellowish red to dark red with hues ranging from 5 YR to 2.5 YR (moist) toward deeper layers. The soil texture varied from sandy loam to sandy clay with increasing clay percentage with depth. Clay cutans were also observed in the third and fourth layers, indicating an argillic horizon. Soils were neutral to slightly alkaline with pH increasing with depth, ranging from 7.1 to 7.8, and electrical conductivity ranging from 0.2 to 0.3 dS m−1.Both organic C (ranging from 2.7 to 4.0 g kg−1) and available N (ranging from 219.5 to 203.8 kg ha−1) decreased with depth. Available P (varying from 37.6 to 26.2 kg ha−1) also decreased with depth but was slightly greater (37.6 kg ha−1) at 40–88 cm deep. In contrast, available K content varied between 253.4 to 302.0 kg ha−1 and increased with depth except at 88 to 100 cm, where it reduced to 253.4 kg ha−1. Exchangeable Ca in the soil profile ranged from 2.64 to 3.30 me 100−1 g soil and increased with depth except at 40 to 88 cm, where it showed a slight decrease. The available Mg in the profile showed a decreasing trend and ranged from 2.17 to 1.86 me 100−1 g soil except a slight increase at 100 to 150 cm. The available S showed an increasing trend and ranged from 24.71 to 39.7 ppm. The diethylen- etriaminepentaacetic acid (DTPA)–extractable micronutrients (viz., Zn, Fe, Mn, and B) decreased with depth and ranged from 3.3 to 2.3 ppm, 10.2 to 7.6 ppm, 19.2 to 15.3 ppm, and 1.06 to 0.63 ppm respectively, whereas available Cu status of the soil decreased up to 88 cm deep and increased at 88 to 100 cm deep.

Initial Nutrient Status in Soil under Different Rootstocks As this experiment was adopted for the present study after 13 years of the rootstock trial, initial characterization of the fertility status was essential to see the variation in soil fertility that occurred due to the differential nutrient absorption behavior of the rootstocks. After this characterization, again the uniform doses of fertilizers and manures, as mentioned

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 previously, were applied and the nutrient status in the soils basins was studied 45 days after application to monitor the changes as influenced by the rootstocks. The data are presented in Tables 1 to 3. Perusal of the data on initial nutrient status revealed significant variations in the majority of the soil fertility parameters, except for available N, exchangeable Mg, and available B at both the soil depths. Because the fertilizer and manure doses were uniformly applied right from the inception of the orchard, these significant variations in fertility could be attributed to differential feeding habits or absorption patterns of the rootstocks at both surface and subsurface horizons. pcpcpc To confirm the differential nutrient absorption behavior of the rootstocks, the soil fertility parameters were studied 45 days after uniform fertilizer application. It was observed that the soil-available N status under different rootstock basins significantly varied at both the depths and increased with depth except in one or two instances. On average, Trifoliate orange rootstock basins recorded greatest available N content before and after fertilizer application, which was at par with Troyer citrange and Sathgudi, indicating less N sink capacity of these rootstocks. When the percentage increase in N content 45 days after Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 1 Soil characteristics and fertility parameters (macronutrients) under Sathgudi sweet orange as inﬂuenced by different rootstocks pH EC (dS m−1)N(kgha−1)P(kgha−1)K(kgha−1) 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted No. Rootstock cm cm average cm cm average cm cm average cm cm average cm cm average Initial (before fertilizer application) 1 Sathgudi 7.00 7.15 7.08 0.27 0.20 0.23 248.8 254.8 251.9 41.9 30.1 35.9 338.8 428.6 384.6 2 Rangpur lime 7.17 7.20 7.19 0.20 0.10 0.15 205.2 235.2 220.5 31.9 26.4 29.1 285.6 343.3 315.0 3 Cleopatra 7.10 7.05 7.07 0.25 0.22 0.23 219.5 237.1 228.5 35.2 31.3 33.2 322.4 348.5 335.7 mandarin

990 4 Troyer citrange 7.02 7.15 7.09 0.22 0.12 0.17 251.3 243.0 247.1 30.1 26.5 28.3 381.4 412.4 397.2 5 Trifoliate 7.02 7.17 7.10 0.27 0.22 0.24 223.4 286.2 255.4 35.1 32.5 33.8 412.2 477.5 445.5 orange CD (P = 0.05) NS NS NS 0.08 NS NS 4.31 3.75 41.1 23.9 After 45 days of fertilizer application 1 Sathgudi 7.10 7.37 7.24 0.15 0.15 0.15 278.3 270.6 274.4 39.5 32.6 36.0 327.2 346.5 337.0 2 Rangpur lime 7.35 7.55 7.45 0.22 0.10 0.16 231.3 243.0 237.3 27.1 24.2 25.6 285.7 279.3 282.4 3 Cleopatra 7.20 7.17 7.18 0.22 0.12 0.17 243.0 250.9 247.0 30.3 28.6 29.4 323.6 343.4 333.7 mandarin 4 Troyer citrange 7.05 7.17 7.11 0.17 0.17 0.17 257.5 313.4 286.0 29.2 24.3 26.7 391.2 335.8 363.0 5 Trifoliate 7.12 7.30 7.21 0.27 0.22 0.24 290.1 290.1 290.1 32.8 28.3 30.5 411.6 488.4 450.8 orange CD (P = 0.05) NS NS NS 0.07 31.2 27.3 1.67 3.57 27.1 37.8 Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 2 Soil fertility parameters (secondary) under Sathgudi sweet orange as inﬂuenced by different rootstocks

Ca (me 100 g−1 soil) Mg (me 100 g−1 soil) S (ppm)

Weighted Weighted Weighted No. Rootstock 0–15 cm 15–30 cm average 0–15 cm 15–30 cm average 0–15 cm 15–30 cm average Initial (before fertilizer application) 1 Sathgudi 2.78 2.53 2.65 2.50 2.52 2.51 26.8 23.0 24.9 2 Rangpur lime 2.60 2.57 2.58 2.55 1.94 2.24 23.9 20.7 22.3 3 Cleopatra mandarin 3.32 2.91 3.11 2.39 2.24 2.31 24.6 20.6 22.6 991 4 Troyer citrange 3.08 3.10 3.09 2.26 2.09 2.17 20.5 18.8 19.6 5 Trifoliate orange 3.20 3.24 3.22 2.60 2.24 2.42 23.5 20.5 22.0 CD (P = 0.05) 0.18 0.40 NS NS 2.08 1.49

After 45 days of fertilizer application 1 Sathgudi 2.77 2.62 2.69 2.51 3.18 2.85 25.7 19.9 22.7 2 Rangpur lime 3.64 2.69 3.16 2.95 2.36 2.65 19.5 18.7 19.1 3 Cleopatra mandarin 2.85 2.86 2.86 2.75 2.28 2.51 20.1 19.3 19.7 4 Troyer citrange 3.19 3.44 3.32 2.78 2.65 2.71 18.1 17.2 17.6 5 Trifoliate orange 3.91 4.38 4.15 2.32 3.10 2.72 21.1 18.9 20.0 CD (P = 0.05) 0.75 0.25 NS 0.41 2.23 1.59 Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 3 Soil fertility parameters (micronutrients) under Sathgudi sweet orange as inﬂuenced by different rootstocks Zn (ppm) Fe (ppm) Cu (ppm) Mn (ppm) B (ppm) 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted 0–15 15–30 Weighted No. Rootstock cm cm average cm cm average cm cm average cm cm average cm cm average Initial (before fertilizer application) 1 Sathgudi 6.85 6.40 6.62 9.45 8.80 9.12 2.26 1.45 1.85 20.4 17.5 18.9 1.03 1.02 1.02 2 Rangpur lime 6.45 5.65 6.04 8.55 8.30 8.42 1.71 1.11 1.40 20.5 18.6 19.5 1.09 1.09 1.09 3 Cleopatra 6.60 6.20 6.40 9.00 8.85 8.92 1.86 1.10 1.47 20.2 18.9 19.5 1.05 1.03 1.03 mandarin

992 4 Troyer citrange 4.53 4.25 4.39 9.95 9.65 9.80 2.04 1.16 1.59 20.0 17.7 18.8 1.00 0.99 0.99 5 Trifoliate 6.10 5.20 5.64 7.70 7.55 7.62 1.81 1.15 1.47 19.0 17.2 18.1 1.04 1.03 1.03 orange CD (P = 0.05) 0.52 0.52 1.12 1.03 0.33 0.14 0.85 1.15 NS NS After 45 days of fertilizer application 1 Sathgudi 4.85 2.08 3.44 11.0 9.65 10.3 2.29 1.30 1.79 17.5 14.1 15.8 1.01 0.99 0.99 2 Rangpur lime 4.33 3.95 4.14 8.70 8.45 8.57 2.04 1.16 1.59 18.3 17.3 17.8 1.10 1.06 1.06 3 Cleopatra 4.55 2.45 3.48 8.90 8.20 8.54 1.71 1.33 1.52 17.7 17.2 17.4 1.04 1.02 1.02 mandarin 4 Troyer citrange 3.40 2.13 2.75 10.3 9.50 9.89 1.84 1.29 1.56 17.5 13.2 15.3 0.99 0.97 0.97 5 Trifoliate 3.75 2.23 2.98 7.90 6.85 7.36 1.79 1.21 1.49 17.1 16.5 16.8 1.03 1.02 1.02 orange CD (P = 0.05) 0.96 0.73 0.77 0.83 0.26 NS NS 0.97 NS NS Nutrient Absorption Patterns of Rootstocks 993

fertilizer application over the initial period was computed, there was an increase of 15.1% in the soil N content in Troyer citrange basins while in Trifoliate orange and Sathgudi basins, the increases were only 11.7% and 8.98%, respectively. This differential increase in N content in soil under different rootstocks exhibits the inherent differential N sink capacity of the rootstocks. However, Rangpur lime rootstock basins had the lowest N contents at both the sampling intervals. It is worthwhile to mention here that when averaged across the rootstocks as well as the depths, the available N content in these soils slightly increased after application of fertilizer. The increase in the N content after fertilizer application may be due to contribution by combined application of fertilizers and manures. However, the variation in the N status in soil could be attributed probably to the differential N uptake behavior of the rootstocks. The rootstock influence resulted in quite significant differences in the available P content in the soils at both the depths after 45 days. The available P content was observed to be high but tended to decrease with depth at both the periods. When averaged over both the depths, before fertilizer application, the greatest available P content of 37.3 kg ha−1 was recorded under Sathgudi rootstock basin, followed by Trifoliate orange rootstock basin (33.8 kg ha−1) and Cleopatra mandarin basin (33.3 kg ha−1), while the least was recorded in the Troyer citrange rootstock basins (28.3 kg ha−1). Even 45 days after fertilizer application, this differential trend remained the same but only with a slight decrease in the available P content in the soils. In comparison, the greatest percentage decreases of available P (12.1% and 11.5%) were recorded under Rangpur lime and Cleopatra mandarin basins, respectively, whereas under Trifoliate orange and Troyer citrange basins, the decreases were only 9.61% and 5.47%. Of all the rootstocks, the least percentage decrease of P content (3.19%) was observed in Sathgudi basin. This variation in the magnitude of decrease of available P in soil under different rootstocks from their respective initial values indicated the differential P absorption behavior of the rootstocks. The available K content in the soils of rootstock basins was quite significant at both depths and at both the periods and was found to be high. Before fertilizer application, the available K content tended to increase with depth in all the rootstock basins, but 45 days later, the soils did not exhibit any immediate response to the applied K and showed an irregular trend in the available K status. When averaged over both the depths, significantly greatest available K was observed under Trifoliate orange basins followed by Troyer citrange basins and the least was under Rangpur lime basins at both the periods. It was also noted that 45 days afterward, there was a decrease in the available K content in all the

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 rootstock basins except under Trifoliate orange rootstocks, which showed a slight increase of only 1.16%. The maximum percentage decrease in available K at 45 days over the initial level was observed under Sathgudi (11.2%) and Rangpur lime (10.2%) basins followed by Troyer citrange (8.42%), whereas the least decrease was under Cleopatra mandarin (0.58%), which confirmed the differential K feeding pattern of the rootstocks. Exchangeable Ca in the soils of the rootstock basins showed an irregular trend of increase and decrease after fertilizer application at both the depths. The greatest content of exchangeable Ca was recorded under Trifoliate orange basin and was at par with other rootstock basins. Rootstocks did not exhibit any significant effect on exchangeable Mg content before and after 45 days. However, after 45 days, an increase in exchangeable Ca and Mg was observed over its initial values in all the rootstock basins except under Cleopatra mandarin in the case of Ca, which showed a decrease to the extent of 8.01%. Soils showed significant differences in the available S content with a maximum content recorded in Sathgudi basins and the lowest under Troyer citrange basins when averaged over both the depths. Decrease in available S content was observed in all the rootstock 994 J. K. Grace et al.

basins after 45 days. Rangpur lime basins recorded a maximum decrease of 14.5% followed by Cleopatra mandarin (12.7%), whereas the least was under Sathgudi, which was 8.55% over the initial status. This decrease may be attributed to the differential utilization of S by the growing trees. Initially, the micronutrient contents in the rootstock basins were observed to be very high, and there was a significant variation in the micronutrient contents (viz., Zn, Fe, Cu, and Mn) under different rootstocks. A similar trend was also observed even after 45 days, except in the cases of Cu and Mn. The influence of rootstocks on available B content in the soils was not significant at both periods of sampling. When averaged over the depths, soil-available Zn content was significantly greater under Sathgudi and Rangpur lime rootstock basins before and after 45 days, respectively, and least under Troyer citrange basins. Available Fe, Cu, and Mn contents were significantly greatest under Troyer citrange, Sathgudi, and Rangpur lime respectively both before fertilizer application and also after 45 days. On the other hand, after 45 days, it was observed that under all the rootstock basins, Zn and Mn contents in soils decreased by 41% and 12% respectively. In the cases of Fe and Cu contents, the rootstock basins showed an irregular trend of increase and decrease after 45 days over the initial level. Cleopatra mandarin and Trifoliate orange rootstocks recorded a decrease in available Fe content, whereas Sathgudi basins showed an increase in Fe content (13.1%) after 45 days. The Cu content in the root stock basins after 45 days was observed to be contrary to Fe content except under Rangpur lime basins, where the Cu content showed an increase to the extent of 13.4%.

Effect of Rootstocks on Nutrient Content of Leaves To study the behavior of different rootstocks on nutrient utilization, the nutrient concentrations in leaves were studied initially and both 45 and 135 days after fertilizer application (Table 4), and the concentrations were compared with the earlier critical standard ranges given by Chapman (1960) for citrus species. Results of the study revealed no signiﬁcant differences in leaf N content of Sweet orange budded on different rootstocks at all the periods of sampling, and the leaf N concentration was more or less in the optimum range as prescribed by Chapman (1960) earlier. However, it was observed that the leaf N concentration increased 45 days after fertilizer application in all the rootstocks. However, 135 days after fertilizer application, the rootstocks performed differently in further increasing or decreasing the leaf N content.

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 After 45 days, Rangpur lime showed a maximum increase in foliar N content up to 33.2% over the initial value followed by Sathgudi (25.1%) and Cleopatra mandarin (22.3%), whereas Trifoliate orange and Troyer citrange showed a slight increase in foliar N content to the extent of 12.0% and 5.69% respectively. When sampled 135 days after fertilizer application, Sathgudi, Rangpur lime, and Trifoliate orange showed a decrease in foliar N content up to the extent of 14.3%, 14.7%, and 11.9% respectively, whereas Cleopatra mandarin and Troyer citrange rootstocks showed further increases of 3.42% and 5.00% respectively in their foliar N content over that recorded at 45 days. Even though some of the rootstocks showed a reduction in their foliar N content at 135 days over that of 45 days, it was interesting to observe that the N concentrations remained greater compared to the concentration recorded initially, except in Trifoliate orange rootstock basins. The increase might be due to the application of N to soil, which increased the N content of orange leaves and was in agreement with the findings of Desai, Choudhari, and Chaudhari (1986). The nonsignificant differences in the leaf N status of sweet orange on different rootstocks were in consonance with the findings of Reddy and Swamy (1986), but the gradual decrease in N Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 4 Nutrient status of foliage of Sathgudi sweet orange at different intervals as inﬂuenced by different rootstocks

N (%) P (%) K (%) Ca (%) Mg (%) S (%)

No. Rootstock BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 1 Sathgudi 2.35 2.94 2.52 0.19 0.38 0.25 1.08 1.68 1.57 1.29 1.58 1.35 0.51 0.61 0.66 0.33 0.42 0.40 2 Rangpur lime 2.29 3.05 2.60 0.20 0.35 0.28 1.00 1.49 1.45 1.23 1.50 1.17 0.55 0.60 0.70 0.37 0.37 0.41 3 Cleopatra 2.15 2.63 2.72 0.19 0.36 0.24 0.85 1.18 1.23 1.52 1.18 1.40 0.73 0.60 0.58 0.35 0.38 0.43 mandarin 4 Troyer 2.46 2.60 2.73 0.30 0.31 0.26 0.93 1.31 1.17 1.44 1.31 1.59 0.61 0.71 0.76 0.32 0.35 0.37 citrange 5 Trifoliate 2.33 2.61 2.30 0.23 0.37 0.25 0.84 1.25 1.17 1.44 1.25 1.74 0.61 0.62 0.67 0.34 0.35 0.42 orange 995 CD (P = 0.05) NS NS NS 0.62 NS NS 0.11 0.14 0.19 NS 0.15 0.31 NS 0.07 0.08 NS NS NS Zn (ppm) Fe (ppm) Cu (ppm) Mn (ppm) B (ppm) BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 BF AF1 AF2 BF AF1 AF2

1 Sathgudi 27.1 22.0 25.0 144.0 103.5 104.5 14.5 15.8 13.6 36.6 36.8 32.3 105.0 87.5 95.0 2 Rangpur lime 24.0 17.1 21.1 134.8 88.8 92.8 20.0 20.2 17.9 36.6 36.9 32.0 133.2 112.5 119.2 3 Cleopatra 18.5 15.0 20.0 151.0 112.2 107.5 17.1 18.3 15.8 44.7 44.9 38.3 96.2 118.7 92.5 mandarin 4 Troyer 22.2 17.2 18.8 154.0 91.8 117.0 19.3 20.1 18.0 23.5 24.3 22.1 155.0 126.2 141.2 citrange 5 Trifoliate 28.7 20.2 24.5 152.2 135.5 137.8 16.0 17.0 15.8 45.6 45.6 39.6 178.7 138.7 143.8 orange CD (P = 0.05) 5.19 3.88 NS NS 14.7 23.9 3.14 2.52 2.46 4.87 4.99 4.69 17.5 23.1 20.5 Notes. BF, before fertilizer application; AF1, after 45 days of fertilizer application; and AF2, after 135 days of fertilizer application. 996 J. K. Grace et al.

content at 135 days after fertilizer application might be because growing organs essentially require N for protein synthesis as reported by Zhuang et al. (1985). When analyzed for foliar P concentration, rootstocks exhibited significant differences during the initial period, whereas at 45 days and 135 days, the differences were insignificant. When sampled immediately after the 13th year of experimentation (for initial reference), Troyer citrange showed significantly greatest concentration of foliar P (0.30%) whereas the least was under Sathgudi and Cleopatra mandarin (0.19%). The foliar P content that was earlier in the “high” range reached the “excess” range at 45 days and thereafter again decreased to the “high” range at 135 days. The increase in foliar P at 45 days over the initial period was quite high on Sathgudi rootstock (100%) followed by Cleopatra mandarin (89.5%), Rangpur lime (75.0%), and Trifoliate orange (60.9%) rootstocks, whereas Troyer citrange showed the least increase of 3.33%. At 135 days, all the rootstocks showed a decrease in the foliar P concentration from 16.1% to 34.2%. Even though a decrease in foliar P concentration from “excess” to “high” was observed at 135 days compared to the concentration at 45 days, the foliar P concentration at 135 days was greater when compared to the initial period except in Troyer citrange rootstock. The absence of significant differences between the mean P content of leaves from the different rootstocks was in agreement with many studies (Iyengar, Iyer, and Sulladamath 1982), Mehrotra, Jawanda, and Vij 1982, 1983). The increase in mean leaf P concentration from the early stage to 45 days after fertilizer application might be due to the greater rate of absorption of P at the early stages of fertilizer application. The fall in concentration of P in leaves of sweet orange as the crop heads towards maturity could be attributed to the dilution and utilization of P for the development of fruits as reported by Ortuno et al. (1970) and Intrigliolo (1985). Potassium is considered to be one of the important nutrient cations that influence car- bohydrate translocation and regulate plant–water relations. In this study, highly significant differences among different rootstocks in their foliar K content at all the periods of crop growth were observed. These differences indicated that various rootstocks influenced the translocation of K differently (Misra and Ranvir Singh 1993). The foliar K concentration in these rootstocks ranged from “low” to “optimal” range at different periods of crop growth. Sathgudi rootstock maintained the significantly greatest foliar K concentrations followed by Rangpur lime, whereas the least was observed in Trifoliate orange rootstocks at all the periods of crop growth. At 45 days, the concentration of foliar K in all the rootstocks increased to an “optimum” level with an increase being 38.8% to 55.6% over the initial period. At 135 days, a slight decrease of 2.68% to 1.7% in the foliar K content was

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 observed on all the rootstocks except in Cleopatra mandarin, where a slight increase of 4.24% was noticed. Though the foliar K concentrations decreased at 135 days compared to 45 days, these levels were greater by 25.8% to 45.3% over the initial period in different rootstocks. The increase in K content after 45 days might be due to the fertilizer application, where the applied K increased the leaf K (Murthy, Anjaneyulu, and Bopaiah 1983; Desai, Choudhari, and Chaudhari 1986). During the initial stages, the significant influence of rootstocks on foliar Ca content was not observed, but at 45 days and 135 days after fertilizer application, the influence was quite significant. According to Chapman (1960) standards, the percentage foliar Ca concentrations in this study, varying from 1.23 to 1.52% in different rootstocks, were in the “deficient” range at all the periods of crop growth. At 45 days after fertilizer application, Sathgudi and Rangpur lime recorded the greatest foliar Ca concentrations of 1.58% and 1.50% respectively, an increase of foliar Ca concentration to the extent of 22.5% and 21.9% respectively over the initial period. On the other hand, Cleopatra mandarin, Troyer citrange, and Trifoliate orange, which had lower foliar Ca concentrations compared to the previous Nutrient Absorption Patterns of Rootstocks 997

two, showed a decrease to the extent of 22.4%, −9.03%, and 13.2% respectively over the initial period. At 135 days, the reverse trend was observed where Trifoliate orange had the significantly greatest foliar Ca (1.74%) whereas Rangpur lime had the least (1.17%) and was on par with others. At 135 days, a decrease in foliar Ca concentrations was observed in both Sathgudi (4.5%) and Rangpur lime (22.0%) rootstocks while an increase in Cleopatra mandarin (18.6%), Troyer citrange (21.4%), and Trifoliate orange (39.2%) was observed after 45 days. When the foliar Ca concentrations at 135 days were compared with those of the initial period, Sathgudi, Troyer citrange, and Trifoliate orange rootstocks showed increases of 4.65%, 10.4%, and 20.8% respectively, whereas Rangpur lime and Cleopatra mandarin showed decreases of 4.88% and 7.89% respectively. The increase and decrease of foliar Ca concentrations in the rootstocks at different periods could be attributed to the immobile nature of the element in the plant body. It has been established that flowers and fruits meet their Ca requirements only from roots through xylem. Ortuno et al. (1985) also reported similar results. Before fertilizer application, Cleopatra mandarin had a high Ca content, which might be due to less P and K where K exhibited antagonism toward Ca uptake (Desai, Choudhari, and Chaudhari 1986). Similar to Ca, a significant influence of rootstocks on foliar Mg concentration was not observed during the initial periods, but only at 45 and 135 days after fertilizer application, and Mg was in “optimum” to “high” range during all the periods. Troyer citrange rootstocks maintained significantly greatest foliar Mg concentrations at both 45 and 135 days and the lowest in Cleopatra mandarin rootstock. Sathgudi and Trifoliate rootstocks behaved similarly in their Mg uptake, showing “optimum” levels at all periods of sampling. Rangpur lime rootstock had “optimum” levels of Mg in their leaves before and after 45 days of fertilizer application but reached “high” level after 135 days. In Cleopatra mandarin rootstock, the high concentration of Mg prevailing in its leaves before fertilizer application reached “optimum” levels after fertilizer application. In the case of Troyer citrange rootstock, it showed “optimum” levels of N before fertilizer application, which later reached “high” levels after fertilizer application. In general, all the rootstocks exhibited significantly positive increase in the Mg content of sweet orange leaves as the levels of N increased 45 days after fertilizer application. This could be attributed to the fact that greater N content lead to the formation of chlorophyll, leading to greater utilization of Mg. Similar findings were made by Mehrotra, Jawanda, and Vij (1982, 1983). When all other rootstocks showed an increase in Mg concentration at different periods, Cleopatra mandarin behaved differentially: It showed a decrease in Mg concentration (17.8%) at 45 days over the ini-

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 tial, 3.33% at 135 days over 45 days, and a decrease of 20.5% at 135 days over the initial Mg concentration. The results indicated no significant difference in leaf S concentration in different rootstocks at different periods. However, S concentrations were “optimum” to “high” and the rootstocks performed equally well in maintaining the foliar S contents. This insignificant difference in rootstock performance in relation to S concentrations was also observed earlier by Iyengar, Iyer, and Sulladamath (1984). The influence of rootstocks on foliar Zn concentrations was quite significant at initial period as well at 45 days after fertilizer application but not after 135 days. However, the Zn concentrations progressively improved from “low” to “slightly optimum” level. At the initial period, the leaf Zn concentration varied from 18.5 to 28.7 ppm and Trifoliate orange had significantly greatest leaf Zn content (28.7 ppm), at par with Sathgudi (27.1 ppm) followed by Rangpur lime (24.0 ppm). Cleopatra mandarin had the least Zn content (18.5 ppm), which was at par with Troyer citrange. After 45 days, significantly greater leaf Zn content was observed in Sathgudi (22.0) and was at par with Trifoliate orange (20.3 ppm) whereas Cleopatra had the least (15.0 ppm), which was at par with Rangpur 998 J. K. Grace et al.

lime and Troyer citrange. Sathgudi sweet orange grafted on Rangpur lime, Cleopatra mandarin, and Troyer citrange rootstock showed similar trends in their nutrient concentrations having low levels of Zn before and after fertilizer application, whereas Sathgudi rootstock recorded low levels of Zn in leaves when sampled at 45 days after fertilizer application. However, Zn concentration in the leaves fell to a “deficient” range and thereafter remained so even at 135 days. At the initial period, sweet orange leaves on Trifoliate orange rootstock were deficient in Zn but slightly rose to the “low” range after fertilizer application. At 45 days, a decrease in foliar Zn concentration was observed to the extent of 18.9% to 29.6% under different rootstocks over the initial period. At 135 days, there was an increase in foliar Zn concentrations over 45 days, where Cleopatra mandarin showed the greatest increase of 33.3% followed by Rangpur lime (23.4%), whereas the least increase was in Troyer citrange (9.3%). The foliar Zn concentrations observed at 90 days showed a decrease to the extent of 7.75% to 15.3% when compared to the initial period in all the rootstocks, except in Cleopatra mandarin, where the Zn concentrations were greater by 8.11% over the initial period. During the initial sampling, rootstocks did not differ significantly in their foliar Fe concentrations but the differences were quite conspicuous at 45 and 135 days, and the leaves maintained “optimum” to “slightly high” concentrations. Trifoliate orange rootstocks recorded significantly greatest foliar Fe concentrations at both 45 and 135 days, whereas Rangpur lime recorded the least. Sathgudi and Rangpur lime rootstocks showed a similar trend in their Fe uptake having optimum levels before and after fertilizer application, whereas Cleopatra mandarin, Troyer citrange, and Trifoliate orange rootstocks had “high” concentrations of Fe initially before fertilizer application that fell to “optimum” after fertilizer application. On computing the percentage increases or decreases, it was observed that the foliar Fe concentrations at 45 days decreased to the extent of 11.0% to 40.4% under different rootstocks over the initial period. At 135 days, the greatest increase of foliar Fe concentration was observed in Troyer citrange rootstocks (27.4%), while the increase was very meager in Sathgudi, Rangpur lime, and Trifoliate orange. Cleopatra mandarin showed a small decrease of 4.19% in its foliar Fe content at 135 days over 45 days. However, when compared to initial concentration, at 135 days, these values were lower by 9.46% to 31.2% across all the rootstocks. Unlike Zn and Fe, foliar Cu and Mn concentrations were significantly influenced by the rootstocks at all the periods. In general, the foliar Cu concentrations were “high,” and Mn concentrations were in the “optimum” range in all the rootstocks. Georgiou (2000) also

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 reported normal levels of Mn and Cu and lower levels of Zn in Nova mandarin grown on 11 rootstocks. In the present study, Rangpur lime rootstocks maintained the greatest foliar Cu concentrations initially and at 45 days, whereas the lowest was observed in Sathgudi rootstocks. At 135 days, Troyer citrange had the greatest foliar Cu concentration, whereas the least was observed in Sathgudi rootstock. In the case of Mn, Trifoliate orange rootstock recorded significantly great foliar Mn concentrations at all the sampling stages, whereas the least was in Troyer citrange rootstocks. On the whole, it was observed that foliar Cu and Mn concentrations showed a slight increase, which was 1.00% to 9.00% and up to 3.4% respectively at 45 days from the initial value. At 135 days, both foliar Cu and Mn concentrations decreased by 7.06% to 13.9% and 9.05% to 14.7% respectively over concentrations at 45 days. Results indicated highly significant differences in the leaf B content among different rootstocks at all the sampling intervals. At both 45 and 135 days, Trifoliate orange rootstocks had the significantly greatest foliar B concentration followed by Troyer citrange. Rangpur line, Troyer citrange, and Cleopatra rootstocks showed greater concentrations Nutrient Absorption Patterns of Rootstocks 999

of B in its leaves before and after fertilizer application, whereas on Cleopatra mandarin rootstock, the B concentration was optimum at all the three periods of sampling. Sathgudi sweet orange on its own rootstock behaved differently and had high concentration of B in its leaves before fertilizer application, but this concentration fell to “optimum” level after fertilizer application. All the rootstocks showed a decrease of 15.5% to 22.4% in their B concentrations at 45 days over the initial value, whereas at 90 days they showed an increase of 3.68% to 11.9% over values at 45 days, with the Cleopatra mandarin as exception, which showed an increase in B concentration at 45 days and thereafter tended to decline. When the foliar B concentrations at 135 days were compared with the initial values, all the rootstocks behaved similarly, showing a decrease in the range of 3.85% to 19.5%.

Relationships between the Soil Nutrients Before fertilizer application, the relationships between the soil nutrients were worked out and the data on these correlation coefficients are presented in Tables 5 and 6. The correlation coefficients were worked out between the soil nutrients before fertilizer application (i.e., before the start of the season). It was observed that available haven had significant positive correlation with available P (0.455∗) in soil. Even with available K, available N showed significant positive correlation but the correlation was found to be high (0.718∗∗). Among the micronutrients, available N had significant positive correlation with Cu (0.499∗) and negative correlation with B (–0.561∗). Similarly, available P showed significant positive correlations with available S (0.680∗), available Zn (0.644∗∗), and Cu (0.590). The available K content in soil recorded a significant positive correlation with exchangeable Ca (0.524∗) but a negative correlation with Mn (–0.666∗). Available S was highly and significantly correlated with Zn (0.833∗). The correlations were worked out between the soil nutrients after 45 days. During this period, the available N was found to have positive correlations with available K (0.721∗) and Ca (0.476∗), whereas a significant negative relationship was observed with available Zn (–0.679∗∗) and Mn (–0.498∗). On the other hand, available P recorded significant positive correlations with S (0.749∗∗) and Cu (0.462∗). Among these, the correlation between P and S was found to be high. Available K recorded a significant positive correlation with exchangeable Ca (0.745∗∗) while a negative correlation was observed with Zn (–0.651∗∗). Exchangeable Ca recorded significant negative correlation with only the micronutrients ∗∗ ∗ Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 [viz., Fe (–0.676 ) and Cu (–0.482 )]. Among the micronutrients, available Zn and Mn had significant positive correlation (0.552∗), whereas Fe showed a significant positive correlation with Cu (0.619∗∗) and negative correlation with Mn (–0.526∗).

Relationships between the Leaf Nutrients To see the influence of concentration of one nutrient on the other in the foliage, inter- correlations were worked out between the nutrients at all the three stages (viz., initially, after 45 days, and after 135 days), and the data are presented in Tables 7 to 9. From the correlation studies, it was observed that available N did not record any significant relationship with other nutrients, whereas significant correlations were observed for P and K with other nutrients. Significant negative correlation was observed between P and Mn (–0.586∗∗) and positive correlation between P and B (0.548∗), whereas available K recorded significant negative correlation with only Mg (–0.455∗), which was earlier established by Georgiou (2002). Among the secondary nutrients, Ca and Mg showed significant Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 5 Pearson’s correlations between soil nutrients before fertilizer application

ParameterpH EC N P K Ca Mg S Zn Fe Cu Mn B pH 1.00 −0.121 −0.424 −0.217 −0.250 −0.199 0.089 −0.004 −0.094 0.076 −0.112 0.187 0.008 EC 1.00 0.531∗ 0.615∗∗ 0.443 0.396 0.149 0.416 0.314 −0.137 0.368 −0.144 −0.176 N 1.00 0.455∗ 0.718∗∗ 0.332 0.141 −0.004 −0.115 0.007 0.499∗ −0.307 −0.561∗ P 1.00 0.304 −0.019 0.433 0.680∗∗ 0.644∗∗ −0.188 0.590∗∗ −0.060 −0.251 ∗ − − − − ∗∗ −

1000 K 1.00 0.524 0.172 0.164 0.376 0.240 0.301 0.666 0.236 Ca 1.00 0.141 −0.418 −0.399 −0.046 −0.212 −0.153 −0.256 Mg 1.00 0.385 0.284 −0.004 0.185 0.005 −0.076 S 1.00 0.833∗∗ −0.615 0.379 0.062 0.172 Zn 1.00 −0.267 0.186 0.281 0.130 Fe 1.00 0.345 0.321 −0.211 Cu 1.00 −0.028 −0.292 Mn 1.00 −0.098 B 1.00 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 6 Pearson’s correlation coefﬁcients between soil nutrients after 45 days of fertilizer application

ParameterpH EC N P K Ca Mg S Zn Fe Cu Mn B pH 1.00 −0.149 −0.535∗ −0.176 −0.397 −0.049 −0.058 0.264 0.655∗∗ −0.224 −0.304 0.452∗ 0.336 EC 1.00 0.386 −0.074 0.699∗∗ 0.738∗∗ −0.103 −0.195 −0.270 −0.484∗ −0.256 0.093 −0.251 N 1.00 0.318 0.721∗∗ 0.476∗ 0.419 −0.044 −0.679∗∗ 0.070 0.139 −0.498∗ −0.432 P 1.00 0.251 −0.246 0.296 0.749∗∗ −0.075 0.278 0.462∗ −0.324 −0.167 ∗∗ − − ∗∗ − − − −

1001 K 1.00 0.745 0.080 0.047 0.651 0.421 0.279 0.237 0.265 Ca 1.00 0.074 −0.338 −0.347 −0.679∗∗ −0.482∗ 0.092 −0.078 Mg 1.00 0.081 0.017 0.153 0.223 −0.061 −0.098 S 1.00 0.230 0.128 0.365 −0.025 0.122 Zn 1.00 −0.107 −0.015 0.552∗ 0.305 Fe 1.00 0.619∗∗ −0.526∗ −0.327 Cu 1.00 −0.296 −0.267 Mn 1.00 0.244 B 1.00 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 7 Pearson’s correlation coefﬁcients among leaf nutrients before fertilizer application

Parameter N P K Ca Mg S Zn Fe Cu Mn B N 1.00 0.294 0.032 0.126 −0.134 −0.162 −0.202 0.165 −0.057 −0.292 0.343 P 1.00 0.094 0.037 −0.245 −0.413 0.083 0.236 0.148 −0.586∗∗ 0.548∗ K1.00−0.407 −0.455∗ −0.153 0.128 −0.006 −0.039 −0.297 −0.268 ∗∗ − − −

1002 Ca 1.00 0.617 0.082 0.308 0.294 0.099 0.060 0.164 Mg 1.00 0.438 −0.526∗ 0.317 −0.007 0.161 −0.086 S 1.00 0.025 −0.067 0.048 0.078 −0.094 Zn 1.00 −0.101 −0.285 0.110 0.357 Fe 1.00 0.034 0.103 0.108 Cu 1.00 −0.279 0.163 Mn 1.00 −0.165 B 1.00 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 8 Pearson’s correlation coefﬁcients among leaf nutrients after 45 days of fertilizer application

Parameter N P K Ca Mg S Zn Fe Cu Mn B N1.00−0.020 0.503∗ 0.484∗ −0.334 0.236 0.021 −0.248 0.015 0.045 −0.412 P 1.00 0.117 0.197 −0.344 0.224 0.370 0.321 −0.220 0.262 −0.252 K 1.00 0.682∗∗ −0.092 0.390 0.564∗∗ −0.334 −0.226 −0.240 −0.681∗∗ − − ∗ − − − ∗

1003 Ca 1.00 0.226 0.299 0.292 0.478 0.147 0.297 0.541 Mg 1.00 −0.140 −0.069 −0.200 0.142 −0.644∗∗ 0.167 S 1.00 0.186 0.023 −0.359 0.195 −0.364 Zn 1.00 0.249 −0.567∗∗ −0.001 −0.208 Fe 1.00 −0.366 0.722∗∗ 0.245 Cu 1.00 −0.335 0.104 Mn 1.00 0.077 B 1.00 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 9 Pearson’s correlation coefﬁcients among plant nutrients after 135 days of fertilizer application

Parameter N P K Ca Mg S Zn Fe Cu Mn B N 1.00 0.037 −0.030 0.091 0.141 0.064 0.088 −0.095 0.160 −0.205 −0.207 P1.00−0.167 −0.345 −0.020 0.292 −0.008 −0.041 0.280 −0.140 0.075 K1.00−0.546∗ 0.022 −0.205 0.246 −0.463∗ −0.254 −0.019 −0.485∗ − ∗∗ − ∗

1004 Ca 1.00 0.123 0.241 0.048 0.607 0.007 0.126 0.537 Mg 1.00 −0.357 0.022 −0.151 0.358 −0.599∗∗ 0.480∗ S 1.00 0.423 0.271 −0.102 0.458∗ −0.268 Zn 1.00 0.032 −0.359 0.299 −0.139 Fe 1.00 −0.063 0.247 0.335 Cu 1.00 −0.170 0.351 Mn 1.00 −0.265 B 1.00 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Nutrient Absorption Patterns of Rootstocks 1005

positive correlation with each other (0.617∗∗), whereas Mg showed a significant negative correlation with Zn (–0.526∗). After a period of 45 days from fertilizer application, the correlation coefficients worked out between the plant nutrients revealed that N showed a significant positive correlation with available K (0.503∗) as well as Ca (0.484∗), whereas P did not show any significant relationship with any other nutrient. Available K revealed a significant positive correlation with Ca (0.682∗∗) and Zn (0.564∗∗) and a negative relationship with B (–0.681∗∗). Among the secondary nutrients, significant negative correlations were observed between Ca and Fe (–0.478∗) and between Ca and B (–0.541∗). Even, Mg also showed a significant negative correlation with Mn (–0.644∗∗). Among the micronutrients, Zn had a negative correlation with Cu (–0.567∗∗), whereas Fe had a significant positive correlation with Mn (0.722∗∗). Correlation matrices between the plant nutrients worked out after a period of 135 days revealed that among the major nutrients except K, N and P did not reveal any significant relationship with any of the plant nutrients. Even the relationships as shown by plant K were found to be significantly negative with Ca (–0.546∗), Fe (–0.463∗), and B (–0.485∗). Among the secondary nutrients, Ca showed a significant positive relationship with Fe (0.607∗∗) and B (0.537∗). Plant Mg showed a significant negative correlation with Mn (–0.599∗∗) and positive relation with B (0.480∗), whereas S showed a significant positive correlation with Mn (0.458∗).

Relationship between the Soil and Foliar Nutrients The relationship between the soil nutrients estimated after 45 days as well the plant nutrients estimated after 45 days are presented in Table 10. It was observed that soil pH did not show any significant relationship with any plant nutrients, but electrical conductivity had significant negative relationship with K (–0.451∗) and S (–0.503∗) and positive correlation with Fe (0.575∗∗). Available soil P showed a significant positive relationship with plant K (0.465∗) and plant Zn (0.630∗∗), whereas it showed a negative relationship with Cu (−0.728∗∗). Available soil K showed a significant positive relationship with Fe (0.721∗∗) and B (0.481∗). Soil exchangeable Ca revealed a significant negative correlation with plant K (–0.454∗) as well as S (0.514∗), whereas the relation was positive in case of Fe (0.521∗) and B (0.621∗∗). Exchangeable Mg significantly influenced the uptake of Zn (0.450∗) during this period, but available S showed significantly positive relationship with many plant ∗ ∗ ∗ ∗ ∗ Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 nutrients [viz., P (0.447 ), K (0.469 ), Ca (0.487 ), S (0.561 ), and Zn (0.499 )] and an antagonistic relationship with Cu (–0.825∗∗). The soil micronutrient contents also showed a quite significant relation in influencing the plant nutrient composition. Soil Zn showed an antagonistic relation in uptake of Mg (–0.561∗) by plant. The Fe content in soil revealed a synergistic influence in the concentration of K (0.595∗∗) in plants. Also, the soil Fe content resulted in a significant negative contribution toward the plant Fe content (–0.529∗) and B content (–0.682∗∗) and as positive relation with Mn (0.636∗∗). The soil Cu content had significant positive correlations with N (0.510∗), K (0.631∗∗), and Ca (0.591∗∗) and a negative influence on plant B (–0.649∗∗). Available Mn in soil showed a significant negative influence on plant Mg (–0.631∗∗). Similar to Fe, the greater content of soil Mn resulted in significantly greater concentration of plant Mn (0.587∗∗). To study how the soil nutrients influenced the plant nutrient concentrations after a period of another 90 days, irrespective of the rootstocks and on Sathgudi sweet orange, correlations were worked out between the soil nutrients analyzed after 45 days and the plant nutrient contents after 135 days (Table 11). Electrical conductivity of the soil showed Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 10 Pearson’s correlation coefﬁcients between soil and plant nutrients after 45 days

Plant parameter No. soil N P K Ca Mg S Zn Fe Cu Mn B 1 pH 0.255 0.168 0.299 0.274 −0.150 0.359 0.006 −0.071 −0.017 0.228 −0.119 2EC−0.254 0.306 −0.451∗ −0.308 −0.007 −0.503∗ 0.092 0.575∗∗ 0.069 0.288 0.308 3N−0.297 −0.156 −0.077 −0.049 0.324 −0.158 0.327 0.291 −0.185 −0.205 0.287 − ∗ − ∗∗ − ∗∗ −

1006 4P 0.013 0.330 0.465 0.226 0.183 0.350 0.630 0.336 0.728 0.250 0.437 5K−0.438 0.108 −0.408 −0.433 0.165 −0.351 0.322 0.721∗∗ −0.265 0.226 0.481∗ 6Ca−0.308 −0.027 −0.454∗ −0.288 0.081 −0.514∗ 0.048 0.512∗ 0.080 0.206 0.621∗∗ 7 Mg 0.129 −0.246 0.441 0.175 0.076 −0.084 0.450∗ −0.141 −0.214 −0.169 0.005 8 S 0.251 0.447∗ 0.469∗ 0.487∗ −0.326 0.561∗ 0.499∗ 0.217 −0.825∗∗ 0.326 −0.400 9 Zn 0.263 0.323 0.357 0.386 −0.561∗∗ 0.228 0.034 −0.314 0.044 0.231 −0.263 10 Fe 0.222 −0.090 0.595∗∗ 0.410 0.282 0.314 0.208 −0.529∗ −0.003 0.636∗∗ −0.682∗∗ 11 Cu 0.510∗ 0.151 0.631∗∗ 0.591∗∗ −0.067 0.255 0.261 −0.286 −0.119 −0.248 −0.649∗∗ 12 Mn 0.360 0.136 −0.181 −0.103 −0.631∗∗ 0.116 −0.236 0.072 0.101 0.587∗∗ 0.206 13 B 0.014 −0.185 −0.040 −0.015 0.036 0.106 −0.074 −0.143 −0.136 0.138 0.281 ∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 11 Pearson’s correlation coefﬁcients between soil nutrients after 45 days and plant nutrients after 135 days

Soil

No. Plant N P K Ca Mg S Zn Fe Cu Mn B 1 pH 0.126 0.117 0.361 −0.196 −0.180 −0.056 0.015 −0.178 0.233 0.141 −0.045 2EC−0.061 0.076 −0.545∗ −0.538∗ 0.172 0.171 0.254 0.425 0.001 0.329 0.335 3N−0.184 −0.232 −0.227 0.637∗∗ 0.423 −0.285 0.335 0.378 −0.157 −0.137 0.451∗ 4P−0.122 −0.147 0.367 0.069 −0.302 0.158 0.572∗∗ 0.106 −0.744∗∗ 0.280 −0.411 1007 5K−0.300 −0.011 −0.559∗ 0.681∗∗ 0.034 0.127 0.269 0.745∗∗ −0.168 0.267 0.484∗ 6Ca−0.198 0.020 −0.536∗ 0.626∗∗ 0.228 0.077 0.137 0.661∗∗ 0.176 0.229 0.633∗∗ 7Mg−0.009 −0.169 0.185 0.170 0.070 −0.089 0.618∗∗ −0.056 −0.346 −0.190 0.128 8S−0.170 −0.143 0.514∗ −0.109 −0.439 −0.019 0.256 −0.054 −0.705∗∗ 0.268 −0.386 9 Zn 0.181 0.196 0.453∗ −0.499∗ −0.274 0.065 0.111 −0.611∗∗ 0.030 0.214 −0.377 10 Fe 0.219 0.018 0.442 −0.263 0.276 −0.296 −0.041 −0.342 0.103 −0.590∗∗ −0.323 11 Cu −0.015 −0.032 0.633∗∗ −0.433 0.260 −0.008 0.335 −0.404 −0.446 −0.181 −0.378 12 Mn −0.143 −0.054 −0.007 −0.153 −0.496∗ 0.191 −0.068 −0.170 0.089 0.540∗ −0.143 13 B −0.289 −0.195 −0.005 −0.143 −0.145 0.113 −0.199 −0.170 0.039 0.027 0.174

∗Signiﬁcant difference at P < 0.05. ∗∗Signiﬁcant difference at P < 0.01. 1008 J. K. Grace et al.

a significant negative influence on uptake of K (–0.545∗) and Ca (–0.538∗) by plant. It was observed that the N content in soil has resulted in a significant positive association with plant Ca, resulting in a greater concentration of Ca in plant leaves even after 45 days. Available P content in the soil showed a significant association only with two micronutrient elements in the leaves of sweet orange rootstocks, namely, a positive association with Zn (0.572∗∗) and a negative association with Cu (–0.744∗∗). On the other hand, it was observed that the greater concentrations of K in the soil resulted in a decrease in the leaf K at 135 days as evidenced by its negative interaction (–0.559∗). However, the soil K content had a significant positive association with leaf Ca (0.681∗∗), Fe (0.745∗∗), and B (0.484∗). It is not only the soil K content but the Ca content in soil also had a negative impact on leaf K (–0.536∗). At the same time, the soil Ca resulted in a positive relationship with the leaf Ca (0.626∗∗), Fe (0.661∗∗), and B (0.633∗∗). The presence of Mg in soil helped in the increased uptake of Zn by leaf tissues as revealed by its significant positive correlation (0.618∗). It was observed that soil S had a positive association with leaf K (0.514∗) and a negative association with leaf Cu (–0.705∗∗). Among the micronutrients, except B, the other micronutrients showed a significant relationship with some leaf nutrients. Soil Zn revealed a positive influence on leaf K (0.453∗) and a negative influence on leaf Ca (–0.499∗) and Fe (–0.611∗∗). Soil Fe was found to be antagonistic to leaf Mn with a negative correlation of −0.590∗∗. The Cu content of soil had a significant positive association with leaf K content (0.633∗). Soil Mn revealed a significant negative association with leaf Mg (–0.496∗) and a positive association with leaf Mn (0.540∗).

Relationship between Soil Nutrients and Leaf Nutrients of Sathgudi Sweet Orange on Different Rootstocks Correlation coefficients between soil nutrients and leaf nutrients of Sathgudi sweet orange on different rootstocks after fertilizer application were worked out (data not presented). Under Sathgudi rootstock, soil N and P had significant positive correlation with leaf Mg (0.787∗) and Ca (0.757∗) respectively, whereas the soil Mg had a negative association with leaf N (–0.787∗). Soil S had significant positive relationship with leaf P (0.764∗) and among the micronutrients soil Zn, Cu, and Mn had positive associations with leaf P (0.862∗∗, 0.719∗, and 0.774) and the rest of the associations were statistically nonsignificant. Under Rangpur lime rootstock, the macronutrients (i.e., N and P) in the soil had significant positive relationship with leaf N (0.914∗ and 0.799∗). Calcium and Mg of soil had negative ∗ ∗∗ Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 relationships with leaf Fe (–0.712 and −0.846 ) but soil Ca had positive relationship with leaf Mn (0.758∗). The micronutrients (i.e., Zn and Cu) in the soil had significant positive association with leaf N (0.839∗∗ and 0.829∗), whereas soil Cu also had a positive relationship with leaf P (0.866∗∗). The soil Mn showed positive correlation with leaf Mn (0.711∗). Soil B showed significant positive correlation with leaf P (0.706∗). Under Cleopatra mandarin rootstock, soil P had significant negative association with leaf K (–0.817∗), whereas soil K had significant positive association with leaf N (0.758∗). Calcium in soil had negative relationship with Mg in leaf (–0.722∗), whereas Mn in the soil had positive association with leaf N (0.709∗). Soil Fe showed significant positive correlation with leaf Cu (0.785∗). Under Troyer citrange, N in the soils had significant negative relationship with P (–0.753∗) while Zn in leaves had positive association (0.899∗). However, P in soil had negative correlation with leaf Fe (–0.801∗). Soil K showed significant negative relationship with leaf S (–0.791∗). Among the micronutrients, the soil Fe and Cu had significant positive relationships with Cu (0.795∗) and P (0.734∗) of leaves. Soil N and Fe showed significant positive correlations with leaf Mg (0.940∗∗) and Cu (0.805∗) respectively. Under Trifoliate Nutrient Absorption Patterns of Rootstocks 1009

orange rootstock, soil N had significant negative association with leaf Fe (–0.707∗) whereas soil K had significant positive relationship with leaf Zn (0.721∗). Soil K, Ca, and Mg had significantly negative relationships with leaf Cu and Mn. Sulfur in the soils had significant negative association with leaf Zn (–0.796∗) and positive correlation with leaf Mn (0.864∗∗). Soil Fe and Cu were significantly correlated with leaf N and P positively but negatively correlated with Ca leaves.

Nutrient Utilization Performance of Different Citrus Rootstocks at Different Stages To determine the nutrient utilization ability (NUA) of different rootstocks, the foliar nutrient data of 11 parameters (N, P, K, Ca, Mg, S, Zn, Fe, Cu, Mn, and B) obtained for all the three stages were subjected to principal component analysis (PCA) as well as linear scoring technique. Principal component analysis was employed as a data reduction tool to select the most appropriate key nutrient elements. Principal components (PCs) for a data set are defined as linear combinations of variables that account for maximum variance within the set by describing vectors of closest fit to the n observation in p-dimensional space, subject to being orthogonal to one another. The prime objective of PCA was to reduce the dimensionality (number of variables) of the dataset but retain most of the orig- inal variability in the data. The first PC accounts for as much of the variability in the data as possible, and each succeeding component accounts for as much of the remaining variability as possible. Those PCs that received higher eigenvalues and variables that had high factor loading were considered as the best representatives of system attributes. As per the criteria set by Brejda et al. (2000a, 2000b), only the PCs with eigenvalues ≥ 1 and those that explained at least 5% of the variation in the data (Wander and Bollero 1999) were considered. The PCA analysis of the nutrient data before fertilizer application resulted in four PCs with eigenvalues >1 and explained 69.0% variance in the data set (Table 12). Within each PC, only highly weighted nutrient parameters (having absolute values within 10% of the greatest factor loading) were retained for the final minimum data set. In PC1 and PC3, only Mg and Zn were the nutrient elements qualified respectively, whereas in PC2 and PC4, two nutrient elements qualified (viz., P and Ca under PC2 and S and Cu in PC4). Hence, the final key nutrient elements that were qualified in the PCA and considered to play a key role in the nutrient utilization performance of the rootstocks before fertilizer application were P, Ca, Mg, Zn, and Cu. In other words, rootstocks exhibited their differential accumulation

Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 response toward these key nutrient elements. The foliar data of the 11 nutrient parameters obtained 45 days after fertilizer application when subjected to PCA analysis resulted in three PCs with eigenvalues >1 and explained again 69.0% variance in the data set. In all the three PCs, two nutrient elements were found to be highly weighted. In PC1, the highly weighted nutrient elements were K and Ca; in PC2, Fe and Mn; and in PC3, Mg and Zn. Hence, the final nutrient elements thath were found to be highly weighted and considered to play a key role in the nutrient utilization performance of the rootstocks 45 days after fertilizer application were K, Ca, Mg, Zn, Fe, and Mn. Similarly, the foliar data of the 11 parameters obtained 135 days after fertilizer application when subjected to PCA had resulted in five PCs with eigenvalues >1 and explained 82.2% variance in the data set. Except for in PC4, only single nutrient elements were found to be highly weighted: B in PC1, Fe in PC2, P in PC3, and N in PC5. In PC4, two nutrient elements, N and Zn, were found to be highly weighted. Hence, the final key nutrient elements that were found to be highly weighted in the PCA and predominantly and differentially accumulated in the rootstock 135 days after fertilizer application were N, P, Zn, Fe, and B. Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012

Table 12 Principal component analysis of foliar nutrients under different rootstocks during three stages

After 45 days of fertilizer Before fertilizer application application After 135 days of fertilizer application

Parameter PC1 PC2 PC3 PC4 PC1 PC2 PC3 PC1 PC2 PC3 PC4 PC5 Total eigenvalues 2.604 2.278 1.479 1.234 3.414 2.701 1.479 2.759 2.377 1.621 1.255 1.025 Variance (%) 23.671 20.705 13.448 11.221 31.040 24.556 13.445 25.081 21.611 14.739 11.409 9.317 Cumulative (%) 23.671 44.376 57.824 69.045 31.040 55.596 69.041 25.081 46.692 61.432 72.840 82.157 Eigenvectors 1010 N −0.332 0.514 −0.017 −0.242 0.598 −0.159 −0.531 0.045 −0.163 0.183 0.672 −0.672 P −0.664 0.587 0.029 0.035 0.336 0.522 0.096 0.049 −0.099 0.845 −0.020 0.235 K −0.509 −0.371 −0.393 −0.358 0.887 −0.206 0.153 −0.556 −0.573 −0.336 0.077 0.186 Ca 0.474 0.649 0.172 −0.210 0.811 −0.289 −0.058 0.575 0.617 −0.399 0.194 −0.157 Mg 0.820 0.433 −0.106 0.069 −0.326 −0.518 0.635 0.616 −0.443 −0.085 0.435 0.308 S 0.483 −0.185 −0.074 0.551 0.556 0.227 −0.005 −0.480 0.486 0.563 0.238 0.102 Zn −0.409 −0.404 0.698 0.194 0.544 0.342 0.618 −0.425 0.246 −0.096 0.698 0.437 Fe 0.129 0.503 0.104 −0.347 −0.247 0.868 0.111 0.275 0.803 −0.015 0.024 0.000 Cu −0.122 0.249 −0.506 0.573 −0.376 −0.571 −0.427 0.537 −0.217 0.518 −0.062 −0.128 Mn 0.562 −0.345 0.484 −0.193 −0.055 0.863 −0.412 −0.508 0.637 0.005 −0.148 −0.014 B −0.386 0.538 0.537 0.413 −0.763 0.128 0.112 0.838 0.202 0.004 −0.004 0.382 Bold numbers represent highly weighted variables. Nutrient Absorption Patterns of Rootstocks 1011

The ﬁnal data set of key nutrient elements that were predominantly and differentially accumulated in the rootstocks was used for the computation of the NAI of the rootstocks using the analogy of linear scoring technique (Andrews, Karlen, and Mitchell 2002) for all the three different stages. Every observation of the each nutrient element was trans- formed using the linear scoring method, and the nutrient scores thus obtained for each observation were multiplied with the weighted factor obtained from the PCA results. Each PC explained a certain amount (%) of the variation in the total data set. This percentage, when divided by the total percentage of variation explained by all the PCs with eigenvectors >1, gave the weighted factors for key nutrient elements chosen under a given PC. The weighted factors (Wi) were percentage variation of each PC divided by the cumulative percentage variation explained by all the PCs. After performing these steps to obtain the NAI, the weighted key nutrient element scores for each observation were summed up using the following relationship: n NAIi=1 = (Wi × Si)

where Si is the score for the subscripted key nutrient element and Wi is the weighing factor obtained from the PCA. From this PCA analysis, it was understood that after the 13th year of experimentation (before fertilizer application), the order of nutrient utilization ability in terms of NAI was Cleopatra mandarin (1.07) > Rangpur lime (1.03) > Sathgudi (0.98) > Troyer citrange (0.15) > Trifoliate orange (0.10) (Table 13). After 45 days from fertilizer application, the order of nutrient utilization ability in terms of NAI was Sathgudi (1.63) > Trifoliate orange (1.57) > Rangpur lime (1.50) > Cleopatra mandarin (1.43) > Troyer citrange (1.35). When studied 135 days after fertilizer application, the order was Trifoliate orange (0.86) > Troyer citrange (0.81) > Rangpur lime (0.74) > Sathgudi (0.71) > Cleopatra mandarin (0.69). To draw a conclusion and better understand the performance of the cultivars, mean NAI values were obtained over all the three study periods and reduced to the scale of 0–1. The values thus obtained were referred to as relative nutrient accumulation indices (RNAI). Thus, the order of the nutrient utilization ability of rootstocks in terms of RNAI emerged as Sathgudi (1.00) > Rangpur lime (0.98) > Cleopatra mandarin (0.96) > Trifoliate orange (0.76) > Troyer citrange (0.69).

Table 13 Downloaded by [J. Kusuma Grace] at 11:26 03 April 2012 Nutrient utilization performance of different citrus rootstocks at different stages

Nutrient accumulation index (NAI) Relative 0 days 45 days 135 days nutrient after fer- after fer- after fer- accumulation No. Rootstock tilization tilization tilization Mean index (RNAI)a 1 Sathgudi 0.98 1.63 0.71 1.11 1.00 2 Rangpur lime 1.03 1.50 0.74 1.09 0.98 3 Cleopatra mandarin 1.07 1.43 0.69 1.06 0.96 4 Troyer citrange 0.15 1.35 0.81 0.77 0.69 5 Trifoliate orange 0.10 1.57 0.86 0.84 0.76 LSD (P = 0.05) 0.08 0.06 0.06 — —

AValues reduced to the scale of one for better understanding. 1012 J. K. Grace et al.

Conclusions In the present study, it was clearly observed that rootstocks chosen for the study reflected differential behavior in terms of nutrient absorption from the soil and consequently created significant variation in majority of the soil nutrient parameters at both the stages before fertilizer application and 45 days after fertilizer application. To further ascertain the differential nutrient utilization behavior of the rootstock, mineral nutrient composition data was also studied. Critical appraisal of leaf mineral nutrient composition data in different rootstocks reflected significant variations in K, Cu, Mn, and B at all the three stages of sampling. In the initial stage, the leaf nutrient concentrations were significantly different in the cases of P, K, Zn, Cu, Mn, and B. After 45 days, significant influence of the rootstocks was also observed additionally on Ca, Mg, and Fe. After 135 days, a similar trend prevailed for all except Zn. Further, to narrow down the findings for drawing specific conclusions, the PCA technique was used. Using this technique, the key nutrient elements whose concentrations in the leaves significantly varied in the rootstocks were P, Ca, Mg, Zn, and Cu at stage 1; K, Ca, Mg, Zn, Fe, and Mn at stage 2; and N, P, Zn, Fe, and B at stage 3. Finally the rootstocks were ranked for their nutrient utilization ability in terms of RNAI in the order of Sathgudi (1.00) > Rangpur lime (0.98) > Cleopatra mandarin (0.96) > Trifoliate orange (0.76) > Troyer citrange (0.69). The variation in RNAI values also reflected the differential nutritional behavior and different abilities of the rootstocks to utilize plant nutrient elements. It is well understood that besides nutritional parameters, optimum rootstock/scion combination required to be worked out based on several other factors such as climate, ecological conditions, productivity, and fruit quality. Nevertheless, nutritional feeding behavior of the rootstocks assumes great importance in influencing the overall growth and quality of produce. Thus, the findings of the present study and the methodology adopted can help the horticultural breeders and nutritionists choose the best rootstock/scion combination having the desirable traits of nutrient utilization ability and plan effective fertilizer schedule programs.

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