INTRODUCTION Increase in the rate of population growth in India (1.3% in 2012, Economic Survey, 2012-13). has necessitates production of additional food from a shrinking land area, without deterioration of soil health. This needs extensive research to help develop a scientific model for enhancing and sustaining food production and soil productivity, entailing minimal environment degradation. To attain this, it is essential that nutrients removed from the soil are replaced through judicious use of fertilizers and manures. Intensive cropping and imbalanced fertilizer application are major causes for depletion of macronutrients like N, P and K from soil. Indian agriculture is running at a ‘net negative nutrient balance’ of a staggering 8-10 million tonnes per year (Tandon, 2004), a figure set to reach around 15 million tonnes by 2025. Application of fertilizers by farmers without information on soil-fertility status and crop nutrient requirement affects both the soil and the crop adversely (Ray et al, 2000). Soil testing is an ideal scientific means for a quick and reliable estimation of soil-fertility status. Soil test crop response studies in field provide soil-test calibration between level of soil nutrients determined in the laboratory, and crop response to fertilizers J. Hortl. Sci. Vol. 10(1):18-23, 2015 Fertilizer-prescription equations for targeted yield in radish under integrated nutrient management system Kaushik Batabyal, Dibyendu Sarkar and Biswapati Mandal Bidhan Chandra Krishi Viswavidyalaya Mohanpur, Nadia, West Bengal-741252, India E-mail: kbatabyal@rediffmail.com ABSTRACT Soil test crop response correlation studies under integrated plant nutrient system were carried out in Inceptisol of West Bengal during 2008 – 2010, with radish as a test crop following Ramamoorthy’s ‘inductive-cum-targeted yield model’. Four fertilizer (NPK) and three farmyard manure (FYM) levels were randomized in three well-established fertility gradients, each comprising 21 plots. Soil and plant analysis data were interpreted to formulate fertilizer adjustment equations, with or without FYM, at varying yield targets. It was computed that 1.40, 0.17 and 2.8 kg N, P and K, respectively, were required for producing 100 kg of radish. Contribution of fertilizer-source to the total NPK uptake in radish was far higher than that obtained from FYM and soil available sources. A ready-reckoner developed from soil-test based fertilizer adjustment equations showed that FYM application at 10 t ha-1, along with NPK fertilizer, resulted in a net saving of 15, 1.8 and 5.0kg ha-1 of N, P and K, respectively, for cultivating radish. Key words: Fertility gradient, fertilizer-prescription equation, Inceptisol, radish, ready-reckoner, yield target observed in the field, for predicting fertilizer requirement of a crop. It is well-documented through various experiments across the country that the actual on-farm yield is lower than potential yield of a crop (Aggarwal et al, 2000; Ladha et al, 2003). These yield gaps provide ample scope for improving yield levels using techniques that prescribe fertilizer nutrients based on soil-test values and yield-targets desired. Fertilizer recommendations based on soil test crop response correlation (STCRC) are more quantitative, precise and meaningful, because, a combined use of soil and plant analysis is involved. This presents a balance between nutrients applied and available nutrients (nutrients already present) in the soil. Besides, it takes into account the farmer’s ability to invest in a crop. STCR treatments are also known to record positive responses in terms of biomass yield and net returns more so when integrated sources of nutrients are used (Santhi et al, 2002). So far, STCRC-IPNS studies have not been made in vegetable crops in West Bengal. As radish (Raphanus sativus L.) is an important vegetable crop grown extensively in India, the present study was made with an objective of developing fertilizer prescription equations for targeted yield in this crop using organic manure (FYM) and chemical fertilizers combined. 19 Fertilizer-prescription equation for radish under INM MATERIAL AND METHODS Experimental site To develop a scientific basis for prescribing fertilizer recommendations in radish, field experiments were carried out during 2008 - 2010 at Central Research Farm, Bidhan Chandra Krishi Viswavidyalaya, Gayeshpur, Nadia, India (22°58¹ N latitude and 88°29¹ E longitude), with fodder maize (cv. Prakash) as the gradient, and radish (cv. Red culpin) as the test crop. Soil at the experimental site was Inceptisol, sandy loam in texture, at pH 6.9 and with organic carbon content of 0.6%. Initial, available N, P and K level in the soil was 308, 24 and 155 kg ha-1, respectively. Fertility gradient experiment Fertility-gradient experiment was conducted prior to the test-crop experiment as per inductive methodology proposed by Ramamoorthy et al (1967), during summer 2008-09, by dividing the experimental field into three rectangular strips along the breadth. Fertility gradients were created by applying graded doses of fertilizer N, P and K on the strips as shown in Table 1. Fodder maize was grown exhaustively to help the fertilizers undergo transformation in soil by the plant and microbes. Test-crop experiment After harvesting the exhaustive crop, each strip was divided into three sub-strips to impose three levels of FYM (0, 5 and 10 t ha-1). Each sub-strip was further divided into seven sub-sub-strips, or plots, of 5m x 5m size. Thus, 21 plots constituted each strip. The test-crop experiment was conducted during rabi season (2008-09 and 2009-10) with radish (var. Red culpin) by superimposing 21 treatment combinations consisting of four levels of N (0, 40, 60 and 80 kg ha-1), four levels of P (0, 9, 13 and 18 kg ha-1) and four levels of K (0, 25, 33 and 50 kg ha-1). In the 21 plots, all the 18 selected treatment-combinations, along with three Controls, were superimposed in each gradient strip, as per Fractional Factorial Randomized Block Design (or incomplete split-plot randomized block design) following the technical programme of All India Coordinated Research Project on Soil Test Crop Response Correlation (AICRP on STCRC) Studies. Half the N, along with full amount of P and K, was applied as a basal dose at the final land- preparation stage, and the rest half of N was top-dressed at 30 days after sowing. Biometric observation Total biomass yield in radish, comprising root and leaf, was recorded plot-wise after crop harvest under each treatment, under all the three fertility strips. Soil analysis Soil samples (0-0.2m depth) were collected before crop-sowing, prior to FYM and fertilizer application, and, after the harvest of both the gradient (maize) and the test (radish) crops. Soil samples were analyzed for available N, P and K as per standard methods (Jackson, 1973). Plant analysis At harvest, representative plant samples were collected from the test crop, washed thoroughly in tap water, followed by a wash in double distilled water. The plant samples were then dried at 60°C to a constant weight, ground and ashed at 550°C for 2 h in a muffle furnace. The ash was dissolved in 2N HCl for determining P and K content as per Chapman and Pratt (1961). Nitrogen content in the dried samples was estimated separately by digesting plant samples with sulphuric acid in the presence of digestion mixture (CuSO4+K2SO4+ Se powder) (Micro-Kjeldahl digestion method), and, subsequently distilled and titrated (Jackson, 1973). Nutrient uptake was computed by multiplying the total dry-matter yield with nutrient concentration. Data computation From data on soil-test values, crop dry-matter yield and nutrient uptake, basic parameters like nutrient requirement (NR), soil efficiency (CS), fertilizer efficiency (CF) and organic efficiency (CO) were calculated, using the following formulae (developed as per Ramamoorthy et al, 1967): Nutrient requirement (NR) Total uptake of nutrient (kg ha-1) (kg of nutrient per = Total biomass yield (100kg ha-1)100kg of produce) Soil efficiency Total uptake in Control plot (kg ha-1) or % contribution = Soil-test value (STV) of nutrient × 100 from soil (CS) in Control plot (kg ha-1) Fertilizer Total uptake in fertilized plot efficiency or % (kg ha-1) – (STV of nutrient in contribution = fertilizer treated plot X CS) × 100from fertilizer (CF) Fertilizer dose (kg ha-1) Table 1. Graded dose of fertilizer applied to a gradient crop, maize Strip Level of fertilizer Fertilizer dose (kg ha-1) N P K I N 0 P 0 K 0 0 0 0 II N 1 * P 1 * K 1 * 100 22 83 III N 2 P 2 K 2 200 44 166 * Recommended dose for fodder maize J. Hortl. Sci. Vol. 10(1):18-23, 2015 20 Organic Total uptake in organic plot efficiency or % (kg ha-1) – (STV of nutrient in contribution from = organic-treated plot X CS) × 100organic component Organic fertilizer dose (CO) (kg ha-1) From these basic parameters, fertilizer prescription equations were developed for radish using targeted yield calculator (TYC) software of AICRP on STCR, developed by Indian Institute of Soil Science, Bhopal. Based on the equations, fertilizer recommendation was prescribed as a ready-reckoner for arriving at desired yield-target in radish. RESULTS AND DISCUSSION Creation of fertility gradient at the experimental site In the present investigation, all the variation needed in soil fertility level was created deliberately in the same field. The gradient crop developed variability in soil fertility in the three experimental strips in a differential manner. Available-nitrogen after harvest increased to 90.4 and 99.1 kg ha-1 in medium (Strip-II) and high (Strip-III) fertility- gradient strip, respectively, from that in the low fertility Strip- I (Table 2). On the other hand, available phosphorus content increased to 37.9 and 44.5 kg ha-1, while, available potassium content increased to 35.2 and 81.4kg ha-1 in medium- and high-fertility gradient strips from the low fertility ones, respectively. Increased availability of N, P and K in soil was due to fertilizer application in graded doses, thus creating a fertility gradient in the same field. The gradient developed with regard to K was stiffer and uniform (Fig. 1), while, the same for N and P was rather non-uniform. Occurrence of non-uniform gradients for N and P is not uncommon (AICRP Bi-annual Report, STCR, 2007-08). This was due to loss of N through different mechanisms and by locking of P by soil components. Maize has been found to develop fertility gradients for the three major nutrients in the experimental strips, because, maize is an exhaustive crop causing overmining of plant nutrients, thus leaving relatively stable nutrient sinks in the soil that result in creating the fertility gradient. Yield response in radish Results showed that yield in radish was significantly influenced by soil fertility gradient and level of FYM and NPK. On an average, irrespective of the dose of organic or NPK fertilizers, highest yield (48.8 t ha-1) was recorded in medium-fertility strip, followed by high (41.6 t ha-1) and low (38.7 t ha-1) fertility strips (Table 3). Profuse growth of leaves in the high-fertility strip may have failed to translocate photosynthates to the roots, resulting in relatively low yield. Application of FYM at 5 t ha-1 produced the highest yield (45.1 t ha-1), followed by ‘no FYM’ and FYM at 10 t ha-1, irrespective of the gradient and dose of mineral NPK applied. Across fertility gradients and FYM levels, yield in radish was significantly influenced by level of N imposed. Maximum yield (45.6 t ha-1) was obtained with application of the highest level of N (80kg ha-1). However, this yield was statistically at par with that obtained with 40 or 60kg N ha-1. This indicates that the optimum dose of N for radish could be 40kg ha-1. With increasing application of N, only vegetative growth increased. Yield increased significantly with increasing levels of P and K, and maximum yields were obtained with 13 and 33 kg ha-1 of P and K, respectively; thereafter, it dropped significantly with further increase in levels of both these nutrients. Thus, optimum levels of P and K for growing radish would be 13 and 33 kg ha-1, respectively. Nutrient uptake Irrespective of the levels of FYM or NPK, no significant difference was seen in N uptake by the crop due to different fertility gradients, but the uptake of P and K was significantly influenced (Table 3). However, in all other cases too, the same trend was seen as in yield. Again, Table 2. Soil chemical properties at completion of the gradient crop Strip pHw Organic C (%) Available nutrient N P K kg ha-1 I 7.21 0.50 267.4 20.2 130.7 II 7.04 0.65 357.8 58.1 165.9 III 7.01 0.62 366.5 64.7 212.1 Fig. 1. Fertility gradient of the experimental field with reference to available N, P and K in soil Kaushik Batabyal et al J. Hortl. Sci. Vol. 10(1):18-23, 2015 21 irrespective of the gradient and NPK levels, FYM application had no significant effect on uptake of either N or K by radish. However, significant variation was observed in P uptake by the crop. Maximum uptake (15.2 kg ha-1) resulted from application of 10 t FYM ha-1, while, the minimum was with zero level of FYM. Across fertility-gradients and FYM levels, application of different levels of N caused significant changes in uptake of N, P and K by radish. Maximum uptake of N and K was associated with the highest level of N application (80kg ha-1), while, minimum values were obtained with no N input (Table 3). However, magnitude of NPK uptake due to application of different levels of P and K followed the same trend as that for yield. Uptake increased with increasing levels of P and K and, maximum NPK uptake was seen with application of optimum levels of P and K, as mentioned earlier, i.e., 13 and 33 kg ha-1, respectively. Developing targeted-yield equations in radish: Basic parameters Pre-sowing soil-test values, and, data on dry matter yield and nutrient uptake by radish, were used for calculating basic parameters, viz., nutrient requirement (NR) in kg for producing one quintal of radish, per cent contribution from soil (CS), fertilizer (CF) and organic source (CO). Average nutrient requirement for producing 100kg dry matter yield in radish was 1.40, 0.17 and 2.8 kg of N, P and K, respectively (Table 4). This is in close conformity with results of Bera et al (2006) and Thilagam and Natesan (2009). Contribution of N, P and K as estimated from soil, FYM and fertilizer sources was 6.8, 7.1 and 26.4; 17.6, 4.9 and 29.8, and 47.3, 27.4 and 186.7%, respectively. These results indicate that nutrient contribution from fertilizer sources is greater than that from soil or organic sources. These findings are in agreement with Ray et al (2000), Meena et al (2001), Shrinivas et al (2001) and Bera et al (2006). Interestingly, it was observed that contribution of K from fertilizer was more than 100% (186.7%). This high value of K could be due to an interaction effect of higher doses of N and P, and the primary effect of starter K dose, in treated plots leading to release of soil K, and consequent higher uptake from native soil sources by the crop (Ray et al, 2000). Similarly, high efficiency of potassic fertilizer was reported for rice by Ahmed et al (2002) and Bera et al (2006) in alluvial soil, and for maize (Reddy et al, 2000) and jute (Ray et al, 2000) in Inceptisol. Fertilizer-prescription equations, developed using basic parameters estimated by the whole-field method, are presented below: Prescription equations FN =2.95 T - 0.14 SN for fertilizer NPK FP =0.62 T - 0.26 SP alone FK =1.47 T - 0.14 SK Prescription equations FN =2.95 T - 0.14 SN -0.37 ON for fertilizer NPK plus FP =0.62 T - 0.26 SP - 0.18 OP organics (FYM) FK=1.47 T - 0.14 SK - 0.16 OK where, FN, FP and FK=fertilizer N, P and K required (kg ha -1); T=yield target [(100 kg) ha-1]; SN, SP and SK=soil available N, P and K (kg ha-1), and ON, OP and OK=quantity of N, P Table 3. Effect of fertility gradient, FYM and NPK level on yield and NPK uptake in radish (mean of two years’ data) Gradient Yield (t ha-1) Nutrient uptake (kg ha-1) N P K Low 38.7b 45.1 11.6b 102.6b Medium 48.8a 49.9 14.7a 126.8a High 41.6b 48.3 13.7a 111.1b NS FYM level (t ha-1) 0 41.8 47.2 11.0c 111.1 5 45.1 49.9 13.8b 116.1 10 42.2 46.3 15.2a 113.3 ns ns ns N level (kg ha-1) 0 28.5b 22.2c 6.5c 52.6b 40 45.6a 56.1a 15.9a 125.5a 60 45.2a 48.9b 13.0b 119.0a 80 45.6a 58.6a 14.0b 132.9a P level (kg ha-1) 0 28.5c 22.2b 6.5c 52.6c 9 44.2ab 47.0a 12.6b 110.5b 13 48.4a 54.1a 15.3a 132.8a 18 42.1b 53.9a 15.1a 122.2ab K dose (kg ha-1) 0 28.5c 22.2c 6.5b 52.6b 25 46.1a 49.8ab 14.4a 123.1a 33 47.3a 56.1a 14.7a 127.6a 50 41.0b 48.9b 14.2a 117.7a Values of mean followed by a different letter were significantly different at p≤0.05 using Duncan’s Multiple Range Test (DMRT); NS indicates non-significant Table 4. Basic parameters of targeted yield equation for radish Parameter Basic data N P K Nutrient requirement 1.40 0.17 2.8 (kg nutrient per 100kg dry matter yield) Contribution from soil 6.8 7.1 26.4 (soil efficiency, %) Contribution from fertilizer 47.3 27.4 186.7 (fertilizer efficiency, %) Contribution from organics 17.6 4.9 29.8 (organic efficiency, %) { { J. Hortl. Sci. Vol. 10(1):18-23, 2015 Fertilizer-prescription equation for radish under INM 22 and K added as FYM (FYM contains 0.46% N, 0.09% P and 0.37% K). A ready-reckoner for fertilizer recommendation in radish Based on generated equations, a ready-reckoner was prepared for different soil-test values for yield target of 35 and 45 t ha-1, under NPK alone and under NPK+FYM. Results showed that for producing 35 t ha-1 of radish at average soil nutrient status of 300, 30 and 200 kg N, P and K ha-1, respectively, fertilizer nutrient required was 39, 4.4 and 10.8 kg ha-1 N, P and K, respectively (Table 5); But, the requirement was reduced to 24, 2.6 and 5.8 kg ha-1 N, P and K, respectively, when the fertilizer was applied together with 10 t ha-1 FYM. This resulted in a saving of 15, 1.8 and 5.0 kg ha-1 N, P and K, respectively. Again, for producing 45 t ha-1 of radish at the same soil-available-nutrient levels, fertilizer nutrient requirement was 63, 6.6 and 20.8 kg ha-1 N, P and K, respectively (Table 6); But, the requirement was reduced to 48, 4.8 and 15.8 kg ha-1 N, P and K, respectively, when used with FYM. This resulted in similar magnitude of nutrient savings, i.e., 15, 1.8 and 5.0 kg ha-1 N, P and K, respectively. Thilagam and Natesan (2009) also Table 5. A ready reckoner for fertilizer dose at varying soil-test values for a yield target of 35 t ha-1 Soil-test value Fertilizer nutrient required (kg ha-1) (kg ha-1) for yield target of 35 t ha-1 Inorganic+ Inorganic FYM (10 t ha-1) N P K N P K N P K 250 5 100 47 7.0 22.5 32 5.7 17.5 275 10 125 43 6.6 20.0 28 4.8 14.2 300 15 150 39 6.1 16.7 24 4.4 11.7 325 20 175 36 5.2 13.3 21 3.9 8.3 350 25 200 32 4.8 10.8 17 3.1 5.8 375 30 225 29 4.4 7.5 15 2.6 2.5 400 35 250 25 3.5 5.0 10 2.2 0.0 Table 6. A ready reckoner for fertilizer dose at varying soil-test values for a yield target of 45tha-1 Soil-test value Fertilizer nutrient required (kg ha-1) (kg ha-1) for yield target of 45 t ha-1 Inorganic+ Inorganic FYM (10 t ha-1) N P K N P K N P K 250 5 100 70 9.2 32.5 55 7.4 26.7 275 10 125 67 8.7 29.2 52 7.0 24.2 300 15 150 63 8.3 26.7 48 6.6 20.8 325 20 175 60 7.4 23.3 45 6.1 18.3 350 25 200 56 7.0 20.8 41 5.2 15.8 375 30 225 52 6.6 17.5 37 4.8 12.5 400 35 250 49 5.7 15.0 34 4.4 9.2 reported that application of FYM at 15 t ha-1 together with chemical fertilizer resulted in a saving of 35, 10.9 and 23.3 kg ha-1 N, P and K, respectively, in cauliflower. CONCLUSION Irrespective of fertility gradient or FYM level, optimum dose of N, P and K for cultivating radish was 40, 13 and 33 kg ha-1, respectively. This also corresponded to a higher removal of N, P and K by biomass of the harvested crop. Contribution of N, P and K from the soil-available pool was 6.8, 7.1 and 26.4% to total N, P and K uptake by the crop, respectively, while, such contribution from applied fertilizer was 47.3, 27.4 and 186.7%, and, that from applied FYM was 17.6, 4.9 and 29.8%, respectively. A ready- reckoner developed using soil-test based fertilizer adjustment equations in radish showed that application of FYM at10 t ha-1 along with chemical fertilizer resulted in a net saving of 15, 1.8 and 5.0 kg ha-1 of N, P and K, respectively, for cultivating radish at average soil-nutrient status of 300, 30 and 200 kg ha-1 N, P and K, respectively. This indicates the usefulness of STCRC-IPNS technology for achieving higher-crop production and a more rational use of fertilizer nutrients. REFERENCES Aggarwal, P.K., Talukdar, K.K. and Mall, R.K. 2000. Potential yields of rice-wheat cropping system in the Indo-Gangetic Plains of India. Rice-wheat cropping system in the Indo-Gangetic Plains of India. Rice- Wheat Consortium Series 10, Rice-Wheat Consortium for the Indo-Gangetic Plains, New Delhi Ahmed, S., Riazuddin, M. and Krishna Reddy, P.V. 2002. Optimizing fertilizer doses for rice in alluvial soils through chemical fertilizers, farmyard manure and green manure using soil test values. Agropedology, 12:133-140 AICRP Bi-annual Report. 2007-2008. All India Co-ordinated Research Project on Soil Test Crop Response Correlation, Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India Bera, R., Seal, A., Bhattacharyya, P., Das, T.H., Sarkar, D. and Kangjoo, K. 2006. Targeted yield concept and a framework of fertilizer recommendation in irrigated rice domains of subtropical India. JZUS-B, 7:963-968 Chapman, J.D. and Pratt, P.F. 1961. Method of analysis for soils, plants and waters. Agricultural Division, University of California, Riverside, California, USA Economic Survey. 2012-2013. Economic Survey of India, Chapter 2, Seizing the demographic dividend, J. Hortl. Sci. Vol. 10(1):18-23, 2015 Kaushik Batabyal et al 23 Department of Economic Affairs, Ministry of Finance, Government of India Jackson, M.L. 1973. Soil Chemical Analysis. Prentice Hall Inc. India Pvt. Ltd., New Delhi Ladha, J.K., Dave, D., Pathak, H., Padre, A.T., Yadav, R.L. and Singh, B. 2003. How extensive are yield declines in long-term rice-wheat experiments in Asia. Field Crops Res., 81:159-180 Meena, M., Ahmed, S., Riazuddin, M., Chandrasekhara, K.R. and Rao, B.R.C.P. 2001. Soil test crop response studies on onion (Allium cepa) in alfisols. J. Indian Soc. Soil Sci., 49:709-713 Ramamoorthy, B., Narasimham, R.L. and Dinesh, R.S. 1967. Fertilizer application for specific yield target of Sonora 64. Indian Fmg., 17:43-45 Ray, P.K., Jana, A.K., Mitra, D.N., Saha, M.N., Choudhury, J., Saha, S. and Saha, A.R. 2000. Fertilizer prescription on soil test basis for jute, rice and wheat in Typic Ustochrept. J. Indian Soc. Soil Sci., 48:79-84 Reddy, C.K., Riazuddin, M. and Ahmed, S. 2000. Soil test based fertilizer recommendation for maize grown in Inceptisols of Jagtial in Andra Pradesh. J. Indian Soc. Soil Sci., 48:84-89 Santhi, R., Natesan, R. and Selvakumari, G. 2002. Soil test based fertilizer recommendation under IPNS for aggregatum onion in Inceptisols of Tamil Nadu. Agropedology, 12:141-147 Shrinivas, A., Prasad, B.R.C., Reddy, K.C.K. and Maruthisankar, M.G. 2001. Soil test based fertilizer recommendations for attaining different yield targets of rice under rice-rice crop sequence in vertisols. J. Res.-ANGRAU, 29:69-74 Tandon, H.L.S. 2004. Fertilizers in Indian agriculture - from 20th to 21st Century. Fertilizer Development and Consultation Organization, New Delhi Thilagam, V.K. and Natesan, R. 2009. Fertilizer prescription equation for desired yield targets of cauliflower under integrated plant nutrient system based on targeted yield model. Agri. Sci. Dig., 29:201-207 (MS Received 13 November 2014, Revised 23 May 2015, Accepted 26 May 2015) J. Hortl. Sci. Vol. 10(1):18-23, 2015 Fertilizer-prescription equation for radish under INM