Field Validation of on STCR Based Fertilizer Recommendations in Paddy on Alfisols of Nagarkurnool District, Telangana State

On farm trails were conducted at six different locations across three villages in Nagarkurnool district of Telangana during Rabi 2017 and 2018 to evaluate the soil test crop response (STCR) based fertilizer prescription for paddy on Alfisols. The treatments include farmers fertiliser practice, recommended dose of fertilizers (RDF) and STCR based fertilizer recommendations for an yield target of 70 q ha -1 . The N, P and K fertilizers for yield target was calculated based on the initial soil test values of the respective locations. The results showed that, against the paddy yield target of 70 q ha -1 , the grain yield at six locations varied from 69.08 to 72.49 q ha -1 with a mean of 71.15 q ha -1 . With respect to farmers practice of fertiliser recommendations, the yield at ten locations varied from 66.18 to 69.82 q ha -1 with a mean yield of 67.92 q ha -1 . The grain yield recorded with STCR recommendations were higher in producing grain yield as compared to RDF and farmers practice of fertiliser recommendations. Adoption of STCR based fertilizer recommendations for paddy was useful to the farmers for saving of P fertilizers from current recommended dose by 25 kg P2O5 ha -1 (42 % of RDP) and saving of cost of P fertilizers applied per hectare to the extent of Rs.1250/-. The treatment of targeted yield found most economic treatment as compare to farmer practices and general recommendation.


INTRODUCTION
Rice the staple food of more than half of the population of the world, is an important target to provide food security and livelihoods for millions. Fertilizer is one of the costliest inputs in agriculture and the use of the right amount of fertilizer is fundamental for farm profitability and environmental protection (Kimetu et al., 2004). Soil test based fertilizer prescription eliminates over or under usage of fertilizer inputs there by increasing the fertilizer use efficiency and yield of crops.
The fertilizer prescription equations developed by the AICRP centre of the project on STCR for different crops of different agro-ecological situations in different states. Substitution of soil test values and target yield in the prescription equations gives us that particular fertilizer nutrient recommendation which need to be converted in to fertilizer quantity to be applied. These fertilizer target yield equations will not only help in saving of fertilizers and improving the economy but also help in improvement of soil health.
The treatment with N application based STCR realized the target yield (Ramesh & Chandrashekaran, 2007). Srinivasan and Angayarkanni (2008) reported that application of fertilizers based on STCR equation will result in buildup of nutrients in the soil. Soil test based application of plant nutrients helps to realize higher response ratio and benefit: cost ratio as the nutrients are applied in proportion to the magnitude of the deficiency of a particular nutrient and the correction of the nutrients imbalance in soil helps to harness the synergistic effects of balanced fertilization (Rao & Srivastava, 2000). Hence the present investigation was undertaken where STCR approach of fertilizer application was compared with farmers practice and recommended dose of fertilizers application. In this contest, STCR based target yield approach will help to provide the required amount of nutrient to the crop and increases the crop uptake and in turn higher yield can be expected.

MATERIALS AND METHODS
On farm trails were conducted at six different locations across three villages in Nagarkurnool district of Telangana during Rabi 2017 and 2018 to evaluate the soil test crop response (STCR) based fertilizer prescription for paddy on Alfisols. The fertilizer prescription equation developed for desired yield target of paddy (T = 70 q ha -1 ) for Southern Telangana soil series are furnished here.
Where, FN, FP 2 O 5 and FK 2 O are fertilizer N, P 2 O and K 2 O in kg ha -1 respectively. T is the yield targeted in q ha -1 ; SN, SP and SK are soil available N, P and K in kg ha -1 respectively. The treatments include T1: Farmers Fertilizer Practice, T2: Recommended Dose of Fertilizers (RDF) and T3: Soil Test Crop Response (STCR) based fertilizer dose for an yield target of 70 q ha -1 . The test crop paddy variety Telangana Sona (RNR 15048). BCR (B: C ratio) was worked out based on the standard procedure (Gittinger, 1982). The cultivation practices were carried out periodically and the grain and straw yield was recorded at harvest.

Initial available soil nutrient status
Initial soil samples were collected in each location and analysed for alkaline KMnO 4 -N (Subbiah & Asija, 1956), Olsen-P (Olsen et al., 1954) and NH4OAc-K (Hanway & Heidal, 1952). Initial soil samples were collected in each location and analyzed for available status of nutrients. The soils across 6 locations were neutral in reaction to non-saline in nature. Available N, P and K were low, high and medium to high in status ranging from 188 to 232, 31 to 46 and 279 to 348 kg ha -1 , respectively (Table 1). The available status of nutrients was used to compute fertiliser doses for paddy through adjustment equations using basic data that had earlier been generated from fertility gradient field experiments for paddy. The detailed procedure has been described by Valayutham et al (1985 Fig.1). Recommended dose of fertilizer application for paddy in Telangana region is 100-50-40 kg N-P 2 O 5 -K 2 O ha -1 .

RESULTS AND DISCUSSION
The fertilizer application as per the STCR equation with yield target 70 q ha -1 to paddy crop for validation were achieved the desired targeted yield ( Table 2). The yield level that could be achievable with 100 % recommended dose (120-60-40 kg N-P 2 O 5 -K 2 O ha -1 ) to paddy crop can be obtained with a lower dose of 130-35-36 kg N-P 2 O 5 -K 2 O ha -1 to the same crop and thus saving 25 kg cost of P input without sacrificing the yield of rice crop. The grain yield under STCR recommendations at six locations varied from 69.08 to 72.49 kg ha -1 with a mean of 71.15 q ha -1 . The variation in yield obtained from the targeted ones ranged from -1.31 to +1.64. The fertiliser application as per the STCR equation with yield target 70 q ha -1 to paddy crop for validation were achieved the targeted yield. With respect to farmers practice of fertilizer recommendations, the yield at ten locations varied from 66.18 to 69.82 q ha -1 with a mean yield of 67.92 q ha -1 . The grain yield recorded with STCR recommendations were higher in producing grain yield as compared farmers practice of fertilizer recommendations (Table 3). Singh et al. (2014) reported that targeted yield of rice was achieved by using the plant nutrients on the basis of targeted yield concept (soil test crop response technology). The present results were in accordance with the study conducted by Singh et al. (2017) and revealed that among the treatments, STCR recorded relatively higher yield, beneit: cost ratio and per cent achievement. Suresh and Santhi (2018) validated STCR equation for hybrid maize and reported that, STCR based fertilizer recommendations with the targeted yield has been achieved within +/-10 per cent variation proving the validity of the equations. The results of the validation experiment on paddy clearly indicated that the per cent achievement was below 10 per cent variation at all the locations for validation was achieved the targeted yield of paddy crop.
The benefit cost ratio of the treatments was estimated using the cost of input and value of output. Economics of fertilizer application based on targeted concept gave benefit cost ratio varying from 2.27 to 2.36 with a mean value of 2.31. The corresponding value for farmers fertilizer practice ranged from 1.96 to 2.02 with a mean value of 2.00 (Table 3). The results are confirming that, the treatment of targeted yield found most economic treatment as compare to farmer practices and general recommendation. Similar results were reported by Singh et al. (2015). The gross and net returns in T1 were Rs. 1,07,988/-and Rs.53,952/-, respectively (Table 4) where as in T3 the higher gross and net returns were obtained (Rs.1,13,123/-and Rs.64,160, respectively). Chaubey et al. (2015) reported that the net returns from the improved practice (STCR technology) were substantially higher than the farmers' practice (GRD).