Field validation of soil test and yield target based fertiliser prescription equation for soybean on vertisol

The validity of the soil test crop response (STCR) equation was tested by conducting ten follow up trials of soybean across three villages of Nizamabad district of Telangana state during Kharif 2016 on Vertisols. The treatments include Farmers fertiliser practice and STCR based fertilizer recommendations for an yield target of 25 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 soybean yield target of 25 q ha-1, the seed yield at ten locations varied from 18.22 to 22.78 q ha-1, with a mean of 21.04 q ha-1. The variation in yield obtained from the targeted ones ranged from -8.88 to -27.12. Except for one location, the measured yields were above 10 % variation of the yield targets. The fertiliser application as per the STCR equation not achieved the targeted yield. With respect to Farmers practice of fertiliser recommendations, the yield at ten locations varied from 18.24 to 22.75 q ha-1 with a mean yield of 20.79 q ha-1. The seed yield recorded with Farmers practice of fertiliser recommendations were more or less similar in producing seed yield as compared to STCR recommendations. The higher benefit cost ratio obtained under Farmers practice of fertiliser recommendations over STCR recommendations. Thus, fertilizer prescription equation for soybean has failed to achieve the target yield of 25 q ha-1.