Abstract

Soil test crop response (STCR) based fertilizer prescription for desired yield target of wheat was developed under Integrated Plant Nutrition System (STCR-IPNS) on Periyanaickepalayam soil series (Vertic Ustropept) of Tamil Nadu. On-farm testing of fertilizer prescription equations are essential to demonstrate the effectiveness of technology delivery to the stake holders in need. The present study was undertaken in six locations to evaluate the model through field experiments in Western Zone of Tamil Nadu. The treatments included control, blanket recommendation, soil test crop response (STCR) based fertilizer dose for an yield target of 3.0 and 4.0 t/ha, STCR-IPNS based fertilizer dose for an yield target of 3.0 and 4.0 t/ha and farmer's practice. Based on the initial soil test values of available N, P and K and the quantities of N, P and K contributed through farm yard manure (FYM), fertilizer doses were calculated and applied for STCR and STCR-IPNS treatments for the respective yield targets. The treatments were imposed and cultivation practices were carried out periodically and the grain yield was recorded at harvest. Using the data on grain yield and fertilizer doses applied, per cent achievement and response ratio (RR) were worked out. Post-harvest soil samples were collected and analyzed for available N, P and K status. The results of the experiments indicated that in all the six locations, the per cent achievement of the targeted yield was within±10% variation proving the validity of the equations for prescribing integrated fertilizer doses for wheat. The highest mean per cent achievement was recorded in the yield target of 4.0 t/ha (101.2) under STCR-IPNS followed by STCR-NPK alone 4.0 t/ha. The highest mean yield was recorded in STCR-IPNS–4.0 t/ha (4047 kg/ha) recording an increase of 62.1% over blanket recommendation. Among the treatments, STCR-IPNS recorded relatively higher RR than other treatments and the highest mean RR of 6.90 kg/kg was recorded under STCR-IPNS 4.0 t/ha. The highest benefit: cost ratio (1.81) was also recorded in STCR-IPNS 4.0 t/ha. The post-harvest soil available NPK indicated the build up and maintenance of soil fertility due to soil test based fertilizer recommendation under IPNS. The fertilizer prescription equations developed for wheat under IPNS can be recommended for mixed black calcareous soils of Tamil Nadu (Vertic Ustropept) for achieving an yield target of 4.0 t/ha with sustained soil fertility and it can be extrapolated to other agro-climatic zones of Tamil Nadu on similar and allied soil types.