Abstract

                                Field experiments were conducted during 2016-17 at Manickapuram village of Theni District, Southern Zone of Tamil Nadu to study the impact of Inductive approach (artificial gradient)on soil fertility,nutrient uptake and fodder yield of sorghum (var CO30) and further,Soil Test Crop Response correlation studies under Integrated Plant Nutrition System (STCR-IPNS) for desired yield targets of maize on Vertisol. The profile study of the experimental site has been described in detail. The artificial fertility gradient was developed by dividing the field into three equal strips and graded levels of fertilizers were applied in the form of Urea, Single Super Phosphate and Muriate of Potash, respectively to strip I (N0P0K0), II (N1P1K1) and III (N2P2K2). The N1level was fixed based on the blanket recommendation of fodder sorghum and P1 and K1 levels were fixed based on the phosphorus (100 kg ha-1) and potassium (80 kg ha-1) fixing capacities of the soil.Sorghum (var.CO30) was grown as gradient crop and green fodder yield was recorded at harvest and plant samples were collected and analyzed for N, P and K contents and their uptake was computed. The results confirmed that the application of graded levels of fertilizer N, P2O5 and K2O significantly influenced soil fertility status, N, P and K uptake and green fodder yield of sorghum. Subsequently, the STCR-IPNS studies on maize (hybrids) revealed that the requirement of N, P2O5 and K2O for maize (NR) was found to be 2.08, 0.73 and 1.38 kg q-1respectively. The per cent, nutrient contribution from soil (Cs) was 43.01, 44.03 and 9.17; from fertilizers (Cf) was 55.00, 49.83 and 76.99, and from organic manure (Co) was 49.01, 19.71 and 39.83 for N, P2O5 and K2O, respectively. Using the basic data viz., NR, Cs, Cf and Co, fertilizer prescription equations (FPEs) have been developed and ready reckoner of fertilizer doses was formulated for desired yield targets of maize for a range of soil test values on Vertisol. The findings also brought forth the fact that when farm yard manure (FYM) was applied @12.5 t ha-1 (with 25 per cent moisture and 0.54, 0.26 and 0.53 per cent NPK, respectively), 45, 22 and 32 kg ha-1 of fertilizer N, P2O5 and K2O could be reduced from the recommended fertilizer doses for Maize. Using the nomograms, critical levels of soil available N, P and K were fixed

Key words : Incubation, Nutrient mixtures, Fertilizers, Yield attributes, Dry matter production, Harvest index.