Long term effect of nitrogen fertilization on yield and soil fertility status of rainfed cotton under vertisols track of Southern district

A field experiment was conducted in the Agricultural Research Station, Kovilpatti under dryland situation from 2011-‘19 to find out the long term effect of nutrient and combined effect of organic and inorganic nutrients on crop yield and soil fertility status in cotton crop. This experiment was conducted in randomized block design replicated thrice under rainfed situation. The characteristics of the experimental soil was clay in texture and belongs to Kovilpatti Soil Series (Typic Chromusterts). The soil pH was towards alkaline in nature. The available nutrient status of the soil was low in available nitrogen, low to medium in available phosphorus and high in available potassium content. The treatment comprised of nine treatments. T1 - Control, T2 - 100% RDF (40:20:40 NPK kg ha-1), T3- 50% RDF (20:10:20 NPK kg ha-1), T4- 50% N (crop residues), T5 -50% N (FYM), T6 - 50% Inorganic N+ 50% organic N (crop residues) + P (50%) + K (50%), T7 -50% inorganic N+ 50% organic N (FYM) + P (50%) + K (50%), T8 -100% RDF + 25 kg ZnSO4 ha-1 and T9 - FYM @ 12.5 ha-1. The results revealed that among the different treatment schedule over the long term basis, application of 100% RDF + 25 kg ZnSO4 ha-1 registered higher number of sympodial branches/plant (19.3 no’s), number of bolls/plant (15.0 no’s), boll weight (3.4 g) and seed cotton yield (1277 kg ha-1), net income (Rs.24868/ha), B:C (1.76) and RWUE (3.4 kg/ha mm). Soil fertility status also has been increased over the years by the supply of nutrients through integrated plant nutrient system (IPNS) approach.