MOBILITY OF N, P AND K AND ROOT GROWTH OF BT AND NON-BT COTTON IN CLAYEY SOIL UNDER DIFFERENT NPK LEVELSM.R. Thakur, V.M. Bhale and A.N. Paslawar
The mobility of applied nutrients in soil and root growth determines the interception and uptake of nutrientsby crop. Present investigation includes two pot culture experiments under glass house condition. Theobjective of first experiment was to study the mobility of N, P and K in soil profile of cotton in respect todifferent NPK levels; whereas, in second experiment root growth of Bt and non-Bt cotton hybrids werestudied under different NPK levels. The first experiment comprised of four NPK levels, i.e. control- 00:00:00,50:25:25, 62.5:31.25:31.25 and 75:37.5:37.5 kg N, P2O5, K2O ha-1 and four depth of sampling, i.e. 15, 30, 45 and60 cm in soil column. Whereas, in second experiment Bt and non-Bt counterpart of same cotton hybridwere evaluated for root growth under above mention NPK levels. Both the experiments consist of four setof replications and experimental design was FRBD. Results illustrate that, concentration of available N, Pand K in soil profile of cotton significantly increased with the highest rate of NPK than control. Irrespectiveof NPK levels, shallow depth of sampling (15 cm) recorded maximum concentration of available N, P andK throughout the period of experimentation. However, N was mobile up to 60 cm depth and K up to 45 cmdepth in 90 days; whereas P mobility was restricted only up to 15 cm depth even in 90 days. Each increasein NPK level increased the downward mobility of N in soil by 15 cm at 30 days after fertilizer application.The increased in available P content with increase in NPK levels remains restricted to placement zone (15cm) only and its downward mobility in soil profile over the period in response to NPK levels was absent.However, K was found mobile up to 45 cm depth under highest level of NPK at 30 days after fertilizerapplication. As regards root growth, Bt hybrid recorded longest root at initial stage whereas, at later stageit was in non-Bt. Application of the highest rate of NPK significantly increased root length over lowerlevels.