Mobility of N, P and K and root growth of Bt and nonBt cotton in clayey soil under different NPK levels

Abstract

The mobility of applied nutrients in soil and root growth determines the interception and uptake of nutrients by crop. Present investigation includes two pot culture experiments under glass house condition. The objective of first experiment was to study the mobility of N, P and K in soil profile of cotton in respect to different NPK levels; whereas, in second experiment root growth of Bt and non-Bt cotton hybrids were studied 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, P2 O5 , K2 O ha-1 and four depth of sampling, i.e. 15, 30, 45 and 60 cm in soil column. Whereas, in second experiment Bt and non-Bt counterpart of same cotton hybrid were evaluated for root growth under above mention NPK levels. Both the experiments consist of four set of replications and experimental design was FRBD. Results illustrate that, concentration of available N, P and K in soil profile of cotton significantly increased with the highest rate of NPK than control. Irrespective of NPK levels, shallow depth of sampling (15 cm) recorded maximum concentration of available N, P and K throughout the period of experimentation. However, N was mobile up to 60 cm depth and K up to 45 cm depth in 90 days; whereas P mobility was restricted only up to 15 cm depth even in 90 days. Each increase in 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 (15 cm) 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 fertilizer application. As regards root growth, Bt hybrid recorded longest root at initial stage whereas, at later stage it was in non-Bt. Application of the highest rate of NPK significantly increased root length over lower levels.