System productivity, nutrient use efficiency and apparent nutrient balance in rice-based cropping systems

A 2-year field experiment was conducted to assess system productivity, nutrient use efficiency and apparent balances of phosphorus (P) and potassium (K) in diversified rice-based cropping systems at Gazipur, Bangladesh. Four cropping systems: wheat-fallow-rice, maize-fallow-rice, potato-fallow-rice and mustard-fallow-rice in main plots and four nutrient combinations: NPK, NK, NP and PK in sub-plots were arranged in a split-plot design with three replications. Receiving the NPK treatment, all the component crops gave the highest yield, and omission of N from fertilizer package gave the lowest yield. The maize-rice system removed the highest amount of N (217kgha(-1)), P (41kgha(-1)) and K (227kgha(-1)) followed by wheat-rice, potato-rice and the least in mustard-rice system. The wheat-rice and maize-rice system showed negative K balance of -35.5 and -60.4kgha(-1) in NPK treatment, while potato-rice system showed a positive K balance of 31.0kgha(-1) with NPK treatment. The N, P and K uptake and apparent recovery by the test crops may be used for site-specific nutrient management. The K rates for fertilizer recommendation in wheat and maize in Indo-Gangetic plain need to be revised to take account for the negative K balance in soil.