Optimal potassium management strategy to enhance crop yield and soil potassium fertility under paddy-upland rotation.

Abstract

An unbalanced application of potassium (K) fertilizer usually destabilizes crop yield and affects soil K fertility. Developing a sustainable K management strategy requires improvements in crop yield without reducing soil K supply capacity over the long term. A combination of field experiments of K fertilization and straw return using rice (Oryza sativa L.)-oilseed rape (Brassica napus L.) rotation was designed to develop an optimal K management strategy. The results showed the best strategy to maintain yield was KG +S (input equivalent K removed by seed treatment and straw return), KS +KG (input equivalent K removed by straw and seed) and KC +S (conventional K fertilization and straw return) treatments, and the yield gap among different treatments expanded with the extension of planting years. There were significant differences present in rice and rape K uptake, although no differences in seed K uptake were observed under different K management strategies. The K balance was approximately maintained under KG +S and KS +KG treatments, and negative K balances were present for KN (no K application), KC (conventional fertilization), +S (straw return) and KS treatments (input equivalent K that removed by straw treatment). A positive balance was observed under KC +S treatment. Slight changes in soil exchangeable and nonexchangeable K were observed under KG +S and +S treatments. However, high inputs of K fertilizer prevented the improvement of agronomic efficiency and recovery efficiency of K. In summary, the optimal K management strategy was KG +S, which stabilizes the crop yield, maintains soil K fertility and maximizes K use efficiency. © 2020 Society of Chemical Industry.