Effect of diversified cropping systems on crop yield, legacy, and budget of potassium in a subtropical Oxisol

Abstract

Diversified cropping systems can benefit plant growth and yield, but their impacts on K budget and legacy in no-till Oxisols are still poorly understood. This study, based on a long-term (19-years) field experiment, aimed to evaluate the effect of cropping system diversification as well as the proportion of maize in summer season on crop yields, and on soil K forms, use efficiency, budget, and legacy K in a subtropical Rhodic Hapludox under no-till in Southern Brazil. Five treatments were evaluated: two monocropping of maize and soybean in sucession to barley, and three crop rotations with 21%, 26% and 47% of maize in rotation with soybean in summer, combined with up to four winter crops (barley, wheat, canola, and oat). Soil (0–0.20 m) was sampled at the 19th year for determination of soil K forms, and all records of K fertilization and grain yields, as well as the initial soil analysis, were retrieved, and soil K accumulation, K budget, K usage efficiency, and K legacy were calculated. Across the 19-years and in comparison to monocropping, the diversification of cropping systems increased barley (33%) and maize (52%) yields, while a 10% increment was observed for soybean yield by increasing the proportion of maize in summer season from 0% to 47%. Increasing K input via fertilization as a consequence of the higher proportion of maize in summer was the main factor related to observed increment on potentially available K content in soil and on the potential use of legacy K from 6 to 10 years. Maximum K budget (−160 kg ha −1 ) and use efficiency (114 kg grains kg −1 K applied) were obtained by equating maize-soybean proportion (50/50%) in summer and diversifying winter crops. According to our findings, intercalating maize and soybean in summer and diversifying winter crops are the key for using K more efficiently in subtropical agriculture. • Cropping system diversification increases crops grain yield. • Equating maize-soybean proportion (50/50%) increment the K budget. • Diversifying crops is the key for using K more efficiently in subtropics.