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

Diversified cropping systems can benefit plant growth and yield, but their impacts on K budget and legacy in notill 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 notill 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.

Automated summary

Diversifying cropping systems can increase barley and maize yields, with a 10% increase in soybean yield by increasing the proportion of maize in the summer. Increasing K input through fertilization due to higher maize proportion in summer leads to higher potentially available K content in soil and legacy K use efficiency. Maximum K budget and use efficiency are achieved by equal proportions of maize and soybean in summer and diversifying winter crops.