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.

多样化的种植系统有利于植物的生长和产量，但它们对免耕 Oxisols 中钾预算和遗产的影响仍然知之甚少。本研究基于长期（19 年）田间试验，旨在评估种植系统多样化以及夏季玉米比例对作物产量、土壤钾形态、利用效率、预算的影响。 ，以及在巴西南部免耕条件下的亚热带 Rhodic Hapludox 中的遗留 K。对五种处理进行了评估：玉米和大豆继大麦的两次单一作物种植，以及夏季 21%、26% 和 47% 的玉米与大豆轮作的三种作物轮作，以及多达四种冬季作物（大麦、小麦、油菜籽和燕麦）。在第 19 年对土壤 (0-0.20 m) 进行采样，以确定土壤 K 形态，并检索所有钾肥和谷物产量记录以及初始土壤分析，并计算土壤钾积累、钾预算、钾利用效率和钾遗留。在过去的 19 年中，与单一种植相比，种植系统的多样化提高了大麦 (33%) 和玉米 (52%) 的产量，而通过增加夏季玉米的比例，观察到大豆产量增加了 10%。 0% 到 47%。由于夏季玉米比例较高，通过施肥增加钾输入是与观察到的土壤中潜在可用钾含量增加和 6 至 10 年遗留钾的潜在利用相关的主要因素。最大 K 预算（−160 kg ha 和 K 遗产被计算。在过去的 19 年中，与单一种植相比，种植系统的多样化提高了大麦 (33%) 和玉米 (52%) 的产量，而通过增加夏季玉米的比例，观察到大豆产量增加了 10%。 0% 到 47%。由于夏季玉米比例较高，通过施肥增加钾输入是与观察到的土壤中潜在可用钾含量增加和 6 至 10 年遗留钾的潜在利用相关的主要因素。最大 K 预算（−160 kg ha 和 K 遗产被计算。在过去的 19 年中，与单一种植相比，种植系统的多样化提高了大麦 (33%) 和玉米 (52%) 的产量，而通过增加夏季玉米的比例，观察到大豆产量增加了 10%。 0% 到 47%。由于夏季玉米比例较高，通过施肥增加钾输入是与观察到的土壤中潜在可用钾含量增加和 6 至 10 年遗留钾的潜在利用相关的主要因素。最大 K 预算（−160 kg ha 由于夏季玉米比例较高，通过施肥增加钾输入是与观察到的土壤中潜在可用钾含量增加和 6 至 10 年遗留钾的潜在利用相关的主要因素。最大 K 预算（−160 kg ha 由于夏季玉米比例较高，通过施肥增加钾输入是与观察到的土壤中潜在可用钾含量增加和 6 至 10 年遗留钾的潜在利用相关的主要因素。最大 K 预算（−160 kg ha^-1 ) 和利用效率（施用 114 kg 谷物 kg ^-1 K）通过将夏季的玉米-大豆比例 (50/50%) 与冬季作物的多样化相等而获得。根据我们的研究结果，在夏季插入玉米和大豆以及使冬季作物多样化是在亚热带农业中更有效地利用钾的关键。