Potassium (K) supplementation strategies are required to enhance farm productivity in rice-upland rotations, where intensive cultivation practices often result in K deficiencies. Straw return improves the adsorption of K by increasing the content of soil humic acid in macroaggregates. Iron/aluminium (Fe/Al) oxides promote soil organic carbon storage and aggregate stability by acting as binding agents. However, limited information is available on the effects of Fe/Al oxides on the distribution of aggregate-associated K stocks. A field experiment was performed in the Yangtze River Basin, an area with low K stemming from intensive cultivation, with four fertilization treatments: inorganic nitrogen-phosphorus fertilizer (NP), (NPK), inorganic NP with straw return (NP+St), and inorganic NPK with straw return (NPK+St). Results showed that the straw return (NP+St), K fertilization (NPK) and the combination of both (NPK+St) increased soil exchangeable K content (EK) by 32.6 %, 23.7 % and 53.6 % in the rice season, respectively, and increased by 49.9 %, 25.5 % and 182.0 % in the oilseed rape season, respectively, compared with that of no K addition (NP) treatment. K stocks in macroaggregates accounted for more than 90 % of the total K stocks in all treatments. Straw return and K fertilization increased EK and non-exchangeable K (NEK) stocks in large-macroaggregates (>2 mm) by increasing the aggregate-associated K content and regulating the abundance of aggregate. Redundancy analysis showed that complex iron oxide (Fep) was one of the main factors influencing soil available K. The NP+St and NPK+St treatments increased the proportion of particle size and K stocks by increasing the Fep content in large-macroaggregates. Pearson’s correlation analysis and random forest model analysis indicated that EK and NEK stocks in the large-macroaggregates were positively correlated with K uptake by rice and oilseed rape, which suggested that they were key factors influencing K uptake. Therefore, straw return increased Fep in large-macroaggregates to expand the K stock in soil and K uptake by crops under this field experiment conditions. Our results provided new insights with implications for improving soil K availability by straw return combined with K fertilization.

中文翻译：

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秸秆还田结合施钾肥通过增加稻-油菜轮作系统下复合氧化铁来提高大团聚体中钾的储量


在水稻-旱地轮作中，需要补充钾 （K） 策略来提高农场生产力，其中集约化种植实践通常会导致钾缺乏。秸秆还田通过增加土壤腐植酸在大团聚体中的含量来改善对钾的吸附。铁/铝 （Fe/Al） 氧化物通过充当粘合剂来促进土壤有机碳储存和团聚体稳定性。然而，关于 Fe/Al 氧化物对聚集体相关 K 原料分布的影响的信息有限。在集约化耕作低钾素地区长江流域进行了田间试验，施用无机氮磷肥（NPK）、秸秆还田（NPK+St）、秸秆还田无机NPK（NPK+St）四种施肥处理。结果表明，秸秆还田 （NP+St）、施钾 （NPK） 和两者合用 （NPK+St） 使稻季土壤交换钾含量 （EK） 分别增加了 32.6 %、23.7 % 和 53.6 %，油菜季分别增加了 49.9 %、25.5 % 和 182.0 %。宏观骨料中的 K 储量占所有处理中 K 储量总量的 90 % 以上。秸秆还田和施钾通过增加团聚体相关钾含量和调节团聚体丰度，增加了大团聚体 （>2 mm） 中的 EK 和不可交换的 K （NEK） 储量。冗余分析表明，复合氧化铁 （Fep） 是影响土壤速效钾的主要因素之一。NP+St 和 NPK+St 处理通过增加大团聚体中 Fep 含量来提高粒径和 K 存量的比例。 Pearson's 相关分析和随机森林模型分析表明，大团聚体中 EK 和 NEK 储量与水稻和油菜对钾的吸收呈正相关，表明它们是影响 K 吸收的关键因子。因此，在该田间试验条件下，秸秆还田增加了大团聚体中 Fep 以扩大土壤中 K 储量和作物对 K 的吸收。我们的结果为通过秸秆还田结合钾肥来提高土壤钾有效性提供了新的见解。