Cover crops improve soil fertility in orchard ecosystems, however, the response of soil microbial metabolism to fruit tree interactions with cover legumes at different stages of the life cycle remains uncertain, thereby limiting our understanding of the mechanisms that regulate nutrient cycling in orchards with cover crop management. Here, the characteristics of microbial energy (carbon, C) and nutrient (nitrogen, N or phosphorus, P) metabolism in the citrus rhizosphere and bulk soil in orchards were analyzed with two managements, that is, smooth vetch (Vicia villosa Roth var. glabresens Koch) cover and clean tillage, using an extracellular enzymatic stoichiometry model. Microbial C limitation was significantly reduced by cover during the vetch growing season owing to the resulting higher plant root C and soil organic C content. Competition for N between plants and microbes in the bulk soil might lead to significant microbial N limitation in covered orchards during the vetch-decomposition season, presumably owing to a significant increase in citrus root N and a concomitant decrease in bulk soil total N. Partial least squares path modeling showed that citrus root nutrient contents negatively affected microbial C limitation, while soil nutrients negatively affected microbial relative nutrient limitation in covered orchards. Conversely, both effects were reversed by tillage. Smooth vetch cover mitigated microbial C limitation, and the microbial relative N/P limitation was also influenced by the life state of smooth vetch. Our study highlights the importance of changes in microbial metabolism driven by seasonal nutrient dynamics for understanding soil nutrient cycling and optimizing cover-legumes management in orchards.

中文翻译：

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野豌豆的生命状态调节柑橘园微生物营养限制的季节动态

覆盖作物改善了果园生态系统的土壤肥力，然而，土壤微生物代谢对果树与覆盖豆科植物在生命周期不同阶段的相互作用的反应仍然不确定，从而限制了我们对覆盖作物果园养分循环调节机制的理解管理。本文以两种管理方式——野豌豆（Vicia villosa Roth var. glabresens Koch）使用细胞外酶化学计量模型进行覆盖和清洁耕作。由于在野豌豆生长季节进行覆盖，植物根部碳和土壤有机碳含量较高，因此微生物碳限制显着减少。在野豌豆分解季节，植物和微生物之间对大块土壤中氮的竞争可能会导致覆盖果园中微生物氮的显着限制，这可能是由于柑橘根氮的显着增加和大块土壤总氮的伴随减少。平方路径模型表明，柑橘根养分含量对微生物碳限制产生负面影响，而土壤养分对覆盖果园的微生物相对养分限制产生负面影响。相反，这两种效应都被耕作所逆转。野豌豆覆盖减轻了微生物 C 限制，微生物相对 N/P 限制也受到野豌豆生命状态的影响。我们的研究强调了季节性养分动态驱动的微生物代谢变化对于了解土壤养分循环和优化果园覆盖豆类管理的重要性。