AMF species groups and species in each group.

Incorporating cover crops into the rotation is a practice applied across many parts of the globe to enhance soil biological activities. In dryland farming, where crop production is highly dependent on rainfall and soil water storage, cover cropping can affect soil water, yet its effects on soil hydrological and biological health require further investigation. The objective of this study was to evaluate the effect of different timing of summer sorghum cover crop termination on soil water, total and labile organic carbon, arbuscular mycorrhizal fungi and their mediating effects on wheat yield. Through on-farm trial, soil characteristics along with wheat biomass, yield and grain quality were monitored. In comparison with the control (fallow), the early terminated cover crop was the most effective at retaining greater soil water at wheat sowing by 1~4% in 0–45cm soil profile. An increase in water use efficiency, yield and grain protein by 10%, 12% and 5% was observed under early termination. Under late terminated summer cover crop, there was 7% soil water depletion at wheat planting which resulted in 61% decline in yield. However, late-terminated cover crop achieved the greatest gain in soil total and particulate organic carbon by 17% and 72% and arbuscular mycorrhizal fungal Group A and B concentration by 356% and 251%. Summer cover crop incorporation resulted in a rapid gain in labile organic carbon, which constituted hotspots for arbuscular mycorrhizal fungi growth, conversely, fungal activities increased labile organic carbon availability. The combined effect of increased soil water at sowing and over the growing season, organic carbon, and microbial activities contributed to greater yield. The findings suggest that summer cover cropping with timely termination can have implications in managing soil water at sowing time and enhancing soil water storage during the season, soil carbon, and facilitating microbial activities while enhancing productivity in the dryland cropping system.

将覆盖作物（cover crops）纳入轮作体系，是全球诸多地区广为采用的提升土壤生物活性的耕作措施。在旱地农业中，作物生产高度依赖降雨与土壤储水，覆盖作物种植会对土壤水分产生影响，但其对土壤水文与生物健康的作用仍需进一步探究。本研究旨在评估不同夏高粱覆盖作物翻压时机对土壤水分、总有机碳与易变有机碳、丛枝菌根真菌（arbuscular mycorrhizal fungi）的影响，及其对小麦产量的介导作用。通过田间试验，本研究监测了土壤性状、小麦生物量、产量与籽粒品质。与休耕（fallow）对照组相比，提前翻压的覆盖作物在小麦播种时0~45厘米土层的土壤储水量提升效果最为显著，增幅达1%~4%。提前翻压处理下，水分利用效率、产量与籽粒蛋白质含量分别提升10%、12%与5%。而晚翻压夏季覆盖作物处理在小麦播种时土壤水分消耗达7%，进而导致产量下降61%。但晚翻压覆盖作物可使土壤总有机碳与颗粒有机碳分别提升17%与72%，丛枝菌根真菌A组与B组的浓度分别提升356%与251%，增幅最为显著。夏季覆盖作物还田可快速提升易变有机碳含量，而该物质恰为丛枝菌根真菌生长的热点区域；反之，真菌活动亦可提升易变有机碳的有效性。播种时土壤储水量提升、生育期内土壤储水优化、有机碳积累与微生物活性增强的综合作用，共同促成了更高的产量。本研究结果表明，适时翻压夏季覆盖作物，可在旱地种植体系中实现播种期土壤水分调控、生育期土壤储水提升、土壤碳库改善与微生物活性促进，同时提升作物生产能力。