Cover crops are promoted to improve soil health and soil carbon (C) sequestration in agroecosystems, yet responses of various soil organic carbon (SOC) and nitrogen (N) components to cover cropping have not been quantified for water-limited environments. This study evaluated the response of SOC and N components to different cover crops and mixtures in limited irrigation winter wheat (Triticum aestivum L.)-sorghum (Sorghum bicolor L. Moench)-fallow rotation. Cover cropping treatments included pea (Pisum sativum L.), oats (Avena sativa L.), and canola (Brassica napus L.); mixtures of pea + oats (POmix), pea + canola (PCmix), pea + oats + canola (POCmix), and a six-species mixture (SSmix) of pea + oats + canola + hairy vetch (Vicia villosa Roth) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.); and a fallow. Cover crop treatments were arranged in a randomized complete block design within each phase of the crop rotation. Soil samples were collected in the summer of 2019 and 2020 from the 0–15 cm depth of study plots established in fall 2015 and analyzed for various soil organic matter (SOM) components. Soil inorganic N was 7–36% lower with cover crops than fallow. The PCmix had 48–73% greater 24-h-carbon dioxide-carbon (CO₂-C) than fallow, canola, and SSmix at termination time. Thirty-six days after termination, particulate organic carbon (OC) content was 61–69% higher with pea, SSmix, and POCmix than fallow. The SOC content was 9.3–22% greater with oats than pea, canola, POmix, and SSmix. Similarly, total N content with oats was 10% and 22% higher than with SSmix and canola, respectively. The increase in SOC and total N were primarily observed in intermediate-size aggregates (250 μm–2 mm and 53–250 μm). However, the minimum data set of soil health included SOC, soil pH, labile organic nitrogen (LON), mineral-associated organic nitrogen (MAON), and microbial biomass carbon (MBC). While this study showed a diverse response of SOC and N components to various cover crop treatments, oats and their mixture as cover crops had greater SOC and total N than other cover crops. Cover cropping could improve soil health in crop-fallow rotations in water-limited environments.

促进覆盖作物以改善农业生态系统中的土壤健康和土壤碳 (C) 固存，但尚未量化各种土壤有机碳 (SOC) 和氮 (N) 成分对缺水环境中覆盖作物的响应。本研究评估了 SOC 和 N 组分对有限灌溉冬小麦 ( Triticum aestivum L.)-高粱 ( Sorghum bicolor L. Moench)-休耕轮作中不同覆盖作物和混合物的响应。覆盖作物处理包括豌豆 ( Pisum sativum L.)、燕麦 ( Avena sativa L.) 和油菜 ( Brassica napus)L.); 豌豆 + 燕麦 (POmix)、豌豆 + 双低油菜籽 (PCmix)、豌豆 + 燕麦 + 双低油菜籽 (POCmix) 的混合物，以及豌豆 + 燕麦 + 双低油菜籽 + 紫云英 ( Vicia villosa Roth) + 草料的六种混合物 (SSmix)萝卜 ( Raphanus sativus L.) + 大麦 ( Hordeum vulgare L.); 和休耕。在轮作的每个阶段内，覆盖作物处理以随机完整区组设计排列。土壤样品于 2019 年和 2020 年夏季从 2015 年秋季建立的 0-15 厘米深度的研究地块中收集，并分析了各种土壤有机质 (SOM) 成分。覆盖作物的土壤无机氮比休耕作物低 7-36%。PCmix 的 24 小时二氧化碳-碳（CO ₂-C) 在终止时间比休耕、油菜和 SSmix。终止后 36 天，豌豆、SSmix 和 POCmix 的颗粒有机碳 (OC) 含量比休耕高 61-69%。燕麦的 SOC 含量比豌豆、油菜、POmix 和 SSmix 高 9.3-22%。同样，燕麦的总氮含量分别比 SSmix 和油菜籽高 10% 和 22%。SOC 和总氮的增加主要在中等大小的聚集体（250 μm-2 mm 和 53-250 μm）中观察到。然而，土壤健康的最小数据集包括 SOC、土壤 pH 值、不稳定有机氮 (LON)、矿物相关有机氮 (MAON) 和微生物生物量碳 (MBC)。虽然这项研究显示 SOC 和 N 成分对各种覆盖作物处理的不同反应，但作为覆盖作物的燕麦及其混合物比其他覆盖作物具有更高的 SOC 和总氮。