Abstract Cover crops are promoted to increase soil organic carbon (SOC) storage and improve soil biological health in agricultural systems. However, cover crop effects on soil microbial communities – key regulators of SOC and nutrients – and functioning are not clear in semiarid environments. This study investigated the response of soil microbial community structure and enzyme activities to cover crop integration under limited-irrigation winter wheat (Triticum aestivum)-sorghum (Sorghum bicolor)-fallow rotation. The study had a randomized complete block design with eight treatments and three replications. Treatments were pea (Pisum sativum); oat (Avena sativa); canola (Brassica napus L.); and mixtures of pea + oat (POmix), pea + canola (PCmix), pea + oat + canola (POCmix), and pea + oat + canola + hairy vetch (Vicia villosa) + forage radish (Raphanus sativus L.) + barley (Hordeum vulgare L.) (diverse-mix) as cover crops; and a fallow. Soil samples were collected in the summer of 2017 and 2018 from 0 to 15 cm depth of each plot established in fall 2015. Microbial community size and structure were evaluated via ester-linked fatty acid methyl ester (EL-FAME) analysis, which showed that total microbial community size and fungal community were similar between soils under oats and diverse-mix, and were 31% and 41% greater than fallow, respectively. The FAME marker for arbuscular mycorrhizal fungi (AMF) was 84% greater under oats than fallow. The combined enzyme activity of acid phosphatase, β-glucosidase, and β-glucosaminidase was 294 mg p-nitrophenol (PNP) kg−1 soil h−1 under diverse-mix, which was greater than fallow (204 mg PNP kg−1 soil h−1, p = 0.021) in 2018. Cover cropping during fallow period in a crop-fallow rotation could increase total microbial community size, fungal abundance, and enzyme activities associated with carbon (C) and nutrient cycling. Among cover crops, oat and its mixture with legumes (pea and hairy vetch) and brassicas (canola and forage radish) were most effective in improving soil health and biogeochemical cycling in a hot and dry semiarid climate.

中文翻译：

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覆盖作物生物量和物种组成影响半干旱作物系统中土壤微生物群落结构和酶活性

摘要 促进覆盖作物以增加土壤有机碳 (SOC) 储存并改善农业系统中的土壤生物健康。然而，在半干旱环境中，覆盖作物对土壤微生物群落（SOC 和养分的关键调节剂）和功能的影响尚不清楚。本研究调查了在限制灌溉的冬小麦 (Triticum aestivum)-高粱 (Sorghum bicolor)-休耕轮作下土壤微生物群落结构和酶活性对覆盖作物整合的响应。该研究采用随机完整区组设计，包括 8 个处理和 3 个重复。处理是豌豆（Pisum sativum）；燕麦（Avena sativa）；油菜（Brassica napus L.）；以及豌豆 + 燕麦 (POmix)、豌豆 + 油菜籽 (PCmix)、豌豆 + 燕麦 + 油菜籽 (POCmix) 的混合物，豌豆 + 燕麦 + 油菜籽 + 多毛紫云英 (Vicia villosa) + 草料萝卜 (Raphanus sativus L.) + 大麦 (Hordeum vulgare L.)（多种混合）作为覆盖作物；和休耕。在 2017 年和 2018 年夏季从 2015 年秋季建立的每个样地的 0 至 15 厘米深度收集土壤样品。通过酯连接脂肪酸甲酯 (EL-FAME) 分析评估微生物群落大小和结构，结果表明：燕麦和多样化混合土壤之间的总微生物群落大小和真菌群落相似，分别比休耕土壤大 31% 和 41%。丛枝菌根真菌 (AMF) 的 FAME 标记在燕麦下比休耕高 84%。酸性磷酸酶、β-葡萄糖苷酶和 β-氨基葡萄糖苷酶的综合酶活性为 294 mg 对硝基苯酚 (PNP) kg-1 kg-1 土壤 h-1 在不同混合条件下，大于 2018 年的休耕（204 毫克 PNP kg−1 土壤 h−1，p = 0.021）。休耕轮作期间的覆盖作物可以增加总微生物群落大小、真菌丰度和酶活性。碳（C）和养分循环。在覆盖作物中，燕麦及其与豆类（豌豆和多毛野豌豆）和芸苔属植物（油菜和草料萝卜）的混合物在炎热干燥的半干旱气候中对改善土壤健康和生物地球化学循环最有效。