Soil microbial transformations of nitrogen (N) can be affected by soil health management practices. Here, we report in situ seasonal dynamics of the population size (gene copy abundances) and functional activity (transcript copy abundances) of five bacterial genes involved in soil N cycling (ammonia-oxidizing bacteria [AOB] amoA, nifH, nirK, nirS, and nosZ) in a long-term continuous cotton production system under different management practices (cover crops, tillage, and inorganic N fertilization). Hairy vetch (Vicia villosa Roth), a leguminous cover crop, most effectively promoted the expression of N cycle genes, which persisted after cover crop termination throughout the growing season. Moreover, we observed similarly high or even higher N cycle gene transcript abundances under vetch with no fertilizer as no cover crop with N fertilization throughout the cover crop peak and cotton growing seasons (April, May, and October). Further, both the gene and transcript abundances of amoA and nosZ were positively correlated to soil nitrous oxide (N₂O) emissions. We also found that the abundances of amoA genes and transcripts both positively correlated to field and incubated net nitrification rates. Together, our results revealed relationships between microbial functional capacity and activity and in situ soil N transformations under different agricultural seasons and soil management practices.

中文翻译：

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土壤健康管理增强微生物氮循环能力和活动

土壤微生物对氮 (N) 的转化会受到土壤健康管理实践的影响。在这里，我们报告了参与土壤氮循环的五种细菌基因（氨氧化细菌 [AOB] amoA、nifH、nirK、nirS、和nosZ）在不同管理措施（覆盖作物、耕作和无机氮肥）下的长期连续棉花生产系统中。多毛野豌豆 ( Vicia villosaRoth) 是一种豆科覆盖作物，最有效地促进了 N 循环基因的表达，该基因在覆盖作物终止后在整个生长季节持续存在。此外，我们在整个覆盖作物高峰期和棉花生长季节（4 月、5 月和 10 月）观察到，在没有施肥的野豌豆下，与没有施氮的覆盖作物相似，高或什至更高的 N 循环基因转录本丰度。此外，amoA和nosZ的基因和转录本丰度都与土壤一氧化二氮 (N ₂ O) 排放呈正相关。我们还发现amoA的丰度基因和转录本均与田间和孵化后的净硝化率呈正相关。总之，我们的结果揭示了微生物功能能力和活动与不同农业季节和土壤管理实践下土壤原位氮转化之间的关系。