Department of Biosystems Engineering & Soil Science, University of Tennessee, Knoxville, Tennessee, USA.
USDA-Agricultural Research Service, Agroecosystem Management Research Unit, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
mSphere. 2021 Jan 13;6(1):e01237-20. doi: 10.1128/mSphere.01237-20.
Soil microbial transformations of nitrogen (N) can be affected by soil health management practices. Here, we report 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] , , , , and ) in a long-term continuous cotton production system under different management practices (cover crops, tillage, and inorganic N fertilization). Hairy vetch ( 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 and were positively correlated to soil nitrous oxide (NO) emissions. We also found that the abundances of 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 soil N transformations under different agricultural seasons and soil management practices. Conservation agriculture practices that promote soil health have distinct and lasting effects on microbial populations involved with soil nitrogen (N) cycling. In particular, using a leguminous winter cover crop (hairy vetch) promoted the expression of key functional genes involved in soil N cycling, equaling or exceeding the effects of inorganic N fertilizer. Hairy vetch also left a legacy on soil nutrient capacity by promoting the continued activity of N cycling microbes after cover crop termination and into the main growing season. By examining both genes and transcripts involved in soil N cycling, we showed different responses of functional capacity (i.e., gene abundances) and functional activity (i.e., transcript abundances) to agricultural seasons and management practices, adding to our understanding of the effects of soil health management practices on microbial ecology.
土壤氮素（N）的微生物转化可受到土壤健康管理措施的影响。在这里，我们报告了在不同管理措施（覆盖作物、耕作和无机 N 施肥）下，长期连续棉花生产系统中参与土壤 N 循环的五个细菌基因（氨氧化细菌 [AOB]、、、、和）的种群大小（基因拷贝丰度）和功能活性（转录物拷贝丰度）的季节性动态。豆科覆盖作物毛野豌豆（Vicia villosa）最有效地促进了 N 循环基因的表达，这些基因在覆盖作物结束后整个生长季都持续存在。此外，在没有肥料的情况下，我们观察到与有肥料的情况下一样高甚至更高的 N 循环基因转录物丰度，在整个覆盖作物高峰期和棉花生长季节（4 月、5 月和 10 月）均如此。此外，和的基因和转录物丰度均与土壤氧化亚氮（NO）排放呈正相关。我们还发现，基因和转录物丰度均与田间和培养净硝化速率呈正相关。总之，我们的研究结果揭示了在不同农业季节和土壤管理措施下，微生物功能能力和活性与土壤 N 转化之间的关系。促进土壤健康的保护性农业实践对参与土壤氮（N）循环的微生物种群具有独特而持久的影响。特别是，使用豆科冬季覆盖作物（毛野豌豆）促进了与土壤 N 循环相关的关键功能基因的表达，其效果与无机 N 肥料相当或超过无机 N 肥料。毛野豌豆在覆盖作物结束后和主要生长季继续促进 N 循环微生物的活性，从而为土壤养分能力留下了遗产。通过检查参与土壤 N 循环的基因和转录物，我们展示了功能能力（即基因丰度）和功能活性（即转录物丰度）对农业季节和管理措施的不同响应，从而增加了我们对土壤健康管理措施对微生物生态学影响的理解。
