Many studies haveexamined soil-borne nitrous oxide (N₂O) emissions from crops, but little effort has gone into determining the N₂O emissions from each phase of a crop rotation. A 4-yr study on a long-term field experiment compared growing season N₂O emissions from continuous corn (CC; Zea mays L.) and a 4-yr crop rotation involving corn (RC), oat (Avena Sativa L.) underseeded to alfalfa (Medicago sativa L.) (RO), and 2 yr of alfalfa (RA1, RA2). Molecular microbial biomass (DNA yield), as well as N-cycling functioning genes (mineralization, nitrification, and denitrification), were also evaluated. Although 4-yr cumulative N₂O emissions from RC (9.25 kg N ha^–1) were significantly greater than from CC (7.94 kg N ha^–1), cumulative emissions from the entire rotation were 54% lower (3.69 kg N ha^–1) than CC because of low emissions from RO (3.1 kg N ha^–1), RA1, and RA2 (1.11–1.27 kg N ha^–1). Years that had substantial early-season precipitation combined with high soil inorganic N from alfalfa plow-down contributed to elevated N₂O emissions from RC. Improved soil conditions and fertility under rotation increased RC grain yields by 35% (9.45 Mg ha^–1) compared with CC (7.01 Mg ha^–1). Microbial biomass was 73% greater in RC compared with CC. Nitrogen mineralization genes were 19% greater in RC but they were not correlated to N₂O emissions, whereas bacterial nitrifiers were positively correlated. Denitrification was likely responsible for N₂O emissions under CC, while nitrifier-denitrification appeared to be the primary pathway under RC. The N₂O emissions and microbial processes from all phases of a rotation should be considered for environmental modeling and policy decisions.

中文翻译：

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不同的轮作影响微生物过程、季节性和土壤中一氧化二氮的总体排放

许多研究已经检查了作物中土壤中一氧化二氮 (N ₂ O) 的排放量，但几乎没有努力确定作物轮作每个阶段的 N ₂ O 排放量。相比生长期N于长期田间试验A 4-YR研究₂从连续玉米O排放;（CC玉蜀黍（燕麦属）和4年的轮作涉及玉米（RC），燕麦苜蓿）。对苜蓿 ( Medicago sativa  L.) (RO) 和 2 年苜蓿 (RA1, RA2) 播种不足。还评估了分子微生物生物量（DNA 产量）以及 N 循环功能基因（矿化、硝化和反硝化）。尽管来自 RC 的4 年累积 N ₂ O 排放量（9.25 kg N ha^-1）比从CC显著更大（7.94千克Ñ公顷^-1），从整个旋转累积排放量为54％以下（3.69公斤Ñ公顷^-1）比，因为来自RO低排放（3.1千克氮公顷的CC ^{- 1} )、RA1 和 RA2 (1.11–1.27 kg N ha ^–1 )。早季降水量大的年份加上苜蓿犁耕产生的高土壤无机氮导致RC 的N ₂ O 排放量增加。改进的土壤条件和下旋转生育增加RC谷物产量35％（9.45镁公顷^-1与CC相比）（7.01镁公顷^-1）。与 CC 相比，RC 中的微生物生物量高出 73%。RC 中的氮矿化基因高 19%，但它们与 N ₂ O 排放无关，而细菌硝化菌呈正相关。反硝化作用可能是CC 下N ₂ O 排放的原因，而硝化菌-反硝化作用似乎是 RC 下的主要途径。环境建模和政策决策应考虑来自轮换所有阶段的 N ₂ O 排放和微生物过程。