Nitrogen (N) management is a critical agronomic challenge, as N losses are a source of pollution affecting both waterways and air quality and a potential economic loss for farmers. One approach to N conservation is through ecologically based agricultural systems that reduce tillage and incorporate cover crops. However, these systems exhibit considerable complexity resulting in potential agronomic trade‐offs. To address these concerns, four crop management systems were implemented within an organically managed corn–soy–winter grain crop rotation. These systems varied in tillage frequency and intensity, cover crop species selection, cover crop termination and establishment methods, fertilizer management, and cash crop season length. We used field measurements to investigate the impact of each system on N pools and to reveal the strengths and weaknesses of each system in addressing N provisioning services, with a focus on the supply and retention of N before and after the corn phase of the rotation. All systems had greater estimated N inputs (via manure and N‐fixation) than outputs (via crop harvest) at the end of the three‐year rotation, demonstrating the importance of prioritizing N retention in cover crops. Interactions among system components were important drivers of temporal N dynamics; cover crop species traits and timing of manure application contributed to differences in total aboveground plant biomass N among systems. For example, one cropping system which included a no‐till corn planting into a rolled cover crop mulch had soil inorganic N availability that was asynchronous with the N needs of the corn crop even though it received the same amount of N inputs as the other systems. In general, neither interseeding cover crop mixtures nor reducing tillage resulted in marked N benefits at the system level; we did not observe improved N retention from either practice in these systems, and there was no increase in N uptake by corn. What did clearly emerge from this experiment is the importance of managing for synchrony between soil inorganic N availability and cash crop N demand as influenced by the N retention capacity of cover crops and the timing of N mineralization due to tillage.

中文翻译：

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结合多种基于生态的管理策略的谷物种植系统中的氮动态

氮的管理是一项重要的农艺挑战，因为氮的损失是影响水道和空气质量的污染源，也是农民的潜在经济损失。氮素保护的一种方法是通过基于生态的农业系统来减少耕作并种植有盖作物。但是，这些系统显示出相当大的复杂性，从而导致潜在的农艺折衷。为了解决这些问题，在有机管理的玉米-大豆-冬季谷物轮作中实施了四个作物管理系统。这些系统在耕作频率和强度，覆盖作物种类，覆盖终止和建立方法，肥料管理和经济作物季节长度等方面各不相同。我们使用现场测量来调查每个系统对N个库的影响，并揭示每个系统在解决N个提供服务方面的优势和劣势，重点是玉米轮换阶段之前和之后的N的供应和保留。在三年轮换结束时，所有系统的估计氮输入量（通过肥料和固氮）都比输出量（通过作物收获）大，这说明了在覆盖作物中优先保留氮的重要性。系统组件之间的交互是时间N动态的重要驱动力；覆盖作物的性状和施用肥料的时间造成了系统间地上植物总生物量氮的差异。例如，一个包括将免耕玉米种植到覆盖的农作物覆盖物中的耕作系统，其土壤无机氮的有效性与玉米作物的氮需求是不同步的，即使它获得的氮输入量与其他系统相同。总的来说，在系统层面上，既不种植覆盖作物的混合物，也不减少耕作不会导致显着的氮素收益。我们在这两种系统中都没有观察到任何一种实践都能改善氮素的保留，玉米的氮素吸收没有增加。从该实验中可以清楚地看出，管理土壤无机氮的有效性与经济作物氮素需求同步的重要性，这要受到覆盖作物的氮素保持能力和耕作导致的氮矿化时间的影响。