Growing cover crops is one of the most promising conservation practices with multiple benefits. However, the impacts of cover crops on the productivity of the maize-soybean [Zea mays L. - Glycine max (L.) Merr.] rotation system in the U.S. Midwest still have large uncertainties based on results obtained from field experiments, specifically across different soil properties, climate conditions, and land management practices. Process-based models fully validated with data from field experiments across these diverse conditions provide an effective tool to quantify cover crop impacts on cash crop productivity and optimize the management of cover crops accordingly. In this study, we aim to answer the following questions: (1) What are the impacts of cover crops on cash crop yield in the U.S. Midwest agroecosystems? (2) What are the mechanistic pathways of cover crop to affect cash crop yield (e.g. through influencing soil water, nitrogen and O₂ dynamics)? (3) What management practices can be used to mitigate the negative impacts on cash crop yield caused by cover crops? To address these questions, we calibrated and validated a sophisticated process-based agroecosystem model, ecosys, using field experimental data from 2013 to 2018 across Illinois, and then used ecosys to assess the impacts of winter cover crops on maize and soybean yield under different management practices. Our study revealed the following findings: (1) planting non-legume cover crops can cause 3.9 ± 3% yield reduction for maize and no significant impacts on soybean yield, while planting legume cover crops has no significant impact on the yield of either maize or soybean; (2) the maize yield reduction caused by planting cover crops can be mainly explained by nitrogen deficiency induced by increased immobilization, water competition in dry areas, cooler soil surface and oxygen competition; (3) later termination of non-legume cover crops before maize can result in larger maize yield loss due to intensive competition for resources (e.g. water and nitrogen), and the impacts of non-legume cover crops on maize yield reduction can be minimized by optimizing cover crop termination time in the spring. Overall, in the U.S. Midwestern maize-soybean rotation system, we found that although non-legume cover crops cause yield reduction for maize through resource competition, this yield reduction can be minimized through management practices, such as controlling termination time of cover crop and proper fertilizer management.

种植覆盖作物是最有前途的保护措施之一，具有多重效益。然而，覆盖作物对玉米-大豆生产力的影响 [ Zea mays L. - Glycine max(L.) Merr.] 美国中西部的轮作系统仍然存在很大的不确定性，这是基于田间试验的结果，特别是在不同的土壤特性、气候条件和土地管理实践中。基于过程的模型在这些不同条件下的田间试验数据得到充分验证，提供了一种有效的工具，可以量化覆盖作物对经济作物生产力的影响，并相应地优化覆盖作物的管理。在本研究中，我们旨在回答以下问题：（1）覆盖作物对美国中西部农业生态系统的经济作物产量有何影响？(2) 覆盖作物影响经济作物产量的机制途径是什么（例如通过影响土壤水、氮和O ₂动力学）？(3) 可以采用哪些管理措施来减轻覆盖作物对经济作物产量的负面影响？为了解决这些问题，我们使用伊利诺伊州 2013 年至 2018 年的田间实验数据校准并验证了一个复杂的基于过程的农业生态系统模型ecosys，然后使用了ecosys评估冬季覆盖作物在不同管理方式下对玉米和大豆产量的影响。我们的研究揭示了以下发现：（1）种植非豆科覆盖作物会导致玉米减产 3.9±3%，对大豆产量没有显着影响，而种植豆类覆盖作物对玉米或玉米的产量没有显着影响。大豆；(2) 种植覆盖作物引起的玉米减产主要是由于固定化增加、干旱地区水分竞争、土壤表面较冷和氧气竞争引起的缺氮；(3) 由于对资源（例如水和氮）的激烈竞争，在玉米之前后期终止非豆科覆盖作物会导致更大的玉米产量损失，通过优化春季覆盖作物的终止时间，可以最大限度地减少非豆科覆盖作物对玉米减产的影响。总体而言，在美国中西部玉米-大豆轮作系统中，我们发现虽然非豆科覆盖作物通过资源竞争导致玉米减产，但这种减产可以通过管理措施最小化，例如控制覆盖作物的终止时间和适当的肥料管理。