Accurate estimation of crop net primary production (NPP) and yields is fundamental for regional analyses of agroecosystem dynamics using process‐based models. In this study, we simulated croplands in the contiguous U.S. using the DayCent ecosystem model with new production algorithms. Crops were divided into crop variety groups based on regional varieties of three major crops (corn, soybeans, and winter wheat) and generic parameter values that were generated for each group. These varieties have been developed through crop breeding programs and enhance production of major crop types in different temperature and precipitation regimes. NPP and yields for the three major crops were evaluated at the county level with reported yields from the National Agricultural Statistics Service (NASS). The predictions of the multiyear average yields in all counties were more accurate than most other published results using process‐based models. DayCent predictions of yields produced an overall R ² of 0.54, 0.54, and 0.38 for corn, soybean, and winter wheat, respectively, with predictions for most counties within ±20% of the NASS reported yields. Our estimations of the total annual NPP for the three crops in the contiguous U.S. are 0.24, 0.09, and 0.06 Pg C yr⁻¹ for corn, soybean, and winter wheat, respectively. Together, they contribute 7.3% to 14.8% of the total NPP for all vegetation in the contiguous U.S. We conclude that crop variety groups capture heterogeneity in NPP for major crop types and can improve biogeochemical model predictions of NPP for croplands.

中文翻译：

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美国连续农田的NPP和粮食产量的DayCent模型预测

使用基于过程的模型，准确估算农作物净初级生产（NPP）和单产对于进行农业生态系统动态区域分析至关重要。在这项研究中，我们使用具有新生产算法的DayCent生态系统模型模拟了美国连续的农田。根据三种主要农作物（玉米，大豆和冬小麦）的区域品种以及为每个组生成的通用参数值，将农作物分为农作物品种组。通过作物育种计划开发了这些品种，并在不同的温度和降水方式下提高了主要作物的产量。根据国家农业统计局（NASS）的报告产量，在县一级对三种主要农作物的NPP和产量进行了评估。使用基于过程的模型，对所有县的多年平均收益率的预测要比大多数其他已发布的结果更为准确。DayCent对收益的预测产生了总体玉米，大豆和冬小麦的R ^2分别为0.54、0.54和0.38，大多数县的预测都在NASS报告的单产的±20％之内。我们估计美国连续三种作物的玉米，大豆和冬小麦的年总NPP分别为0.24、0.09和0.06 Pg C yr ^-1。它们在一起为美国连续的所有植被贡献了总NPP的7.3％至14.8％。我们得出结论，农作物品种组捕获了主要农作物类型的NPP异质性，可以改善农田NPP的生物地球化学模型预测。