Cover crops are an important component of sustainable cereal cropping systems by providing nutrient retention and improving soil quality. However, the successful establishment and growth of cover crops depend on a timely harvest of the preceding annual crops. To assess the viability of growing cover crops in Denmark, a phenology model was developed, calibrated, cross-validated and applied to predict the harvest date of spring barley and winter wheat in Denmark using data from field experiments in Denmark during 1991 to 2018. A simple phenology model was used for the period from sowing to maturity, and this was extended to simulate the duration from maturity to harvest. This extended model was used to predict the harvest date in the ongoing season, and it provides the capability for assessing the performance of cover crops as a basis for improved cover crop management. The model uses temperature sums and day length to calculate the developmental rate of spring barley from sowing to harvest and for winter wheat from 1st January to harvest. The standard deviation of the estimated harvest date based on the uncertainty of the model parameters was 10-14 days and 1-4 days for spring barley and winter wheat, respectively. The model was evaluated using historically recorded temperature data (20 years, 1999–2018) to simulate harvest date, which was within the range of observed harvest dates. The interannual range of estimated harvest dates is 7–10 days for spring barley and 5–10 days for winter wheat. This interannual variation of harvest date was lower than the spatial variation across the country. The model can be used for forecasting cereal harvest time and thus readiness for autumn field operations, including the establishment of cover crops. Simulations of growing degree days from date of harvest to 1 November shows that cover crops can be reliably established in southern parts of Denmark to ensure low nitrate leaching. Advancing the harvest date to the date of physiological maturity of the cereals would allow the establishment of efficient cover crops in all years in the entire country.

覆盖作物通过提供养分并改善土壤质量，是可持续谷物种植系统的重要组成部分。但是，覆盖作物的成功建立和生长取决于对先前一年生作物的及时收获。为了评估丹麦生长的覆盖作物的生存力，使用了1991年至2018年丹麦田间试验的数据，开发了一个物候模型，对其进行了校正，交叉验证并用于预测丹麦春季大麦和冬小麦的收获日期。从播种到成熟期使用简单的物候模型，并将其扩展以模拟从成熟到收获的持续时间。该扩展模型用于预测当前季节的收获日期，它提供了评估覆盖作物性能的能力，可以作为改善覆盖作物管理的基础。该模型使用温度总和和日长来计算从播种到收获的春季大麦以及从1月1日到收获的冬小麦的发育速率。基于模型参数的不确定性，估计收获日期的标准差分别为春大麦和冬小麦为10-14天和1-4天。使用历史记录的温度数据（20年，1999-2018年）对模型进行评估，以模拟收获日期，该日期在观察到的收获日期范围内。春季大麦的估计收获期的年际范围是7-10天，冬小麦的估计收获期的年际范围是5-10天。收获日期的年际变化低于全国的空间变化。该模型可用于预测谷物收割时间，从而可以为秋田作业做好准备，包括建立覆盖作物。从收获之日到11月1日的生长日数的模拟表明，可以可靠地在丹麦南部建立覆盖作物，以确保低硝酸盐浸出。将收获日期提前到谷物的生理成熟日期，将可以在整个国家的所有年份建立有效的覆盖作物。