Nitrate leaching from agricultural soils is a considerable environmental concern related to nitrogen (N) application, and in some countries N fertilizer application is regulated by legislation to reach environmental goals. Information about the change in nitrate leaching with changes in mineral N fertilizer rates is important under such conditions. The increase in nitrate leaching due to extra mineral N application near the economic optimal N application for crop production, called marginal nitrate leaching, depends on a number of factors like soil type, crop types, climatic conditions and N fertilization rates. In this study, we collected published experimental data from 44 site-years from Denmark and 31 site-years from other European countries (Germany, Sweden, UK) with measured nitrate leaching at increasing mineral N fertilizer rates. We focused on obtaining marginal nitrate leaching around optimal N rates based on available information from the different field experiments. The measured nitrate leaching varied from 3 to 92 kg N ha^-1 in the Danish dataset. For the European data set, it varied from 1 to 124 kg N ha^-1. The median and mean of the estimated marginal nitrate leaching at the optimal N rates were 17.0% and 20.5%, respectively, in the Danish dataset and 9.0% and 14.9%, respectively, in the European dataset. At the optimal N rate, a positive relationship was found between yearly nitrate leaching and marginal nitrate leaching. Both nitrate leaching and marginal nitrate leaching at the optimal N rate were positively correlated with precipitation during the hydrological year and winter periods, but not to any other environmental factors tested. There was no significant difference in either marginal nitrate leaching or nitrate leaching between growing spring cereals versus winter cereals. No significant effect of winter vegetation cover on marginal nitrate leaching was detected. Furthermore, the marginal nitrate leaching at the optimal N rate in the first year of the experiments with increasing N rates was significantly lower than the accumulated effect of two or more years with low or high N rates. Therefore, the long-term effects of N rates should be accounted for when estimating marginal nitrate leaching. The marginal nitrate leaching is highly variable between years and only a part of this variation was explained in this study. The positive correlation between marginal nitrate leaching and nitrate leaching at optimum N rates implies that cropping system and management factors reducing nitrate leaching also reduce the marginal nitrate leaching.

从农业土壤中浸出的硝酸盐是与氮 (N) 应用相关的一个相当大的环境问题，在一些国家，氮肥的应用受立法监管以达到环境目标。在这种情况下，有关硝酸盐浸出随矿物氮肥用量变化的变化的信息很重要。由于在作物生产的经济最佳施氮附近施用额外的矿物氮而导致的硝酸盐浸出增加，称为边际硝酸盐浸出, 取决于许多因素，如土壤类型、作物类型、气候条件和施氮率。在这项研究中，我们收集了来自丹麦 44 个地点年和其他欧洲国家（德国、瑞典、英国）的 31 个地点年的已发表实验数据，这些数据在增加矿物氮肥施用率时测量了硝酸盐浸出。我们专注于根据来自不同田间实验的可用信息获得最佳 N 率附近的边际硝酸盐浸出率。在丹麦数据集中，测得的硝酸盐浸出量从 3 到 92 kg N ha ^-1不等。对于欧洲数据集，从 1 到 124 kg N ha ^-1. 在最佳 N 率下估计的边际硝酸盐浸出率的中位数和平均值在丹麦数据集中分别为 17.0% 和 20.5%，在欧洲数据集中分别为 9.0% 和 14.9%。在最佳 N 率下，年硝酸盐浸出量和边际硝酸盐浸出量之间存在正相关关系。最佳 N 率下的硝酸盐浸出和边际硝酸盐浸出均与水文年和冬季期间的降水呈正相关，但与任何其他测试的环境因素无关。生长的春季谷物与冬季谷物之间的边际硝酸盐浸出或硝酸盐浸出没有显着差异。未检测到冬季植被覆盖对边缘硝酸盐浸出的显着影响。此外，提高施氮量试验的第一年最佳施氮量下的边际硝酸盐浸出显着低于低或高施氮量两年或两年以上的累积效应。因此，在估算边际硝酸盐浸出时，应考虑 N 率的长期影响。不同年份的边际硝酸盐浸出量变化很大，本研究仅解释了这种变化的一部分。边际硝酸盐浸出与最佳 N 比率下的硝酸盐浸出之间的正相关意味着减少硝酸盐浸出的种植制度和管理因素也减少了边际硝酸盐浸出。在估算边际硝酸盐浸出时，应考虑 N 率的长期影响。不同年份的边际硝酸盐浸出量变化很大，本研究仅解释了这种变化的一部分。边际硝酸盐浸出与最佳 N 比率下的硝酸盐浸出之间的正相关意味着减少硝酸盐浸出的种植制度和管理因素也减少了边际硝酸盐浸出。在估算边际硝酸盐浸出时，应考虑 N 率的长期影响。不同年份的边际硝酸盐浸出量变化很大，本研究仅解释了这种变化的一部分。边际硝酸盐浸出与最佳 N 比率下的硝酸盐浸出之间的正相关意味着减少硝酸盐浸出的种植制度和管理因素也减少了边际硝酸盐浸出。