Overuse of chemical fertiliser in cereal cropping systems has resulted in severe degradation of air and water quality. Diversifying cropping sequence with legumes provides a natural source of nitrogen (N), but also increases N leaching risks after their growing period. Here, we hypothesize that legumes and other break crops, i.e., crops grown to diversify the cropping sequence, reduce N leaching at the rotation scale due to their contribution to increasing nutrient use efficiency and crop N recovery of the following cereal crops. In two 4-year experiments conducted in northern France, we monitored agronomic performance and the changes in the soil mineral N content at field scale in six preceding crop-current crop combinations including winter wheat (Triticum aestivum), pea (Pisum sativum L.) and oilseed rape (Brassica napus L.). We quantified N leaching after each crop as a function of the preceding crop with a water-fluxes model based on soil mineral N content, climate data and soil characteristics. We then simulated N leaching at the rotation scale, for 20 years of climate conditions and various cropping management systems. We show that growing pea or oilseed rape reduced soil mineral N content at harvest of the following cereals (up to mean values of −28 and −19 kg N ha⁻¹ respectively), and N leaching risks during winter of the following cereals compared to the wheat-wheat cropping sequence. Although N leaching was higher during the winter after pea was cultivated, the cumulative losses over four experimental years of the pea cropping sequences were not significantly higher than the no-break cropping sequences. Over the 20 climate years, sequences including pea, oilseed rape, volunteers or catch crops reduced simulated N leaching by up to 40 % compared to wheat monoculture. Our study confirms that N leaching not only depends on the current crop but is also affected by the preceding crop. A large potential reduction in nitrogen leaching could be achieved in many intensive cereal-growing regions with very limited cropping sequence diversity.

在谷物种植系统中过度使用化肥导致空气和水质量严重下降。豆类的多样化种植顺序提供了氮 (N) 的天然来源，但也会增加其生长期后的氮浸出风险。在这里，我们假设豆类和其他杂粮作物，即为使种植顺序多样化而种植的作物，由于它们有助于提高后续谷类作物的养分利用效率和作物氮素回收，从而减少轮作规模的氮浸出。在法国北部进行的两个为期 4 年的试验中，我们监测了农艺性能和田间土壤矿物质 N 含量的变化，包括冬小麦 ( Triticum aestivum )、豌豆 ( Pisum sativum ) 等六种先前作物-当前作物组合。L.) 和油菜 ( Brassica napus L.)。我们使用基于土壤矿物质 N 含量、气候数据和土壤特征的水通量模型，将每茬作物后的 N 浸出量化为前茬作物的函数。然后，我们在轮作范围内模拟了 20 年气候条件和各种作物管理系统的氮浸出。我们表明，种植豌豆或油菜在收获以下谷物时降低了土壤矿物质 N 含量（高达 -28 和 -19 kg N ha ^{-1 的}平均值）分别），以及与小麦 - 小麦种植顺序相比，以下谷物在冬季的氮浸出风险。尽管豌豆栽培后的冬季氮淋失率较高，但豌豆种植序列在四个试验年的累积损失并不显着高于不间断种植序列。在过去的 20 个气候年中，与小麦单一栽培相比，包括豌豆、油菜、志愿者或捕获作物在内的序列将模拟的 N 浸出减少了 40%。我们的研究证实，氮浸出不仅取决于当前作物，还受前一作物的影响。在许多种植序列多样性非常有限的谷物集约化种植区，可以实现氮浸出的大量潜在减少。