De Waele J, D'Haene K, Salomez J, Hofman G, De Neve S
Department of Soil Management, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Plant Sciences Unit, Institute for Agricultural and Fisheries Research (ILVO), Burg. Van Gansberghelaan 109, 9820 Merelbeke, Belgium.
J Environ Manage. 2017 Feb 1;187:513-526. doi: 10.1016/j.jenvman.2016.10.048. Epub 2016 Nov 16.
Nitrate (NO) leaching from farmland remains the predominant source of nitrogen (N) loads to European ground- and surface water. As soil mineral N content at harvest is often high and may increase by mineralisation from crop residues and soil organic matter, it is critical to understand which post-harvest management measures can be taken to restrict the average NO concentration in ground- and surface waters below the norm of 50 mg l. Nitrate leaching was simulated with the EU-rotate_N model on a silty and a sandy soil following the five main arable crops cultivated in Flanders: cut grassland, silage maize, potatoes, sugar beets and winter wheat, in scenarios of optimum fertilisation with and without post-harvest measures. We compared the average NO concentration in the leaching water at a depth of 90 cm in these scenarios after dividing it by a factor of 2.1 to include natural attenuation processes occurring during transport towards ground- and surface water. For cut grassland, the average attenuated NO concentration remained below the norm on both soils. In order to comply with the Nitrates Directive, post-harvest measures seemed to be necessary on sandy soils for the four other crops and on silty soils for silage maize and for potatoes. Successful measures appeared to be the early sowing of winter crops after harvesting winter wheat, the undersowing of grass in silage maize and the removal of sugar beet leaves. Potatoes remained a problematic crop as N uptake by winter crops was insufficient to prevent excessive NO leaching. For each crop, maximum levels of soil mineral N content at harvest were proposed, both with and without additional measures, which could be used in future nutrient legislation. The approach taken here could be upscaled from the field level to the subcatchment level to see how different crops could be arranged within a subcatchment to permit the cultivation of problem crops without adversely affecting the water quality in such a subcatchment.
农田中的硝酸盐（NO）淋失仍然是欧洲地下水和地表水氮负荷的主要来源。由于收获时土壤矿质氮含量通常较高，且可能因作物残茬和土壤有机质的矿化作用而增加，因此了解采取哪些收获后管理措施能够将地下水和地表水中的平均NO浓度限制在50毫克/升的标准以下至关重要。利用欧盟的rotate_N模型，在佛兰德种植的五种主要耕地作物（割草地、青贮玉米、土豆、甜菜和冬小麦）之后，在粉质土和砂质土上模拟了硝酸盐淋失情况，设置了有和没有收获后措施的最佳施肥方案。我们将这些方案中90厘米深度处淋溶水中的平均NO浓度除以2.1这个系数，以纳入向地下水和地表水输送过程中发生的自然衰减过程，然后对这些浓度进行了比较。对于割草地，两种土壤上的平均衰减NO浓度均低于标准。为了符合《硝酸盐指令》，对于其他四种作物，砂质土似乎需要采取收获后措施；对于青贮玉米和土豆，粉质土需要采取收获后措施。成功的措施似乎包括冬小麦收获后尽早播种冬季作物、在青贮玉米中套种牧草以及去除甜菜叶。土豆仍然是个问题作物，因为冬季作物吸收的氮不足以防止过量NO淋失。针对每种作物，提出了收获时土壤矿质氮含量的最高水平，包括有和没有额外措施的情况，这些可用于未来的养分立法。这里采用的方法可以从田间尺度扩大到子流域尺度，以了解在一个子流域内如何安排不同作物，以便在不负面影响该子流域水质的情况下种植问题作物。
