对需 N 量多的作物(如玉米)做出准确的氮肥推荐变得越来越重要,因为氮肥的施用与农业区的地表水和地上水产生 NO_,污染有关。近来,在玉米种植系统中有助于改善 N 素管理的几种土壤和植物N素试验的评价方法已见报道(Binford 等,1990等)。所有这些 N 素试验方法包括以下步骤:土壤或植株样品的采集 It is more and more important to make accurate nitrogen recommendations for crops that require large amounts of N, such as corn, because application of nitrogen fertilizers is associated with NO_ and pollution of surface and groundwater in agricultural areas. Recently, methods for evaluating N-test of several soils and plants that help to improve N-management in maize planting systems have been reported (Binford et al., 1990 et al.). All these N prime test methods include the following steps: Collection of soil or plant samples