在美国玉米生产中,氮素的供应特别重要。多年来,每年施用氮素的效果尚未充分论证,许多长期氮素试验结果的最高产量施氮量为每英亩109—179磅(122—200公斤/公顷)。氮素很容易从土壤——玉米系统中损失,因此,估算氮素的积累、损失、回收和平衡是十分重要的。本文是作者于1983年2月到1984年2月访美期间和美国内布勒斯加大学土壤肥力教 In the United States corn production, nitrogen supply is particularly important. The effect of annual nitrogen application over the years has not been fully demonstrated and many of the long-term nitrogen trials yield the highest yield of nitrogen at 109-179 pounds per acre (122-200 kg ha -1). Nitrogen is easily lost from the soil-maize system, so it is important to estimate the accumulation, loss, recovery and balance of nitrogen. This article is written by the author from February 1983 to February 1984 during a visit to the United States and the University of Nebraska Soil Fertility Teaching