旱地或水田施用氮肥,过去多采用表层撒施的方法,肥分大多集中在表土层。氮肥挥发、流失及反硝化作用损失严重。因此提高氮肥肥效,特别是防止易挥发性氮素化肥损失,是生产中急待解决的一个突出问题。这项工作曾列为1973年全国肥料试验网的重点研究项目之一。近几年来在各级党委领导下,我国广大贫下中农和科技人员大力开展 Nitrogen fertilizer is used in dryland or paddy fields, and in the past, the method of applying topsoil was adopted. Most of the fertilizer was concentrated in the topsoil. Nitrogen volatilization, loss and denitrification suffered serious losses. Therefore, improving nitrogen fertilizer efficiency, especially to prevent the loss of volatile nitrogen fertilizer, is an outstanding problem to be solved urgently in production. This work was listed as one of the key research projects of National Fertilizer Trial Network in 1973. In recent years, under the leadership of party committees at all levels, the vast majority of poor and middle-ranking peasants and scientific and technical personnel in our country have vigorously carried out