盲目偏施化学氮肥,不仅影响蔬菜的品质、色泽、风味、耐贮性,而且使蔬菜中硝酸盐含量大幅度增加,威胁人体建康。一、早施蔬菜以苗期追施氮肥为好,既有利于促进蔬菜幼苗早发、早熟、高产,又可使氮素有充分的时间转化,能有效地减少硝酸盐的积累。叶菜类和生育期短的蔬菜更要早施,生育期较长的蔬菜,也应在收获前 Blind partial chemical nitrogen fertilizer, not only affects the quality of vegetables, color, flavor, storability, but also greatly increased the nitrate content of vegetables, threatening the health of human beings. First, as early as the topdressing of nitrogen fertilizer at the seedling stage is good, both conducive to promoting early seedling, early maturing, high yield, but also have enough time to convert nitrogen can effectively reduce the accumulation of nitrate. Leafy vegetables and vegetables of shorter growth period should be given earlier, longer growing vegetables, should also be harvested before