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稻田施用氮素化肥,一般多采取表层追施的方法,即在水稻生育季节把化肥一次或几次扬撒在水田地表面。这种施肥方法有很多缺点,其中特别突出的是肥料利用率低。据湖北省农业科学院用同位素示踪法测定,化肥表层追施,碳铵的利用率只有25％,尿素的利用率也只达到35％左右。美国加里福尼亚州用N~(15)标记的硫铵回收率仅29％,
Nitrogen fertilizer applied to paddy fields, the general approach to take top-dressing, that is, in the rice growing season, the fertilizer once or several times spread in the paddy field surface. There are many disadvantages to this method of fertilization, with particular emphasis on low fertilizer availability. According to the Hubei Academy of Agricultural Sciences by isotope tracer method, fertilizer top dressing, ammonium bicarbonate utilization rate of only 25%, urea utilization rate reached only about 35%. The recovery rate of ammonium sulfate marked by N ~ (15) in California was only 29%