水稻施用氮素化肥,一般于生育季节采用表层追施的方法。据湖北省农业科学院用同位素示踪法测定结果,化肥表层追施,碳酸氢铵的利用率只有25％,尿素的利用率达35％左右,即撒在地表面的化肥只有四分之一到三分之一左右能被水稻吸收利用,其余的则通过脱氮、渗漏、流失而耗损了,其中以脱氮损失为最多。这是由于水稻田在灌水以后,在土壤的耕作层里形成两 Nitrogen fertilizers applied to rice are generally used in the growing season topdressing method. According to the results of the isotope tracer method of Hubei Academy of Agricultural Sciences, top-dressing of chemical fertilizers shows that the utilization rate of ammonium bicarbonate is only 25% and the utilization rate of urea is about 35%, that is, only one quarter of the fertilizers sprinkled on the ground surface About one-third can be absorbed and utilized by rice, while the rest is consumed through denitrification, leakage and loss, of which the loss of nitrogen is the largest. This is because paddy fields form two in the tillage layers of the soil after irrigation