人们发现,有时施用尿素后作物的产量并没有提高。经过研究发现,在土壤表面有一种叫尿素酶的物质对尿素起水解作用。当尿素施用后,如不能被降雨或耕作使其渗入土壤内,则尿素在尿素酶的作用下水解成氨挥发掉,氮的损失可高达30％。土壤的酸碱度、离子交换能力、离子类型及数量,以及风速等都影响土壤中氨的挥发。另外由于土壤中氨含量的增加,还会对正在发芽的种子产生毒性。土壤中尿素酶的活 It has been found that sometimes the yield of crops does not increase after the application of urea. After the study found that in the soil surface has a substance called urease hydrolysis of urea. When urea is applied, it can not be rained or tillage to infiltrate the soil. The urea is hydrolyzed under the action of urease to evaporate ammonia, and the loss of nitrogen can be as high as 30%. Soil pH, ion exchange capacity, ion type and quantity, as well as wind speed and so affect the ammonia volatilization in the soil. In addition, due to the increase of ammonia in the soil, it will also produce toxicity to the germinated seeds. Soil urease activity