土壤水分对包膜尿素养分释放特性的影响

试验采用土壤培养的方法,以释放期分别为60 d(肥料A)和90 d(肥料B)的两种肥料作为供试肥料,研究了土壤绝对含水量、干湿交替、相对含水量和水势因素对3种土壤中包膜尿素养分释放特性的影响。结果表明:在3种土壤中,土壤绝对含水量从50 g/kg增到200 g/kg时,包膜尿素养分释放率均随土壤水分含量的增加而显著增加,此时水分因素是控制包膜尿素养分释放的主要因素。在干湿交替条件下,两种供试肥料间释放率的差异变大,其中肥料B在潮土中释放速率较其他两种土壤中下降更多。当相对含水量在0%~50%田间持水量范围内,或水势在60~100k Pa范围内时,供试肥料在红壤中的释放显著低于潮土和水稻土,这与红壤中黏粒含量高有关;当相对含水量大于100%田间持水量时,或水势低于60 k Pa时,土壤水分和土壤类型对包膜尿素养分释放的影响基本不再显著。常用的Sugihara方程可以较好地拟合包膜尿素在试验设定水分条件下的养分释放特性,相关系数r0.95。3种不同土壤水分参数均可以用来预测包膜尿素的释放率和释放期,其中水势(x)与包膜尿素释放期(y)的拟合效果最好,关系式为y=64.79e~(0.0066x),r=0.91。

Effects of Soil Moisture on Nutrient Release from Coated Urea in Soils

A series of soil incubation experiments were conducted to study the effects of soil moisture on the nutrient release characteristics of coated urea in soils, soil moisture indexes, including the absolute water content, relative soil water content, soil water potential together with the alternation of wetting and drying treatment were employed. The experiments used two kinds of fertilizers that their duration were 60 days and 90 days, referred to as fertilizer A and fertilizer B .The results showed that the nutrient release rate of coated urea increased significantly when the soil absolute water content increased from 5% to 20% in soils, at this time soil moisture was the main influence factor of coated urea nutrient release. Under dry-wet alternate condition, the differences of the release rate between two fertilizers became bigger, the release rate of the coated urea B was much lower in alluvial than that in the other soils. When the relative water content increased from 0% to 50% or soil water potential within the scope of 60kpa to 100kpa, the release rate of the coated urea was much higher in krasnozem than that in the other soils. This is associated with high clay content in krasnozem. When the relative water content surpassed 100% or soil water potential was below 60kpa, the effects of soil moisture and soil type became slight on the nutrient release of coated urea. The frequently-used Sugihara equation could well describe the nutrient release characteristics of coated urea under the soil moisture conditions designed in the experiment, and r>0.95. All of the three soil moisture indexes can be used to predict the nutrient release rate and duration of the coated urea, but the best fitting effect was between water potential(x) and duration, the relation is y=64.79e0.0066x (r=0.91).