Effects of organic materials on maintaining soil microbial biomass nitrogen
有机物料在维持土壤微生物体氮库中的作用

The incubation experiments conducted in laboratory and fields showed that the effects of mineralization processes of organic materials on soil microbial biomass nitrogen were closely related to the properties and constitution of organic materials and relied on the soil fertility and nitrogen application. Adding organic material with high C/N ratio, the net fixation of fertilizer nitrogen by microorganisms maintained a longer period, on the contrary the period was shorter. The fixation period in soil with high fertility was shorter than in those with low fertility. Different organic materials had different impacts on soil microbial biomass nitrogen. The soil microbial biomass nitrogen decreased in sequence from adding mung bean straw, wheat straw, non decayed excrements of horse, excrements of sheep, decayed excrements of horse, decayed excrements of pig to manure. The organic material with rich avialable energy substance (e.g. mug bean straw) or with higher C/N ratio (e.g. wheat straw) had greater impacts on soil microbial biomass nitrogen than other organic materials. In low fertility soils, the effects of organic materials on soil microbial biomass nitrogen was rather apparent, about 4 times of high fertility soil.Thereby, it's essential for considering the properties and constitution of organic materials,soil fertility and mineral nitrogen content, and incubation time to estimating the effects of organic materials on soil microbial biomass nitrogen.