Dynamics of soil fixed NH4+ and soil microbiomass nitrogen in the growing season of winter wheat
冬小麦生长期土壤固定态铵与微生物氮的动态研究

Dynamics of soil fixed NH _4 and microbiomass N in the growing season of winter wheat were studied by field experiment. The results show that the soil fixed NH _4 increases significantly after the application of basal fertilizer, decreases significantly after spring and reaches to the lowest point at flowering stage. It reaches nearly the same level before harvest as that of sowing period because the soil fixed NH_4 pool is complemented by nitrogen mineralization in the late crop growing stage when crop has a low nitrogen uptake. Soil microbiomass N changes with the season. It has a slight increase in short period after the application of basal fertilizer and a second increase after the application of spring fertilizer, reaches to the lowest point at the flowering stage and is recovered in the latest stage because of lower crop N uptake.