The dynamics and availability of soil fixed ammonium in rice-duck complex ecosystems;

Profile distribution of fixed ammonium in some paddy soils in Hunan province;

Relationship Between the Release of Fixed ammonium from Yellow Brown Soil and the Density of Ryegrass;

Paleoclimatic significance of fixed-NH_4~+-N in the Luochuan loess section during the last 130 ka;

The kinetics of release of fixed ammonium from several types of cultivated upland soils and paddy soils derived from chief parent materials in Hunan province, China, were studied with sampling on fields, and laboratory incubation and determination.

This paper summarizes the data on the study of fixed ammonium in soils as follows:comparison and evaluation of determination method of fixed ammonium, origin and content of fixed ammonium and its distribution in soil profile, factors affecting fixation and release of ammonium in soil,availability of fixed ammonium to plant.