Nitrogen mineralization in soils amended with sewage sludge composted with different crop straws as bulking agent

An incubation experiment was conducted to investigate the differences of nitrogen mineralization among three soils amended with four sewage sludge composted with the straws of wheat(XMC)， rice(SDC)， corn(YMC) and rape(YCC). The purpose was to understand the effect of sewage sludge composted with different crop straws on nitrogen mineralization in soils and establish a scientific way for sewage sludge compost application in agriculture. The soils tested included an acidic purple soil， a yellow soil and a calcareous purple soil. All the compost treatments could significantly improve the values of potentially mineralizable nitrogen(N0)， promoted nitrogen mineralization， and consequently increase the NH4+-N and NO3- -N concentrations in soils. The optimal amounts of nitrogen mineralized and the N0 values were found in the treatments of YCC and XMC for the calcareous purple soil， in the treatment of XMC for the acidic purple soil and in the treatment of YCC for the yellow soil. The amount of nitrogen mineralized increased after 90 days incubation in the compost treated calcareous purple soil, while it became stable at 60 days and 30days incubation in the compost treated- acidic purple soil and yellow soil, respectively. However, no obvious tendency of the mineralization rate constant (k) values was found in the three soils treated with the four composts. The results illustrated that the effect of sewage sludge compost on the mineralization of nitrogen varied with soils and the properties of crop straws. Based on the results of the present study, some advices on the application of sewage sludge compost were put forward.