| Sewage sludge compost(SSC) contains a lot of organic matter, nutrients, such as nitrogen and phosphorus, when it used in forestry can provide nutrients for the plants, changing the soil properties. However, these nutrients in the sewage sludge compost may flow into the water environment by surface runoff and groundwater seepage, pose a potential risk to the surrounding water body. In this study, sewage sludge compost came from a sludge compost plant in Beijing was taken as a research object to explore the distribution of nitrogen and phosphorus after forestry utilization of sludge compost, and study the transformation behavior of nitrogen and phosphorus in the soil environment.In order to study distribution characteristics of nitrogen and phosphorus in the forest soil, this paper selected acreage about500m2of ginkgo and plum field as the sample area, sewage sludge compost were applied to ginkgo and plum field with dosage of0,1.5,3.0,4.5and6.0kg/m2by two kinds of method, furrow application and annularity application. The experimental results showed that the application of sewage sludge compost after a month, nitrogen and phosphorus content in forest soil increased, especially the surface of0-10cm. Total nitrogen increased by1.65%～37.59%, total phosphorus increased0.89%～8.52%, NH4+-N increased50.81%～114.70%, NO3--N increased68.43%～152.94%, available phosphorus increased by23.59%～50.19%, but then the rules changed. Inorganic phosphorus content of the order:Ca-P> Oc-P> Fe-P> Al-P> Ex-P, organic phosphorus content of the order:moderate labile organic phosphorus(ML-OP)> moderate resist organic phosphorus(MR-OP)> high resist organic phosphorus(HR-OP)> labile organic phosphorus(L-OP).The pot experiment was applied to explore the effect of different fertilizer proportion on nitrogen and phosphorus content, sewage sludge(SS) and SSC by10%,25%,50%ratio were applied to soil. The experimental results showed that sewage sludge and sewage sludge compost can significantly increase the content of nitrogen and phosphorus in soil, and was positively correlated with fertilizer proportion; After15weeks, application of sewage sludge and sewage sludge compost soil total nitrogen decreased by33.98%～53.99%and33.79%～54.21%respectively; NH4+-N decreased by34.04%～53.99%and34.12%～34.04%respectively. And NO3--N increased by54%～238.83%and62.97%～54%respectively; Total phosphorus decreased by3.27%～14.94%and7.48%～3.27%respectively; Available phosphorus decreased by 3.27%-14.94%and7.48%-3.27%respectively. NO3--N can’t easily be adsorbed soil vulnerable to leaching, which may increase the risk of the loss of NO3--N, phosphorus reduction may be due to plant uptake and availability of phosphorus reduced.Soil incubation experiments was apllied to study the transformation behavior of nitrogen and phosphorus in sewage sludge compost. The showed that:After sludge compost applied to soil organic nitrogen mineralization will occur, and the first-order kinetics Nt=N0(1-e-Lot). Moisture and temperature have a significant effect on the release of nitrogen mineralization in sewage sludge compost. For net nitrogen release rate, the content of which in sewage sludge compost was first increased then decreased with the increasing of moisture and constantly increased with the increasing of temperature. At high soil moisture or temperature conditions, a high concentration of NO3-N accumulated in the soil immediately after sludge compost application may pose a potential environmental risk for NO3--N leaching. Different forms of phosphorus content in soil were slightly increased after application of sewage sludge compost. However, the rise of unstable phosphorus content in soil, increased the risk of loss of phosphorus. Therefore, we suggest that we should try to control fertilizer rate and fertilization time, avoid the summer and more rain season for sewage sludge compost application in forest. |
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