Effect of Sewage Sludge and its Biomass Composting Product on the Soil Characteristics and N2O Emission from the Tomato Planting Soil

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In this study, tomato plants were cultivated in the greenhouse in five consecutive experiments: fertilized with 800 kg N ha -1 fresh sludge (S-H), 400 kg N ha -1 fresh sludge (S-L), 800 kg N ha -1 straw composting product (VM-S), 800 kg N ha -1 swine manure composting product (VM-M) and no fertilization (CK), and the soil properties, inorganic nitrogen forms and N2O emission characteristics were investigated. The results showed that, treatments with composting product significantly increased the soil electrical conductivity (EC) (p<0.05), and the VM-M treatment exhibited the largest soil EC. With the addition of sludge and composting products, pH of soil increased significantly (p<0.05) and ultimately tend to be neutral, and the inhibitory effect of VM-M on soil acidification was better than VM-S. Soil NO3 -concentration increased significantly with application of sludge and composting, and the NO3 -concentration of each treatment decreased gradually with time. Most of the NO3 -was absorbed by tomato plants, partially leached from the upper soil layer to the lower. Most of the NH4 + was oxidized to NO3 -and partially absorbed by plants. With the equal application of inorganic nitrogen, the promoting effect on the tomato growth was VM-M>VM-S>S-H. In addition, the excess application of nitrogen fertilizer from S-H than S-L did not promote the growth of tomato markedly (p<0.05). Compared with the control, N2O emission from soil was significantly improved by sludge or biomass composting (p<0.05). The N2O emission from all treatments were focused on the first 20 days after fertilization, and the emission of soil N2O was S-L (0.76 kg N2O-N ha -1 y -1 ))<VM-M (0.95 kg N2O-N ha -1 y -1 )<VM-S (1.19 kg N2O-N ha -1 y -1 )<S-H (1.71 kg N2O-N ha -1 y -1 ). Therefore, during the utilization of sludge in farmland, the mixed compost by sludge and pig manure could be a priority to prevent soil acidification, promote crop growth and meanwhile reduce the greenhouse gas emission.