Effects Of Sewage Sludge And Garbage Blended Fertilizers On Soil Properties And Crop Growth

The effects of sewage sludge and garbage blended fertilizers (SGBFs) with different nutrient concentrations on soil properties, plant growth, and accumulation of heavy metals in soil and plants were studied with pot experiments.The results of different type SGBF experiments showed that all of the experimental SGBFs with different nutrient concentrations significantly improved the growth of both Brassica Campestris and Poa annua Linn turf. The fresh weight and dry weight of both Brassica Campestris and lawn grass were higher than that of treatments with equal nutrient chemical fertilizer in various degrees, and the contents of total N, K, and chlorophyll of rape increased too in the SGBF treatments.SGBF improved both yield and quality of the crops. SGBFs with different nutrient concentrations also increased the contents of soil organic matter, N, P and K in various degrees, promoted the activities of the CAT and the alkalinity phosphatase, and had significant effect on soil fertility and soil improvement The SGBFs with lower nutrient concentrations was better than that with higher nutrient concentrations in improving soil fertility property. After application of SGBFs, the contents of total Pb, Cu, Cd, Cr in soil and plants increased, but were still far from the control standard of farmland pollution.Generally, the heavy metal in soil and plants increased as the nutrient concentrations of SGBFs reduced, but the contents of heavy metals in soil and plants were not significantly higher than that in the treatments with equal amounts of chemical fertilizers as the nutrient concentrations of SGBF was 20%. Therefore, sewage sludge and garbage can be safely utilized as the components of compound fertilizers.The results of the pot experiment applied SGBF continuously showed that SGBFs increased soil organic matter, available N, P, K nutrients, and improved soil properties. Contents of heavy metals in the treatments used with SGBFs continuously were higher than that in CK, but still in safe. The contents of total Cu, Cr, Pb in Brassica Campestris also slightly increased, but not significantly higher than that in CK, and also lower than the national standards of no-pollution food by far. Therefore, SGBFs can improve the soil organic matter and available nutrients, reduce the accumulations of heavy metals in soil comparing to the inorganic heavy metals. Most of heavy metals in SGBFs is in organic form, and their biological availabilities are very low and not easy to be absorbed and accumulated by crops, so can be used safely in farmland.