Influences And Environmental Significance Of Application Of Biomass Composted Manure On Soil Nutrients And Crops Growth

With the development of large-scale and intensive modern agriculture, a huge amount of agricultural wastes are accumulated, which causes a severe environmental problem. Agricultural wastes, however, are potential biomass resources, and can be composted and made into organic manure. This is also a good way for its re-utilization as sources. Liantang Town, Qingpu District in the western suburb of Shanghai is a well-known water-bamboo（Zizania latifolia） town, and produces a huge amount of water-bamboo leaves every year, which poses threat to the environment. Field experiments of tomato and eggplant cultivation were carried out to study the fertilizer efficiency of composted water-bamboo leaves manure（composted manure）, compared with that of rapeseed cake manure（cake manure） and synthetic chemical fertilizer（chemical fertilizer）. Effects of the composted manure on soil nutrients and enzyme activities, crop growth, and fruit yield and quality were also studied to evaluate its environmental effects and economic benefits. This is beneficial to develop low-input farming systems and to utilize agricultural wastes as sources in the suburbs of Shanghai. The results are as follows:（1） The processes of producing the composted manure from water bamboo leaves included transportation, crushing, addition of fermenting accessories and microbial inoculation, the first fermentation, turning, sieving, the second fermentation, granulation and packaging. Contents of total N（TN）, total P（TP）, total K（TK） and organic matter in the composted manure were 23.6 g kg^-1, 11.4 g kg^-1, 13.4 g kg^-1 and 480.9 g kg^-1, respectively. The composted manure was rich in trace elements such as Fe, Mn, Zn and Cu, which were 1005.4 mg kg^-1, 659.8 mg kg^-1, 66.7 mg kg^-1 and 51.7 mg kg^-1 in content respectively. It contained low contents of toxic metal, Pb, Ni and Cd being only 0.11 mg kg^-1, 2.5 mg kg^-1 and 0.3 mg kg^-1, respectively.Compared with chemical fertilizer, the composed manure was low in TN and TP. Therefore, the application of the manure would not lead to excessive accumulation of nitrogen and phosphorus in soil and water eutrophication. Application of the composted manure was more beneficial to enhance available potassium content in soil, which increased by 111.5 % and 95.4 % in the soils in the early stage of tomato and eggplant growth, respectively. The composted manure provided soil with exogenous biological carbon containing large amounts of cellulose, and promoted the formation of soil organic matter, which could significantly increase soil organic matter content. In the tomato experiment, for example, the content of soil organic matter increased by 15.8 %.Application of the composted manure improved the activity of catalase and sucrase significantly, which increased by 93.1% and 63.2% in the period of tomato growth respectively, and increased by 47.9% and 31.2% in the period of eggplant growth. Application of chemical fertilizers increased soil nutrient contents rapidly, thus providing substrates for urease and increasing urease activity highly. Chemical nitrogen was also beneficial to raise soil phosphatase activity significantly. Excessive application of chemical fertilizers often leads to nutrient loss and diffuse pollution, which poses threat to soil and groundwater. Nutrients in the composted manure were slow-releasing and persistent, which could reduce agricultural diffuse pollution and maintain soil nutrient levels.Application of the composted manure, chemical fertilizer and cake manure increased the yield of tomato by 20.4 %, 66.7 % and 31.5 %, respectively; and increased the yield of eggplant by 27.79 %, 48.30 % and 32.34 %, respectively. Application of the composted manure improved the growth of tomato and eggplant significantly and increased fruit yield. However, the yield increase effect of the composted manure was lower than that of chemical fertilizer and cake manure, due to its low content of N and P and slow release of nutrients.Compared with chemical fertilizers, application of the composted manure increased soluble sugar content in tomato and eggplant fruits by 24.0 % and 39.3 %, respectively,, and reduced nitrate nitrogen content by 28.2 % and 16.8 %, respectively. Compared with the application of chemical fertilizer, application of the composted manure significantly increased the content of soluble sugar in fruits, and effectively prevented nitrate from being excessively accumulated due to its enriching K and deficiency and slow release of N, thus improving fruit quality more significantly.Compared with other commercial organic fertilizers, the raw material of the water bamboo leaves composted manure was agricultural waste straw. Its application to the fields would not adversely affect soil p H and cation exchange capacity, or increase the content of heavy metals in the soils. It would be beneficial to improve the soil moisture content. Moreover, the cost of the composted manure was only a quarter that of chemical fertilizers. Therefore, application of the composted manure could attain more environmental and economic benefits than application of chemical fertilizers.In short, making abandoned water-bamboo leaves into compost manure is a promising way of recycling, which could avoid pollution caused by waste discard or burning. Moreover, the composted manure could partially replace chemical fertilizers, thus reducing agricultural costs and environmental pressure and realizing waste recycle and sustainable agriculture development. Compared with chemical fertilizers, the composted manure was high in K and organic matter content, but low in N content. The application to the fields, therefore, significantly increased soil organic matter and enzyme activity, and raised soluble sugar content and reduced nitrate content in fruits, which attained better environmental and economic benefits.