Environmental Benefits And Economic Benefits Analysis Of Rice In Three Kinds Of Farming Systems

As people emphasis on safety of environmental eco-agriculture and agricultural products day by day, rice-duck farming system continues to rise in major domestic rice region. However, the rice-duck farming system is not perfect, there are still many technical problems in the production practice to be solved in order to improve production and quality of the rice and duck, improve production efficiency and environmental benefits. Based on a study of monitored soil samples collected from conventional paddy fields, transformed paddy fields and organic paddy fields, some nutrients were studied during some growth periods.; the differences of soil microbial biomass, enzyme activity and soil respiration intensity in three kinds of farming systems soil; the profile changes of soil nutrient content and heavy metal content; surface water of paddy fields quality differences.Main findings as follows:1. The changes of rice growth, soil fertility, soil enzymes and microbial biomass in three kinds of farming systemsBased on a study of monitored paddy soil, the results show that the organic rice-duck farming can reduce soil bulk density, increase soil porosity and improve the gas, and thermal state of the soil; the same time can significantly increase the contents of soil organic matter, available N, available P and available K. These show that the straw and duck feces excretion have a certain amount of control, buffering and facilitating role to nutrient status of soil. While the conventional rice rarely takes return of straw and use of organic fertilizer and other measures, the soil nutrient indicators such as organic matter, available N and other available nutrient indicators are greatly constrained by the application of chemical fertilizers. The soil urease, acid phosphatase, catalase, microbial biomass carbon and microbial biomass nitrogen in organic rice-duck paddy fields were significantly higher than the transformed paddy field and conventional paddy field, and sometimes the different is significant. It is concerned with return of straw to field, rapeseed cake, organic fertilizer and the discharge of the duck in organic rice-duck paddy fields. Organic rice-duck farming system paddy field could produce organic rice, so it has good economical effect. The economic income of organic paddy field and transformed paddy field were higher23266.4yuan-hm-2and2011.4yuan-hm-2than that of conventional paddy field respectively. 2. The profile changes of soil nutrient content and heavy metal content in three kinds of farming systemsThe paper investigated paddy soil pH, organic matter, total N, available N, available P, available K, and heavy metals Pb, Cu content. The result showed that the profile changes of organic matter, total N, available N and available P are basically the same trends increasing with the profile depth reduced. As organic paddy fields with non-application of chemical fertilizers, organic manure, return of straw and duck activities related to emissions from manure, the reduction slope of organic paddy fields was smallest. Because of the conventional long-term application of chemical fertilizers and pesticides, the pH has an increasing tendency from the cultivated horizon to its underlying layer, which is likely to cause soil acidification. Heavy metals Pb and Cu are also have similar trends decreasing from the cultivated horizon to its underlying layer.The heavy metals concentrated in the arable layer of soil in the main with a large number of applications of chemical fertilizer and pesticide, return of wheat straw and so on.3. The differences of surface water body quality in three kinds of farming systems Rice-duck farming system, feeding ducks in the rice fields, playing in the water, and trampling and other activities and their faeces excretion, produced manifold effects on the physicochemical properties of water environment. Of nutrients from the surface water body point of view, total nitrogen, total phosphorus, total potassium, and chemical oxygen demand in rice-duck farming area increased than conventional rice area. The reason was mainly that duck excreta and feed residues increase the nutrient for the system, organic matter content increased. When the farmland drain, the total nitrogen, the total phosphorus and soluble orthophosphate are far below than those of conventional rice area in surface water body of rice-duck farming area, which induced by lowering the risk of eutrophication in the vicinity of water body. The reasons need to be further studied.The above findings provide scientific guidance and theoretical support for the promotion of organic rice-duck farming system.