Releasing Of Non-point Pollutants From Straw Affected By Simulated Water Control

Nowadays, non-point pollution is a serious environmental problem, and because so many characteristics of this pollution such as regional dispersibility, uncertainty, hysteresis, fuzziness and latent nature on time, it's hard to predict the nutrient element lost. Meanwhile in practical working, It's difficult to obtain enough information and the result of pollution is on a widen scales, moreover, there exist some tough tings such as controlling and management, so a lot of attention was paid on the module for calculating nutrient element lost and the estimation of pollution. In the field of farming production, nutrient element lost caused the decreasing of fertilizers utilization efficiency, meanwhile through the rainfall and irrigation, nutrient element went into the source of surface water or infiltrated into depth of water body, which caused water pollution, and made the quality of water going worse.On the other hand, in China there exist about 18 hundreds million tons straws to be disposed. The application of straws for fertilizer is a double-edge sword. Though the application of straws can promote fertility, it became a disorder pollution source to let out numbers of nutrient elements such as N, P, and COD because of lacking not standardized utilization, which was a part of non-point pollution and damaged the eco-environmental quality. Currently, some reports had did the research about the application of straws on sloping field to illustrate the impact on nutrients lost, but in fact the returning straws back to field made fewer impact on soil and water lost, which can created the pollution of surface water and groundwater. Moreover there is on any comprehensive studies on pollution load caused by this application.In this paper, on the background of straws recycle utilization, it discussed the dynamic characteristics of N, P and COD releasing after covering and burying for returning back to field, through three management modules to stimulate paddy field, dry field and rotation field to control water. Meanwhile it qualified the pollution load to offer enough and effective foundations to control the source of non-point pollution in farming.In the simulated paddy field, the concentrations of TN, TP in overlying water of covering group was higher than burying group, the max concentrations after burying was less than 1/2 concentration after covering. The occurrence time of max value was later 3d than covering. Furthermore, the total releasing amount of burying group was lower than covering one. Additionally, the change trend of COD was entirely reversed.In the simulated dry field, the water is necessary medium to transport N, P. through burying treatment, the concentrations of TN; TP in overlying water of burying group was higher than covering group. The risk of water pollution caused by burying treatment was more dangerous. In the simulated rotation field, the nutrient element lost mainly occurred prior to first 4 weeks. The extreme value of TN, TP in covering group occurred the third week. The concentration of nutrients in burying group showed a feeble ascending trend. Furthermore, the gross quantity of releasing from covering group was higher than the burying one. Meanwhile the trend of COD was reversed (except gross quantity of releasing).So, the total impact of paddy field, dry field and rotation field on the N, P, COD releasing from straws were all concluded as follows: covering back field, the way of rotation can enhance the N, P releasing higher than paddy field and dry field. Burying back field, the way of rotation can enhance the N; P releasing higher dry condition, the releasing was lowest in the condition of paddy field. The P releasing from unit straws was higher than rotation; the releasing P capability from paddy field was weakest. In the same way of water management, the max releasing quantity of N and P was consistent with the trend of N, P releasing from unit straws. All above conclusions can support the recycle utilization of agricultural byproducts for a scientific base. However, the limitation of simulated experiment, the mimic condition was different from the practical farming condition, and only natural air-dry straws were used in the experiment, the results of research were not all perfect, further studies will be done to promote our research.