| The common plastic film mulching technology causes a series of environmental issues while it controls or increases soil temperature and maintain soil humidity to increase crop yields and improve produce. The new pattern of plastic mulch film, it's called"Environmental Degradable Mulch Film"(EDMF),which successfully achieves degradation of appearance from pieces to powders. Therefore the effect of polyethylene powder products of EDMF on physical property and chemical property of soil and crop development becomes new hotspot of discussion. This study was financially supported by National "Eleventh Five-Year" Technology Support Program (2007BAE42B04),and made use of several kinds of molecular weight polyethylene powders to simulate different degradable levels products of EDMF as soil additive of potted plant.Tested soil fertility and enzyme activity;biological properties of soybean,wheat and mung bean.The results showed that:1. In the response study of soybean development and soil environment to different molecular weight polyethylene powdersThere were negative response effects to plant height of seedling period and efficient P of ripe period, whose value were decrease along with dosage of polyethylene powder, but the height and efficient P all equal to or more control group(CG), the maximum increase of which were 1.12,2.21 times as many as CG respectively, the difference is significant. There were positive response effects to plant fresh weight and dry weight of pod period, efficient K of ripe period,whose value were increase along with dosage of polyethylene powder,the maximum increase of which were 1.18,1.19 ,1.31 times as many as CG respectively,the difference is significant.2. In the response study of wheat development and soil environment to different molecular weight polyethylene powders?With treatments in doras,there were positive response effects to efficient N of head emergence period, whose max increase was 1.65 times as many as CG, the difference is significant. There were negative response effects to efficient K of head emergence period, whose value were lower than CG, and the max decrement was 21.74%,the difference is significant.With treatments in clay,there were positive response effects to spike length and yield along with dosage of polyethylene powder , whose max increase were 1.22,1.19 times as many as CG respectively, the difference is significant. With treatments in sand,there were positive response effects to orgnic matter of head emergence period, efficient P of ripe period ,spike length and yield along with dosage of polyethylene powder ,whose max increase were 1.13,1.29,1.37,1.50 times as many as CG respectively, the difference is significant.There were positive response effects to urease activity along with dosage of polyethylene powder in three kinds of soil, whose max increase were 1.59,1.41,1.61 times as many as CG respectively, the difference is significant. The response effects of acid phosphatase activity was not regular. There were positive response effects to efficient P of head emergence period in clay, efficient N of jointing period in sand along with molecular weight of polyethylene powder, whose max increase were 1.20,1.38 times as many as CG respectively, the difference is significant.3. In the response study of mung bean development and soil environment to different molecular weight polyethylene powdersWith treatments in doras,there were positive response effects to efficient K , urease activity and acid phosphatase activity of flower-pod period along with dosage of polyethylene powder, whose max increase were 1.17,1.18,1.75times as many as CG respectively, the difference is significant.There were negative response effects to efficient P of pod-drum period and 100-seed weight along with dosage of polyethylene powder,whose value were lower than CG,and the max decrement were 48.31%,14.23% respectively, the difference is significant.With treatments in clay,there were positive response effects to urease activity along with polyethylene powder, whose max increase was 1.11 times as many as CG, the difference is significant. There were negative response effects to 100-seed weight along with dosage of polyethylene powder and acid phosphatase activity along with molecular weight of polyethylene powder, whose value were lower than CG,and the max decrement were 18.53%,61.88% respectively, the difference is significant.With treatments in sand, there were positive response effects to urease activity along with dosage of polyethylene powder,whose max increase were 1.49 times as many as CG, the difference is significant. There were negative response effects to plant height of flower-pod period and pod-drum period, plant fresh weight of pod-drum period ,efficient N of pod-drum period along with dosage of polyethylene powder, whose value were lower thanCG,and the max decrement were 24.87%,17.19%,47.05%,50.10% respectively, the difference is significant.4. Mathematical model simulation analysis showed thatThe relationship model between dosage of polyethylene powder and every index were logistic model,power function,exponential function,negative exponential function,hyperbola,S curve,logarithmic function and conic;and the relationship model between molecular weight of polyethylene powder and every index were all logarithmic function.In conclusion, The polyethylene powder products of EDMF had no significant effects on soil environment and crop development, there were merely several indexs were influenced by polyethylene powder,and the effects of which were caused by dosage of polyethylene.The molecular weight of polyethylene powder mainly influenced enzyme activity of soil. The interaction of dosage and molecular weight of polyethylene powder wasn't significant in the study of soil fertility and crop biological property,but both of them have a little significant interaction in the study of enzyme activity.The optimum dosage of polyethylene powder products of EDMF was 10-50 years, go beyond this range would bring about negative effect. As the same time,the smaller molecular weight of polyethylene powder,the more positive effect and more degradation, this work pointed out the optimum molecular weight was 4614.52 and less than 4614.52. |
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