Degradation Of Biodegradable Mulch Films And Its Effects On The Growth Of Corn

Degradable mulch film are effective ways to solve"white pollution". Effect of film cover on the growth of corn was studied by field experiment; degradation of degradable mulch film was observed; quality of degradable mulch film before and after degradation was studied with the method of weight loss; microstructure of film samples before and after degradation was observed by SEM; and composition and characters of film were analyzed by infrared spectrum. Effects of temperature, moisture condition and ultraviolet radiation on the degradation degree of bio-degradable mulch film were studied in the laboratory.Films cover could conserve moisture, increase temperature and improve yield; there was no significant difference in temperature-conserving, moisture-retaining and yield increase between bio-degradable films and polyethylene films; Temperature-conserving and moisture-retaining of non-degradable film were not good from jointing stage to filling stage of corn. And its yield increase was not significant compared to that of bio-degradable film and polyethylene film.Degradation processes of bio-degradable film and non-degradable film were different. Degradation process of bio-degradable film began with small holes, and then holes became bigger. With the crisp and thinning, films broke down and fatherly degraded. Physical and mechanical properties of non-degradable films was poor, it cracked first under natural environment and then broke down and finally degraded.SEM can be used as the way studying degradability of degradable material and degradation, so as infrared spectrum. It can be seen from the photo of SEM, that the microstructure of mulched film had been changed obviously after degradation. The infrared spectrum of mulched film can show some changes of film's component and characters; different kind of film had their own infrared spectrum, different films can be differentiated by infrared spectrum.According to the experiment results of degradation in field, degradation mechanism of the biodegradable mulch film can include four stages: the first, the material surface appeared deficiency while the surface area and interstice increased of material in the action of natural environment and microorganism(inducement period); the second, along with the surface area and interstice of material increased and the gap strengthened, the chemical chain of the high polymer's principal chain broke as a result of the hydrolysis or the enzymatic effect in the action of hydration, causing the molecular weight and mechanics function descended(dissociation period); the third, the molecular of high polymer split the low polymer after its physical mechanical function descended, the material decomposed the fragments, the mass defect intensified(decomposition period); the fourth, the low polymer of fragments form in the natural environment, the microorganism, the biological enzyme (catalysis) became the smaller fragments, thus absorbed by the phagocytes, or further turn into CO2 and H2O due to hydrolysis (degradation period).In soil, the main degradation product of biodegradable mulch film is the hydrocarbon which caused hardly the heavy metal pollution and the organic matter pollution, and its degradation product can be the carbon source material of the microorganism, which has the good ecology effect.The degradation degree of the bio-degradable mulch film varied under different temperature, moisture condition and the ultraviolet illumination, though in the short time the degradation effect was not obvious and the degradation degree is smaller, the degradation tendency was evident. The degradation process of bio-degradable mulch film could be accelerated by some factor, but degradation process was not a simple addition of single factor, the environmental factors had coordinative effects on its degeneration.