| China’s use of plastic film ranks first in the world,and is increasing at a rate of 9% every year.With the increase of the use of plastic film,the ecological environmental problems and economic development problems caused by plastic film residue,such as soil hardening,reduced tillage capacity,blocked farming,crop production,etc.,have attracted much attention.Although many scholars have studied the application of degradable mulching film at present,few scholars have made in-depth comparative analysis on the application of different types of degradable mulching film in cotton fields in northern China,and there are few studies on the temperature and moisture factors that affect the degradation of degradable mulching film.This study black plain white polyethylene film,PE films,two kinds of biodegradable Xifeng film,Tianye film as the research object,mainly through the indoor experiment and field experiment,study the effects of different moisture content and temperature on membrane degradation rate and different kinds of cotton growth in northern area of plastic film mulching and the influence of the soil.(1)The induction period of Xifeng and Tianye degradable mulching film is about 45 d,and the degradation process of Tianye film is faster than that of Xifeng film.In the harvest period of floc opening,the film on the film surface is basically broken and the mechanical properties are lost,except for the surrounding buried soil.After the induction period,the degradation process accelerated.Under the condition of 30℃ and 30% mass moisture content,the weight loss rate of Xifeng film was the highest,and the degradation rate was faster with the prolongation of time.At 40℃ and 20% mass water content,the weight loss rate of Tianye film is the highest.(2)Plastic film mulching significantly increased seed cotton yield,plant height,leaf area,dry matter weight and photosynthesis at the early growth stage,but had no significant effects on chlorophyll content and photosynthesis at the late growth stage,and there was no significant difference among different plastic films.(3)The water content of 0-40 cm soil and the temperature of 0-20 cm soil layer can be significantly increased by film treatment.Xifeng and Tianye degradable mulching films can achieve similar thermal insulation and water retention effect as ordinary mulching films before degradation,but after degradation,the thermal insulation and water retention effect is slightly worse than that of ordinary PE mulching film,but both are better than that of no film treatment.Under the same temperature and water conditions,the soil enzyme activities generally showed that the greater the degradation,the higher the enzyme activities.(4)Scanning electron microscope observation showed that ordinary polyethylene mulching film did not degrade in a short time,the surface before and after the test was uniform and compact,and no or a small amount of particles were formed.The surface of Xifeng and Tianye degradable mulching film is rough before degradation,but after degradation,the surface roughness is aggravated,the structure is loose,and the particulate matter is increased.The results of infrared spectroscopy showed that the infrared spectrum of degradable mulching film had characteristic peaks of PBAT and PLA.After degradation,the characteristic peaks of carbonyl group and hydroxyl group of degradable mulching film changed greatly,which indicated that the degradation of Xifeng film and Tianye film was obvious,and the degradation degree was consistent with the weight loss rate and morphology characteristics.In summary,Xifeng and Tianye biodegradable mulching films have similar composition,degradation performance and degradation methods,and the degradation solution is the fastest at 30% and 40℃.In the induction period,compared with ordinary polyethylene mulching film,it had similar effects on cotton growth,yield and soil thermal insulation and water retention performance,which were significantly better than that of no mulching film. |
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