Effects of degradation film on soil hydrothermal and yield of drip irrigation cotton in extremely arid areas

In order to explore the application effect of degradation film on cotton planting under drip irrigation in Hami basin,four different degradation films（ M1,M2,M3 and M4） were selected. The common plastic mulch PE was used as the control（ CK） to carry out control experiments to analyze the degradation performance of different degradation films and its influence on soil hydrothermal,heat change,and yield of cotton under drip irrigation. The results showed that the earliest degradation occurred on M2 around 80 days after mulching. M2 entered the survival stage on day 180 after mulching together with M4. There were still small pieces of plastic film at the end of growth period. However,the degradable films M1 and M3 only entered the disintegration at the end of growth period,while the plastic mulch did not degrade all the time. In the seedling stage and bud stage,all kinds of degradation films have not yet begun to degrade, and the performance of heat preservation and moisture preservation was similar to CK. After florescence stage,all kinds of degradation films showed different degrees of degradation,and the difference of average soil temperature between degradable film and common plastic film was largest. The average soil temperature of degradation film M1,M2,M3 and M4 was 11.62%,10.02%,7.67% and 10.45% respectively,lower than that of CK,while there was little difference between boll stage and boll opening stage. The average soil temperature of degradation film was 2.05%-5.52% lower than that of CK at boll stage and wadding stage. The average soil mass moisture content of M1,M2,M3 and M4 treatments were 5.92%,8.09%,7.14% and 12.41% respectively,lower than that of CK,as the great difference of soil moisture retention performance is large. The yield of seed cotton treated with degradable film was 2.05%-13.72% lower than that of CK,and the yield of degraded film M2 treated with degradable film was second only to that of CK. Therefore,it is feasible to replace the common plastic mulch with the colorless transparent oxidization-biodegradable film M2 in the cultivation practice of cotton in extreme arid regions such as Hami basin.