| The mulch film had the functions of temperature increase,moisture retention,salt suppression,and weed control.However,with the large amount of residual film used in the farmland,there are more and more residual membranes,which adversely affect the farmland ecological environment and crop growth and development,and biodegradation.The mulch film was an important way to solve the residual film pollution.In order to clarify the degradation characteristics of the biodegradable mulch film and the cotton field ecological environment and cotton growth and development,four biodegradable mulch films(T1,T2,JF,BSF)were set up in the southern Xinjiang oasis cotton area.The normal mulch film was used as a control to analyze the degradation characteristics of different biodegradable mulch films and the changes in water,heat,salinity,nutrient cycling and yield composition of cotton fields under the cover.The results of this study provide theoretical support for the screening and safety evaluation of biodegradable mulch film in the Oasis cotton area.The research results of the thesis are as follows:1.The degradation rate of different biodegradable mulch films is different.The degradation rate of T2 treatment is 75.6%,and the degradation rate of BSF treatment is the lowest,which is 43.5%.The final T2 treatment enters the crushing period,and the other treatments finally enter the cracking period.JF treatment of a large number of weeds is not conducive to crop period,BSF increased the number of weeds after the bell period.2.Biodegradable mulch film had significant effects on cotton growth and development.BSF treatment had no significant difference with CK in plant height and leaf number,but the number of fruit branches was 13.7%higher than CK,and T2,T1 and JF were lower than CK.Compared with CK,BSF treatment is more conducive to the accumulation of dry matter.Its dry matter accumulation is only 0.38%lower than CK.The distribution of roots,stems and leaves treated by BSF was 7.45%and 6.03%higher than that of CK,and the distribution of buds was only 0.06%lower than that of CK.The water use efficiency and irrigation water use efficiency of BSF treatment were higher than those of T2,T1 and JF,and lower than CK,but there was no significant difference compared with CK.3.Different biodegradable mulch films have different effects on cotton photosynthesis.The earlier the degradation,the lower the intercellular CO2 content,the lower the canopy temperature,the higher the canopy CO2 content.The canopy temperature treated by BSF was higher than that of CK and other treatments,and the difference in leaf temperature treatment was not significant.When the film was coated for 60-100 d,the temperature of 10 cm under the BSF treatment film was 1.6℃ higher than that of CK.The average water content of 0-80 cm treated by BSF was 2.4%-19.2%higher than that of CK,and other treatments were lower than CK.4.Biodegradable mulch film can increase the content of ammonium nitrogen and nitrate nitrogen in 0-60 cm soil layer and reduce the leaching degree of ammonium nitrogen nitrate nitrogen.BSF was 37.81%and 61.28%higher than CK,respectively.Compared with CK,BSF treatment can increase the content of available phosphorus in the 0-40 cm soil layer by 40.43%,and the salt inhibition effect is better than CK treatment.At the flowering stage,the nitrogen uptake of T1 and BSF treatments was not significantly different from that of CK.The nitrogen uptake by BSF treatment was significantly higher than that of CK during the boll stage.The nitrogen use efficiency of JF and BSF was significantly higher than that of CK,and the utilization efficiency of phosphate fertilizer was not different from that of CK. |
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