| In order to solve the problem of residual film contamination in farmland,a field experiment is conducted with three oxo-biodegradable films with different degradation rates,common film and bare land as control.The degradation performance(degradation rate,tensile strength,elongation at break and surface microstructure)of oxo-biodegradable film and its effects on soil moisture,soil temperature,maize growth and yield are studied to find out a oxo-biodegradable with suitable degradation rate in local area.The purpose of this paper is to provide a scientific basis for the replacement of common plastic film by oxo-biodegradable plastic film and its application in Northeast China.The main conclusions are as follows:(1)The degradation rate of film and the loss rate of tensile strength and elongation at break of the film increased with the content of additives for degradation in the oxo-biodegradable film.When maize was harvested,the degradation rates of DM1,DM2 and DM3 in 2017 and DM1,DM2 and DM3 in 2018 were as follows:DM3<MD2<MD1.The degradation rate and loss rate of mechanical property of oxo-biodegradable film on ridge side were significantly higher than that on ridge top.SEM(Scanning Electron Microscope)results showed that the surface microstructure of the film was uniform before using.After using in field,the surface became rough,and even appeared cracks on the ridge-side the film,which resulted the degradation degree in ridge-side film was higher than that in ridge-top film.(2)In the early growth stage of maize,the water storage in the soil layer of 0～40 cm was significantly higher in oxo-biodegradable film treatment than that in the bare land,while the difference in the soil layer of 40～60 cm was not significant.In the middle and late growth period of maize,the degradable film was broken and the residual film clung to the soil surface,which could increase soil temperature and moisture.In addition,the cracked part of the film increased rainfall infiltration and water storage in soil reservoirs,and water storage in DM1was higher than DM2 and DM3.Compared with common plastic film and bare land,the temperature of soil layer 0～25 cm in maize seedling stage was significantly increased by oxo-biodegradable film,and the difference in temperature increase value was the highest compared with other period.The soil temperature under DM1,DM2 and DM3 treatment was basically the same,and with the increase of soil depth,the difference of temperature between treatments gradually decreased.In the whole period of maize,the average temperature of0～25 cm soil layer under DM1,DM2 and DM3 treatment was increased by 4.5℃,4.4℃and4.4℃than that under CK respectively,and there was no significant difference among them.The oxo-biodegradable film had the most significant warming effect on the soil layer of 0～15cm,and the film mulching effectively avoided the adverse effect of low temperature stress on maize seedling emergence and root growth in early spring in northeast China.In jointing stage of maize,the variation of soil temperature in each treatment decreased,and there was no significant difference between degradable film and common film.The difference of soil temperature between different treatments further reduced after maize canopy coverd ridge completely.The soil temperature of each treatment was as follows:DM3>DM2>DM1>PE>CK,that was,with the increase of the degradation rate of film,the warming effect of film weakened.Value of soil temperature increase of mulching treatment reached the minimum at 80 d after mulching approximately,so the safety period of film mulching of maize in this area was 80 d approximately.(3)The oxo-biodegradable film significantly increased the plant height,leaf area index and root growth index in the early growth stage of maize,and advanced the appeared time of maximum of the three indexes,that was to say,oxo-biodegradable film accelerated the growth process of maize.Compared with bare land,oxo-biodegradable film significantly increased maize yield,but there was no significant difference with common plastic film.Compared with CK,the yield of DM1,DM2,DM3 and PE was increased by 14.3%,14.3%,10.4% and 13.2% in 2017,respectively,and 11.6%,24.7%,22.4%and 19.1%in 2018,respectively.The yield of DM1 in 2018 was obviously lower than that of other film mulching treatments.There was no significant difference in protein,starch and oil among different treatments,but protein content in grains decreased with the increase of degradation rate.(4)Compared with bare land,The time of LAI reaching the maximum growth rate was advanced by 6～10 d,and the time of LAI reaching maximum was advanced by 4～7 d.The compensation coefficient and compensation value of accumulated temperature were calculated by the relationship between soil temperature and air temperature and the conversion relationship between accumulated soil temperature and accumulated air temperature.It was found that the compensation coefficient and daily average compensation value of jointing stage under mulching treatments were higher than that at seedling stage.Under the condition of mulching,the maize leaf area index growth was simulated based on Logistic model.Thereinto,R~2=0.96,and NSE=0.98,the residual value was well-distributed,and the fitting value and the measured value were uniformly distributed near the 1:1 line,which meant that the simulation effect of the model was good.In the seedling stage of maize,the correlation coefficient between air temperature and soil temperature was between 0.703and 0.949,which meant there was a good correlation of them.In the jointing stage,the correlation between them dropped to 0.392～0.532.In the heading stage of maize,the correlation coefficient between air temperature and soil temperature was between 0.730 and0.920.After that,the correlation decreased slightly with plant senescene.In conclusion,oxo-biodegradable film had good effect of increasing temperature and preserving moisture,and had the same effect of increasing production as ordinary plastic film.It could replace common plastic film in agricultural production. |
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