Degradation Of Bast Fiber Mulching Film And Its Effects On Soil Properties

The extensive application of plastic films mulching has greatly improved the modern agriculture in China.While,the residual of plastic mulch film was becoming a restrict problem for the sustainability of agriculture in China.The development and application of biodegradable plastic film such as the bast fiber mulching film?BFMF?might be an effective measure to solve such problem.The degradation of BFMF under different soil environmental conditions and its effects on soil properties after degradation will affect the future prospect of its applications.Therefore,bag-buried pot experiments and a plot field experiment were conducted to study the degradation of BFMF under different soil pH,soil moisture content,nitrogen application,use seasons and pakchoi planting.The changes of BFMF structure characteristics as well as soil microbial biomass and enzyme activities were determined.Further,the effect of BFMF degradations on soil properties and crop growth were studied too.The main conclusions are as follows:?1?BFMF could be degraded rapidly after entering the soils.The degradation processes of BFMF obeyed the Olson attenuation model?R²=0.689⁰.996,P<0.05?.According to the model,the semi-degradation time of BFMF under different soil environmental conditions was between 31.1¹23.8 d,and the complete-degradation time was between 134.3⁵35.0 d.The application of nitrogen and planting of pakchoi during the autum-winter season significantly inhibited the degradation of BFMF.Further,the degradation rate of BFMF was significantly higher during summer than autumn-winter season.The degradation rate of BFMF under soil moisture content 25%was significant higher than under 15%soil water and continuous flooding.While,limited effect of soil pH?5.80⁸.34?on the degradation of BFMF was observed?P>0.05?.?2?Soil microbial biomass and soil catalase,invertase and acid phosphatase,urease and cellulase activities mianly related to the soil environmental conditions.There were significant positively relationship between the degradation rate of BFMF and the soil microbial biomass carbon,nitrogen?MBC,MBN?and cellulose activities at the end of the experiments periods?P<0.01?.These results indicated that the different degradation characters of BFMF might be due to the changes in soil microbial biomass and enzyme activity under different soil environment conditions.?3?The results of the SEM showed that obviously damage of the surface observed at degradation rate over 40%.The surface structure of BFMF during degradation process was as wrinkles—folds/cracks—folds/pores.The FTIR spectrum of BFMF showed that a large number of functional groups such as-OH,-CH,C-O,C-O-C and-CH₂-existed in the BFMF.The C=O characteristic peak appearance when the degradation rate reached 40%.These might indicate that the degradation process of the BFMF was concluded to be cellulose broken chain,forming a straight chain glucose with C=O bond.During the test period?72 d?,the contents of N,P and K in BFMF mainly showed as enrichment.?4?The contents of soil alkali-hydrolyzed nitrogen,available phosphorus and available potassium significantly increased after BFMF barried over 175 g/m²?the amount of mulching film for 5 times?.Further,the fresh and dry weight of the aboveground parts of Chinese cabbage significantly increased by 85.08%and 23.09%,and the contents of N,P and K increased by 16.88%,11.23%and 34.67%,respectively,after BFMF barried at 350 g/m².The CaCl₂ extractable Cd,Mn and Zn in soil?P>0.05?and the contents of Ni in pakchoi?P<0.05?reduced after the degradation of BFMF.In conclusion,the bast fiber mulching film could be degraded in a relatively short period after entering the soil,and can improve soil nutrient supply and promote crop growth.However,its degradation process was affected by environmental conditions.In order to achieve a win-win situation between crop production and environmental protection,soil environmental conditions should be fully considered in practical use of BFMF.