Effects Of Biodegradable Mulch Film And Nitrogen Application On Soil Microenvironment And Maize Yield Formation In Dry Farming Fields

The Loess Plateau is an important spring maize producing area in our country.It is a typical semiarid regions.The limited and uneven distribution of rainfall,low temperature in spring and unscientific nutrient management have seriously threatened the growth and development of spring maize.Film mulching technology could overcome the low and unstable grain production capacity caused by insufficient water and heat conditions,but long-term use of plastic mulch can also cause environmental pollution problems.Biodegradable film mulching is an effective means that can reduce plastic film pollution while regulating soil humidity and temperature conditions,but the impact of differences in its degradation characteristics on farmland soil microenvironment,crop water and fertilizer utilization,and yield formation is not yet clear.In this study,field trials of spring maize were carried out at the Changwu Loess Plateau Agro-ecological Experiment Station in 2020 and 2021.Experiment design:Three fertilization levels(N1:240 kg ha^-1,N2:180 kg ha^-1,N3:120 kg ha^-1))under three biodegradable membranes（60%biodegradable membrane BMF1,40%biodegradable membrane BMF2,30%biodegradable membrane BMF3,with polyethylene mulch PE mulch as control）,field test,analyze the degradation characteristics of different biodegradable films,soil temperature regulation,the temporal and spatial changes of soil moisture and nutrients under different nitrogen application levels and the effects of maize growth and development,nutrient uptake,grain yield and water and fertilizer use efficiency.The differences between biodegradable film and PE in regulating soil microenvironment,crop water,fertilizer use and productivity sustainability under different nitrogen application rates were discussed.The main findings are as follows:（1）The damage and weight loss of the biodegradable film mainly occurred in the late grow stage of spring maize with increased content of degradable component,the degradation rate of the plastic film was obviously speeded-up.The average daily temperature of BMF1,BMF2,BMF3 and PE maize growing period increased by 1.40,1.46,1.67 and 2.88℃respectively compared with the uncovered area.It was inversely proportional to the amount of degradable materials.The warming effect of biodegradable film weakens with the increase of air temperature in 10-30℃.PE has a stronger warming effect than biodegradable plastic film.It leads to large temperature difference between day and night.Compared with the biodegradable mulch films,the soil moisture content of PE has no significant difference in the early stage of crop growth,and decreased the deep soil water content in the late stage of crop growth and development.The evapotranspiration（ET）under PE coverage was 9.13,5.68 and 8.11 mm higher than that of BMF1,BMF2 and BMF3,respectively.Under the mulching of biodegradable film,the ET under the nitrogen application level of N1 was significantly lower than that of the N2 and N3 treatments,and the reduction of the nitrogen application rate increased the soil water consumption of 0-100cm.（2）The soil organic matter（SOM）of BMF1,BMF2,BMF3 and PE mulching increased by 0.24,0.29,0.28 and 0.61 g kg^-1in spring maize growing period in 2020,and decreased by 0.64,0.15,0.31 and 0.67 g in 2021.the change of SOM under PE coverage was significantly bigger than those under biodegradable film treatment in two years.Increasing nitrogen application could promote the regulation of SOM by biodegradable membranes.During the fallow period,the SOM content under biodegradable film mulch increased,and BMF1 increased by 0.95 and 0.70 g kg^-1compared with BMF2 and BMF3.Both biodegradable film and PE reduced the total nitrogen content of soil surface.But the soil total nitrogen loss under BMF1,BMF2 and BMF3 coverage was only 21.4%,7.7%and 0.7%than that of PE.Under the nitrogen application level of N1,the content of nitrate and ammonium nitrogen under the biodegradable membrane was significantly higher than that of PE.（3）The effects of biodegradable mulch films and nitrogen application on the growth and development of maize are regulated by environmental factors.During the vegetative growth period,BMF1 has more advantages in the accumulation of dry matter than BMF2and BMF3 under the nitrogen application levels of N1 and N2,and N3 The fertilization level was the opposite;the dry matter accumulation of PE in the corn harvest period was11.9%,4.2%and 13.0%higher than that of BMF1,BMF2,and BMF3,respectively.The total nitrogen content between the biodegradable mulch films and PE in the shoot and in the grain from high to low is:BMF1>PE>BMF2>BFM3.The transfer rate of nitrogen content in leaves under biodegradable mulch films mulching was significantly higher than that of PE,and the increase rates were respectively were 46.1%,29.5%and 38.5%,and the transfer rate of PE in the nitrogen content of the stem was higher than that of the biodegradable mulch films.（4）There was no significant difference between the average yield and PE of the two seasons of spring maize under the mulching of biodegradable film,and there was no significant difference between the treatments under the N1 and N2 fertilization levels.10.6%,8.9%and 9.0%.Biodegradable mulch films increased the yield significantly at the N1 and N2 fertilization levels,but under the N3 fertilization level,the yield of PE was higher than that of biodegradation mulch.In 2020,there was no significant difference in nitrogen use efficiency between biodegradable mulch films and PE,but in 2021,when the water temperature was suitable,it was significantly higher than PE.There was no significant difference in nitrogen harvest indexbetween the two years.At the nitrogen application levels of N1 and N2,the biodegradable mulch films have better water use efficiency(WUE_GY),nitrogen fertilizer production efficiency（NPE）,absorption efficiency（NUPE）and all increased with the increase of the degradation rate.Compared biodegradable mulch films Nitrogen level PE can improve WUE_GY,NPE and NUPE.Considering the comprehensive performance of biodegradable films in resource use efficiency,soil nutrient retention and soil condition under different nitrogen application levels,BMF1 showed better to increase yield under N2 fertilization level,significantly improved water and nitrogen use efficiency,and reduced soil nutrient loss and film residues.It can be recommended as a mulching cultivation mode with high and stable yield,taking into account resource utilization and environmental safety in dryland spring maize cultivating areas on the Loess Plateau and similar agro-ecological regions.