Difference Of Soil Microbial Communities And Relationships With Soil Nitrogen And Corn Characters In Different Film Mulching Farmlands In Weibei Dryland

Soil microorganisms and enzyme activities played a key role in the mineralization and decomposition of organisms,nutrient conversion,and improvement of crop stress tolerance,and can be used as important biological indicators for evaluating soil fertility and soil quality.Film mulching measures in the Loess Plateau can increased crop yields,but it will cause negative environmental effects such as"white pollution".The use of degradable film can effectively alleviated the adverse effects of residual film.Therefore,it was important for evaluating the environmental effects of different film mulching measures that studying how different types of film mulching affected microbial communities and enzyme activities,and their response to soil nitrogen and corp agronomic characteristics.Soil nitrogen,corp agronomic characteristics,enzyme activities,soil microbial biomass and community structure and the key influencing factors for soil microbes and enzyme activities were measured under different film mulching treatments during the growth period of maize in the Weibei drylands of the Loess Plateau using phospholipid fatty acids（PLFAs）.The following five treatments were evaluated:white non-biodegradable film mulching（ND-WP）,black non-biodegradable film mulching（ND-BP）,white biodegradable film mulching（D-WP）,black biodegradable film mulching（D-BP）,and flat planting without mulching as a control（CK）.It provided biological indicators for evaluating the soil health status of different mulched farmland,and also provided scientific guidance for the selection of the best types of mulching in dry land and field management of mulching corn.The main findings were as follows:（1）From the perspective of the differences in soil properties of different types of film-mulched corn fields,the soil temperature,water content,nitrate nitrogen,ammonium nitrogen,and total nitrogen content in each growth period of film mulching treatments were all higher than CK,but the organic carbon content and C/N were lower than CK.The mulching material（degradable or non-degradable）and the color of the mulching film（black or white）had significant effects on the content of nitrate nitrogen,ammonium nitrogen,inorganic nitrogen,and total nitrogen,but their effects varied depending on the type of nitrogen and the growth period.（2）From the perspective of the differences in crop agronomic characteristics of different types of film-mulched corn fields.The plant height,leaf area,dry matter stem and leaf dry matter were higher in non-degradable film mulching treatments than in degradable film treatments in the tasseling and the milk stages but no significant differences in maturity stage.In the mulching treatment of the same material（the same degradable film or the same non-degradable film）,the agronomic indicators in the early stage（jointing and tasseling）showed that the white film mulching treatment were higher than the black film mulching treatment,but the difference become smaller in the later stage.The nitrogen content of stems,leaves,and ears were all affected by the type of mulching and growth period,the nitrogen content of a single plant was significantly higher than that of CK in the film mulching treatment,and the difference become smaller in maturity.（3）From the perspective of the differences in the soil microbial community structure,film-mulching measures increased the total PLFA,gram-positive bacteria,gram-negative bacteria,common bacteria,actinomycetes and fungal PLFA concentrations.The soil microbial activity were higher in the non-degradable film mulching treatment than the degradable film mulching treatment,the white film mulching treatment in the early stage of growth were higher than the black film mulching treatment,and the later stage of growth the black film mulching treatment were higher than the white film mulching treatment.From the perspective of microbial community structure,F/B were lower in CK than mulching treatment in jointing and tasseling stages,but were higher than mulching treatment in milk maturity and maturity stages.The white film mulching treatment in the early stage of growth were higher than the black film mulching treatment,the black film mulching treatment in the later stage were higher than the white film mulching treatment.The G⁺/G^-of the mulching treatment was lower than CK in multiple growth periods.Cy/Pre was similar to SAT/MONO,the non-degradable film mulching treatment were higher than the degradable film mulching treatment in the early stage of growth,and the non-degradable film mulching treatment were lower than the degradable film mulching treatment in the late stage of growth.Iso/Ant was lower in CK than the mulching treatments in multiple growth periods.From the perspective of the differences in soil enzyme activities,the type of film mulching significantly affected soil enzyme activities,but its impact varied with the types of enzyme activities and growth periods.The urease,ammonia monooxygenase,nitrate reductase and nitrogenase activities were higher in the black film mulching treatment than the white film treatment of the same material in the late growth stage,indicating that the black film mulching had the function of accelerating the rate of nitrogen conversion.In general,film mulching measures can help optimized the soil nutrient environment and improved the tolerance of microorganisms to environmental stress,in the early growth stage,the soil nutrition status under non-degradable film mulching treatment was better,but the microorganisms under degradable film mulching treatment were tolerant to environmental stress in the later growth period.In the white film mulching treatment,the soil has a better nutrient environment and higher stability in the early stage of growth,but in the black film mulching treatment,the soil was more stable and the microorganisms were more resistant to environmental stress in the later stage of the.（4）From the analysis of the correlation between soil physical and chemical properties and soil microbial PLFA concentration,community structure,and enzyme activity,the soil temperature,soil water content,nitrate nitrogen,ammonium nitrogen,inorganic nitrogen,total nitrogen,C/N were related to soil microbial community and enzyme activity.Redundancy analysis（RDA）showed that the environmental factors that had a high impact on soil microbial factors（P<0.05）were mainly soil water content（SWC）（F=9.2,P=0.002）,soil temperature（ST）（F=8.8,P=0.002）,ammonium nitrogen（NH₄-N）（F=8.0,P=0.006）and inorganic nitrogen（SIN）（F=6.9,P=0.018）,indicating that the differences in soil microbial and enzyme activities were mainly affected by soil hydrothermal and nitrogen conditions.In general,the degradable film mulching in the early stage of crop growth showed no inferior to the non-degradable film mulching treatment in increasing temperature and moisture,and promoting the development of microorganisms and plants.At the same time,due to degradation and fragmentation of degradable film in the later stage,the ground temperature was reduced,the soil aeration rate was increased,and the microorganisms were reduced,but degradable film mulching increased the nitrogen content,improved the soil environmental quality,extended the growth period of the plant,and exhibited an environmental effect.The black film mulching treatment had low light transmittance,which can effectively hindered the development of weeds,and increased the soil nitrogen content and microbial activity in the later stage of crop growth,so it was more beneficial to agricultural production.Comprehensive considerations,film mulching measures were beneficial to increase soil nitrogen content,microbial activity and crop yields,among which degradable black film was the best type of mulching.