Effects Of Long-term Grassing On Soil Micro-ecological Environment And Fruit Quality In Pear Orchard

Orchard grass growing is a modern sustainable orchard management mode vigorously promoted at China and abroad in recent years.Reasonable grass growing cultivation can optimize soil structure,increase soil water and nutrients content,improve soil enzyme activity and soil microbial biomass,improve orchard microclimate,help maintain orchard ecological balance,promote fruit tree growth and development,and improve fruit quality,thus,it’s beneficial to the development of fruit industry.In previous studies,there are few studies on long-term grass orchards,and most of the studies on soil microorganisms are based on relative quantitative sequencing,which ignores the effect of absolute abundance of soil microorganisms on grass orchards.In this study,the pear orchard was used as the experimental site for growing grass,and four different kinds of grasslands were set up,natural grassing(NG),Festuca elata(FE),Vulpia myuros(VM)and Trifolium repens(TR)in Yantai Agricultural Science Research Institute of Shandong Province.With conventional tillage(CT)as control,the effects of long-term grass on soil physical and chemical properties,soil microorganisms and fruit quality of pear orchard and the interaction between them were studied,so as to provide theoretical support and scientific basis for subsequent selection of orchard grass varieties and improvement of orchard soil management.The main research results are as follows:(1)Long-term grassing decreased soil p H value and electrical conductivity,increased the contents of organic matter,total carbon,alkali-hydrolyzable nitrogen and total nitrogen,and provided more available nutrients for fruit trees.The improvement of enzyme activity also proved the promoting effect of grassing on soil nutrient cycling.The effect of three kinds of artificial grass treatments on soil nutrients and enzyme activity was better than that of natural grassing treatments.Long-term grass growth had little or no significant effect on phosphorus and potassium.(2)The community structure of bacteria and fungi in long-term grass treatment was different from that in CT,and the fungal community was more sensitive to grass varieties.Grass treatment can increase the total absolute abundance of bacterial community,and the microbial community is more active.Grass treatment significantly increased the abundance of Nitrospirae,decreased the abundance of Thermi,Cyanobacteria,Chytridiomycota and Aphelidiomycota,and could significantly reduce the abundance of some common pathogenic bacteria,such as Gibberella,Fusarium,Neurospora and Moesziomyces etc.,which provided a healthier soil environment for fruit trees.(3)The results of correlation analysis among soil physical and chemical properties,soil microbial community and fruit quality showed that organic matter,available potassium,available nitrogen,available phosphorus,total nitrogen,total carbon,urease,sucrase,phosphatase and catalase were important environmental factors affecting the composition of microbial community.It has a significant positive correlation with the absolute abundance of Planctomycetes,Actinobacteria,Chloroflexi,Gemmatimonadetes,Nitrospirae,Armatimonadetes,Chlamydiae,Cyanobacteria,Euryarchaeota,Mortierellomycota,and Rozellomycota and so on.These bacteria and fungi work together to improve the soil microecological environment.(4)There were significant differences in fruit firmness,titratable acid content,vitamin C content and soluble solid content of pear fruit quality among FE,VM and TR.Among the three artificial grass treatments,the best comprehensive evaluation of fruit quality was VM treatment,followed by TR and FE treatment.Soil p H value,organic matter,total carbon,total nitrogen,phosphatase activity and catalase activity had great effects on fruit quality.In conclusion,the four kinds of grasses have different improvement effects on soil.FE,TR and VM are better than NG in improving soil nutrients and enzyme activity.At the same time,grassing also changed the soil microbial community structure,reduced the abundance of plant pathogens,promoted soil nutrient cycling supply,and provided a healthier soil environment for orchards.It is beneficial to the sustainable development of orchard.