Effects Of Different Mulching Materials On Tree Trays On Soil Properties And Apple Tree Development In Xunyi Densely Planted Apple Orchard

Apple’s(Malus domestica Borkh.)cultivation area and production are among the top in the world and occupy an important position among fruit trees.China is a large apple-growing country,meanwhile,the Loess Plateau region is one of the dominant production areas.However,the scarcity and uneven distribution of precipitation in this region seriously restrict the productivity and efficiency of the local apple industry,so that the development of orchard water conservation and drought resistance technology is of great significance to the development of apple industry in the Loess Plateau region.Mulching,a soil management method that affects the growth and development of fruit trees by regulating the soil environment,has been widely used in recent decades.In this study,we analyzed soil physical and chemical properties,soil enzyme activity and microbial community,apple tree growth and development,fruit quality by covering young orchards with ground cloth,sawdust,drug residue and coconut bran,commercial orchards with drug residue and ground cloth,and compared the effects of different mulching materials on soil quality,apple tree growth and fruit quality,in order to investigate suitable mulching materials and techniques that can improve orchard quality and yield as well as providing a theoretical basis for the management of orchard soil.The main results are as follows:1.Different mulching materials can all regulate soil temperature.In the annual development of apples,ground cloth mulch reduced soil temperature,while drug residue mulch showed a good buffering effect by reducing soil temperature during high temperature in summer and increasing soil temperature during low temperature in winter.In two consecutive years of treatment,different mulches changed the water content of the shallow soil layer(0-20 cm).During early fruit development,ground cloth mulching and slag mulching increased soil water content,organic matter,fast-acting phosphorus and fast-acting potassium to different degrees.Respectively,slag mulching had a better effect.However,the content of total soil nitrogen did not change,indicating that the different mulching treatments did not affect soil nitrogen levels.2.Different mulching materials could affect soil enzyme activity and bacterial community.The slag mulch not only increased soil peroxidase activity at different developmental stages(young fruit,expansion and ripening)of apple fruit,but also increased soil sucrase and urease activities at early fruit development.Ground cloth mulching increased soil catalase and sucrase activities at the early stage of fruit development,but it had no effect on soil urease activity.The 16 s r RNA sequencing of soil microorganisms revealed that both mulches increased soil bacterial Alpha diversity,with the drug residue mulch having a better effect,in addition,the Beta diversity of soil bacterial communities was more similar under both mulches,while these two were significantly different from the control.In terms of bacterial community distribution,the ground cloth mulching treatment significantly increased the abundance of bacterial Actinomycetes.Among that,Bacillariophyta and Thick-walled Bacillariophyta accounted for44.7%,65.7% and 79.7%,respectively,while the slag mulching treatment significantly increased the abundance of Actinomycetes and Bacillariophyta by 15.5% and 19%,respectively.3.Different mulching treatments had some influence over leaf conductivity,chlorophyll content,leaf light and capacity,leaf area and leaf nutrient content of apple trees.After different mulching treatments,the leaf chlorophyll content was more or less in the order of ground cloth mulching > coco coir mulching > drug residue mulching > sawdust mulching > control.The relative conductivity of the leaves was in the order of control > ground cloth mulch > sawdust mulch > drug residue mulch > coconut husk mulch.The net photosynthetic rate of the leaves was in the order of sawdust mulching > drug residue mulching > coconut bran mulching >ground cloth mulching > control,and sawdust mulching and drug residue mulching showed significant differences compared with the control.The leaf area size was in the order of coconut husk mulch > coconut residue mulch > ground cloth mulch > sawdust mulch > control,and the difference between sawdust mulch and coconut husk mulch and control reached a significant level.As for leaf nutrients,sawdust and drug residue mulching remarkablely increased leaf nitrogen content,while ground cloth mulching apparently decreased leaf nitrogen content.Moreover,sawdust mulching and drug residue mulching significantly increased leaf phosphorus content,and all four mulches enhanced leaf potassium content.4.Both mulching treatments changed apple fruit quality.The residue mulching prominently increased the single fruit weight and flesh crispness,while both mulches reduced the flesh hardness.The soluble solids content of fruits increased by 7.0% in 2021 after residue mulching with the difference reaching a significant level.For two consecutive years,slag mulching notably increased fruit nitrogen,phosphorus and potassium contents.Besides,ground cloth mulching dramatically increased nitrogen and potassium content in fruits.5.In actual production,the application of drug residue mulching was the best considering soil quality,fruit tree growth and fruit quality as well as the cost and utilization of mulching materials.