Effects Of Covering With Vicia Villosa Roth Var On Soil Aggregates And Nutrients In Peach Orchards At Different Slope Positions

Orchard grass mulching is conducive to improving the soil environment and soil fertility,but there are relatively few studies on the impact of grass mulching in orchards on soil aggregates and nutrients.In order to explore the regularity of soil aggregates and nutrient changes under grass mulching,this study took peach orchard soil at different slope positions in Baoshi Village,Longquanyi District as the research object.In late October2019,a grass mulching experiment was conducted,and two treatment methods,namely,covering with Vicia villosa Roth var（T1）and clearing tillage（CK）,were set up on the upper,middle,and lower slope positions.Soil sampling was conducted in three stages:flowering stage,fruit maturity stage,and dormancy stage,with sampling depths of 0-20cm and 20-40cm,respectively.The effects of grass mulching on soil aggregate structure,aggregate organic carbon,and nutrients in peach orchards at different slope positions were studied in order to provide scientific basis for the construction of ecological orchards in the study area.The main conclusions are as follows:（1）The content of mechanically stable aggregates in peach orchard soils under the cover of Vicia villosa Roth var at different slope positions showed a trend of first decreasing,then increasing,and then decreasing with the decrease of particle size.At the same slope position,the mechanical stability aggregate content(R_0.25)of T1 treatment was higher than that of CK treatment.Under the same treatment,with the decrease of slope position,the mechanical stability aggregate R_0.25showed an overall upward trend.From the perspective of soil depth,R_0.25increases with the increase of soil depth.The mechanical stability aggregate R_0.25decreases first and then increases with the growth period of peach trees.（2）The content of water stable aggregates in peach orchard soils with different slope positions under the cover of Vicia villosa Roth var showed a trend of first decreasing and then increasing with the decrease of particle size.At the same slope position,the water stable aggregate R_0.25,mean weight diameter（MWD）,and geometric mean diameter（GMD）of T1 treatment were higher than those of CK treatment,while the fractal dimension（D）and The percentage of aggregate disruption（PAD）of T1 treatment were lower than those of CK treatment.Under the same treatment,with the decrease of slope position,R_0.25,MWD,and GMD showed an increasing trend,while D and PAD showed a decreasing trend.The aggregate stability generally showed a downward slope position,a middle slope position,and an upward slope position.From the perspective of soil depth,the water stable aggregates R_0.25,MWD,and GMD increase with the increase of soil depth,while D and PAD decrease with the increase of soil depth.The water stable aggregates R_0.25,MWD,and GMD first decrease and then increase with the change of peach tree growth period,D first increases and then decreases with the change of peach tree growth period,and PAD continuously increases with the change of peach tree growth period.（3）The content of organic carbon in mechanically stable aggregates of peach orchard soils under the cover of Vicia villosa Roth var at different slope positions showed a trend of increasing with the decrease of particle size.At the same slope position,the organic carbon content of mechanically stable aggregates in all particle fractions of T1 treatment was higher than that of CK treatment.Under the same treatment,the organic carbon content of mechanically stable aggregates generally increased with the decrease of slope position.From the perspective of soil depth,the organic carbon content of mechanically stable aggregates decreases with the increase of soil depth.The organic carbon content of mechanically stable aggregates increases first and then decreases with growth and long-term changes.（4）The contents of total nitrogen,alkali hydrolyzable nitrogen,available phosphorus,and available potassium in mechanically stable aggregates of peach orchard soils at different slope positions under the cover of Vicia villosa Roth var tended to accumulate in small particle size aggregates.At the same slope position,the content of total nitrogen,alkali hydrolyzable nitrogen,available phosphorus,and available potassium in aggregates of all particle fractions under T1 treatment were higher than those under CK treatment.Under the same treatment,with the decrease of slope position,the total nitrogen,alkali hydrolyzable nitrogen,available phosphorus,and available potassium contents of aggregates generally showed an increasing trend.From the perspective of soil depth,the contents of aggregate total nitrogen,alkali hydrolyzable nitrogen,available phosphorus,and available potassium decrease with the increase of soil depth.The total nitrogen,alkali hydrolyzable nitrogen,available phosphorus,and available potassium contents of aggregates generally decreased with the growth and long-term changes.To sum up,covering with Vicia villosa Roth var at different slope positions can promote the formation of large aggregates,enhance the stability of soil aggregates in peach orchards,and improve the content of organic carbon and nutrients in soil aggregates.It can be seen that orchard grass mulching is a scientific modern orchard management method.