Copper Speciation In The Rhizosphere Of Apple And Its Effect On Nutrient Uptake And Distribution In Young Trees

With the extensive use of pesticides and fungicides,as well as the discharge of pollutants from industry,the problem of copper pollution in soil is becoming more and more serious.The amount of absorption and accumulation of heavy metals by plants depends on the bioavailability of heavy metals in the soil,which is mainly determined by the form of heavy metals.The rhizosphere is a soil microsphere with special physical,chemical and biological properties.These unique properties of the morphology and distribution of heavy metals in rhizosphere environment and biological effectiveness has a certain influence,therefore,apple rhizosphere soil of copper and its influence on apple saplings,can better understand the chemical behavior of copper in orchard soil,and the reasonable adjustment of the use of pesticides and provides the basis for controlling the quality of the fruit.This paper mainly investigated the orchards in Tai ’an,Jinan and Jining,and analyzed the morphology and distribution characteristics of copper in rhizosphere soil from three aspects of different years,soil types and soil management patterns.The effects of different copper compounds(copper nitrate,copper acetate,copper sulfate and copper chloride)on the soil environment of apple saplings and rhizosphere were studied by pot experiment.The experimental results are as follows:1.With the increase of planting years,the content of available copper in the rhizosphere soil of the orchard also increased,and the content of copper in various forms generally increased.The content of exchangeable copper in rhizosphere soil was lower than that in non-rhizosphere soil.Except for 35-year orchard,the main form of exchangeable copper in rhizosphere soil was residual state.The available copper content in the rhizosphere soil of the three soil types of orchards was Cinnamon soil < aquic soil < brown soil,and the main form of copper in the rhizosphere soil was residual form,followed by that in the brown soil orchards,the main form of copper in the rhizosphere soil was carbonate,the brown soil orchards were Fe and Mn oxides combined form,and the tidal soil orchards were organic form.The available state content of copper in the rhizosphere soil under three different soil management modes was in the order of mulching Grass < Sward < Clear Tillage,and the main form of copper in the rhizosphere soil was in the participating state.The exchangeable state in the rhizosphere soil under clear tillage mode was the highest.2.The number of rhizosphere soil microorganisms under the four treatments was significantly lower than that of the control,and the number of rhizosphere bacteria under the copper nitrate and copper acetate treatments was the least.The number of actinomycetes in rhizosphere was the lowest under copper sulfate treatment.The number of rhizosphere fungi was the least under copper sulfate treatment.The values of B/F and A/F in the rhizosphere were the lowest under copper acetate treatment,indicating that the soil treated with copper acetate had worse health status than other soils.The alkaline phosphatase activity of rhizosphere soil under copper nitrate treatment was the lowest.The urease activity of rhizosphere soil was the lowest under copper acetate treatment.The rhizosphere catalase activity was the highest under copper nitrate treatment.3.The carbonate-bound and Fe-Mn oxide-bound copper forms are the main forms after four kinds of exogenous copper are applied.The contents of exchangable and residual copper in rhizosphere soil were the highest,while the contents of carbonate-bound,Fe-Mn oxides bound and organic copper were the highest.The nitrate nitrogen content in rhizosphere soil was the lowest under copper acetate treatment.The effect on ammonium nitrogen was not significant.4.Four treatments all increased the contents of N,P and K in leaves,among which the lowest contents were copper chloride,copper chloride and copper sulfate.The lowest contents of N,P and K in roots were copper acetate and phosphorus,copper acetate and copper nitrate,respectively.The lowest contents of Ca and Fe in leaves were copper nitrate;The treatments with the lowest calcium and iron content in roots were copper acetate and copper sulfate.The highest copper content in leaves and roots was copper nitrate,copper sulfate and copper acetate,respectively.The lowest zinc content in leaves and roots was copper nitrate;The lowest Mg content in leaves was copper sulfate and copper acetate,but the difference was not significant in roots.There was a positive correlation between exchangeable copper content and mineral elements in leaves.The content of carbonate bound copper was negatively correlated with the mineral elements in leaves,while the residual copper was significantly correlated with the mineral elements in leaves.There was a negative correlation between the carbonate-bound copper and the iron-manganese oxide-bound copper and the mineral elements in leaves.Under the four treatments,the contents of a large number of elements N,P and K in leaves were higher than those in roots,and the contents of Fe and Cu in roots were higher than those in leaves,while other elements were mainly distributed in leaves.5.The effects of cupric acetate and cupric nitrate on photosynthetic performance,root architecture,biomass and leaf enzyme activity of apple saplings were the greatest,and the effects of cupric chloride were the least.