Distribution Characteristics Of Soil Aggregates And Organic Carbon In Citrus Orchard

Soil is an important part of the citrus orchard ecosystem and the basis for the survival of citrus trees.The quality of orchard soil directly affects the growth of citrus trees.Therefore,the citrus orchard soil on Hunan Province,Hubei Province,Jiangxi Province,Guangdong Province,and Chongqing City is selected as the research object.Analysis the distribution and stability of soil aggregates,and the content and reserve of soil organic carbon,by divided into five kinds of soil-forming parent materials:Quaternary red clay,limestone,slate,sandstone,and river alluvium,and three kinds of planting years:0-10 years,10-20 years,and 20-30 years.In order to provide scientific basis for improving soil quality and maintaining the balance of citrus orchard ecosystem.The main results are as follows:(1)The distribution of soil aggregates in citrus orchards is mainly distributed with large aggregates(>0.25mm),and the content of each particle size of the aggregates tends to decrease as the particle size decreases.With the increase of planting years,the MWD and GWD of soil aggregates in citrus orchard decreased,and D increased,indicating that the stability of soil aggregates decreased with the increase of planting years.The order of MWD and GWD of soil aggregates developed from different soil-forming parent materials is as follows: Quaternary red clay> limestone>sandstone>slate shale>river alluvial,and D from high to low is river alluvial>Slate shale>limestone>sandstone>Quaternary red clay,indicating that the stability of soil aggregates developed in the Quaternary red clay is the best,followed by limestone and sandstone,followed by slabshale and river alluvial matter.The MWD and GWD of soil aggregates in citrus orchard in different regions are shown as Hunan Province>Hubei Province>Jiangxi Province>Chongqing>Guangdong Province,and D represents Guangdong Province>Hubei Province>Chongqing City>Hunan Province>Jiangxi Province,indicating that the soil aggregates of citrus orchards in Jiangxi,Hunan and Hubei provinces have better stability,while the soil aggregates of Guangdong and Chongqing have worse stability.In the analysis of the correlation between soil aggregates MWD,GWD,D and the particl size of soil aggregates,the correlation coefficient with >2mm aggregates is the largest,indicating that >2mm aggregates are the main factors affecting the stability of soil aggregates.(2)Under different planting years,soil-forming parent materials,and regions,>2mm aggregates has the highest organic carbon,and the organic carbon content of large aggregates is higher than that of micro aggregates.The reserve of organic carbon in aggregates decreases with decreasing particle size.With the increase of planting years,the content and reserve of soil organic carbon have increased.The order of organic carbon content in soil developed form different soil-forming parent materials is: Quaternary red clay>slate shale> limestone>river alluvial> sandstone.The order of organic carbon reserves is: quaternary red clay> slate shale>Sandstone>Limestone>River alluvium.The order of organic carbon content in different regions is: Hunan Province>Chongqing City> Hubei Province>Jiangxi Province>Guangdong Province.The order of organic carbon reserve is: Hunan Province>Jiangxi Province>Chongqing City> Guangdong Province>Hubei Province.The contribution rate of organic carbon in each particle size of soil aggregates to soil organic carbon decreases with decreasing particle size in citrus orchards.The contribution rate of >2mm aggregates is the largest.In addition,the range of change of >2mm aggregates is the largest Under the influence of different planting years,soil parent materials,and regions.(3)The content and reserve of soil organic carbon are positively correlated with the content of >2mm aggregate,and negatively correlated with the content of aggregates of2-0.25 mm,0.25-0.053 mm,and <0.053 mm.The content and reserve of soil organic carbon are extremely positively correlated with MWD and GWD,and negatively correlated with D,indicating that the higher the content and reserve of soil organic carbon,the more stable the soil structure.(4)Measures such as applying biochar,increasing straw,and reasonable management model can be used to enhance the stability of soil aggregates,and increase the content of soil organic carbon by applying organic fertilizer,soil no-till,suitable high-density planting.