Biopore And Non-biopore Characteristics Of Typical Agricultural Land In Southern Guangxi

Guangxi is located in a karst area,where the geological environment is fragile and complex.The frequent extreme climate conditions of this area in recent years have caused the agricultural environment to face the plight of drought stress.Therefore,to optimize the finite regional agricultural water resources utilization and crop yield maximization,this study has focused on the soil macropores function.The outcomes of this research have important significance to increase our understanding of the soil water transport and storage which are closely related to the structure and type of soil pores.Studying Guangxi typical farmland biopores and non-biopores structure characteristics was conducted to explore different tillage or cover measures impacts on soil pore structure and mechanism of the possible influences.For,this research a typical farmland in southern Guangxi was selected as the research object,and four treatments of non-tillage plus non-cover(NT0),tillage plus non-cover(T0),no-tillage plus cover(NT100),and cover plus tillage(T100)were studied.Using CT scan and image separation 2D-3D characteristics of soil pore structure were quantitatively analyzed.The obtained results are as follows.(1)In the 2D characteristics,the pore area,two-dimensional pore number,and pore size of biopores in T0 and T100 zones are significantly increased,while them of non-biopores are reduced,and the boundary distortion of non-biopores increased.The effect of these increases or decreases in T100 zones is delayed compared with that in T0 zones.The two-dimensional quantitative characteristics of biological pores in NT100 area also improved,while the change of non-biopores was mainly due to the decrease of quantitative characteristics.The change of morphological characteristics was small as compared to non-biopores.(2)In the 3D characteristics,the porosity of non-biopores is in the order of NT0(2.514 %),T100(2.307 %),NT100 and T0(about 1.421 %),while the porosity of biological pores is T0(1.579 %),T100 and NT100(about 0.810 %),NT0(0.144 %),orderly.The volume,number,diameter,branch length,vertical angle ratio,and connectivity of biopores are all increased in T0,NT100,and T100 zones,while the bending degree decreased.Besides,the density changed slightly and the volume,number,average diameter,and branch length density of non-biopores decreased.Among them,the three-dimensional characteristics of biopores and non-biopores in T0 zones are the most obvious,followed by T100 zones,and relatively small in NT100 zones.In 3D visualization,there are large biopores in the surface layer of T0 and T100 zones.Most of the biopores in T0 and NT100 zones are in the upper part of the soil.The distribution of biopores in T100 zones is more uniform along the depth.There are more non-biopores in T100 and NT100 zones than in T0 zones.The pores of NT0 zones are dominated by non-biopores,and the development of biopores is rare.(3)In the comprehensive analysis,the increase of organic matter content in T100 zone and the increase of soil saturated water conductivity in T0 zone were the most obvious.The relationship between total porosity and organic matter content is closer,and also the relationship between biopores porosity and saturated water conductivity is closer.The average length,vertical angle ratio and local connectivity of total pores are significantly positively correlated with organic matter,and some characteristics of total pores can explain 83.19 % of organic matter change.The porosity and connectivity of biological pores are significantly positively correlated with saturated water conductivity,and some characteristic variables of biopores can explain the change of saturated water conductivity of 92.49 %.In conclusion,Tillage measures breaks the original macropores into secondary non-biopores,and mixes the soil layer to make the distribution of organic matter even,which creates conditions for the development of subsequent root biopores.Cover measures can delay the external effects on the soil,increase the source of organic matter,protect the development of biopores.Compared with single tillage or cover measures,cover tillage measures will not only facilitate the development of biopores and the improvement of organic matter,but would also delay the external influence on soil,create better soil pore structure,and improve the soil permeability and nutrient conditions.Therefore,in the typical farmlands of Guangxi,the soil with cover tillage measures can provide a good growth environment for the development of sugarcane and its root system through more favorable conditions for soil water transport.