Study On The Effect Of Biochar On Soil Water Retention

Due to its rich pore structure and physicochemical properties such as oxygen-containing functional groups,biochar is widely used in soil improvement,increasing soil water holding capacity,improving soil fertility,and improving soil heavy metal pollution.However,the research on biochar's own ability to absorb and retain water is still scarce.At the same time,there are few reports on systematic analysis of fresh and aging biochar to improve soil hydraulic properties.This paper first selects three types of biochar,studies its own water absorption and water retention characteristics,and selects high-quality raw materials for producing biochar.Furthermore,the effects of different proportions of fresh biochar,chemically aging biochar and natural aging biochar on the saturated water content,saturated hydraulic conductivity,available water of plants,and suitable water for plant growth were studied.The main conclusions are as follows:(1)The physical and chemical properties and structural characteristics of biochar are related to factors such as production materials and cracking temperature.With the increase of the cracking temperature,the p H and ash content of the biochar increase to varying degrees,the polarity and hydrophilicity of the biochar decrease,and the aroma is enhanced.The structure is constantly changing,and the development of skeleton and pore structure becomes clearer and more perfect.(2)Biochar made from pine sawdust,rice straw,and wheat straw,respectively,has a significant difference in moisture absorption performance.The capacity of straw biochar to adsorb water molecules is much greater than that of wood biochar.Biochar produced by loose-texture fibers has a better water absorption capacity.The comparison of the three shows that wheat straw biochar has the strongest water absorption capacity.(3)The regulation of soil p H by biochar is closely related to the properties of the soil,the properties of biochar itself,and the addition rate.The application of biochar in the soil can increase the saturated moisture content of the soil,the amount of water available to plants and the available water range suitable for plant growth.Higher addition ratios and cracking temperatures have a better effect on soil.(4)Biochar is weakly acidic after chemical oxidation,and the p H value of the soil will be lowered when it is applied to the soil.The oxidized biochar cracked at low temperature can increase the saturated water content of soil,and the oxidized biochar cracked at high temperature will inhibit it.Chemically oxidized biochar has a positive effect on the plants available water and the available water range suitable for plant growth.Compared with fresh biochar,the promotion effect is reduced.(5)After one year of natural oxidation,the p H of the bio-carbon-soil mixture is lower than before,the surface hydrophobicity is reduced,the specific surface area is increased,and the saturated hydraulic conductivity is decreased.The amount of water available to plants in the soil increased compared with the control,but the effect was slightly lower than that of fresh biochar.The range of available water for plants to grow in soil has increased significantly compared to fresh biochar.