[Effects of Different Modified Corn Straw Biochar on Soil Hydraulic Properties in Hilly Loess Areas]

In order to investigate the influence of modified corn straw biochar on the hydraulic properties of water infiltration, evaporation, and water holding, corn straw biochar was prepared by pyrolysis at 500 ℃ for 2 hours in an N₂ environment. Three solvents （H₃PO₄, NaOH, and NH₄Cl） were selected, and different modified corn straw biochars were obtained by immersion modification at two concentrations （1 mol·L^-1 and 3 mol·L^-1）. The physical and chemical properties of all biochars, such as elemental composition, pore structure, functional groups, and surface morphology, were systematically characterized. Each type of corn straw biochar was selected to perform soil hydraulic properties tests under three different additions （1%, 2%, and 3%）. The influence of different corn straw biochar on the soil saturated hydraulic conductivity, water accumulation evaporation, and volume water content were analyzed by constant head method, soil evaporation test, and soil moisture characteristic curve. The results showed that the addition of modified corn straw biochar can significantly reduce the soil saturated hydraulic conductivity by 5.74%-46.69%, improve the soil volume water content by 0.74%-37.33%, and promote the soil water evaporation, while reduce the soil water accumulation evaporation by 0.63%-8.46% before the modification. With the increase in biochar addition, the saturated hydraulic conductivity of the soil decreased significantly, the cumulative evaporation gradually increased, and the volume water content showed a trend of first increasing and then decreasing. There was no correlation between the modified solution concentration and the soil saturated hydraulic conductivity, accumulated evaporation, and volume water content. This study can provide theoretical basis and technical support for improving the water retention performance of soil in the loess arid region of Shaanxi and Gansu.