Investigating the effect of natural and urban waste compost biochars on hydraulic parameters in sandy soils

This study looked into the effect of different natural and urban waste compost biochar levels (0, 1, 3, and 5%), incorporated in sandy soil (total of 16 soil types), on the saturated hydraulic conductivity coefficient. For this purpose, the hydraulic conductivity of all 16 soil samples was determined using the constant head method. Then, for all soils, parameters of Van-Genuchten-Mualem (VGM) model for soil moisture characteristic curve (SMC) were determined by RETC and ROSETTA software and inverse modeling based on easily accessible parameters such as soil particle size percentage (sand, silt, and clay), bulk density, field capacity, and permanent wilting point. These parameters were soil residual water content (θr), soil saturated water content (θs), α, m, n and Ks. Results indicated that increasing biochars results in an increase in the Ks for all soils. Soil No. 11 (soil + 5% natural biochar + 1% urban waste compost biochar) and then soil No. 13 with 64 and 61% reduction, respectively, had the highest reduction percentage in Ks. The maximum and minimum value of Ks were 707.9 and 254.8 cmd-1 which were related to soil No. 1 and 11, respectively. All doses of biochars had a significant effect on all VGM parameters (P<0.01) and increasing biochars resulted in an increase in θr, n, and m and decrease in θs and α.