Effect of Cattle Manure and Palm Residue Biochars Produced at Different Pyrolysis Temperatures on Saturated Hydraulic Conductivity and the Coefficients of Chloride Transportation in a Sandy Loam Soil

Diffusion-dispersion and the other parameters of solute transport are important characteristics in material transportation within soil that can be influenced by several factors including addition of soil amendments and organic materials. Therefore, this research aimed to evaluate the effects of cattle manure and palm residue biochars produced at different pyrolysis temperatures on the diffusion-dispersion coefficient (D) of chloride, saturated hydraulic conductivity (K), immobile water content (θim), and mass exchange coefficient (α) of chloride in a sandy loam soil. Treatments consisted of control, cattle manure (CMB), and palm residue (PRB) biochar produced at 400 and 600 ˚C (CMB400, CMB600, PRB400, and PRB600, respectively). Each biochar type was applied at three levels of 0.5, 1, and 2 % wt. The experiment was conducted using a completely randomized design with three replications on soil columns under laboratory condition after 70 days incubation. Application of 0.5,1 and 2% PRB400, and PRB600 increased D parameter by 89%, 80%, 40%; and 39%, 141%, 139% as compared to that of control, respectively. Furthermore, application of 0.5%, 1%, and 2% CMB400 and 1% and 2% CMB600 significantly increased D parameter by nearly 95%, 48%, 95%; and 81% and 159% as compared to the control, respectively. On the contrary, application of 1% CMB600 had no significant effect on D parameter as compared to the control. Besides, application of 0.5% and 1% CMB400 and application of 2% CMB600 resulted in significant increases by 24%, 18%, and 29% in K as compared to the control. Application of 0.5% PRB400 and 1% and 2% PRB600 increased K by 24%, 20%, and 18% as compared to the control, respectively. In general, application of CMB and PRB increased the θim and α in the studied soil. In the present study, there were no significant differences between the effect of CMB and PRB and the applied temperatures (except for the effect of PRB on D parameter) on the studied hydraulic characteristics of the soil. Results suggest that although biochar may have positive effects on different soil properties, application of both studied biochars may intensify transportation of the solute and chloride and their entrance into water resources, particularly ground waters, by increasing the hydraulic and solute transportation coefficients. This point should be considered in the application of these soil amendments.