Pyrolytic conversion of sewage sludge to biochar and its agricultural application is considered as one of its management methods. Although chemical and physical properties of sewage sludge biochar have been studied, less attention has been given to the effect of pyrolysis temperatures on water repellency and water-holding capacity of sewage sludge biochar. We hypothesized that sewage sludge biochar has significant effects on soil physical and hydraulic properties, could reduce heavy metals availability for plants, and might decrease nitrate and heavy metals leaching from the soil and can increase maize dry matter yield. Our results showed increasing pyrolysis temperature decreased biochar yield and total nitrogen. Conversions of sewage sludge to biochar decreased water repellency severity from very at 300 °C to low severe at 700 °C. Biochar application increased and decreased maize shoot yield relative to the control in clay loam and loam soils, respectively. Sewage sludge and its biochar application increased soil repellency index, saturated hydraulic conductivity, relative stability ratio and decreased water-dispersible clay. Nitrate concentration in the leachate was lower in sewage sludge- and biochar-treated soils compared to control, which might be attributable to greater N immobilization due to higher C/N ratio in these treatments. HYDRUS-1D could accurately simulate the water flow but did not successfully predict the nitrate traort. Keywords: Sewage sludge, Pyrolysis, Biochar, Maize, Nitrate, HYDRUS-1D.
