Characterization of Rice Husk Biochar and Its Particle Size Effects on Soil Properties in Sandy Loam Soil

This study aimed (i) to characterize biochar derived from rice husk using a traditional kiln method, and (ii) to evaluate leaching reduction potential by differentiating sizes of rice husk biochar (RHB). For this study, RHB was produced at 300 to 550° C using the traditional kiln method and was conducted at Naresuan University, Thailand. Morphology of RHB was classified using Field Emission Scanning Electron Microscope together with Energy Dispersive X-ray Spectrometer (FESEM-EDS). Three different sizes of RHB: (i) less than 0.25 mm, (ii) 0.25 – 1 mm, and (iii) 1 – 2 mm were used at the rate of 2% w/w to mix with the sandy loam soil and tested in soil column. The results showed that the traditional kiln method could produce RHB of about 40% of the total fresh weight. The average pore size was 10.64 μm. Carbon was a highest element content in RHB (> 60%), then oxygen (~20%) and silica (~15%), respectively. Observed pore sizes were similar for all three RHB samples. After soil incubation, a smallest biochar size (<0.25 mm) was 17% greater potential in leaching reduction as compared to control. Besides, medium (0.25 – 1 mm) and large (1 – 2 mm) sizes of RHB reduced leaching by 13%, and 10%, respectively. Application of RHB decreased bulk density and increased soil nitrogen adsorption capacity.