Effect of Particle Size, Amounts, and Sources of Biochar on Saturated Hydraulic Conductivity in Two Texturally Different Soils

Biochar application to agricultural soils has been proposed as a way to increase crop production by improving soil properties. The present study aimed to investigate the effects of sources, amounts, and particle sizes of biochar on saturated hydraulic conductivity (Ksat) in two silty clay loam and sandy loam soils. In this study, palm leaf and lemon peel biochars were pyrolyzed at 500 °C for 3h. The obtained biochar was sorted into three particle sizes of ≤ 0.8, 0.8-2, and 2-4 mm, mixed into the soils at rate of 0.5%, 1%, 2%, and 4%wt, and incubated in a research glasshouse of Shiraz University for 15 months (2019 to 2020). Results showed that the application of 0.5%, 1%, 2%, and 4% of biochar caused a significant decrease in the mean value of Ksat in sandy loam by about 9%, 32%, 58%, and 65%, respectively, and also caused significant increase in the silty clay loam soil (except for 0.5%) by about 51%, 104%, and 231%, respectively, as compared to the control. Compared to lemon peel biochar, palm leaf biochar caused a significant increase in Ksat by 42% in the silty clay loam soil, but a significant decrease by 12% in the sandy loam soil. Furthermore, greater effects of the Ksat in both soils were observed after application of the fine size fraction of biochar (< 0.8 mm). The highest increase of Ksat in the silty clay loam soil and the highest decrease of Ksat in the sandy loam soil was observed in the soils treated by 4% of palm leaf biochar with particle size of smaller than 0.8 mm. In general, the results of this study can be used as a guide for selecting the amount and size of the applied biochar in terms of their effects on soil saturated hydraulic conductivity..