Effect of Type, Particle Size and Application Rate of Biochar on Some Physical Properties in a Silty Clay Loam Soil

Biochar application has been proposed as a suitable amendment for soil properties to sustainable agriculture. However, its effect depends on biochar application and soil properties. The purpose of this study was to investigate the sole and combined effects of different sources, rates and particle size of biochar on soil bulk density, aggregate stability, penetration resistance and shear strength in a silty clay loam soil. Palm leaf and lemon peel biochar prepared at a pyrolysis temperature of 500∘C with three particle sizes 2–4, 0.8-2 and smaller than 0.8 mm, mixed in the soil at application rates of 0, 0.5, 1, 2 and 4 % (by weight). After 15 months (2019 to 2020) incubation at standard condition in research glasshouse of faculty of agriculture Shiraz University, soil properties analyzed by standard methods. In general, the applied biochar decreased soil bulk density, penetration resistance, and shear strength and increased aggregate stability significantly, as compared to the control. Palm leaf biochar played better roles in improving soil properties as compared to lemon peel biochar. On average, by increasing biochar rates to 4%, the soil bulk density, penetration resistance and shear strength decreased by 14.5, 85 and 59.8% respectively and the aggregate stability increased by 50.5%. The greatest effect of biochar was obtained at particle size smaller than 0.8 mm for aggregate stability and penetration resistance. Bulk density and tension strength of the soil did not considerably change using different particle size of biochar. Base on the results, improvement in soil physical properties can be accomplished by application of appropriate particle size and rate of different sources of biochar.