The effect of time on application of rice straw biochar on some physical properties of clay loam soil

Biochar is a carbon-rich organic compound that has recently been recommended for use as a soil conditioner. Little research has been done on the effect of biochar amount and elapsed time after biochar addition on soil physical properties. This research performed at Shahrekord University, in 2018. The aim of this study was to evaluate the long-term effects of different amount of rice straw biochar on soil bulk density (ρb), total porosity (n), mean weight diameter of dry (MWDdry) and wet (MWDwet) aggregates, air filled porosity (AFP) and capillary porosity (CP) of clay loam soil. This experiment was performed as a factorial experiment based on completely randomized design with three replications in a greenhouse. Biochar have four levels of zero as control (B0), 0.5 (B1), 1 (B2) and 2 (B3) weight percentage and the time have four levels of 2 (T1), 3 (T2), 6 (T3) and 9 (T4) months after biochar adding to the soil. The results indicated that two months after adding rice straw to the soil, ρb decreased by 6% compared to the control. At the same time, ‘n’, ‘MWDdry’ and ‘MWDwet’ increased by 3, 11 and 13%, respectively, compared to the control. Means comparison showed that the lowest ρb was obtained in B1T2, the highest ‘n’, ‘AFP’ and ‘CP’ were obtained in B1T2, B0T1 and B1T3, respectively, and the highest ‘MWDdry’ and ‘MWDwet’ were obtained in B3T4 and B0T4 respectively. Different times are needed for the effect of biochar on soil physical properties improvement. Based on the findings of this study, 1% of rice straw biochar can be used to durabil improvement of the physical properties of clay loam soil.