Effects of rice husk biochar on rill detachment capacity in deforested hillslopes

Biochar addition to soil has been found to be a useful practice to control erosion. However, few studies have explored the effects of biochar produced from husk of rice on rill erosion, due to overland flow in deforested areas. This study has evaluated the rill detachment capacity (Dc) and erodibility (Kr) in soil samples treated with rice husk biochar in comparison to untreated sites (control), collected in deforested hillslopes of Northern Iran. Dc was measured in a lab-scale hydraulic flume at four-bed slopes (9.7, 14.3, 19.5, and 24.2%) and five water discharges (0.24, 0.36, 0.47, 0.59, and 0.69 L m- 1 s-1). Moreover, organic carbon, aggregate stability and bulk density of soils were measured. Dc was lower (on average -32%) in the treated soil compared to the control. Dc was not correlated to the other physico-chemical properties of soil. Kr, estimated by linear regressions between Dc and shear stress, was noticeably lower (-79%) in the treated soil compared to the control. These results evidence that rice husk biochar is effective at controlling and mitigating soil detachment, and at improving organic matter content and aggregate stability in deforested hillslopes. The proposed values of rill erodibility and shear stress of deforested hillslopes (treated or untreated) are helpful to model soil resistance to rill erosion in process-based erosion models.