Rainfall simulation experiments indicate that biochar addition enhances erosion of loess-derived soils

Biochar addition to soil has increasingly demonstrated the potential to improve soil and mitigate climate change. However, the effects of biochar additions for sloping cropland amendments and soil erosion remain unclear. In this study, experiments with simulated rainfall (25, 50, 75, and 100 mm hr(-1)) were conducted on a soil box (0.45-m length x 0.3-m width) to assess the effects of different biochar addition rates (2%, 5%, and 8% [wt/wt]) and incubation time (i.e., 140 days) on runoff, soil loss, and interrill erodibility. The soil and biochar were loess-derived Miami soil and commercial charcoal made from seasoned oak and hickory hardwoods, respectively. Compared with the control soil, biochar addition decreased the total runoff by 2.4-10.8% (p > 0.05) and significantly increased the total soil loss and interrill erodibility (p < .05) by 20.8-50.8% and 20.4-29.2%, respectively. The changes in runoff, soil loss, and interrill erodibility were ruleless with an increase in the rate of biochar addition from 2% to 8%. The differences in runoff, soil loss, and interrill erodibility were nonsignificant among most biochar-added treatments. After a 140-day incubation period, total runoff and soil loss increased by 1.5-6.2% and 5.7-10.3%, respectively, and interrill erodibility increased for the 2% biochar addition and decreased for the 5% and 8% biochar additions. However, nonsignificant differences in runoff, soil loss, and interrill erodibility were observed before and after incubation. Our results implied that biochar addition to soil could increase the risk of erosion on sloping croplands, and thus, one should exercise caution when amending soil with biochar on sloping croplands.