Effects of biochar from invasive weed on soil erosion under varying compaction and slope conditions: comprehensive study using flume experiments

Biochar amendment technique having been applied in the landfill cover or green roof was found to have the potential of erosion control. The strategy of utilizing excess biomass resource from an invasive weed (water hyacinth) in China and converting it into a new type of biochar is proposed to address the erosion issue. It is noted that the erosion process influenced by multiple factors (i.e., slope conditions, soil properties, and rainfall intensity) in biochar-amended soils has not been well understood. The aim of this study is to estimate the individual and coupled effects of five investigated factors (i.e., biochar content, soil compaction degree, slope gradient, slope length, and rainfall intensity) on infiltration, runoff, and soil erosion using in-house designed flume tests. Flume tests were planned based on factorial experiment design on bare soil (BS) and soil-biochar composites (SBCs). The results showed that biochar addition could reduce soil erosion by 10-69% and improve rainwater storage by 20-59%. Soil with 5% biochar amendment achieved the best amendment efficiency. This is likely due to the enhanced formation of water-stable macroaggregates in the presence of biochar. Biochar content was assessed as the most important factor in determining water retention and erosion reduction with 33% and 40% contribution, respectively. The total impact of slope conditions was vital on improving rainwater storage and erosion control by 29% and 43%, respectively. This study broadened the understanding of water erosion and hydrologic responses under the influence of biochar on SBCs and provided a sustainable perspective for the hydrologic management practice.