Mitigating rainfall-induced sediment hazard and soil erosion using organic amended soil improvement

Soil-organic amendment (SOA) is one of the sustainable soil improvement measures to mitigate climate change related issues such as rainfall-induced hazard and soil erosion. Organic wastes particularly compost and biochar can be reused and recycled into viable resources. However, there are limited data on incoporating organic wastes into a soil that is susceptible to erosion by rainfall. Therefore, objective of this study is to investigate properties of a soil from Okinawa prefecture (Kunigami maaji) that are associated with resisting ability against artificial rainfall intensities of 30, 60, 90 and 120 mm/h after adding two organic matters: household-derived compost and rice hush-derived biochar. The properties were soil-water retention, runoff, soil loss, infiltration and electrical conductivity. The compost was mixed with the soil at application rates of 0.5, 1.0, 1.5 and 2.0 kg/m ² . The compost of 1.0 kg/m ² was mixed with the soil and the biochar at application rates of 1, 3, and 5% by total weight. Experimental results indicate that the soil water retention properties of the soil were improved by the treatment of compost and biochar. However, soil loss was not significantly reduced under initially saturated soil condition, applied rainfall intensities, testing duration and experimental conditions. The results of this study could be used as baseline data for evaluating correlation between properties of soil water retention curves to soil erosion.