Controlling Loess Erosion by Bio-Stimulated Microbial Induced Calcite Precipitation

Wind-induced soil erosion is one of the main factors contributing to desertification in drylands, resulting in reduced biological diversity, loss of cultivated land, environmental deterioration, and disruption of human activities. Here we present a study focusing on the mitigation of aeolian erosion of loess soil from the Negev Desert (Israel) using Microbial-induced calcite precipitation (MICP). Changes in the treated soil's chemical, physical, and microbial community were characterized by bio-stimulation of native, ureahydrolyzing soil bacteria. Erodibility experiments were performed on loess sprayed with treatment media with varying concentrations of urea and CaCl2, with a constant 1:1 ratio. The effectiveness of treatments was studied in a wind tunnel and by image analysis of desiccation cracks. The experiments revealed a complicated reality with urease activity, community composition, and calcium carbonate precipitation depending on the concentration of the treatment medium. Specifically, we show a twofold reduction in the area (from 21% to 8%), and the length (from 363 cm to 206 cm) of the desiccation cracks can be achieved by spraying the soil with 0.5M concentration media, resulting in effective MICP or a high concentration treatment ( > 1M) without achieving MICP. Our results show that erosion mitigation in loess soil depends on an interplay between biotic and abiotic processes based on the treatment media concentration.