Roadside devegetation by microbially induced carbonate precipitation using osmosis, ammonium toxicity, and cementation effects

Abstract

Microbially induced carbonate precipitation (MICP) uses urease-producing bacteria to precipitate calcium carbonate (CaCO₃), leading to soil improvement. MICP technology is directly related to the vegetation in the soil resulting from chemicals and cementation; however, only few studies have been conducted on this topic. This study aims to elucidate the application of MICP in the management of roadside vegetation using laboratory- and field-scale tests. At the laboratory scale, the effects of several chemical components of MICP, such as deionized water, growth media, bacteria, urea, and CaCl₂, on seed germination and growth were explored using soil column testing in a growth chamber. A series of field tests were conducted on a highway embankment considering different initial ground conditions, such as original, cutting, and cultivated grounds. Leaf height and soil properties, such as electrical conductivity, ammonium concentration, pH, exchangeable calcium, and CaCO₃ mass, were measured over time. The results showed the efficacy of devegetation by MICP and clarified that the devegetation mechanism occurs in three steps: as a short-term effect by osmosis, an intermediate-term effect by ammonium toxicity, and a long-term effect by cementation.