Algalization of acid soils with acid-tolerant strains: Improvement in pH, carbon content, exopolysaccharides, indole acetic acid and dehydrogenase activity

Widespread occurrence of acid soils across the globe is a serious issue in agriculture that has been generally managed with intensive use of chemical amendments. Although green microalgae are the primary colonizers of soils even under extreme acid conditions, only a few investigations focused on their role in health improvement of such soils. In this study we tested the hypothesis: that acid-tolerant microalgae have the potential for ameliorating soil acidity and enhancing soil health through enrichment of carbon content, exopolysaccharides, indole acetic acid besides stimulating dehydrogenase activity in acid soils. Inoculation of two acid soils collected from Australian fields with acid-tolerant microalgae, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, alone or in combination, resulted initially in the development of a soil algal crust as evidenced by significant increase in chlorophyll a in both the soils. Also, there was a significant increase (>200%) in the release of exopolysaccharides that facilitated soil aggregate stability. The increase in soil pH was about one unit (from 4.8 to 5.6 in soil A or 4.3-5.3 in soil B) under the influence of individual or co-cultures of the microalgal strains after 90 days. Algalized acid soils exhibited a significant increase in carbon content (29-57%), dehydrogenase activity (>500%) and production of indole acetic acid (200-500%). Thus, the present study reports for the first time on the great potential of green microalgae in amelioration of acid soils besides improving soil health and fertility.

Automated summary

This study demonstrates the potential of acid-tolerant microalgae in ameliorating acid soils by increasing carbon content, releasing exopolysaccharides, indole acetic acid, and stimulating dehydrogenase activity. The inoculation of acid soils with acid-tolerant microalgae led to the development of a soil algal crust, increased soil pH, and improvements in soil health and fertility.