2022 年 32 巻 S 号 p. 49-52
One of the measures to enhance the water use efficiency or to prevent desertification in arid and semi-arid countries is to improve water holding capacity (water retention) of soils. This study focused on Spirulina, a planktonic blue-green unicellular microalgae classified as cyanobacteria. Since the Spirulina inhabits strongly alkaline water body which is generally seen in the tropics, the Spirulina is expected as a locally available soil amendments. Further, the Spirulina secretes Extracellular Polymeric Substances (EPS). The current study assessed the effect of the Spirulina and the EPS powders to improve the soil water holding capacity. Slight addition (0.5 to 5%) of the Spirulina and EPS powders to sandy soils resulted in a significant increase of the readily available water content for crop growth (RAWCC). The effect of the Spirulina on the RAWCC of the sandy soils was similar of that of the bentonite. Meanwhile, soils with textures of Silty Loam and Sandy Loam had little increases in the RAWCCs with those amendments. In addition, the RAWCCs of the soils treated with both Spirulina and EPS powders did not decrease significantly after heat treatment indicating the persistence of the effect. The results of the current study demonstrated the efficiency and its persistence of the Spirulina and the Spirulina-derived EPS to improve soil water holding capacity particularly in sandy soils.
