Perfecto S. Ramos, Jr.

Potassium supplement for optimised culture medium for outdoor cultivation of Nostoc commune in the Philippines

Abstract Nostoc commune is a nitrogen-fixing cyanobacterium. It could serve as an alternative source of biofertiliser that is both ecologically beneficial and sustainable. In this study, different concentrations of potassium (0, 3, 6, and 9 mg/kg) were added to an optimised culture medium containing 10% soil-water extract with 2.6 mg/kg of phosphorus. The soil-water extract solution was prepared using the Maligaya heavy clay soil series. The findings revealed that Nostoc commune grown on an optimised culture medium supplemented with 6 mg/kg or 9 mg/kg of potassium showed significant growth and development, as evidenced by increased fresh weight, persistent dark green colouring, and a high number of heterocysts for up to 28 days after inoculation. This optimised culture medium, supplemented with 6 mg/kg or 9 mg/kg of potassium, can be used to inoculate large-scale outdoor cultures.

Doi https://doi.org/10.35513/Botlit.2026.1.6

Keywords biofertiliser, environment-friendly, N-fixing cyanobacteria, nitrogen fertiliser

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