Enhancing Rice Production on Acid Sulfate Soils in Peninsular Malaysia Through Biochemical Amendments

Malaysia plans to produce 80% of its rice requirement by 2030. To achieve the plan, new agronomic approaches have to be put in place to enhance the fertility of rice soils in the country. One of the options is to turn the infertile acid sulfate soils endemic in the low-lying coastal plains of Peninsular Malaysia into a new granary area. Using traditional agro-techs, rice yield in the area is below the national average of 4 t/ha/season. The low yield is due to soil acidity stress (pH < 4) together with Al3+ and/or Fe2+ toxicity. The critical pH for rice is 6, while the respective critical Al3+ and Fe2+ concentrations are 5.2 µM and 14.6 µM. The adverse conditions contributing to yield reduction can be resolved by applying appropriate soil amendments known to raise water pH, eliminating the toxic cations. The recommended agronomic practice is to apply ground magnesium limestone (GML) or ground basalt, or better still, apply GML or ground basalt in combination with bio-fertilizer, fortified with phosphate-solubilizing bacteria (PSB). The PSB increases water pH as well as helps rice plants secrete organic acids that reduce the toxic effects of Al3+ and Fe2+ via chelation. When pH rises >5, the toxic metals are precipitated, forming inert hydroxides. Ultimately, rice yield can be increased from 3 to 5 t/ha/season, which can last more than three consecutive cropping seasons. If this agro-tech is adopted throughout ASEAN, food security in the region will be sustained.