pH is the dominant factor controlling the levels of phytate-like and DNA-like phosphorus in 0.5 M NaHCO3-extracts of soils: Evaluation with phosphatase-addition approach

To elucidate the factor(s) controlling the concentrations of readily available organic phosphorus (Po) in soils, we assessed the phosphatase-hydrolyzable Po pools in 0.5 M NaHCO3-extracts of arable and forest soils and evaluated their association with soil properties in several soil types collected in Japan. Concentrations of phosphatase-hydrolyzable Po (simple monoester P, phytate like-P, and DNA-like P) in 0.5 M NaHCO3-extracts were determined using three phosphatases with different substrate specificities. Monoester P (i.e., simple monoester P and phytate like-P) was dominant in the phosphatase-hydrolyzable Po of 0.5 M NaHCO3-extracts in all soils. In monoester P, the concentration of phytate-like P was greater than that of simple monoester P in all soil types except Fluvisols. Both phytate-like P and DNA-like P in 0.5 M NaHCO3-extracts significantly increased with decreasing soil pH, suggesting that soil pH would play a crucial role in determining the availability of Po in soils.