Rhizosphere phosphatase activity and phosphatase hydrolyzable organic phosphorus in two forested spodosols

The cycling of organic phosphorus has a large effect on P availability in forest ecosystems. Organic P must be hydrolyzed to inorganic P before it can be utilized by plants. We examined the acid phosphatase activity in the rhizosphere of slash pine (Pinus elliottii) growing in A and Bh horizon soil from two forested Spodosols; and determined the amount of soluble organic P in these soils that could be hydrolyzed following the addition of an acid phosphomonoesterase. Significant acid phosphatase activity was observed in the A and Bh horizons of the two soils. Acid phosphatase activity was greater in the rhizosphere of the Leon A and Bh horizons and the Pomona Bh horizon soil. Phosphorus fertilization decreased the phosphatase activity in the rhizosphere soil. Soluble organic P comprised 15–25% of the total soluble P in the two A horizon soils and over 75% in the Bh horizon soils. Between 20 and 30% of the water-soluble organic P in the A and Bh horizons of the two soils was hydrolyzed when an acid phosphomonoesterase was added. Our results suggest that organic P may contribute to the P nutrition of slash pine growing on these soils.