Phosphatase activities of pasture plants and soils: Relationship with plant productivity and soil P fertility indices

Summary Phosphatase activities of herbage roots and soil were measured at low- and high-fertility pasture sites over 12 months. Seasonal trends were examined and relationships with herbage yields, plant P contents, soil moisture and available P were assessed. The phosphatase activities generally followed complex seasonal patterns, although some trends were apparent. At the low-fertility site, where organic P provides most plant P, herbage and root phosphatase activities were correlated significantly (P<0.05) with available organic P, although generally, the plant phosphatases were not good indices of plant yield or P status. Soil moisture content appeared to be the major factor controlling plant phosphatase activity. Herbage phosphatase responded negatively at the low-fertility site, probably as a consequence of lower P availability from dry surface soil. Root phosphatase responded positively at both sites, indicating a different physiological role from that of the herbage enzyme. At the low-fertility site, soil phosphatase was correlated significantly (P<0.05) with herbage yield.