Grazing Effects On Phosphorus Form and Availability in Organically Managed Grassland.

Phosphorus (P) is an essential element for plants and animals, but can be a limiting nutrient in organically managed soils. Our objective was to determine the P forms and availability in two certified organic grasslands. The treatments were as always grazed or always for hay production. Phosphorus forms were determined by fractionation; P availability was determined using several common soil test procedures and sorption-desorption Quantity/Intensity relationships. Organic P content was larger in the always grazed treatment than in the hay production treatment.