PHOSPHATIC FERTILISER GUIDELINES FOR GRAZING PERMANENT PASTURES

Resumen

Phosphorus is an essential element for plant and animal growth. While productive agriculture is not possible on soils with very low soil P, there is increasing evidence that high soil P can lead to leakage of P from agricultural systems to water bodies. In this paper the guidelines are drawn up for application of P to grazed grassland. The guidelines are aimed at ensuring the optimum yields with minimum P inputs. The P fertiliser strategy is based on three principies. The fírst is to achieve a soil P status that ensures optimum production. For intensive agriculture, the P status required is between 6.1 and 10.0 mg P/l of soil (Morgan's extractant). For more extensive farming systems a soil P of between 3.1 and 6.0 mg P/l is adequate. Once this P status is achieved, the second principie is that phosphorus is used to replace P removed by the farming system. At stocking rates of 2.0-2.5 cows/ha, maintenance dressings for dairying range are from ten to twenty kg P/ha, respectively depending on milk yields. The third principie is that soil P status needs to be checked every three to four years in order to ensure the fertiliser strategy employed is correct