Phosphorus uptake and return in grazed, steep hill pastures

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Abstract
The uptake of phosphorus (P) in pasture and return in plant litter and animal dung were measured on campsites, 25° slopes, and 45° slopes within two separate north aspect and south aspect hill pastures, for 1 year. Annual Puptake by pasture, and more particularly P return via dung from grazing sheep, were high on campsites, but both decreased sharply as ground slope increased. By contrast P return via litter was much more uniform, but under the intensive grazing was equivalent to only approximately 13—21% of pasture Puptake. The derived net P balances showed a large annual gain of P on campsites (50.1 and 119.8 kg/ha on north and south aspects respectively). The net loss ofP from slopes was equivalent to 29—71% of annual Puptake. It was therefore concluded that the maintenance of soil P levels and of pasture growth would continue to depend highlyon fertiliser inputs, particularly on steep slopes. Because ofthe high P concentration in pasture from all strata the respective annual net P balances should be regarded as near a maximum for the situations examined.