Abstract
The effect of cattle dung and of superphosphate, applied once, on the yield of pasture, nutrient uptake, and on several soil properties was measured in the field over about 3 years. The soil had very high phosphate sorption. Compared with superphosphate applied at equivalent rates of P, cattle dung decreased phosphate sorption and increased soil pH. The recovery of applied phosphate in herbage was higher from dung than from superphosphate. The likely reasons for this are discussed. Yield responses of herbage to dung and superphosphate persisted for 2 years and 11 years respectively. Yields of P were affected for the duration of the experiment. The area on which dung influenced P uptake was probably about five times the area physically covered by it. Thus under medium rates of stocking with cattle (3-4 per hectare) the phosphate uptake of established pasture is likely to be influenced by dung spots on over half of the grazing area at any one time. Under conditions of in situ grazing dung may have a cumulative beneficial effect on phosphate sorption and therefore on the long-term efficiency of the phosphorus cycle.