A long-established, moderately steep hill pasture was visually mapped into five strata (A to E) according to occurrence, colour, and vigour of pasture species and distribution density of obvious urine patches.An!,lUal pasture production and major nutrient concentrations of the pasture, except magneSIUm, decreased markedly from stratum A to stratum E. Phosphorus and potassium soil tests were distinctly higher in stratum A than in the remainder of the paddock.From the measured nutrient uptake in pasture and from dung counts carried out on each stratum, it was estimated that large quantities of P, K, and N were transferred into camp areas, mostly from the least productive two-thirds of the paddock.Because of the irregular distributi.on of the. strata. it is !'lot practic::ble to compensate fully for the observed transfer of nutnents by dlfferentJal aenal topdressmg; but phosphatic topdressing of 10 percent of this paddock could probably be omitted without measurably affecting total production.The significance of the five strata in soil sampling and the incidence and correction of potassium deficiency are discussed.

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 tiJis are discusse.d. Yield responses of herbage to dung and superphosphate persisted for 2 years and 1 t 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 witiJ cattle (3-4 per hectare) the phosphate upt~lke of established pasture is likely to be influenced by dung spots on over half of the grazing area at anyone 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.

No abstract

The different sources of variation in soil tests estimated in the previous paper in this series are discussed, and methods of increasing precision considered. It is shown that simply increasing the number of cores taken effects only a slight improvement in precision.

No abstract