The effect of cattle dung patches on pasture growth, botanical composition, and pasture utilisation was studied over a period of five years.The rate of disappearance of the dung varied with the seasons. The bulk of the dung disappeared in one-two months in autumn and four-six months in Jalte spring and summer, although extremes ranged from half a month to 17 months.The effect of dung patches on pasture growth was generally fairly small.Whitc clover (Trifolium repens L.) was more prevalent on dung patches than in the remainder of the trial area and often remained so for one to one-and-a-half years.Grazing was most uneven in spring, when herbage around dung patches was left 2-3 in. higher than unaffected pasilure.Chain-harrowing after each grazing depressed pasture growth but improved pasture utilisation in spring by grazing steers... Ruakura

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.

Dung patches were applied in spring on a soil high in P and low in K. Under dung patches to below 7.6 em depth. the increase in Truog P was rapid and sustained. A rise in exchangeable K and Na was rapid, reaching a peak 1112 months after dung application, but short-lived. Exchangeable Ca and Mg increased more slowly, reaching a peak after 4 months. In spite of its gradual release from dung, Mg moved to some depth; thus Mg could be leached under dung patches. Downward movement of faecal Ca was slight. Dung patches increased pasture yields in an area within 12.7 em of the boundary of the dung patch for 3 months after application and again during the following spring. Total yield increase in this 12.7 ern wide band over 1112 years was approximately 50%. Ryegrass (Lolium perenne L.) growth increased in this area. Dung raised Mg concentration of herbage, particularly in clover. It depressed Na concentration of clover. and raised it in grasses after a short initial depression. A rapid and large increase in herbage K concentration aided a rapid apparent recovery of K applied in dung: recovery was 62% at 1 1 / 2 months, 80% at 3 112 months, and 93% at 14 months after dung was applied. Interactions of faecal nutrients are discussed 471

This paper examines a simple model requiring monthly estimates of the maximum weather-dependent evapotranspiration and daily rainfall to predict the reduction in monthly dry land pasture growth relative to irrigated production. The basic assumption is that dry matter production is proportional to transpiration. The model is tested using results from two irrigation experiments on ryegrass-white clover pastures rotationally grazed by beef cattle. These trials took place in the central Waikato Valley on two soil types; an Aquic Hapludult (HAM) from 1953 to 1964 and a Typic Vitrandept (HOR) from 1962 to 1966. For this period dryland conditions reduced yields over the November through April period by 39 and 27% respectively on the two soils. Predicted monthly dry land yields using irrigated yields and the estimated water use showed no systematic bias compared with actual pasture production and accounted for 83% and 77% of the yield variation for the HAM and HOR soils respectively. Errors caused by the lack of fit of the model combine with those of measurement and the spatial variability of pastures so that the standard deviation of a predicted monthly yield is about 250 kg DM ha-1 • Errors attributable to the model are of a similar magnitude to those of conventional pasture yield measurements. The model is not sensitive to the details of the transpiration-soil water storage relationship assumed. Limitations and applications are discussed.

ABSTRACI Yield responses of irrigated pasture to nitrogenous fertiliser were studied on a grass/clover sward and on a grass sward. At rates of application of up to 400 Ib nitrogen/acre/year responses on a grass/ clover sward averaged 5 to 6 Ib dry matter per pound of fertiliser nitrogen in a mowing trial. The amount of fertiliser nitrogen required on a grass sward to equal the yield of a grass/clover sward receiving no fertiliser nitrogen was 450 Ib to 500 Ib under mowing conditions (annual yield 14,000 lb dry matter per acre) and approximately 300 lb under grazing (annual yield 17,000 lb dry matter per acre). Suppression of white clover by high rates of fertiliser nitrogen was much less severe than usually found in experiments in Europe and the U.S.A. At a rate of application of about 800 Ib nitrogen/acre/year on a grass/clover sward, white clover still accounted for 15 percent of the yield, but at an application rate of 250 lb to 300 lb fertiliser nitrogen per acre, white clover apparently ceased to make a positive contribution to the nitrogen supply of associated grasses. Grown as pure swards receiving 360 lb fertiliser nitrogen/acre/ year, cocksfoot (Dactylis glome rata L.) gave a higher summer and annual yield than perennial ryegrass (Lolium perenne L.