Pastures with a 6-year history of grazing by cattle (cattle pasture) and sheep (sheep pasture) were used to measure the effects on soil disturbance of a single severe grazing/treading event by sheep (S), one by cattle (C1), or 2 events within 3 weeks by cattle (C2). Treatments were stocked at 35 500 kg LW 0·9 /ha (≡ 200 cattle/ha) for 48 h when the soil was wetter than the plastic limit. A control plot (untrodden, U) was grazed only lightly by sheep to control pasture cover while causing minimal observable surface damage. Change in surface contour, random roughness, soil surface damage, and pasture cover were determined with a ‘contometer’. The construction and use of the contometer to measure change in microtopography and to describe the soil surface and vegetative state by grazing is described. Disturbance was calculated as the change in height (mm) of soil level at fixed positions along transects within treatment plots. Both sheep and cattle pastures were affected similarly (P > 0·05) in relation to absolute and net disturbance of soils. Averaged across both pasture types, very little absolute surfacesoil disturbance was measured on S, whereas cattle-treading caused significant upward and downward movement of soil. Mean ( s.d.) absolute surface disturbance (sum of upward and downward movement on a transect) was greater by cattle (C1, 11·2 8·1; C2, 9·9 5·0 mm) than by sheep (5·1 1·8 mm) (P < 0·01) after the single treading and 9·0 4·1 mm for C2 after the second treading. Net disturbance (average of upward and downward movement on atransect) was 1·9 4·0, 1·8 4·0, and 3·0 1·8 mm for C1, C2, and S (P > 0·05), respectively, after the first treading and 4·1 3·7 mm for C2 after the second treading. Cumulative net disturbance resulting from C2 on sheep pasture was greater than on cattle pasture (P <0·05), especially after the first treading, suggesting sheep pasture was more susceptible to compaction than the previously damaged cattle pasture. Random roughness and percentage of surface soil penetrated by hooves, based on observation, was greater following cattle than sheep treading. Random roughness tended to increase more (P < 0·07) following treading of sheep than of cattle pastures, which were already rougher. It was concluded that the effect on soil surface configuration of severe short-term treading events on wet soils was greater by cattle than by sheep stocked at the same metabolic liveweight per hectare and that this occurred irrespective of the previous grazing history. Although absolute disturbance in each of the 2 cattle treadings in C2 was similar, net disturbance (compaction) on sheep pasture was more than twice that on cattle pasture (P < 0· 05).

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This study aimed to develop calibrations for the measurement of pasture mass and pasture growth rate on sheep and beef pastures. Herbage within quadrats (0.12-0.2 m2) was measured with either an electronic rising plate meter (RPM) (n=2279), capacitance pasture meter (CPM) (n=693) or pasture ruler (n=2528) for the development of linear and curvilinear seasonal calibrations for pasture mass. Keywords: pasture mass, growth, rising plate meter, capacitance height, dead, dry matter, sheep, cattle

Farmer perceptions of the productive potential of land influence their attitudes to productivity improvement. Pasture production information has generally been gathered within management systems that were considered feasible at the time. A sheep grazing trial was run over 2 years in southern Hawkes Bay hill country in which a Fer tiliser treatment involving a very high rate of nitrogen (N) fertiliser (400 kg N/ha annually as 8 split dressings of 50 kg N/ha) was applied to blocks with historically low, medium or high fertility. Additional fertiliser P and S was also applied as part of the Fertiliser treatment, however the responses were judged to have been mainly due to the N fertiliser Annual pasture production increased from an average 9.2 t DM/ha in Control areas to 17.1 t DM/ha in Fertiliser treatment areas. Similar responses of 18 to 22 kg DM/kg N fertiliser occurred across the 3 fer tility blocks. Average annual pasture production for the historically high fertility-Fertiliser treatment combination was 19.4 t DM/ha, higher than on most dairy farms. Pasture content of high-fertilityresponsive grasses such as ryegrass increased, at the expense of low-fertility-tolerant grasses such as browntop, legumes such as white clover, and herbaceous weeds. Nitrate leaching measurements suggested annual losses were increased by 25 kg N/ ha or 6% of the N applied. Given present-day cost structures and returns, these results suggest use of higher rates of N fertiliser than is current practice is an economic option for hill farmers. However longterm sustainability of systems receiving such high dressings of fertiliser N r equires further investig ation before such an approach should be adopted as part of commercial practice. Keywords: botanical composition, hill country, New Zealand, nitrate leaching, nitrogen fertiliser, pasture production potential

Urine deposited by grazing animals represents the largest source of N2O emissions in New Zealand. Sheep-grazed hill pastures are an important component of New Zealand pastoral land, but information on N2O emissions from these areas is limited. The purpose of this study was to investigate the effect of increasing rates of fertiliser nitrogen and of a nitrification inhibitor on N2O emissions from urine patches. The study was carried out in grazed paddock-scale trials at the Ballantrae and Invermay Research Stations, New Zealand. The fertiliser N treatments were 0, 100, 300 and 750 (500 for Invermay) kg N/ha.year. Nitrous oxide measurements were conducted in the spring of 2005 and 2006, following applications of synthetic sheep urine with or without dicyandiamide (DCD) in these four N treatments. In both years and at both sites, N2O emissions increased with N fertiliser application rate in both urine and non-urine affected areas. The addition of DCD to the synthetic urine reduced N2O emissions from the urine affected areas during the measurement period by 60–80% at Ballantrae and by 40% at Invermay. The N2O emission factors for the artificial sheep urine (expressed as N2O-N lost as % of N applied) ranged from 0.01 to 1.06%, with the higher values generally found in the high N fertiliser treatments. The N2O emission factors were generally less than or similar to those from sheep urine applied to flat land pasture.