In the Starborough-Flaxbourne area the local farming community, alarmed at the increasing hill slope erosion, set up a soil conservation group. Accelerated erosion was a symptom of the past 12 years of below average rainfall. Removal of vegetative cover by livestock had enabled wind to erode areas of the thin topsoil exposing vulnerable sodic subsoil to rill and tunnel erosion. This highlighted the need for farms to adapt their livestock systems to a drier environment if they were to survive. Keywords: adaptation, conservation, decision making, drought, erosion, lucerne, Medicago sativa

The South Island hill and high country is defined as those areas which were in natural grassland at the time of early European settlement. This includes the major geographical regions of dry hill and high country of Marlborough, Canterbury and North Otago, and the wet acid tussock grasslands of Otago and Southland. To define the most appropriate pasture species for farming in these areas, it is first necessary to define the appropriate environmental factors since they largely determine the types of farming systems possible. Once this has been done, it will be found that there are only one or two pasture species which are the best option in each environment or farming system.

Two Dorycnium species. 0. hirsutum and 0. pentaphyltum. have been under trial since the mid-1970s. They show most promise on North Island yellow-brown sands and the drier browngrey/ yellow-gray earth soils of the South island. Both species, native to the Mediterranean region. are perennial with deep taoroots. They are adapted best to drought-prone. free draining, weakly acid to alkaline soil types; heavy, wet soils are not tolerated. Severe winter frosting has little effect on Dorycnium. Major advantages of Dorycnium are the ability of plants to establish and grow in low fertility soils and the provision of an evergreen winter plant cover. Establishment has been successful both by oversowing and direct seedmg on to diverse sites including depleted grassland and newly formed road batters. More extensive farm trials are planned for Dorycnium because of its ability to provide stock and bee forage under cold, dry, low soil fertility conditions. Keywords: Dorycnium, leguminosae, pastur rejuvenation, soil conservation, semi-arid revegetation. nitrogen fixation. forage, browse, Hunter strip seeder

Poplar (Populus spp.) trees are planted on pastoral hill country throughout New Zealand, primarily for soil conservation. The effect of wide-spaced trees (16-100/ha) aged 8-15 years on understorey pasture growth, botanical composition, and microenvironmental characteristics, was determined at Pohangina (1997-2000) and Lawrence (1998- 2000) in the lower North and South Islands, respectively. Relative to environments without trees, at Lawrence pasture growth (13 100 kg dry matter (DM)/ha/yr) was reduced by 20% and 34% on north and south sides of trees, respectively. At Pohangina (7915 kg DM/ha/yr), trees had less influence (7% and 14% reduction) on understorey pasture growth. There were also strong seasonal effects at both sites, corresponding to when the trees were foliated. Swards at each site comprised 81-93% grass. At Lawrence, swards had similar botanical composition beneath and beyond trees. Swards on the north side of trees at Pohangina comprised relatively high grass and low legume content compared with those on the south side and in the open. Compared with open pasture, areas beneath young poplars received up to 24% less rainfall and 31% less solar irradiance, and soil water content (0-200 mm depth) was up to 33% lower in summer and autumn. At intermediate soil water contents (0.25-0.35 m3/m3), the profile of soil water content around trees during drying was frequently U-shaped, being lowest beneath the stem and increasing with distance away from the tree. Likely reasons for the pasture responses and variation in tree-pasture interactions between sites are discussed. The results will be used to model changes in tree-pasture interactions over time. Keywords: agroforestry, poplar, Populus, silvopastoralism, soil conservation, soil water, treepasture interactions

Intermediate and pubescent wheatgrasses (Thinopyrum intermedium) are potentially useful as dryland forage grasses in New Zealand. The recent literature on their international and local use in pasture and cropping situations is reviewed. Under semi-arid conditions at Bendigo Station over a 13-year period, cv. Luna wheatgrass has spread several metres from the original drill lines and it provides very high ground cover. In terms of dryland soil resource conservation this contrasts with adjacent cocksfoot and, to a lesser extent, lucerne plots which have wide-spaced plants interspersed with litter and much bare ground. In a mixed drilling containing wheatgrass, hairy dorycnium, birdsfoot trefoil and sheep's burnet, the first two species now dominate. At Takapau, central Hawke's Bay, annual yields from intermediate and pubescent wheatgrasses produced over 80% of the yield of 10 New Zealand cultivars in spring, summer and autumn, and 65% in the winter. Of the wheatgrasses, cv. Topar intermediate wheatgrass and a pubescent wheatgrass (unnamed line) were the lowest yielding, whereas cv. Oahe and cv. Mandan produced the highest yields. Cv. Greenleaf pubescent wheatgrass had higher foliar nitrogen content than all other species, but in vitro organic matter digestibility was less than 700 g OM/kg DM. Although the wheatgrasses had satisfactory herbage yield and nutritional value, better alternative species are available for pastoral farming in central Hawke's Bay. On Belfield in the Hakataramea Valley, cv. Rush has been the most vigorous wheatgrass for establishment and it seems to handle cold winds and frost well. Hay made from a wheatgrass/ lucerne mix is considered better than that from the individual species as this can increase production by 40-50%, depending on soil and climatic conditions. Usually only one cut per year is taken from the mixed pasture. Crop maintenance includes the application of 200 kg/ha of sulphur super extra every 3-4 years and the pH is maintained at about 5.9-6.4 by liming. A significant advantage is that no stock health, pest or plant disease problems have been noted as yet with any of the wheatgrass varieties available in New Zealand. Keywords: dryland agriculture, New Zealand, Thinopyrum, wheatgrass