The low level of plant nutrients in exposed high-altitude subsoils, and the effects of soil frost and needle ice on plants attempting to colonise these subsoils combine to make natural revegetation very difficult. Artificial revegetation trials established in 1965 at three sites in the Canterbury mountains tested the effect of a fertiliser mixture which supplied a wide range of nutrients, and compared ten herbaceous species as providers of an initial protective cover, and of a cover that would persist.
Hieracium, or hawkweed species, serious weeds in South Island high country, may be controlled by appropriate pastoral management. Experimental trials at Lake Tekapo, related to S and P fertiliser rates of 0-100 kg ha-1 yr-1, 27 different combinations of over-drilled and resident species and different seasons or intensities of grazing treatments on Hieracium dominated fescue tussock were conducted. These were monitored for 9 years in terms of fertiliser inputs used, sheep stocking rates, and vegetation changes.
The improvement of New Zealands pastures over the last 150 years has increased the nutrient status of the soil as a result of the application of fertiliser, an increased soil organic matter content and increased biological activity. The grazing animal has also influenced the nutrient status of the soil by increasing the rate at which nutrients cycle between the soil, plants and animals.