Issues and options in high country farming: 4. Cycling nutrients for sustainable management

Paper presented at the 58th New Zealand Grassland Association Conference, 21-24 October 1996, Oamaru.Nutrient balances are recognised as the key to understanding the environmental context for sustainable management in pastorally used mountain lands and for monitoring possible effects of pastoral practices on the life-supporting capacity of soil. The paper draws on a larger survey of recent and current soil fertility research in the high country to examine briefly, three themes in nutrient cycling. The role of nutrient accessions to open systems is recognised for improved range. Current long-term revegetation studies show the need to take account of income from rock weathering. The importance of understanding the role of different plant species, soil amendments and pastoral practices in activating or impeding nutrient cycling proper is indicated from recent studies involving monitoring of exchangeable aluminium, comparing lupins with other legumes and studying the effects of planted conifers on the mineralisation of grassland organic matter. The dimensions and magnitudes of grazing induced nutrient transfers are outlined in relation to their risks of loss from periodic hydrologic events, as well as recognising the roles of pasture improvement and grazing management in accelerating nutrient cycling