Some aspects of grazing ecosystems : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University

Abstract

The conversion of plant material to meat and milk by ruminants is one of the main ways in which the demand for energy and more especially protein for human consumption is met. While research in soil, plant and animal sciences is all more or less relevant to this conversion process a considerable amount of the agricultural research effort in Australasia has been directed more specifically to the grazing situation. Much of this work has been concerned with specific components of the grazing ecosystem such as the factors limiting pasture production (Brougham 1968), the definition of those plant factors contributing to nutritive value (Butler et al. 1968; Minson 1968), animal nutrition (Moir 1968) and pasture establishment (Swain 1968). While such research is basic to the understanding of the processes operating within a grazing system it must be complimented by a recognition of the interactions which exist within such grazing ecosystems and the way in which such interactions can affect interpretation of evidence from isolated parts of the grazing ecosystem. For example, the adoption of defoliation systems based on evidence from experiments of which grazing animals are not an integral part is often difficult to reconcile with the reality of having to graze a more or less fixed number of animals on a fixed area of land over a long period of time (Campbell 1969). In an effort to take account of the interactions which may invalidate conclusions based on evidence from component parts of the grazing ecosystem, the "whole-farm" approach to experimentation has been evolved. However in many cases such experiments have been designed to study the importance of different management factors on animal production from a given area of land (McMeekan 1961; Willoughby 1968) rather than to study the inter-relationships occurring between the soil, plant and animal components of the ecosystem. For example there is little information available on these inter-relationships from over 150 experiments of this kind carried out in Australia, evaluation of treatments having been carried out almost entirely in terms of animal production (Allden 1968).