Some advantages of long-term grazing trials, with particular reference to changes in botanical composition

Abstract

Comments are made about some advantages of long-term grazing trials, with special reference to the fact that important botanical changes may occur only after many years, sometimes with subsequent changes in animal production. Rainfall variability is a major reason for these delayed changes, but other factors such as changing soil fertility, longevity of individual plants, and the cumulative effect of stocking rates are involved. The need for trials to document the long-term effect of treatments on botanical change is in conflict with the current (1995) trends for research funding to be directed towards shorter term projects; and yet, botanical change is an important component of sustainability, which is currently accorded high priority. Various ways of addressing the problem of predicting long-term botanical change are discussed, including the use of modelling. Suggestions are made about ways in which long-term grazing trials can be made more effective. Extensive 'on-farm' surveys, provided the pastures concerned are in widespread commercial use, may be a partial alternative to grazing trials.