Objectives of management

The primary objective of management is to maximise the intake of nutrients by the animals from the pasture on a sustained basis. This is achieved by optimising the balance between pasture shoot growth, losses due to tissue senescence, and the yield of pasture removed by grazing or cutting (Parsons, Johnson & Harvey, 1988).

Crop agronomists seek to maximise growth, and the yield harvested at the end of the crop growing season reflects previous photosynthesis. Maximum growth is a mistaken objective for scientists dealing with grass pastures since maximum rates of pasture growth only occur under conditions of suboptimal utilisation which are followed by high rates of tissue senescence. Plant material not eaten eventually senesces. The constant problem before the pasture manager is to reconcile the competing requirement of the animals for daily forage and the need to maintain a minimum sward leaf surface which will intercept and utilise current radiation.

The complexity of decision-making also arises from the nature of the feed requirements of the animal. Continuity of forage supply is sought. The seasonality of this is modified by defoliation practice; for example, close clipping of Paspalum notatum in Georgia, USA, reduces seasonal differences in feed availability relative to those which occur under more lenient defoliation (Beaty et al., 1980). Alternatively forage consumption may be rationed in periods of abundance to provide for a seasonal shortfall. Systems involving a conservation cut differ in their effects from continuous grazing systems, as discussed later.