Use of a model to optimize the interaction between frequency and severity of intermittent defoliation and to provide a fundamental comparison of the continuous and intermittent defoliation of grass

Abstract A previously described model of grass growth was used to analyse the effect of the severity of defoliation and the duration of the subsequent regrowth on the overall balance between photosynthesis, gross tissue production and leaf death and so on the amount that could be harvested/consumed per hectare under intermittent defoliation. Maximum yield per hectare was shown to be achieved whenever the fluctuations in LAI during regrowth and defoliation led lo the same low average LAI that was previously shown to give maximum yield (amount harvested/consumed per hectare) under continuous grazing. Thus, it is suggested that production under both continuous and intermittent defoliation may best be characterized, and diverse managements may be rationalized, on the basis of the average sward state, the average achieved. The analysis leads us to reconsider some widely held concepts of the growth and utilization of grass applied in both agronomic and ecological theory, and the provision of practical guidelines for management.