A Simple Pasture Model for Predicting Biomass Responses to Continuous and Rotational Defoliation.

The literature is equivocal about pasture biomass responses to continuous and rotational stocking of livestock. These management options affect many factors such as distribution of dung and urine, amount of labor, need for fencing and water, and animal grazing selectivity, that can affect choice of management to be used on farms. The obvious and immediate impact of variable amounts of biomass cover between these treatments is perhaps where the greatest uncertainty in impact occurs. Some studies report higher forage production for continuous stocking, some report higher production for rotational stocking, and some studies finding no difference between managements. Our research proposes a causal relationship between pasture growth rate and forage biomass, where at very low and very high biomass growth rate is slow, but at an optimum biomass growth rate will be maximum. The impact of contrasting defoliation management on pasture growth rate and overall production is determined by the overall biomass relative to the optimum. The objective of this study was to incorporate previously derived equations relating biomass and growth rate into an Excel model that can be used to predict total biomass for continuous and rotational stocking. This model was validated using data from a field grazing study comparing continuous and rotational stocking.