Quantifying Spatial Heterogeneity in Herbage Mass and Consumption in Pastures

Abstract

A sward-based technique for quantifying the spatial heterogeneity in herbage mass and consumption was developed and tested in a bahia grass (Paspalum notatum Flugge) pasture grazed by cattle. For five, 2-day grazing periods from May to October, preand post-grazing herbage masses were nondestructively estimated with an electronic capacitance probe at 182, 50 x 50 cm locations along 2 permanent line transects. At the same time, undisturbed herbage accumulation during grazing was measured inside exclosures and the results used to estimate accumulation under grazing at each location. Estimation of herbage mass was relatively good; R2= 0.88 to 0.98. Spatial heterogeneity in herbage mass and the stability of the spatial pattern were well quantified. The pattern of spatial heterogeneity observed early in the grazing season remained quite stable for 5 months until the late grazing season. Spatial heterogeneity in the rate of defoliation was also well quantified in spite of some negative values. The technique is of potential value for quantifying the spatial heterogeneity in herbage mass and consumption by animals in grazed pastures, though further studies are necessary for testing the applicability of the technique to pastures of other plant species or of multiple species.