Patch grazing of Tall Grassveld by cattle after a spring burn

Abstract

Patterns of herbage removal by rotationally stocked cattle (at a density of 4.85AUE ha-¹) on initially structurally homogenous Tall Grassveld were examined over a single season. Three unreplicated camps were stocked early (29 days), at the recommended '10-15cm' sward height (44 days), and late (80 days) after a spring burn. Temporal change in the spatial distribution of herbage in each treatment was described by intensive measurement of compressed sward height (CSH) with a disc pasture meter and analysed with parametric and spatial statistics. Grazing pressure at the start of the grazing was highest in the early graze, intermediate at the recommended, and least in the late graze treatment because of variation in initial herbage mass related to period of deferment after the burn. The early graze paddock was most spatially uniform and the late graze paddock the most uneven and patchy before grazing. Such initial conditions significantly affected subsequent herbage removal patterns: the greater the amount and spatial variability of herbage accumulated before grazing, the greater the chance for patches to develop through area-selective grazing. The early graze paddock was utilised non-selectively during the first two grazing periods but similar to other treatments, became patchier with time. Spatial pattern, a mosaic of short, intermediate and tall patches, peaked in late summer and was most pronounced in the late graze treatment. Intensive, early stocking after a burn is recommended for minimising intraseasonal development of patches and efficient use of high-quality forage available after a burn.


Keywords: deferment; grazing pressure; selective grazing; spatial heterogeneity; sward structure


African Journal of Range & Forage Science 2002, 19(2): 107-116