The influence of stocking rate, range condition and rainfall on residual herbage mass in the semiarid savanna of KwaZulu/Natal

Abstract

Grazing trials at two sites in the semiarid savanna of KwaZulu-Natal were stocked with cattle at light (0.17 LSU ha^-1), intermediate (0.23 LSU ha^-1) and heavy (0.30 LSU ha^-1) stocking. Pasture disc meter data collected over 116 three-week periods were used to develop a step-wise multiple linear model to predict the amount of residual herbage at the end of the summer growing season and the period (days) over which forage supplementation would be required to maintain animal mass during the winter dormant season. Residual herbage mass at the end of summer was significantly related to cumulative summer grazing days, rainfall and range condition (indexed as the sum of the proportions of Themeda triandra, Panicum maximum and P. coloratum). The period of forage deficit during which herbage mass declined below a grazing cut-off of 1 695 kg ha^-1 was significantly related to residual herbage mass at the end of summer.

Keywords: Forage deficit, regression model, risk