Estimating seasonal herbage production of a semi‐arid grassland based on veld condition, rainfall, and evapotranspiration

Abstract

The relation between above‐ground phytomass production and three independent variables, namely, seasonal rainfall, evapotranspiration (E _t ) and veld condition, were investigated using fourteen years’ data (1977–1991) from the dry Themeda‐Cymbopogon grassveld of the central Orange Free State. The data showed that rainfall and E _t have equivalent estimation value. The multiple curvilinear regression equation (r = 0.88) that was established, with seasonal rainfall and veld condition score as the independent variables, can be used with great success in this veld type to estimate seasonal production potential. In terms of the above‐ground phytomass production, it would appear that veld in good condition responds more efficiently to rainfall than veld in poor condition. Basal cover decreased linearly with a deterioration in veld condition.