The effect of stocking rate on botanical composition and soils in natural grassland in South Africa.
Abstract
Climax grassland consisting mainly of Trachypogon spicatus, Tristachya hispida, Elyonurus argenteus, Digit-aria tricholaenoides and Heteropogon contortus was grazed for 8 years at 1 or 2 steers/morgen. Light stocking had no effect on botanical composition, but heavy stocking caused a trend towards a serai stage in which Eragrostis curvula and Cynodon dactylon were dominant. Under light stocking, 8.6% of the pasture was affected by dung and urine each year and steers avoided these areas; their colonization by serai species was considered to have been counterbalanced by competition from the climax vegetation. Under heavy stocking, 16.5% of the pasture was affected by excreta and these areas were grazed, nutrient cycling was more rapid, and serai species increased in the sward, presumably because of the toxic effect of high N on climax grasses. Rolling to simulate treading at the high stocking rate decreased the yield of climax grassland by about 23% and that of serai grassland by about 10%. [l morgen = 0.86 ha]-R.B.