Seasonal changes in nutrient content under three defoliation treatments in two casual grassland communities of Transkei.

Abstract

Changes in nutrient concentrations were monitored over a two-year period in two coastal grassland communities. Dry matter digestibility, crude protein, phosphorus, potassium, calcium and magnesium were determined from handclipped samples of experimental treatments; namely, burning with and without subsequent grazing and protection from defoliation. Marked seasonal variations were evident in crude protein, dry matter digestibility, phosphorus and potassium. Defoliation treatment effects were superimposed on the seasonal changes. Burning stimulated large increases in crude protein, dry matter digestibility, phosphorus and potassium. Grazing led to higher protein levels, no change in dry matter digestibility and variable responses in mineral concentrations. Crude protein and phosphorus concentrations were frequently below the maintenance requirements for a LSU. In terms of nutrient stocks, optimum grazing conditions for growth existed only 5-6 months following a fire.

Keywords: burning; calcium; condition; crude protein; defoliation; digestibility; dry matter digestibility; fire; grassland; grassland communities; grazing; magnesium; minerals; mkambati game reserve; nutrient content; phosphorus; pondoland sourveld; potassium; protein; seasonal changes; seasonal variation; south africa; transkei; treatments