The effects of frequent hard grazings at different times of the year on the productivity and species yields of a grass-clover pasture

Abstract

An experiment is described in which the effects of frequent hard grazings at different times of the year on the productivity and species yields of a pasture of short-rotation ryegrass, cocksfoot, and red and white clover were determined over an eighteen-month period. Frequent hard grazings during the winter encouraged the growth of all sown species, and dry-matter (d.m.) yields were high for these pastures after a change to less-intensive grazing in later seasons. Frequent hard grazings during the spring reduced immediate d.m. yields markedly but because there were no detrimental effects on plant survival of any of the sown species except red clover, subsequent d.m. yields of these pastures were also relatively high when the management system reverted to the less-intensive system. Frequent hard grazings during the summer resulted in widespread death of all sown species except white clover. Subsequent d.m. yields obtained from these pastures were ,thus severely reduced. Frequent hard grazings during the autumn reduced immediate d.m. yields by approximately 20% but, it is suggested that because the light-shielding clover canopy was controlled, yields obtained from the sown grass species in fhe following seasons were high. The results highlight the importance of summer grazing management to ensure persistency of pasture species, the importance of intensive grazing in the late autumn to bring about a rapid change in botanical composition from dominance of summer-growing species to dominance of winter-growing species, and the relatively high yields obtained by avoiding long spelling during the winter. The results are discussed in relation to existing pasture-management principles and productivity.