A note on the effect of sheep grazing on the yield of grass swards

Abstract

Herbage yield obtained from grass swards is influenced by the presence of grazing animals (Brockman, Rope & Stevens, 1971a, b; Holmes, 1968; Shaw, Brockman & Wolton, 1966). The net effect of grazing in a particular situation depends on the balance between the effects of excretal-N return, which tends to increase yields (Brockman & Wolton, 1963) and those of treading and other sward damage, which tend to reduce yields (Edmond, 1970). This net grazing effect on yield can be measured by comparing yields of cut and grazed swards under management that is in all other respects identical (Shaw et al. 1966). Available data have been examined to obtain quantitative estimates of the net effect of grazing and of the changes in these effects that occur with changes in sward N supply.