PERSISTENCE OF A LARGE LEAVED WHITE CLOVER VARIETY UNDER SHEEP GRAZING

Abstract

Measurements of photosynthesis, leaf appearance, leaf death and clover stolen characteristics were made during late summer on an established mixed perennial ryegrass (5241 white clover (Blanca) sward continuously grazed by sheepto maintain sward heights of either 2-3cm (hard grazed) or 10.15cm (lax grazed). In both hard and lax grazed swards, each stolen tip had three petioles on average, and a new leaf appeared and an old leaf (petiole) died every seven days. Under intensive grazing, new clover leaves were grazed within l-2 days of appearance, sometimes before leaflets had unfolded, leaving only petioles on the stolon. The contribution of clover leaflets to the gross photosynthesis of the sward was greater than would be expected from their contribution to the total leaf area. The photosynthesis of petioles was appreciable, though some 25% that of leaves on an area basis. Although white clover became more prostrate and smaller leaved under hard grazing, the adaption was insufficient to prevent most photosynthetic tissue being grazed. The results are discussed in relation to white clover persistence. Keywords: White clover, stolons, leaf size, leaf appearance, photosynthesis, continuous grazing.