ANNUAL RYEGRASS SEED YIELD RESPONSE TO GRAZING DURING EARLY STEM ELONGATION

Spring grazing annual ryegrass (Lolium multiflorum Lam.) seed fields w ith sheep (Ovis aries) is a common practice. The effects of grazing du ration in early stages of stem elongation on seed yield and its compon ents are not well known. We studied four durations of spring grazing a nnual ryegrass with sheep over a 2-yr period on an Argiaquic Xeric Arg ialboll soil. Grazing was begun before onset of stem elongation. Treat ments were no grazing (G0) and grazing until one-third (G1), two-third s (G2), or all (G3) primary tillers had their apical meristems removed . Leaf area was progressively reduced by grazing duration. The number of fertile tillers increased with grazing duration in the first year, but the effect was not significant in the second year Grazing did not affect the number of spikelets per spike or florets per spikelet in th e first year. In the second gear, G2 and G3 reduced spikelets per spik e and had no effect on the number of florets per spikelet, whereas G1 did not affect either character. Both GZ and G3 decreased seed weight in the first gear, while G1 had no effect; treatments did not affect s eed weight in the second year. Grazing treatment did not affect total herbage dry matter at seed maturity seed yield, or seed quality in eit her year. We conclude that, in western Oregon, grazing annual ryegrass in late winter and early spring up to the time when the apical merist em of all primary tillers are removed (G3) does not reduce seed yield. Grazing until about one-third of primary tillers lose their apical me ristem (G1) may actually improve seed yield.