Researchers in Oregon set out to determine the effects of four grazing durations by sheep in early stages of stem elongation on annual ryegrass (Lolium multiflorum) seed yield. Results of this experiment suggest that annual ryegrass may be grazed, up to the time when all primary tillers have had their apical meristems removed, without a deleterious effect on seed yield. Results also suggest that a short grazing period, such as G1 (grazing until 1/3 of primary tillers had their apical meristems removed), may actually increase seed yield. The primary effect of all grazing treatments was to increase the number of tillers per unit area, and consequently also increasing the number of fertile tillers. Grazing did not affect the number of spikelets per spike or florets per spikelet in the first year. In the second year, G2 (2/3 removed) and G3 (3/3 removed) reduced spikelets per spike and had no effect on number of florets per spikelet. Both G2 and G3 decreased seed weight in the first year, while G1 had no effect. These findings suggest that grazing annual ryegrass with sheep, prior to the onset of stem elongation and continued until meristems of all primary tillers are removed, would not reduce seed yield. Results further suggest that under these conditions, grazing until one-third of primary tillers have lost their apical meristems may actually increase seed yield.
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