Graduate Thesis Or Dissertation
 

The effect of winter grazing on production and dynamics of a Lolium perenne (L.)-Trifolium repens (L.) pasture

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9306t275z

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  • Perennial ryegrass (Lolium perenne) - white clover (Trifolium repens) hill-land pastures were grazed at different times in the winter to study the effect of time of winter grazing on plant response and forage production. The same pastures were grazed by sheep once in early December, January, February, March, or April and compared to an ungrazed control in each of three forage years (December 1983 to July 1986). Winter stock grazing densities were based on a three day grazing period and a 400 kg ha⁻¹ dry matter residual. Grazing in the winter reduced herbage mass but had relatively little effect on subsequent forage production. This is consistent with the poor conditions for growth (relatively cold and low light levels) during the winter. Rates of herbage accumulation on the ungrazed control treatment averaged 6, -9, 2, 13, and 53 kg dry matter ha⁻¹ day⁻¹ in December, January, February, March, and April, respectively. Dead material accounted for more than 50% of the herbage mass in almost every month between December and March. By May, herbage mass on grazed treatments was similar to the ungrazed control except for treatments grazed in December and April which averaged 20 and 47% less forage than the ungrazed control, respectively. In May of the third year the December grazed treatment had significantly less perennial ryegrass and numerically more annual grass than the ungrazed control, and the January, February, and March grazed treatments. Total annual forage production and forage harvested annually were highly variable but tended to be higher on the January, February, and March grazed treatments than on the ungrazed control, and the December and April grazed treatments. Grazing management programs in temperate hill land pastures, such as are found in western Oregon, would require that forage grown in the fall be carried into the winter if pasture is to be used as a winter feed source. Date of winter grazing has minimal effect on subsequent spring production except for grazing in December which results in lower yields in May. Repeated annual grazing in December may reduce pasture production and increase annual grass dominance after several years.
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