This 3-year experiment in West Virginia was designed to determine the effects of repeated defoliation, based on canopy height, on the seasonal distribution of herbage mass and growth rates of cool-season grasses. The seasonal distribution of cool-season grass dry matter was influenced by defoliation regimes based on canopy height and intensity of removal (50 vs 75%). The grasses investigated had rapid and sustained increases in instantaneous growth rates when managed as hay in the early season, but when defoliated during the early season they had relatively low and constant instantaneous growth rates (IGR). This could be a result of culm elongation in the hay management, with movement of leaves into the harvest zone. Early-season IGR, in swards clipped throughout the early season, were substantially lower than those with canopies allowed to accumulate herbage during the period. High growth rates of prairie grass early in the study, were followed by stand degradation, regardless of defoliation treatment, and may indicate unsuitability for use in low-input or marginal environments. Autumn recovery of herbage production did not occur under any defoliation treatment.
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