Effect of defoliation intensity on regrowth of tallgrass prairie.

Abstract

Grazing trials were conducted in north and south-central Oklahoma throughout the growing season of 1989 and 1990 in an attempt to explain live herbage accumulation rate of tallgrass prairie as a function of live residual herbage level. A 1-2 day grazing period on 8 treatment paddocks began 26 May (Trial 1), 7 July (Trial 2), and 18 August (Trial 3) of each year. Two replicate paddocks per trial were subjected to stocking densities of 7,600, 15,200,22,700, and 30,300 kg animal weight ha-1. Live herbage was measured immediately after grazing to determine live residual herbage level and 2,4,6, and 8 weeks after grazing to determine live herbage accumulation. Live herbage accumulation rate was determined as the first derivative with respect to day after grazing day of polynomial regression equations fit to live herbage accumulation data. Maximum live herbage accumulation rate decreased as season progressed but the time required to reach maximum live herbage accumulation rate was not dependent upon season. Live residual herbage level was a significant parameter in equations describing live herbage accumulation rate in 6 of 9 trials.