Seasonal Growth Rates of Tallgrass Prairie After Clipping

Abstract

Intensive rotation grazing is dependent on the proper timing of livestock movement for success. The timing of livestock movement is in turn dependent on the rate of forage growth, but quantitative information on growth rates of tallgrass prairie is limited. The objective of this study was to develop information on seasonal growth parameters of tallgrass prairie following uniform clipping. Plots were mowed to 10 cm on various starting dates during the growing season and sampled weekly for live standing crop for 10 weeks following mowing. Four and five regrowth trials were completed in 1984 and 1985, respectively. Regrowth trials were analyzed by fitting second degree polynomial regression models to the weekly standing crop data and calculating several growth parameters from the fitted models. The maximum standing crop of forage regrowth declined significantly as the time of initial clipping was delayed (2,300-280 kg ha-1, 1984; 2,400-1,130 kg ha-1, 1985). The maximum net growth rate also declined significantly with season (52-0 kg ha-1 d-1, 1984; 36-16 kg ha-1 d-1, 1985). The time required to reach maximum regrowth standing crop or maximum net growth rate did not vary significantly with season. If livestock movement under rotation grazing was based strictly on the time to reach maximum net growth rate, the length of the rest period for a given pasture would remain constant or even decrease slightly with season. The attainment of a given level of forage in a pasture as a criterion for livestock movement would result in a better balance between forage livestock production than the use of the time to maximum net growth rate.