Effect of defoliation height on regrowth of timothy and meadow fescue in the generative and vegetative phases of growth

Summary

Post-defoliation carbohydrate stores, leaf area and the number of active meristems are important factors affecting the subsequent regrowth of grasses. Defoliation height affects the magnitude of all these factors. Timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) are the two most common pasture species in Finland, but little is known about their response to defoliation height. In this study the effect of three defoliation heights, 3, 6 and 9 cm, on the regrowth rates of timothy and meadow fescue in both the generative (June–July) and vegetative (August) phases of growth were examined in two one-year experiment in year 2000 and 2001. In addition, the main postdefoliation parameters were measured and their contributions to regrowth were studied. In June–July 2000 the regrowth rates, kg dry matter ha-1 d-1, of both species increased linearly by 19% by increasing the cutting height from 3 to 9 cm. In August 2000 the regrowth rates increased by 27% and the cumulative regrowth dry matter yield increased by 29%. In 2001 the defoliation height had no effect on the regrowth rates but the cumulative regrowth yield increased by 10% by increasing the cutting height. Meadow fescue produced 8–21% higher cumulative regrowth yields than timothy. In the reproductive phase, the regrowth rate of timothy is dependent on the population density of vegetative tillers but for meadow fescue population density did not have such importance. In vegetative phase there was no single factor essential for regrowth rates of either of the species.