Regrowth rates of timothy and meadow fescue cut at five phenological stages

The relationship between phenological stage at the first cut and subsequent regrowth rates was studied in six field experiments with timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis Huds.) under two levels of N application. The field sites were selected to cover a wide range of climatic conditions in Norway. Five weekly yield samplings during the regrowth periods were fitted to an expolinear growth equation to determine initial maximum relative regrowth rates (R-m) and maximum regrowth rates (C-m). The step from actual to potential rates was accomplished by weighting the obtained rates with a weather index. For both species R-m was highest after an initial cut at the early vegetative stage. It was reduced by 50% at jointing, after which there was no change with later cuts. For both species the C-m declined sharply with cutting time through the early stages of phenological development, whereas from early heading to anthesis there was no significant change. Compared with timothy, the C-m values of meadow fescue were higher after cut at the leaf stage and lower after cut at anthesis. For both species and for all stages of first cut the C-m increased with increasing N application, whereas R-m was not significantly affected.