The effect of differences in intensity and frequency of defoliation on the growth of Phalaris aquatica L. and Dactylis glomerata L

Abstract

The response of phalaris (Phalaris aquaticu cv. Sirosa, Sirolan and Seedmaster) and cocksfoot (Dactylis glomerata cv. Currie) to 2- or 4-weekly cutting at heights of 2 or 7 cm was compared in a glasshouse experiment. Treatments were imposed over a period of 16 weeks.Dry matter production was greatest under the most lenient defoliation regime (4 week17 cm) and least under the most severe defoliation regime (2 week12 cm). Differences in harvested dry matter per tiller and leaf area per pot among cultivars increased with increasing leniency of defoliation. There were significant cultivar x cutting frequency x cutting height interactions for total winter leaf and spring stem production. Harvested dry matter from Sirosa and Sirolan was greater than that from Seedmaster under 4-weekly cutting, although differences in harvested dry matter per tiller were evident under all cutting regimes. Currie cocksfoot consistently maintained higher tiller numbers than the phalaris cultivars, but leaf, stem and leaf area production per tiller were generally ranked Sirolan > Sirosa > Seedmaster> Currie. When reproductive tillers were decapitated, Sirolan and Sirosa tended to produce more new tillers than Seedmaster under frequent cutting. More crown buds were found at the base of Sirolan tillers than on those of other phalaris cultivars, but the number of buds was reduced more on Sirolan with increasing severity of defoliation than on other cultivars. It is postulated that Sirolan and Sirosa may benefit from spelling in spring, and defoliation to a higher residual herbage mass andlor sward height than Australian-Seedmaster type.