Primary growth and regrowth responses of temperate grasses to different temperatures and cutting frequencies

Abstract

Primary growth and regrowths of Italian ryegrass (Lolium multiforum), prairie grass (Bromus catharticus) and tall fescue (Festuca arundinacea), grown in glasshouses at temperatures ranging from 15/10 to 30/25¦C, were measured when defoliated every 4 or 8 weeks. Prairie grass, tall fescue, Ucivex Italian ryegrass, and Tama Italian ryegrass each had different patterns of regrowth. Growth was fastest at 21/16 and 24/19¦C in primary growth and at 15/10¦C in regrowth, except for fescue which had fastest regrowth at 24/19¦C. Frequent defoliation (every 4 weeks) halved the total dry matter yield harvested throughout the experiment. The mean number of tillers and leaves produced was halved by frequent defoliation and leaf area was reduced to one-quarter of that for plants defoliated every 8 weeks. Reproductive development was earlier in plants grown at lower temperatures and did not occur in those grown at 24/19 and 30/25¦C. Primary growth of Italian ryegrass and prairie grass was faster than that of tall fescue. Yield and the number of tillers increased at successive regrowths under 8-week defoliation, but only Tama Italian ryegrass maintained its productivity under frequent defoliation owing to its ability to maintain a high tiller population and high individual leaf areas. Productivity of prairie grass was limited by low tiller number despite its high yield per tiller, and productivity of tall fescue was restricted by both low tiller number and low yield per tiller. The extent to which current growth was influenced by prior growth and, by implication, previous defoliation management differed between the grasses. For example, productivity in any regrowth of Tama was essentially independent of growth during the primary growth or previous regrowth periods, whereas regrowths of prairie grass were highly dependent on growth during previous regrowth periods.