Relationship Between Tillering and Forage Yield of Tall Fescue. I. Yield1

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Abstract
Little information exists regarding the influence of tiller density on yield of forage grass swards, but tiller density has been shown to be associated positively with yield of spaced plants. Therefore, three field experiments were conducted on developing and developed swards to evaluate the relationship between tiller density and forage yield of tall fescue (Festuca arundinacea Schreb.). Genotypes were selected that displayed high (HYT) medium (MYT) and low yield/tiller (LYT). As spaced plants, these genotypes were known to have a slow, medium, and rapid rate of tiller development, respectively. Plots were established in early spring from vegetative tillers and were allowed to develop into swards. Cutting heights of 5 and 10 cm above ground level were compared, and in one experiment the genotypes were grown with birdsfoot trefoil (Lotus corniculatus L.) to evaluate their competitive ability. All plots were cut four times during the growing season. Before equilibrium tiller density was reached (when addition of new tillers offset death of others), a close relationship existed between forage yield and tiller density. However, in all experiments, forage yield was closely associated with yield/tiller once tiller density approached equilibrium and tended to stabilize. Under those conditions, the highest yielding genotype of tall fescue was the one characterized by low tiller density and high yield/tiller. Increasing cutting height from 5 to 10 cm did not affect tiller density, but did increase yield/tiller and forage yield for the season. This difference was probably due to residual leaf area remaining on the stubble after cutting. Birdsfoot trefoil grown in a mixture with the HYT genotype was 26% more productive than when grown in a mixture with the LYT genotype of tall fescue. Selection of tall fescue for high tiller weight and reduced rate of tillering may be beneficial for grass grown alone and for use in mixtures with legumes.