Competition among pasture plants

Abstract

Competition between Agrostis tenuis and Trifolium repens, as affected by a 2 x 2 application of cutting height and frequency on simulated swards, was quantified by the de Wit (1960) model. Cutting height and frequency treatments were discontinued after 6 and 17 months respectively, all plots being cut uniformly for the last 7 months of the experiment.A. tenuis was strongly suppressed by T. repens during the first summer, under infrequent cutting, and this suppression was maintained for the remainder of the experiment. There was a clearly defined difference between the competitive power of A. tenuis in the hard and laxly cut frequent cutting treatments, this effect continuing into the final phase of the experiment when, under monthly cutting, T. repens gained competitively in the frequent -hard treatment, whereas A. tenuis maintained its competitive power in the frequent -lax treatment.Yield increases of mixtures over monocultures under frequent cutting are attributed to effects of nitrogen transfer from legume to grass and different seasonal growth periodicities. The results imply that in regions where A. tenuis ingress is important, increase in the intervals between defoliations will allow T. repens and ryegrass to shade and suppress A. tenuis. This will result in more efficient use of phosphate through reduced competition by A. tenuis and better use of phosphate and other nutrients by desired species.