Competition among pasture plants

Yield, survival, and competition, quantified by the de Wit (1960) model, of the ryegrass cultivars ‘Grasslands Manawa’ and ‘Grasslands Ruanui’ with Agrostis tenuis were examined under a 2 x 2 application of cutting height and frequency. Initially, A. tenuis was markedly suppressed by the ryegrasses, especially by Manawa and where defoliation was infrequent or lax. This was attributed to the low growth rate of A. tenuis during establishment and its shading by the more erect ryegrass plants. Generally, increased content of A. tenuis in the swards decreased yields except in the second year when declining Manawa yields were compensated in mixture by the change to dominance of A. tenuis . It is indicated that A. tenuis has a useful role as a successional species, but its rate of ingress can be controlled by sowing appropriate ryegrass cultivars and by increasing the interval between defoliations.