Analysis of competitive ability among genotypes of perennial ryegrass. II. Effect upon dry matter production

Abstract

An analysis of the effects of competition upon the dry matter production per plant (after square root transformation) revealed no significant differences between the two genotypes of perennial ryegrass (Lolium perenne) used as regards the pressures which they exerted upon each other. Their response to these pressures differed significantly however. Using these estimates of the pressure and response parameters it was shown that the impact of intra-genotypic competition upon these two genotypes was considerably greater than that of inter-genotypic competition. In general this will be true whenever the pressure and response parameters take the same sign. Intensity of competition increased linearly with vigour of growth in both cutting regimes, though changes in vigour had a significantly greater effect upon the intensity of competition under frequent cutting.