The Production of Contrasting Genotypes of Perennial Ryegrass (Lolium Perenne L.) in Monocultures and Mixed Cultures of Varying Complexity

An experiment was set up to measure the production from donally propagated micro‐swards of four contrasting ryegrass genotypes, grown in monocultures and in all possible combinations of mixed cultures consisting of two, three and all four genotypes. Water and nutrients were supplied frequently in non‐limiting quantities and the swards were subjected to two cutting frequencies. The yield ranking of the monocultures and mixed cultures diifered at the two cutting frequencies. Under infrequent cutting, though not under frequent cutting, two mixtures, each containing two genotypes, were more productive than their highest yielding components in monoculture. The physiological basis of this apparent synergy is hriefly discussed and it is suggested that the increased yield may he due to more efficient light utilization hy the mixtures. In general, yields of other mixtures, including those consisting of 3 or 4 genotypes were intermediate between the highest and lowest yielding components in monoculture. The agronomic and plant‐breeding implications of the results are discussed.