A Revised Analysis of Plant Competition Experiments

When grown in a mixture, plants of the dominant component show a greater dry matter yield than they do in a monoculture of the same overall density. Plants of the other component usually show a decrease, relative to their own monoculture. Recent studies suggest that the proportional changes are commonly very similar. An earlier analysis, which was based on absolute increases and decreases being approximately the same, is amended in the light of these studies. Central to the new analysis is the concept of Relative Yield Total introduced by de Wit and van den Bergh 1965. The random error structure of mixture diallel experiments is examined and the standard errors of various interpretive parameters derived. A numerical example is given.