Population studies with wheat: III. Seed rates in nursery trials and field plots

The discrepancies between nursery plots and field plots, found by previous workers when investigating yield problems with wheat, are discussed. The reason for these differences is given, and the true optimum plant density identified. It is shown that the intensity of competition for water and soil nutriments influences the optimum plant density, and that a high intensity of competition is associated with a low optimum plant density. A summary of literature is given, and the varying values for the optimum seed rates in different parts of the world interpreted in the light of water and soil nutriment supplies.