Conference on Applied Statistics in Agriculture

DESIGNING ALFALFA YIELD TRIALS FOR COMPARING LONG-TERM YIELDS

An aspect of experimental design that must be taken into consideration for variety trials of perennial crops is the number of years to continue the trial. By tradition, alfalfa forage yield trials are harvested for three or four production years, but the consumers of information from these trials, the producers, often keep their stands in production for more than four years. This study developed a statistical efficiency measure for evaluating the adequacy of forage trial designs with specified numbers of years and replicates, based on a multivariate linear model. The measure was applied to data from four long-term trials grown in western Canada. Variances and covariances for varieties and for residual errors varied from trial to trial. Estimates of variety differences for the four-, five-, and six-year total yields using equally weighted combinations of three, four, and five years' data, respectively, were reasonably efficient. Four replicates were sufficient for the four- or five-year total yield, but more replicates were needed for efficient evaluation of the six-year total yield.