a1 Scottish Agricultural Statistics Service, University of Edinburgh, Kings Buildings, Edinburgh EH9 3JZ, UK
a2 National Institute of Agricultural Botany, Huntingdon Road, Cambridge CB3 OLE, UK
Methods are described for estimating interplot interference in variety trials. The effects on variety yield performance of interference from varieties in adjacent plots was studied for more than 600 UK National and Recommended List variety trials in the years 1987–1991. The crops examined were barley, wheat, oats, grain peas, beans, oilseed rape, forage maize and sugarbeet. Estimates of differences in variety performance may be biased by as much as 4% in some crops. Factors associated with interference included plant height, standing ability and disease susceptibility. An approach is outlined for limiting the effects of interference through controlled randomization within trials.
(Received June 27 1994)