Control of Interplot Interference in Grain Maize: A Multi‐Site Comparison

Abstract

Interplot interference is known to be potentially a major source of bias in cultivar trials of several plant species, but there are few published results concerning grain maize (Zea mays L.) in France. Two series of field experiments were conducted in the North and in the South of France from 1994 to 1996 to quantify interference in grain maize trials and compare methods of control. Each experiment typically consisted of a reference trial with two or three unharvested rows on each side of each plot, a four‐row‐plot trial with one unharvested row on each side of each plot, and a two‐row‐plot trial. Trials had seven cultivars in 1994 and 1996, and four additional cultivars in 1995. Interference was found to occur in two‐row‐plot trials and to be related to plant height. When a cultivar was 10 cm shorter than each of its neighbors, its yield was reduced by 0.16 Mg ha−1 in the North series and by 0.30 Mg ha−1 in the South series on average. Interference appeared much lower in the four‐row‐plot trials. Methods for controlling interference were assessed by comparing their cultivar estimates with those from the reference trials. Bias due to interference in the two‐row‐plot trials was reduced by using models for interference, but the four‐row‐plot trials appeared as a more reliable method to avoid such bias.