Competition between cultivars of fodder kale (Brassica oleracea L.) in yield trials with single-row plots

Summary Two experiments were done to evaluate the use of single-row plots for assessing digestible organic-matter (DOM) yield.In the first experiment 29 cultivars were grown in both single-row plots (unguarded) and five-row plots from which only the centre row was harvested (guarded single-row plot). The correlation between yields in the unguarded and guarded plots was very low (r=0.20). Yield was correlated (r=0.89) with cultivar height in the unguarded plots, but not in the guarded plots (r=0.19). Therefore selection for yield in unguarded single-row plots is undesirable and would favour tall kales which are prone to lodging.In the second experiment 16 cultivars were grown in single row-plots guarded by the short cultivar Maris Kestrel, the tall cultivar Vulcan and by the cultivars themselves as control. The correlations between yield in the control plots and yields in the plots guarded with Maris Kestrel and Vulcan were only moderate (r=0.56 and r=0.64 respectively). Therefore the use of a single distinct cultivar to guard single row-plots is undesirable.Selection for DOM yield should therefore be made in multiple-row plots, from which the outer rows are discarded, in order to avoid the undesirable effects of competition.