A New Method to Assess Competition in Coffee Clonal Trials with Single‐Tree Plots in Côte d'Ivoire

A new method is proposed for the assessment of competition in clonal trials with completely randomized single‐tree plots, without needing to choose a covariable a priori linked to competition. This method is applied to a coffee clonal trial planted in a completely randomized single‐tree plot design located in Côte d'Ivoire. Microenvironmental effects were first taken into account using the conventional Papadakis method. The competition effect ( C k ) of each clone ( k ) was then estimated as the influence of its presence on the residual value, after removal of the clonal effect, of its neighbors. Residuals were thus modeled as a linear regression of the neighboring clones’ C value. Competition effects were shown this way to explain 4% of the residual yield in young trees and 10% in adult trees. Several clones had C values significantly different from 0. Some were identified as aggressive for their neighbors ( C < 0), others as stimulating (i.e., promoting yield, C > 0). Architecture and vigor variables that were likely to be related to the C value of clones were then sought. For young trees, vigor, estimated by stem diameter, was best correlated to competition effects: vigorous clones were more aggressive than others. When trees became adult, the length of the orthotropic internodes ( L ort ) was the trait that most effectively explained (42%) the competition effect of clones: the shorter the internodes, the less aggressive was the clone. In the future, L ort may thus be used in a selection index to prevent from selecting aggressive coffee clones that would undergo their own aggressiveness when grown alone in plantations.