High Robusta coffee plant density is associated with better yield potential at mixed responses for growth robustness, pests and diseases: which way for a farmer?

Plant density in Robusta coffee is an unresolved issue in low volume producing countries especially when compared with leading producers. In this study, we aimed to compare the response of Robusta coffee to pest incidence, disease severity, growth and yield potential in two contrasting spacing regimes. Two spacing regimes of 3mx3m and 3mx1m were evaluated for selected parameters in a randomized complete block design with three replications. There was a highly significant difference in pest incidence between the spacing regimes (p<0.01) for all the pests except scales (p=0.126). The black coffee trig borer incidence was higher under close spacing of 3mx1m than for 3mx3m with a mean difference of 13.2%. There was no significant association between spacing regime and leaf rust disease incidence while the association was significant for red blister disease (χ2=33.56, df=1, p<0.001). Significant difference in growth response between spacing regimes (p<0.05) were also obtained for change in canopy height (dCAH), number of primaries, number of stems and leaf size. For instance, dCAH was higher under 3mx1m spacing than for 3mx3m spacing. A significant difference in yield potential existed between the spacing regimes (p<0.05) for average yield per tree and average yield per hectare (aYH). Close spacing produced a higher aYH (5.82 t cc/ha) than wide spacing (4.80 t cc/ha). Whereas yield potential is high at high tree densities, associated prevalence of biotic constraints calls for supportive stress management package for farmers.