Whereas under optimal environmental conditions complementarity in resource use by coffee and shade trees has been demonstrated, in suboptimal dry conditions there can be competition for water, severity of which depends on tree species and soil conditions. Channels created by dead tree roots through the pan may benefit subsequent coffee root growth. This study compares rooting behaviour in Arabica coffee both unshaded and shaded by two previously untested tropical timber species (deciduous Tabebuia rosea Bertol. and evergreen Simarouba glauca DC.) in andisol soils with a shallow compacted soil layer (talpetate) in sub-optimal environment conditions (455m altitude, 26-27°C, 1200-1400mm rain/year, six months dry season) in Nicaragua. The talpetate varied greatly in terms of depth, thickness and physical structure. 12 trenches 200cm deep were dug in shade both near and far from tree stems, and six trenches in non-shaded plots. Roots were counted per unit area on two perpendicular soil faces. Most coffee fine roots were concentrated in the top 30cm and were less dense under shade than when unshaded. There were more numerous tree roots per unit area in Simarouba glauca than Tabebuia rosea, but nevertheless coffee roots in the profiles located close to Simarouba glauca trees were denser than in Tabebuia rosea plots. A linear model showed the effect of talpetate on diminishing coffee root density in both the full sun and the shade plots. The root system of Simaruba glauca was denser in deep layers than that of Tabebuia rosea. S. glauca seems better suited as a coffee shade tree than Tabebuia rosea in such environmental conditions. More studies are underway, both to confirm these observations on root system of coffee and shade trees (to be presented during the congress) and to understand the consequences of these differences of tree root density on competition between timber trees and coffee.