Scattered shade trees improve low-input smallholder Arabica coffee productivity in the Northern Lake Kivu region of Rwanda

In suboptimal conditions for coffee growth, the use of shade tree is usually considered beneficial to production. This study aimed to evaluate this benefit in the poorly documented East African smallholder Arabica coffee systems in optimal climatic but suboptimal management conditions. In a 4 year observational trial in 50 coffee farms, the association of shade trees and coffee generated an average 55 % cherry production increase. Neither delay in berry maturation nor buffer in alternate bearing patterns were observed, probably due to the low productivity of unfertilized coffee plants. Quality wise, the presence of shade trees did not result in an increase of larger green beans, but it reduced the proportion of altered and lighter cherries in 2009, a low production year. A shade species effect was detected through the positive influence of two non-leguminous shade trees, Persea americana and Ficus thonningii on production. The effect was correlated to greater canopy openness and increase in K soil content. In general, soil mineral content was not influenced by the presence of trees, but the legume species Inga oerstediana appeared responsible for a slight increase of total C and N soil content. It is concluded that in the small holder context of the Northern Lake Kivu region, the association of mature trees is beneficial to coffee production and can contribute to the improvement of producer’s income.