In central Costa Rica, coffee trees are intercropped with Erythrina poeppigiana shade trees on steep slopes to reduce soil erosion. The shade trees reduce runoff and boost water infiltration into the soil. They can also enhance coffee production by protecting coffee trees against drought. However, introducing these trees into the system can have negative impacts such as harbouring pests and diseases that can be transmitted to coffee trees, or intercepting sunlight. Whilst yields are typically higher when grown in direct light, shade-grown coffee beans are larger, weighing 0.15g per bean as opposed to 0.13g per bean, and are of higher quality.
To maximise the benefits whilst reducing competition between the two species, Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) worked with a local coffee cooperative to test a novel way of overcoming these challenges. By dividing the farmers into different typologies based on environmental conditions and socio-economic situations, researchers were able to create a model to provide recommendations tailored to farmers within each grouping. For example, because the plots of the “labour-intensive” and “shaded system” groups receive a lot of sunlight, they could plant more shade trees to control for erosion. In contrast, for “input-intensive” and “extensive” groups, whose plots receive less sunlight but more rainfall and humidity, planting more shade trees would increase the risk of attacks by the fungus Mycena citricolor, that causes American leaf spot disease.
The conceptual model helped analyze the key processes and trade-offs for each group and helped make recommendations of adapted erosion control practices. The model also showed that for some groups, less time-consuming erosion control actions such as building drainage canals, terraces or vegetative barriers that do not impact coffee production might be more suitable altogether. In contrast, using shade trees or manual weeding worked better to control erosion as opposed to herbicide use. Overall, the method of prototyping agricultural systems as they respond to different constraints can offer a basis for more productive discussions in participatory research programmes.