The necessity of on-farm research to assess the relationship between shade ecological features and yields has been broadly recognised. On this basis, a more sustainable coffee system could be developed, with better conservation of natural resources. An on-farm research project was conducted in the municipality of Chilon. Chiapas, Mexico, with the objectives of investigating the effect of shade structure on coffee grain yield and assessing the potential uses of associated plant species. Results showed that shade cover percentage and coffee shrub density had significant effects on yields. Maintaining coffee shrub density as a constant, a regression equation related yield to percentage shade by a quadratic polynomial. Coffee density had a significant effect on yields but shade tree density had no effect. Coffee cultivar, age of coffee stand, species richness, shade tree density, basal area, slope and aspect did not have significant effects on coffee yields. Shade tree cover had a positive effect between 23 and 38% shade cover and yield was then maintained up to 48%. Production may decrease under shade cover >50%. A total of 61 shade species were found, with an average density of 260 trees per hectare, the majority of them being indigenous species, used as food, construction materials and as firewood. The role of ecological features associated with shade on yields and availability of natural resources obtained from coffee systems are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.
