Ten year balances of organic matter and nutrients in agroforestry systems at CATIE, Costa Rica

In the ‘Experimento Central’ of CATIE (Centro Agronómico Tropical de Investigación y Enseñanza, Turrialba, Costa Rica) studies on organic matter and nutrient cycling have been carried out in the following agroforestry systems, planted in 1977: • - Theobroma cacao with Cordia alliodora and Erythrina poeppigiana; • - Coffea arabica with the same shade trees; • - Cynodon plectostachyus (star grass) associated with the same trees. Results are presented and discussed using the T. cacao systems as an example. The accumulation of organic matter, measured for the different species (leaves, branches, trunks, roots, fruits and litter) at an age of 5 years (1982) and of 10 years is very large: 50.3 and 110.6 t ha −1 for T. cacao/C. alliodora. The average cacao bean harvest at an age of 6–10 years reached 1036 and 1057 kg ha −1 a −1 under shade of C. alliodora and E. poeppigiana, respectively. Total stem volume growth of C. alliodora is presently 9.6 m 3 ha −1 a −1. Measurements of the natural leaf fall and of prunings were made over 5 years, reaching 8.11/3.29 t ha −1 a −1 for T. cacao/C. alliodora and 9.29/13.57 t ha −1 a −1 for T. cacao/ E. poeppigiana, respectively. With the values obtained, quinquennial models for organic matter and nutrients are presented and discussed.