Earthworm Populations, Microbial Biomass and Coffee Production in Different Experimental Agroforestry Management Systems in Costa Rica

Coffee management systems are diverse and can have significant impacts on soil biota. Earthworms are important members of the soil biotic community and may enhance soil fertility in agricul- tural soils. The impact of coffee management on earthworms and other factors related to productivity are not well known. Our main objective was to determine the impact of coffee management on earthworm popu- lations, microbial biomass, and coffee production in Turrialba, Costa Rica. Three experimental coffee (Coffea arabica 'Caturra') management systems were studied: full sun, shade with Erythrina poepiggiana and shade with Terminalia amazonia. Within these systems there were three sub-treatments with different levels of inputs: high conventional or medium conventional sub-treatments with chemical fertilizer, herbicide and fungicide additions, and organic inputs in the shade systems. We found the earthworms Pontoscolex core- thrurus and Metaphire californica in shade treatments, but M. californica was absent from sun systems and Terminalia high conventional systems. Mean earthworm density was lowest in the sun high conventional treatment (63 ind. m �2 ), higher in medium conventional treatments (from 108 ind. m �2 to 225 ind. m �2 ), and highest in Terminalia organic systems (334 ind. m �2 ). In 2003, coffee production was highest in sun high conventional treatments (17.6 Mg ha �1 ), but in 2004 it was highest in the Terminalia organic treatments (9.2 Mg ha �1 ). Microbial biomass was not different among treatments, but was correlated with total earthworm density and biomass. Results indicate that shade organic management favors high earthworm density and biomass and that coffee yields under organic management can equal those of conventional systems.