The objective of this work was to evaluate the effect of cover crops on the biological activity of the soil in the rainy and dry seasons, under the intercropping of passion fruit, pineapple, cassava and maize. The experiment was carried out in Rio Branco, in the state of Acre in Brazil, in a plinthic allitic Yellow Argisol. The experimental design used was of complete randomised blocks with split lots and four replications: with the evaluation periods for the lots (March, May, August and October of 2011) and the cover crops for the sublots [tropical kudzu (Pueraria phaseoloides), crotalaria (Crotalaria spectabilis), pinto peanut (Arachis pintoi), jack bean (Canavalia ensiformis) and weeds]. The following were evaluated: respiration (edaphic and basal), microbial biomass, and metabolic (qCO2) and microbial (qMIC) quotients. At the end of the rainy season, under adequate conditions of moisture and oxygenation in the soil, crotalaria cover enhances microbial activity together with the jack bean, which provides better edaphic respiration. During the period when soil oxygen is more restricted (from October to March - the rainy season) and water (August - characteristic of the dry season), the pinto peanut helps maintain high microbial activity. In the period of greatest rainfall (March), the soil under weed cover displays greater microbial biomass and metabolic efficiency.
Intercropping; CO2 emission; Carbon dynamics
