Water, energy and carbon dynamics over an intercropped sun-grown coffee and corn system

Abstract

The energy dissipation and the evapotranspiration processes, are factors involved in the ecosystem net carbon exchange and are determinants in the ability of a self-regulating system to balance high carbon emissions. To discover these relationships, a corn production system intercropped with coffee was monitored during the first 19 months after the system establishment, to determine the flux of energy, water, gases, and carbon by implementing the eddy covariance technique. From the net carbon exchange ecosystem balance, during the first cycle of corn intercropped with coffee, 63 g C m-2 was fixed. For the next phase of coffee culture, maintaining the corn stalks and coffee branches, 5.4 g C m-2 was emitted. In the second cycle with intercropped corn, thefixation was 291 g of C m-2; and in the last period of the first reproductive stage of the coffee trees, 172 g C m-2 was fixed. Throughout the analysis period, the system behaved as a carbon sink with a potential fixation between 4.7 and 5.6 ton C ha-1. The energy, measured as net radiation, was estimated at 274.53 ± 5.2 W m-2 day-1, and it was dissipated mainly as sensible heat (26.5% - 53.6%), latent heat (45.7% - 71, 9%) and soil heat (0.5% - 1.6%). The crop coefficient (Kc) in the coffee vegetative stage in the monoculture, fluctuated between 0.79 ± 0.05 and 0.99 ± 0.04. For the intercropping system with corn, the Kc was calculated at 0.84 ± 0.05, 1.05 ± 0.06, 1.60 ± 0.09, and 1.22 ± 0.05 for the vegetative, pre-flowering, maximum foliar development and harvest maturity stages of corn, respectively. Key words: Eddy covariance; Net ecosystem exchange; Evapotranspiration; Water fluxes; Carbon dioxide fluxes.