Arabica coffee fruits phenology assessed through degree days, precipitation, and solar radiation exposure on a daily basis

Abstract

Knowledge regarding reproductive cycle duration is important in terms of scheduling harvests and estimating coffee cultivars adaptability. Nine Coffea arabica cultivars were evaluated during two successive reproductive cycles. Dates of occurrence of the major blossoms, and the green and ripe fruits, on 64 branches for each cultivar, were registered during each reproductive cycle. These dates were used to calculate the duration of the fruit development (blossom to green) and ripening (green to ripe) phases, the quantities of degree days, precipitation, and solar radiation accumulated throughout each phase, and also degree days, precipitation, and radiation on a daily basis, all of which are novelties in coffee research. The differences between cultivars and reproductive cycles were tested by ANOVA. Cultivars were grouped in clusters according to the above-cited variables. Principally, the daily quantities of degree days and precipitation determined the differences between reproductive cycles and coffee cultivars during development phases. Early and very early cultivars accumulated high numbers of degree days.day⁻¹, in periods of relatively good water availability, with high exposure to solar radiation. Late cultivars accumulated less degree days.day⁻¹ and were exposed to lower amounts of daily solar radiation and longer periods of water scarcity. Regarding the fruit ripening phase, cultivars were principally distinguished by degree days and solar radiation on a daily basis. Two of the coffee cultivars were classified or confirmed as early and very early and another three as late and very late. One cultivar, Siriema, displayed an interesting conjugation of early and intermediate characteristics.