Climate Variability Influences On The Flowering Of Coffee In Colombia.

The Colombian coffee area is influenced by several sources of climate variability at different spatial and temporal scales, one of  the most important being the El Niño-La Niña (ENSO). During  El Niño episodes it is common to register a reduction in the rainfall and an increase in the air temperature and sunshine; conversely during La Niña episodes  increases  in the rainfall and reduction in the air temperature and the sunshine are the common characteristics. Both phases of the ENSO influence directly coffee phenology and production.  At the crop level, during El Niño it is frequent to observe a reduction in the seed filling specially in those zones where the soil has low water retention capacity and high crop evapotranspiration rates and  during La Niña the  water excess in the soil  and reduction in the air temperature and sunshine produce a  reduction in the number of flower buds,  delays in flower differentiation, and increased  duration of flower bud latency. Between May 2008 to April  2010, weekly counts of flowers  at pre-anthesis stage were realized  in six branches of 30 coffee plants (two and three years old) at  8  sites across the Colombia coffee zone, between  02°24´ N to 10°25´N and 1.134 m to 1.735 m of elevation; during that period two La Niña episodes and one El Niño episodes were observed.  The flowering data  were analysed quaterly (November-December- January, February-March-April, May-June-July, August, September, October). To relate the influence of the climate on  the flowering were used the following agrometeorological indices which integrate the soil-plant-atmosphere continuum: Soil moisture indices (SMI), thermal accumulation or thermal time  (TT), daily thermal amplitude (TA ) and sunshine hours deficit (SD).It was observed a reduction in flowering during the La Niña directly related to periods with more than 20 days with SMI over critical values (water excess), increases  in the SD (days with mean sunshine lower that 4.5 hours), and reduction in TT, and TA.  During El Niño the number of flower bud  increase was related to the increase of the soil water deficit (more than  60 days of moderate water deficit or  20 days with strong water deficit), reduction in the SD (days with mean sunshine over 4.5 hours), increase of the TT (more than 1.100 °C by quarter) and TA (most of 50 days by trimester with TA> 10°C). With these results were developed  composite indices known as hidrothermic (HiT) and hidroheliothermic (HiHeT), which explain better the relationship between the agrometeorological conditions and flowering in coffee, and during 20111 and 2013 those indices has been correlated well with the flowering measured in field.