Identification of appropriate flowering and fruit setting periods of Arabica coffee in relation to probability analysis of precipitation occurrence at Melko

For healthy flowering and subsequent fruit setting after a dry season mature arabica coffee trees in the tropics require certain amounts of rain shower, and shortage of such amounts of rainfall during the critical phonological stages could have an adverse effect on finally yield and quality. Under our condition, however, knowledge on such important relationships as the amount of water in a particular month/season which would be conductive for flower initiation and then fruit development, is still lacking. In this regard, an experiment was superimposed on a 10-year old coffee plantation of five varieties (741, 74110, 74112, 74158 and 74208) planted at Melko. Twenty five trees, systematically selected from the plantation, each with three samples of current fruiting branches were tagged with labels. Flowers and berries (fruits) as they appeared on the branches, and important climatic factors prevailed during 1991-1993 seasons at the location were timely assessed and recorded. The assessment showed that quite a good number of flowers flourished in December to March after receiving about 20 to 50 mm of rain shower within 10 to 15 days before flower opening. As a consequence, a reasonable number of berries, as compared to the observed number of flowers, could develop when the rainfall was more than 50 mm which started in April and continued through the following months. This could be supported by the significant (P=0.01) relationships (r = +0.94 and +0.95) of flower to berry set ratios observed in the respective years. On the other hand, based on the 10-days probability analysis of Precipitation Occurrence (PO) and moisture availability index (MAI) observed over the last 26 years (1969-95) at the location, flowering and fruit setting seasons could be divided into three consecutive periods: Period one (1st Nov. -20th Feb.) a dry period with less than 20 mm rain shower, and 15-40% MAI: Period two (21st Feb.-end of Apr.) with adequate (20 to 50 mm) rainfall for flowering more than 50% of the time and the MAI was also 50 to 85%Period three (1st May - end of Aug.) with sufficient (more than 50 mm) rainfall for fruit development, and MAI exceeding 100%. The appropriate flowering and fruit setting periods seem to be periods two and three, respectively, to harvest a good quality coffee before the onset of the dry season in a contemporary year. Otherwise, if heavy flowerings occurred in period three, supplemental irrigation should be applied for profitable coffee production under Melko condition and probably in neighbouring areas with similar environment.