Does rainfall affect the oil palm bunch ripening and increase the number of loose fruits?

Abstract

The harvest time of oil palm bunches is generally determined based on the bunch color and the number of loose fruits on the weeding circle. The abscission process initiates fruit separation from the bunch. Endogenous plant conditions and environmental factors influence the abscission. The general opinion in the field is that bunches ripen more quickly and fruits fall out more during high rainfall periods. This study aimed to prove the opinion based on the Pearson correlation test between daily rainfall at lag-0 to lag-20 days and the number of loose fruit that fell per day. The study was conducted on five-year-old oil palm at the Sei Aek Pancur Research Station, Indonesian Oil Palm Research Institute (IOPRI), during five harvest periods (10-day harvest interval). The results showed that the value and pattern of the correlation coefficient between rainfall and the amount of loose fruit vary greatly. However, there is a tendency for optimal precipitation (no more than 40 mm/day) that occurs at the beginning (lag-17 to 20), mid (lag-9 to 12), or the end of the fruit ripening phase (1-3 days before the bunches are ready to harvest) can accelerate the ripening of bunches and increase the number of loose fruit. Therefore, the planters should applied good harvesting management, especially during the rainy season when bunch numbers and the chance of many bunches simultaneously ripening is higher.