Yield Forecasting for Olive Trees: A new Approach in a Historical Series (Umbria, Central Italy)

In recent years the relationship between flowering and fruit production was studied and evaluated in several wind-pollinated species. In olive (Olea europaea L.) the pollen monitoring technique was introduced to determine pollen indexes as indicators of flowering, evaluating in some cases the predictive role of the variable. Recently, in these investigations, to investigate the reproductive efficiency the Pollen Index (calculated during the entire flowering period) was replaced by the pollen emissions during the effective pollination period (EPP). In this study, in particular, an EPP elaborated value was derived from the EPP values and the average values of the meteorological variables. The regression analysis considering winter chill accumulation, summer sums of minimum temperatures and the elaborated EPP confirmed the strong relationship among meteorological variables, pollen emission and final production in our study areas. This study has shown the need to use pollen data obtained from aerobiological monitoring in harvest forecasting models in anemophilous plants such as olive. In particular in the statistical models pollen provides a synthesis of the historical information of the entire biological-reproductive cycle of the plant while meteorological trends interpret the incidental phenomena.