A Predictive Model for the Definition of Harvest Window and Yield of Peach Fruit of the Variety 'Royal Majestic (R)'

A simple predictive model based on fruit ripening and growth was tested to predict harvest window and yield per tree. Both the ripening, expressed as Index of Absorbance Difference (I-AD), and fruit growth diameter, were monitored during Stage 3 (cell enlargement) of fruit development. Two aspects need to be considered: a) both fruit ripening (decreasing trend) and growth curve (increasing trend) follow a linear model in Stage 3 of fruit development; b) for a given cultivar, the I-AD value at harvest is constant every year. As a consequence, connecting two values obtained at the beginning of the ripening straight line, it is possible to extend the line until the known I-AD value selected for performing the harvest. Therefore the vertical line passing through the I-AD value at harvest intercepts the fruit growth curve at the estimated fruit diameter value reached at harvest. By transforming fruit diameter into a weight and determining the number of fruit per tree it is possible to estimate the yield. The experimental data showed that the model was capable of predicting the harvest window, with an error of 3-4 days, and predicting yield, with an error ranging from 2 to 10%.