A Statistical Model to Estimate Potential Yields in Peach before Bloom

Spring frosts are usual in many of Spain's fruit-growing areas, so it is common to insure crops against frost damage. After a frost, crop loss must be evaluated, by comparing what crop is left with the amount that would have been obtained under normal conditions. Potential crop must be evaluated quickly through the use of measurements obtainable at the beginning of the tree's growth cycle. During the years 1997 through 1999 and in 86 commercial plots of peach and nectarine [ Prunus persica (L.) Batsch], the following measurements were obtained: trunk cross-sectional area (TCA, cm 2 ), trunk cross sectional area per hectare (TCA/ha), estimated total shoot length per trunk cross-sectional area (SLT, shoot m/cm 2 TCA), crop density (CD, amount of fruit/cm 2 TCA), fruit weight (FW, g), yield efficiency (YE, kg of fruit/cm 2 TCA), yield per tree (Y, kg fruit/tree) and days between full bloom and harvest (BHP, days). CD and average FW were related to the rest of the variables through the use of multiple regression models. The models which provided the best fit were CD = SLT - TCA/ha and FW = SLT + BHP - CD. These models were significant, consistent, and appropriate for all three years. The models' predictive ability was evaluated for 32 different plots in 2001 and 2002. Statistical analysis showed the models to be valid for the forecast of orchards' potential yield efficiency, so that they represent a useful tool for early crop prediction and evaluation of losses due to late frosts.