Statistical model estimates potential yields in 'Golden delicious' and 'Royal Gala' apples before bloom

摘要

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 1998 and 1999 and in 62 commercial plots of 'Golden Delicious' and 'Royal Gala' apple (Malus x domestica Borkh.), the following measurements were obtained: trunk cross-sectional area (TCA, cm(2)), space allocated per tree (ST, m(2)) trunk cross-sectional area per hectare (TCA/ha), flower density (FD, number of flower buds/cm(2) TCA), flower density per land area (FA, number of flower buds/m(2) land area), cluster set (CS, number of fruit clustersumber of flower clusters, percent), crop density (CD, number of fruit/cm(2) TCA), fruit clusters per trunk cross-sectional area (FCT, number of fruit clusters/cm(2) TCA), fruit clusters per land area (FCA, number of fruit clusters/m(2) land area), fruit number per cluster (FNC), average fruit weight (FW, g), average yield per fruit cluster (CY, g), yield efficiency (YE, fruit g(.)cm(-2) TCA), and tree yield (Y, fruit kg/tree). FCT and average CY were related to the rest of the variables through the use of multiple regression models. The models which provided the best fit were FCT = FD - TCA/ba - FD and CY = -FCA - FCT. These models were significant, consistent, and appropriate for both years. Predicted yield per land area was obtained by multiplying TCA/ha x FCT x CY. The models' predictive ability was evaluated for 64 different plots in 2001 and 2002. Statistical analysis showed the models to be valid for the forecast of potential yields in apple, so that they represent a useful tool for early crop prediction and evaluation of losses due to late frosts.