Statistical Model Estimates Potential Yields in Pear Cultivars `Blanquilla' and `Conference' before Bloom

Abstract

<jats:p>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 1996 and 1997 and in 95 commercial plots of `Blanquilla' and `Conference' pear (<jats:italic>Pyrus communis</jats:italic> L.), the following measurements were obtained: trunk cross-sectional area (TCA, cm<jats:sup>2</jats:sup>), space allocated per tree (ST, m<jats:sup>2</jats:sup>), trunk cross-sectional area per hectare (TCA/ha), flower density (FD, number of flower buds/cm<jats:sup>2</jats:sup> TCA), flower density per land area (FA, number of flower buds/m<jats:sup>2</jats:sup> land area), cluster set (CS, number of fruit clusters/number of flower clusters, %), crop density (CD, number of fruit/cm<jats:sup>2</jats:sup> TCA), fruit clusters per trunk cross-sectional area (FCT, number of fruit clusters/cm<jats:sup>2</jats:sup> TCA), fruit clusters per land area (FCA, number of fruit clusters/m<jats:sup>2</jats:sup> 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<jats:sup>-2</jats:sup> TCA), and tree yield (Y, fruit kg/tree). CS and average CY were related to the rest of the variables through the use of multiple regression models. The models that provided the best fit were CS = TCA/ha - FA and CY = -FA - FCT. These models were significant, consistent, and appropriate for both years. Predicted yield per land area was obtained by multiplying FA × CS × CY. The models' predictive ability was evaluated for 46 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.</jats:p>

Simple and accurate allometric model for leaf area estimation in Vitis vinifera L. genotypes

“…Two techniques reported by Jiménez and Díaz (2003a), and Jiménez and Díaz (2003b) were used to validate the models: (1) the validation data set was used to produce a validation model by re-estimating the model parameters using the stepwise regression option approach to develop the estimation model and the models were compared for consistency; (2) regression parameter estimates from the estimation models were used to predict outcomes for observations in the validation data set and then the mean squared prediction error (MSPR) was calculated and compared with the MSE of the regression fit to the model building data set (Neter et al 1996). In order to compare the predicted LA (PLA) to the observed LA (OLA) for the genotype 'Italia', graphical procedures (Bland and Altman 1986) were used.…”