PEACH THINNING OPTIMIZATION MODEL

The optimum economic fruit load to leave on a tree by hand thinning may depend on many different factors such as date of harvest, time of thinning, initial crop load, fruit size potential, fruit size response to thinning, and the distribution and economic value of different sized fruit.
To evaluate the effect of these factors on the optimum fruit load, a simple computer model was developed.

The model was based on field data collected from 4 different cultivars which were hand thinned to a wide range of fruit loads per tree (Johnson and Handley, 1989). Information was collected at harvest on mean fruit weight vs. fruit load and the distribution of fruit weights vs. fruit load.
The user can enter economic data including picking, packing, transporting, and assessment costs.
Sales commission and price per box for different sized fruit can also be specified.
The main outputs from the model are total revenue, total costs, and net revenue at different fruit loads.

The different biological inputs to the model were varied systematically to test their effects on predicting the fruit load with the highest net revenue.
The model was very sensitive to the slope of the relationship between mean fruit weight and fruit load.
However, it was not very sensitive to the distribution (as measured by coefficient of variation) of fruit sizes around the mean.
Many different economic conditions were also varied to test their effects on net revenue.

Further data are being collected so that time of thinning and fruit size potential in any given year can be included in the model, thus making it a useful management tool.

II International Symposium on Computer Modelling in Fruit Research and Orchard Management

R. Scott Johnson, John M. Rasmussen

https://doi.org/10.17660/ActaHortic.1990.276.27