The initial 2011-12 California Valencia orange forecast of the National Agricultural Statistics Survey is 28 million cartons.
The forecast is based on a survey carried out from mid Jan to late Feb. Measurements of trees, combined with weather conditions, indicate a likelihood of a normal crop.
For the survey a sample of 578 groves was randomly selected, proportional to acreage, county, and variety representation for the state, with 533 of these groves being utilized in this survey.
Once a grove was randomly chosen and grower permission was granted, two trees were randomly selected for each grove. For each randomly selected tree, its trunk was measured along with all connected branches. A random number table was then used to select a branch, and then all connected branches from the randomly-selected branch were measured.
This process was repeated until a branch was reached with no significant limbs beyond it. This randomly-selected branch, called the terminal branch, was then closely inspected to count all fruit connected to it, as well as all of the fruit along the path from the trunk to the terminal branch. Since each selected path has a probability of selection associated with it, a probability-based method was then applied to estimate a fruit count for the entire tree.
In the last week of the survey period, fruit diameter measurements were made on the right quadrant of four trees surrounding the two trees of every third sampled grove. These measurements were used to estimate an average fruit diameter per tree.
Of the 533 utilized groves, 219 were in Tulare County, 102 were in Kern County, 53 were in San Diego County, 57 were in Ventura County, 34 were in Fresno County, 36 were in Riverside County, 13 were in San Bernardino County, 14 were in Madera County, 2 were in Imperial County, and 3 were in San Luis Obispo County.
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