The initial 2014-15 Navel orange forecast is 81.0 million cartons. Of the total Navel orange forecast, 78.0 million cartons are estimated to be in the Central Valley. This forecast is based on the results of the 2014-15 Navel Orange Objective Measurement (O.M.) Survey, which was conducted from July 13 to September 2, 2014. Estimated fruit set per tree, fruit diameter, trees per acre, bearing acreage, and oranges per box were used in the statistical models estimating production.
The varieties forecast in this report include conventional, organic, and specialty Navel oranges (including Cara Cara and Blood orange varieties).
Survey data indicated a fruit set per tree of 333, above the five-year average of 328. The average September 1 diameter was low at 2.205, below the five-year average of 2.256.
A sample of 575 Navel orange groves was randomly selected proportional to county and variety bearing acreage, and 534 of the groves were utilized in this survey. Once a grove was randomly chosen and grower permission was granted, two trees were randomly selected. The Navel orange sample included organic, Cara Cara, and Blood orange groves.
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 grove. These measurements were used to estimate an average fruit diameter per tree. Of the 534 utilized groves, 8 were in Madera County, 90 were in Fresno County, 309 were in Tulare County, and 127 were in Kern County.
A Navel Orange Objective Measurement Survey has been conducted in the Central Valley every year since the 1984-85 crop year, except for the 1991-92 season due to a lack of funding. The data from the first two years were used for research purposes in developing crop-estimating models.
Check out the full California Navel Orange Objective Measurement Report here. (.pdf)