WALNUT PRODUCTION FORECAST DOWN SLIGHTLY
The 2013 California walnut production is forecast at 495,000 tons, down less than 1 percent from 2012’s production of 497,000 tons. This forecast is based on the 2013 Walnut Objective Measurement (O.M.) Survey, which was officially conducted August 1 through August 23, 2013. There were a few samples completed before August 1 for training and scheduling purposes.
Growers in the Sacramento Valley received above average rainfall during November and December, which helped the trees build a more vigorous root system. Weather during the spring was unusually dry and warm, which contributed to a longer bloom. Favorable weather conditions and dense foliage have helped limit sunburn damage. California experienced several short periods of hot weather; however the healthy conditions of many orchards helped the trees withstand the heat.
The 2013 Walnut O.M. Survey utilized a total of 740 blocks with two sample trees per block. Survey data indicated an average record low nut set of 1,239 per tree, down 10 percent from 2012’s average of 1,375. Percent of sound kernels inshell was 98.8 percent Statewide. In-shell weight per nut was 23.3 grams, while the average in-shell suture measurement was 33.1 millimeters. The in-shell cross-width measurement was 33.1 and the average length in-shell was 39.0 millimeters. All of the sizing measurements were above average levels. Estimated nut sets, sizing measurements, average number of trees per acre, and estimated bearing acreage were used in the statistical models.
The Walnut O.M. Survey began in 1958 to fulfill industry needs for an accurate walnut production forecast prior to harvest.
The original sample was chosen proportionally to county and variety of bearing acreage. With each succeeding year, additions and deletions have been made in the sample to adjust for acreage removed, new bearing acreage, and operations that choose not to participate in the survey.
Once a block is randomly selected and permission is granted by the operation for enumerators to enter the block, two trees are randomly selected. An accessible branch is chosen, which is 5-15 percent of the total cross-sectional area of the primary limbs and reachable with a twelve-foot ladder. Measurements are made on the trunk, each primary, and each split leading to and including the accessible branch. The sample tree and accessible branch are marked by a single tag.
On the accessible branch, every first of five nuts is picked for use in size and grade determinations. If available, at least ten nuts are harvested from the accessible branch for this purpose.
The following measurements are made on nuts selected for sizing:
- Weight of nut including hull
- Width of shell at suture
- Width of shell 90 degrees to suture line (cross-suture)
- Length of shell
- Kernel grade
- Weight of nut in-shell
The 80 percent confidence interval is from 447,000 tons to 543,000 tons.