The 2017 California walnut production is forecast at 650,000 tons, down 5 percent from 2016’s record production of 686,000 tons, according to USDA’s National Agricultural Statistics Service (NASS). This forecast is based on the 2017 Walnut Objective Measurement (O.M.) Survey, which was officially conducted August 1 through August 19, 2017. There were a few samples completed before August 1 for training and scheduling purposes.
The 2017 walnut season began with adequate chilling hours and record amounts of rain during the winter and spring months. There were reports of orchards being saturated for several weeks which resulted in a compromised root system. A higher than average insect problem was also reported. During the excessive heat waves over the summer, growers applied sunburn preventative materials. Harvest is expected to begin during the middle of September.
The 2017 Walnut O.M. Survey utilized a total of 737 blocks with two sample trees per block. Survey data indicated a record low average nut set of 1,141 per tree, down 19 percent from 2016’s average of 1,406. Percent of sound kernels in-shell was 98.1 percent Statewide. In-shell weight per nut was 23.4 grams, while the average in-shell suture measurement was 32.7 millimeters. The in-shell cross-width measurement was 33.3 and the average length in-shell was 38.6 millimeters. All of the sizing measurements were above the previous year’s levels.
Estimated nut sets, sizing measurements, average number of trees per acre, and estimated bearing acreage were used in the statistical models.
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 596,000 tons to 704,000 tons.