Walnut Objective Measurement Report

Record Walnut Production Forecast

The 2016 California walnut production is forecast at 670,000 tons, up 11 percent from 2015’s production of 603,000 tons, according to USDA’s National Agricultural Statistics Service.  This forecast is based on the 2016 Walnut Objective Measurement (O.M.) Survey, which was officially conducted August 1 through August 23, 2016.  There were a few samples completed before August 1 for training and scheduling purposes.

The 2016 walnut season began well with adequate chilling hours and a fair amount of winter rains.  Weather during bloom was considered average, with some ideal days and some days of stronger winds and wet weather.  Spring rain increased the threat of blight.  Hot weather in August resulted in an earlier than usual start to harvest, which is expected to begin in early September.

The 2016 Walnut O.M. Survey utilized a total of 729 blocks with two sample trees per block.  Survey data indicated an average nut set of 1,406 per tree, up 11 percent from 2015’s average of 1,272.  Percent of sound kernels in-shell was 98.7 percent Statewide.  In-shell weight per nut was 21.6 grams, while the average in‑shell suture measurement was 32.2 millimeters.  The in-shell cross-width measurement was 32.7 and the average length in-shell was 38.2 millimeters.  All of the sizing measurements were below average levels since 1985.

Estimated nut sets, sizing measurements, average number of trees per acre, and estimated bearing acreage were used in the statistical models.

Survey History

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.

Sampling Procedures

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:

1. Weight of nut including hull
2. Width of shell at suture
3. Width of shell 90 degrees to suture line (cross-suture)
4. Length of shell
5. Kernel grade
6. Weight of nut in-shell

Data Reliability

The 80 percent confidence interval is from 612,000 tons to 728,000 tons.

Rear the full 2016 California Walnut Objective Measurement Report (.pdf)