2008 California walnut production is forecast at 375,000 tons, up 15 percent from 2007's production of 325,000 tons. The forecast from the National Agricultural Statistics Service’s California office is based on the 2008 Walnut Objective Measurement (O.M.) Survey, which was officially conducted Aug. 1 through Aug. 25, 2008. There were a few samples completed before Aug. 1 for training and scheduling purposes.

The 2008 Walnut O.M. Survey utilized a total of 689 blocks with two sample trees per block. Survey data indicated an average nut set of 1,416 per tree, up 4 percent from the 2007 average of 1,357. The Hartley nut set was down 14 percent; Chandler was up 33 percent; Serr was down 20 percent from 2007. Percent of sound kernels in-shell was 98 percent statewide.

In-shell weight per nut was 22.2 grams, while the average in-shell suture measurement was 32.6 millimeters. The in-shell cross-width measurement was 32.9 and the average length in-shell was 39.3 millimeters.

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.