Raisin harvesting equipment has sure changed since I was auditing Sun-Maid raisins with CPA firm KPMG back in the 1980s. Of course that was over 30 years ago, as my son enjoys reminding me! We closed the equipment appraisal office on opening day of the State Fair and took a field trip over to Sacramento to enjoy some BBQ with our friends at Wallace Valuation Advisors. While touring the fair after the BBQ we dropped into the Sun-Maid raisin display which made a big impression, especially the videos of the harvesting equipment for overhead trellises. In my immediate neighborhood, most of the grapes are grown for wine, so the overhead trellises aren’t popping up.
Traditionally raisin drying involved the labor-intensive method of hand cutting the grape clusters and placing them in the sun parchment paper between between the rows. Off the vine drying could be disastrous if early fall rain storms blow in — the raisins would need to be quickly transported to a mechanical drying facility and related additional costs incurred. Drying the raisins on the vine reduces labor costs and some of the related risk associated with rain.
A Western Farm Press 2001 article described in some detail the advantages of Drying On the Vine (DOV) methodology, along with side-by-side comparison of standard trellising and overhead systems. Pretty interesting reading if you like that sort of thing, and as an equipment appraiser, I do like it. Of course there’s much more information regarding the mechanization of raisin agriculture — open gable v pancake/arbor systems, the grape varieties available, and the corresponding grape harvesters available — than a single blog post can contain.
Overhead trellises are focused in the San Joaquin Valley, which pretty much contains all the US raisin acreage. According to a recently released USDA report, the overhead trellis management system totaled 19,543 acres during 2011. That’s not quite 10% of the total 200,000 raisin acreage in the San Joaquin Valley. But it does seem to be the future – that same report states that “31.5% of the the total raisin type acreage planted since 2004” uses this system.
These overhead trellis systems are, of course, considered equipment in an raisin ranch appraisal. Along with DOV harvesters such as the AGH extra-wide grape harvester. The current DOV harvesting equipment has been a long time coming — much longer than 30 years!
Cutterbar harvesting (1953) was the first mechanical grape harvesting equipment. While this primitive harvester drastically cut labor needs during peak harvest, it did so by spreading out the labor requirements, not lessening them. It also needed special trellising. Perhaps its most important contribution to mechanical harvesting was that it inspired more research in grape harvest mechanization.
The next big breakthrough was the combination of cane-severing and shake harvesting (either rod- or vertical-impact shaking). Thompson Seedless was a great raisin for this, especially with rod-shaking:
A three-person crew could harvest at a rate of about 1 acre per hour and they could pick the raisins up at approximately the same rate.
Cane-severing introduced the possibility of today’s current trend toward DOV raisins and the advanced trellising and harvesting methods still developing. Ironically enough, the process of cane-severing remains — best done by hand, despite attempts to create a piece of equipment that would mechanize this process. Raisin growers and researcher may be dreaming of NDOV raisins (naturally dried on vine, without vine-severing) but no one has yet developed a viable, production-effective alternative.
A special thanks to former UC Davis scientist Henry Studer for the information presented in Chapter 32 of Raisin Production Manuel, L. Peter Christensen, ed.