Written by Franz Niederholzer, UCCE Farm Advisor, Colusa/Sutter/Yuba Counties
So far, the weather in the Sacramento Valley has been unusually moist early in the 2014 harvest season. Higher humidity and rain last week (Aug 4-5 = 0.1-0.6”) slowed nut drying just as the season began. A chance of thundershowers is forecast for the coming week (Aug 11-15), so we won’t spring right back to the usual August weather – hot and dry. Growers anxious to get nuts up and out of the orchard will have to wait longer than expected to deliver a dry, quality crop. Wet nuts are more vulnerable to damage (chipped, broken and embedded shell), which can reduce return to grower.
Patience to allow the nuts to dry to an adequate level along with careful sampling ahead of windrowing and/or pickup is necessary to delivering nuts that will process smoothly with minimal damage. Before windrowing, check all locations across the orchard floor. Take samples from the highly shaded areas near the tree trunks as well as out in the warmer, sunnier locations. Also, when checking windrow moisture following rain, sample from throughout the windrow – top to bottom – to get the whole picture. In research by Bruce Lampinen, Extension specialist with UC Davis, nut moisture levels differed by as much as 2% from near the trunk (more shade = more nut moisture) to the middle of the drive row (driest nuts) and from top (driest) to bottom (wettest) in windrows. Non-uniform nut moisture at delivery, with some nuts exceeding recommended moisture levels, can mean non-uniform quality when processed. Uniform moisture sampling can help improve grade sheet results.
To deliver a quality crop as soon as possible, some growers are moving to conditioning at harvest (see photo) to accelerate drying. Soon after shaking, sometimes within a day, conditioning removes dirt, leaves and other trash that slows drying and drops the wet nuts in a wide, thin windrow at the center of the drive row where nuts get maximum sun exposure. This speeds drying (and pickup) by as much as 2 days, according to a Sacramento Valley grower who uses this practice. With the cost of an additional pass through the orchard, harvest moves along faster and irrigation can begin sooner.
The current forecast for the Sacramento Valley is for a return to more normal weather conditions by next weekend (Aug 16-17). Knock, knock.