What is in this article?:
- Harvest management, stockpiling guidelines for almond crop quality
- Sampling before stockpiling
- Earlier research, in the late 1970s and 1980s, demonstrated the value of timely harvest for crop quality, particularly related to insect damage. Current emphasis is on stockpiling and crop moisture content to avoid mold growth in piles, particularly the Aspergillus fungus that produces aflatoxin.
Sampling before stockpiling
Crop moisture should be determined while the crop is on the orchard floor, either before or after sweeping. Remember, almonds should not be stockpiled if either the average hull moisture content exceeds 13 percent, or the kernel moisture content exceeds 6 percent.
If sampling is done before sweeping, take a representative sample across the orchard floor, from trunk to middle of the drive row, and along the tree row. Typically, samples from the north side of the canopy adjacent to the trunk and along the tree row will have the highest moisture: on average, 2 percent higher moisture content than nuts in the drive rows and middles.
Samples taken after windrowing should be taken from both the bottom and the top of the windrow; moisture content of samples taken from the bottom of the windrow can be 2 percent higher than at the top.
The crop will dry slower in sections of orchards with denser canopies. If your orchard is producing above 3500 kernel pounds per acre (about 70 percent of available light is intercepted by the canopy), particular attention should be paid to facilitate in-orchard drying; e.g., hedging before harvest, conditioning and turning, to reach the acceptable kernel and hull moisture contents given above.
Several factors contribute to stockpiling that minimizes condensation, mold growth and aflatoxin production.
• Orientation and shape. Research shows that orienting the long axis of piles in a north to south direction is preferable. Condensation and mold growth tends to be worse on the north sides of piles with the long axis oriented east to west. Smoothing the tops of piles helps to minimize the concentration of moisture from condensation and resulting mold growth.
• Tarp type and color. Researchers have found that white-on-black tarps are best for minimizing temperature fluctuations and resulting condensation. Consider using this type of tarp for piles with a higher moisture content of in-hull almonds. In studies, almonds covered with white-on-black tarp were up to 40 degrees cooler than nuts under clear tarp. They also had much narrower temperature fluctuations and lower condensation. Clear tarps had the highest potential for condensation and mold growth, but can be used on dry, in-hull product. White tarps are intermediate, in terms of temperature ranges and condensation, between black-on-white and clear.
• Air circulation. If piles are stacked with higher than recommended percent of moisture, it is important to open them up in the daytime, when the rH is lower, and close them at night when the rH is high.
Three years of research reports on almond stockpiling and aflatoxin by Bruce Lampinen and Themis Michailides (plant pathologist, UC Kearney Agricultural Center) are available at the Almond Board website. Go to AlmondBoard.com/farmpress18, choose research reports, proceedings and posters, then Aflatoxin Field Research.