Buckwheat Harvesting, Drying, and Storage

Bill Wilcke, Extension Engineer

Department of Biosystems and Agricultural Engineering
University of Minnesota

Jump to Harvesting  Storage   Measuring Moisture    Artificial Drying

The information in this hand out was obtained from published literature, the WorldWideWeb, responses to a question on buckwheat posted on a stored product listserv, and some extension and industry personnel who have buckwheat expertise. If you have questions, or have information on buckwheat drying and storage that you would like to share, email wwilcke@mes.umn.edu or call 612-625-8205.
 

Harvesting

Buckwheat has an indeterminate growth habit, which means it keeps flowering until frost and not all the seeds mature at one time. The crop can be harvested standing (direct cut) with a conventional grain combine, but be aware that seeds will have varying maturity and moisture content. For direct cutting, harvest when 75 to 95% of the seeds have matured (turned dark brown or black) and when plants have lost most of their leaves. Harvesting before 75% of the seeds are mature will result in excessive amounts of high moisture green seeds and plant fragments that will cause problems in storage. Delaying harvest until all seeds are mature will result in high shattering losses, especially after a killing frost. Artificial drying is likely to be necessary for direct-cut buckwheat.

It might be possible to avoid artificial drying if buckwheat is swathed and allowed to dry in the swath before combining. Start swathing when flowering is complete and 75% of the seeds are mature, and try to swath when the plants are damp to reduce shattering losses.

Storage

Suggested storage moisture for buckwheat is 13 to 16%. At moistures greater than 16%, seeds are likely to mold and heat. At moistures less than 13% moisture, buckwheat is hard to mill, and consequently, some buyers discount the price when seed moisture is less than 13%.

It is a good idea to provide some kind of aeration system (fan and perforated ducts or full perforated floor) to control the temperature of any stored grain crop. Operate aeration fans to cool the crop in stages during fall and early winter until it reaches the target temperature of 20 to 30 F. (This storage temperature is appropriate for the northern corn belt; 30 to 40 F might be more appropriate for the central part of the corn belt.) Storage bins that were designed for wheat or barley should work well for buckwheat.

Buckwheat millers want a light-green colored, mild-tasting groat. Since the groat darkens and its flavor changes over time, try to keep storage time short for buckwheat destined for human food to minimize these undesirable changes. Some varieties of buckwheat to be used for seed, however, might require a storage time of at least 30 to 60 days before the seed will germinate.

Measuring moisture

One brand or moisture meter that is known to be calibrated for buckwheat is the Motomco. For other brands, check product literature or contact the manufacturer to see if buckwheat calibrations are available. If you have samples at different moisture content, you can make your own approximate calibration curve by comparing the values with the ones obtained on your buyer's Motomco.

If a moisture meter is not available, or if you want to calibrate or check a moisture meter, an oven test can be used to determine moisture content. The Japanese Society of Agricultural Machinery recommends weighing wet buckwheat samples and then drying them for 24 hours at 135 C (275 F) to remove free water. Wet basis moisture content is then calculated:

 Wet basis moisture content (%) = 100% x (wet weight - oven dry weight) / wet weight
 

Note from T. Björkman: In a test at one NY grower field, we compared a John Deere TY9304 hand-held moisture meter with the value given by the official Motomco meter at the Yates Blodgett (Birkett Mills) receiving house. The measurements were made on two bins taken from different parts of the field. The results indicate that there is no simple correction, and that a calibration of your own meter against the receieing house meter is worthwhile. The receiving house manager is usually happy to help you do that.

John Deere:
( Barley setting )		 13%
16%

Motomco		 18%
19.5%

Artificial drying

Although we don't have much information on drying characteristics or airflow resistance of buckwheat, experience indicates that bin dryers designed for natural-air drying (no heat added) of barley or wheat can be used for buckwheat. Damp buckwheat is placed in a bin that has a full perforated drying floor and the drying fan is operated continuously until the drying zone has moved completely through the bin and all buckwheat in the bin has dried to 13 to 16% moisture. Drying time depends on airflow, initial crop moisture, and weather, but can be expected to take several weeks.

Heated-air dryers can also be used to dry buckwheat. Keep the drying air temperature below about 110 F to avoid killing the germ, darkening the groat, or causing other seed damage. As soon as the buckwheat has dried to 16%, use unheated air either in the dryer or in storage to cool the grain to within 10 F of the outdoor temperature.

References and other sources of information
ìBuckwheat.î E.S. Oplinger, E.A. Oelke, M.A. Brinkman, and K.A. Kelling. In Alternative Field Crops Manual. University of Minnesota Center for Alternative Plant and Animal Products and the Minnesota Extension Service, St. Paul MN. 1989.

ìBuckwheat in Ohio,î AGF-116-95. Walter H. Schmidt. Ohio State University Extension, Department of Horticulture and Crop Science, Columbus OH. 1995.

ìLatent heat of vaporization in buckwheat using the data of equilibrium moisture content.î A. Tagawa, S. Murata, and H. Hayashi. Transactions of the ASAE 36(1)113-118. 1993.

Personal communication. Steve Edwardson. Minn-Dak Growers, Inc., Grand Forks ND. 1996.

Personal communication. Kenneth J. Hellevang. North Dakota State University Extension Service, Department of Agricultural Engineering, Fargo ND. 1996.

ìWheat and Barley Storage,î AG-FS-5947. William F. Wilcke and Kenneth J. Hellevang. Minnesota Extension Service, Department of Biosystems and Agricultural Engineering, St. Paul MN. 1992.

ìWheat and Barley Drying,î AG-FS-5949. William F. Wilcke and Kenneth J. Hellevang. Minnesota Extension Service, Department of Biosystems and Agricultural Engineering, St. Paul MN. 1992.

Dr. Bill Wilcke
Department of Biosystems and Agricultural Engineering
University of Minnesota
219 Biosystems and Agricultural Engineering Building
1390 Eckles Avenue
St. Paul, MN 55108-6005  
 

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