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CropTalk: The Dry Down on Soybeans

October 2019

Published on Tuesday, October 01, 2019

Last year's soybean harvest was among the latest on record, resulting in fields harvested at higher than average moisture levels. Farmers may likely have experienced peace of mind as combines rolled, only to face the concern of storing and drying their wet soybeans. As a result, many farmers discovered for the first time that soybeans can be dried relatively easily using air alone or in combination with low temperature heat.

While we don’t anticipate another harvest like 2018, last fall’s conditions may inspire new thinking among some farmers in terms of harvesting and drying higher moisture soybeans in the future. Here is why drying soybeans might pay off:

  1. Waiting until 13% to begin soybean harvest often assures an average moisture well below 13% as soybeans dry in field. Yield reduction due to this weight loss is over 1.1% for each moisture point below 13%. (Field average of 11% moisture = $0.20/Bu./A. at $9.00 soybeans, or -$10/A. in 50 Bu./A. soybeans)
  2. Combine losses such as shatter loss and splits are higher below 13%. (Harvest losses can be as high as 10% or -$18.00/A.)
  3. Field losses from lodged plants and opening pods will likely be greater if you wait until 13% moisture.
  4. If existing on-farm drying equipment for corn can be used, drying soybeans helps spread fixed costs over more bushels.

Most modern rotor combines can effectively thresh soybeans with up to 20% moisture in the grain. However, seed bruising and splitting increases above 15% moisture, which reduces grain quality and germination and increases storage concerns. Storing soybeans above 13% moisture is not recommended, so it’s necessary to quickly bring moisture levels to 13% or lower to prevent heat damage or even potential storage fire.

Soybeans can be dried with aeration alone (<15%) or in combination with low heat (15 to 18%). Grain quality will deteriorate accordingly with the use of higher drying temperatures. When using heat, remember that heating ambient air by 20°F drops relative humidity by 50%. Even moderate temperatures will damage seed coats and increase splits; the severity of damage will vary depending on variety and drying equipment. A high aeration capacity bin (>1cfm/Bu.) can assure higher quality retention using ambient air temperature. Fan capacities of 0.1 to 0.2cfm/Bu. can be effective up to 15% moisture.

The table below is an average drying expectation from various drying scenarios. Your individual drying system and experience may vary.

Soybean seed is softer than corn and more easily damaged by drying temperatures above 140°F as well as augers or other rough handling equipment. Here are some recommendations from Iowa State University when using in-bin dryers:

  1. Avoid dryers that recirculate or stir grain constantly. Also, avoid the use of bin spreaders that are normally used for corn.
  2. Prolonged exposure to air <40% humidity increases soybean cracking.
  3. Limit temperature rise to 20°F above ambient air temperature.
  4. Shut off heat when the relative humidity drops below 45%.

If you plan to store soybeans through the winter, it is best to cool the soybeans to below freezing by running aeration fans during periods below 32°F.

Last fall, we published a paper with guidelines for storing damaged, or less than ideally-harvested grain. You can review the white paper on the Agronomy Resources Tab of the Beck’s website, or by visiting https://bit.ly/2m3U0Li.

As harvest 2019 gets underway, we hope that this article is not needed and that each of you has optimal harvest conditions. If you’d like more information on making a harvest plan and how to manage drying your crop, please reach out to your local Beck’s representative.

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Craig Kilby
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Craig Kilby

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