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Delayed harvest or poorly adjusted harvest equipment can result in soybean losses of 10% or more, but losses can be reduced to about 3% with good harvest practices.
Soybeans can dry quickly and close monitoring of seed moisture is required for timely harvest. Start monitoring seed moisture before all the leaves have dropped. Soybeans should be harvested at 13-14% moisture. Once soybeans reach physiological maturity, they can lose and reabsorb moisture readily. Several cycles of wetting and drying can contribute to preharvest pod shattering and stem losses. Once soybeans reach physiological maturity, they can reach 13% seed moisture in a couple of weeks with good conditions for drying. At full maturity (95% of pods have mature pod color, 35% seed moisture) 5 to 10 good drying days are typically needed before harvest.
Source: Philbrook, B.D. and Oplinger, E.S. 1989. Soybean field losses as influenced by harvest delays. Agronomy Journal 81: 251-258.
Pod shattering can be the largest factor contributing to total harvest losses. A University of Wisconsin study measured losses at 2 week intervals once soybean reached full maturity.1 Shattering losses increased with a harvest delay of at least 2 weeks (Figure 1). The study also found that pre-harvest, pod shatter, and stem losses increased with harvest delays, but stubble and threshing losses remained constant regardless of the length of the harvest delay.
Pod shatter may occur in areas of the field with poor fertility or severe pod-feeding from grasshoppers and bean leaf beetles. Late-season spider mite infestations can accelerate soybean senescence and increase pod shattering.
When harvest is delayed and soybeans are less than 13 percent moisture there can be more pre-harvest shatter loss, greater sickle-bar shatter loss during harvest, and increased number of split beans. Nearly 80% of harvest losses occur while cutting and gathering plants in the combine. Most of these are due to shattering.
The following recommendations can help reduce losses:
1 Philbrook, B.D. and Oplinger, E.S. 1989. Soybean field losses as influenced by harvest delays. Agronomy Journal 81: 251-258. 2 Staton, M. 2011. Reducing soybean harvest losses. Michigan State University Extension. Web sources verified 8/252/16. 150924094248