The cool, damp weather has put the brakes on many acres of soybean harvest this year. Although South Dakota has seen late harvest seasons in the past, this year is testing many farmers’ patience considering the wet weather of the past few weeks and current climate outlook.
October has started out very wet, which has followed on the heels of an exceptionally wet September. In the Sioux Falls area, 9.5 inches of rain was reported between September 1 and October 9. This excessive moisture has made field access impossible and stalled grain drying in field. Cool temperatures have further limited evaporation and the ability to dry grain in the field.
At the time of this writing, the latter part of October is trending drier in many forecast models. The area of cool temperatures will also gradually move to the east. However, there is limited ability to warm up substantially at the end of October as days are shorter and we have lower sun angle than in mid-summer. The additional moisture in the soils and atmosphere will also limit warming after the rain ends.
For most, the best case scenario is to wait out the weather. This means waiting until the precipitation stops and the sun comes out, making soils dry enough for field traffic-ability and hopefully lowering seed moisture content. With many commercial outlets taking only ‘dry’ soybeans (less than 13-14% moisture), the increase in commercial storage costs in some areas, and the current market outlook, many producers have made the decision that their beans will be heading to the bin. For long-term storage of soybeans (several months up to a year) it is recommended to dry soybeans down to 11% moisture; with drying facilities available on-farm, some producers may choose to harvest wet beans, but others will most likely wait out the damp fall as long as reasonably possible. For information on the limits of natural air-drying verses low or high temperature drying, view Grain Storage: Climate Inside The Bin.
As soybean pods mature and turn brown, seed moisture begins to decrease quickly. In a three-year Iowa State University study, researchers found that the dry down weight was affected by maturity group selection, planting date, and year. The study found that in the first 12 days after plant maturity begins, soybeans dried rapidly at 3.2% per day. Then, after 12 days, dry down was stabilized at approximately 13% moisture (Figure 1). Under these cool and humid conditions, seeds will tend to absorb additional moisture from the atmosphere, which will most likely cause many fields to be harvested above 13% this year if dry weather is not predicted soon.
Figure 1. Average seed moisture dry down (blue line) across four soybean varieties representing a range of maturity groups at four planting dates from 2014 through 2016 near Ames, IA. Horizontal dashed line represents 13% grain moisture, open circles are actual data. Courtesy: Iowa State University Extension & Outreach
Depending upon how long crops may need to remain in the field, grain quality may become a concern. Many fungal soybean diseases such as Diaporthe pod and stem blight, Frogeye leaf spot, Anthracnose, and many other secondary fungi can impact seed quality. The weather conditions we have had during the growing season may have favored some of these diseases. At this point in the season, our main concerns are moisture and storage temperatures to prevent spoilage during storage. The best way to protect your crop from seed quality problems, is to get it out of the field and dried down as soon as possible. However, when balancing the forecast and drying costs with potential quality issues, each producer needs to consider what is best for their operation.
If soybeans are heavily affected by a late season fungi, they may reflect poor seed quality. In addition, although these soybean fungi are not known for toxicity, a livestock nutritionist should be consulted before adding any soybeans to a feeding ration. For additional information on feeding soybeans, view Adding Value to Soybeans Through Cattle.
When storing infected grain, keeping it dry is the key to prevent further colonization and maintain the best seed quality possible. We can avoid reoccurrence of some of these late season diseases by implementing crop rotation, planting resistant lines in 2019, utilize a fungicide seed treatment, and regularly scouting for disease infestation on stems and pods. For additional grain storage tips, view Storage Mold: Precautions to Avoid Grain Spoilage During Storage.
This year has been the perfect storm of late season moisture and temperature to cause harvest and seed quality issues. We cannot always avoid these problems, but salvaging the best harvest possible and managing for next year should be first priority.
Resources and References:
- How Fast do Soybeans Dry Down in the Field?
- Grain Storage: Climate Inside The Bin
- Adding Value to Soybeans Through Cattle
- Storage Mold: Precautions to Avoid Grain Spoilage During Storage