Grain Harvesting Issues
Grain harvest has started but not without problems. Late planting, and a wet summer, especially with the wettest August on record; is causing grain problems in both soybeans and corn. Harvest lately has been delayed due to slow dry down and wet weather.
In soybeans, farmers are reporting black soybeans. Black discolored soybeans at harvest can is often linked to dry and wet soybean growing stress and fungal diseases affecting the plants during their growth cycle. Saprophytic fungi can colonize dead plant material, leading to black dust clouds during harvest.
Fungi like Cercospora or Diaporthe can cause discoloration and some viruses may cause discoloration. Enlist soybeans also has a trait that causes soybean coat discoloration which is not related to fungi or virus infection.
A drying (drought like) cycle followed by repeated wet cycles can cause seed discoloration and mold, particularly in areas with late rains in August and September. While primarily causing purple discoloration, darker hues may occur and it may affect seed quality especially if mold occurs. In some cases, significant discounts may occur and in severe cases with mold, loads may be rejected.
On corn, corn kernels sprouting on the ear before harvest can still be combined, but widespread sprouting increases the risk of grain damage, elevator discounts and storage problems. According to Purdue University Extension, this condition is known as vivipary, and develops when mature kernels are rewetted by rain, particularly when upright ears trap moisture inside their husks.
Mature kernels are most likely to sprout when reasonably dry grain, below roughly 20% moisture, is rewetted, especially in warm weather. This occurs when dry grain with ears still pointed upright is rained on capturing moisture by the husk leaves, which typically produces sprouted kernels near the butt of the ear. Grain at higher moisture contents is much less likely to germinate on upright ears. Hybrids whose ears stay upright with open husks at maturity tend to be more susceptible. Sometimes corn ears lying near wet soil after severe stalk breakage or lodging can germinate. Also, ears damaged by hail, birds or ear molds can also sprout, even before full maturity. With harvest running behind, the corn kernel sprouting issue is becoming more common. Every week mature corn stands through wet weather extends the window for rewetting.
At combining, the challenge is recovering grain without adding damage. Operators should check harvested grain for broken kernels, incomplete shelling out of cobs and the ground behind the combine for losses. Threshing and cleaning settings should be adjusted to actual field conditions, balancing effective shelling with minimal breakage and grain loss. Once corn dries below about 20% moisture, more kernels shell out at the corn head, and that slower ground speed helps gather ears in down or stalk-weakened corn. Most harvest losses start at the header, making deck plate settings, stalk roll speed and gathering chain speed the first adjustments to check say Purdue Extension. On 250-bushel corn, a 1% loss leaves 2.5 bushels an acre in the field.
On sprouting corn, severely affected fields should be harvested first. Purdue recommends timely harvest, drying to stop further seedling growth and screening grain before storage to remove damaged kernels and sprout material. Removing fines concentrated in the center of a bin can also help manage storage problems.
Dry corn at higher temperatures to keep the young seedlings from growing further, and for “coring” a filled bin by removing several loads from the center, where broken corn and foreign material concentrate during filling. Purdue storage guidance warns that concentrated fines encourage mold and insects and block airflow. Monitor stored grain closely for hot spots, mold and further sprouting, testing for mycotoxins where ear molds are present and making sure the crop insurance adjuster knows about sprouting before harvesting those fields. Where sprouting corn ear damage is widespread, waiting for additional field drying could sacrifice grain quality while saving on minimally on drying expense.
Sprout-damaged kernels count toward total damaged kernels, one of the four factors, along with test weight, broken corn and foreign material (FM) and heat damage, that set corn’s numerical grade. U.S. No. 2 corn allows no more than 5% total damage and 3% FM with a minimum test weight of 54 pounds per bushel. Loads that fall below No. 2 face large discounts which may be triggered by sprouting corn.
Purdue estimates corn standing in the field can lose 1 percentage point of moisture or more per day on warm September days, but only 0.25 to 0.5 point a day in October, and almost zero by November. For sprouted fields, those late-season drying days reduce little moisture while leaving the grain exposed to more rain.