Tips to Prepare for a Successful Corn Harvest

Corn harvest should ramp up soon as grain matures and dries down to an agreeable moisture for harvest. Corn maturity is a little earlier than recent years, so we should start to see some corn being harvested soon. We have had numerous complications from storms this summer which have promoted lodging and other stalk damage which may potentially affect harvest as well. Understanding how weather and other factors affect grain drying, potential harvest losses, moisture dockage and potential aflatoxin issues can greatly help improve your harvest efficiency and success.

Corn grain maturity, drydown and harvest aids – When corn reaches maturity a “black layer” forms at the kernel base when hard starch accumulation is complete. This black layer is an abscission layer that effectively cuts off moisture transfer and all physiological activity from the plant. Thus, grain drying rate is essentially completely dependent upon environmental conditions, rather than plant health or disposition. Furthermore, since corn is an annual plant, the vegetation will naturally senescence or die after maturity, particularly when temperatures are hot and/or soil moisture is limited. Consequently, using a harvest aid will have little or no effect on grain drying, since the black layer halts moisture flow to the grain, and the plants are already naturally dying.

The black layer separates the kernel from the cob, making drying reliant on weather.

Grain drying rate in the field – Climate basically dictates corn grain drying in the field. Fortunately, we are normally blessed with plenty of heat and dry weather during August and September, so our corn drying rates are usually considerably greater than states further north, including the Corn Belt. However, when rainfall persists, along with cloudy days, high humidity and cool temperatures, grain drying will slow considerably or be suspended. Mississippi corn normally dries at an average rate of 0.6% per day from physiological maturity (when grain moisture is around 30%) down to 15% moisture. However, this drying rate will inherently be faster when grain moisture is high, and then scales back as it drops into the teens, when the disparity between grain moisture and the environment diminish. Accordingly, you may see grain moisture dry as much as 0.8 or 0.9% per day given sunny, hot weather as grain approaches 20% moisture.

Factors that affect harvest efficiency and losses – The best time to begin corn harvest may vary considerably, primarily depending upon how long it takes to harvest your crop. This will depend on how many acres you have, relative to your harvesting capability, including combine, trucking, and storage capacities. These factors, along with the other crops you grow on your farm, determine the potential harvest duration and the relative risk associated with harvest losses, delays or other complications. Those potential risks include various types of stalk lodging and/or grain quality deterioration, which can result from stormy weather, insect pest damage, and late‐season weed growth. The most significant weather-related threat to Midsouth corn is likely storms containing high winds promoting stalk lodging. One dropped ear per 100 feet of row or two corn kernels per square foot or equals about 1 bushel per acre yield loss. The bottom line is that the longer corn stays in the field, the greater the likelihood of substantial field losses and complications.

Lodging caused by storms can substantially increase losses and hinder harvest progress.

How grain moisture affects dockage and yield ‐ Corn grain may be harvested any time after it reaches physiological maturity, which occurs at around 30% moisture. However, high moisture grain requires special handling and considerable drying until it stable enough for storage. Thus, grain elevators discount wet corn to account for drying expenses and moisture weight loss during drying. Moisture dockage schedules may vary between elevators, but historically will assess about 2.5‐3.0% per each percent moisture above the moisture standard, with rates possibly increasing at higher moisture levels. Water evaporated during drying (shrinkage) accounts for 1.18% of the grain weight per percent moisture. You lose this weight regardless of whether you sell wet grain to the elevator, dry it mechanically or let the grain field dry. Thus, you should subtract this value from the dockage rate to show your realized or “actual” dockage. Furthermore, corn delivered to market at less than the standard moisture weighs less, so you are essentially docking yourself (1.18% per percent moisture) if you do so.  For this reason, along with mounting harvest losses, you should generally strive to finish harvest before grain moisture falls below 15%.

Grain and aflatoxin management during and after harvest – Although harvesting corn earlier will normally reduce potential field and harvest losses, it does require considerably more effort to properly handle and store grain in our climate. Furthermore, drought stress is known to increase the likelihood of aflatoxin development in corn. Therefore, these recommendations help maintain grain quality and minimize aflatoxin contamination issues. Grain is a living organism which may spoil quickly when the grain moisture and temperatures are high. For example, temperatures during harvest in the South will be well above 85 degrees F, which is a stark contrast to the Corn Belt. Furthermore, moist grain and high temperatures also cause fungal growth to flourish, potentially causing aflatoxin to escalate rapidly in improperly stored or handled grain. This has historically created some aflatoxin issues, especially when unseasonable rainfall has promoted harvest of high moisture grain. If you are hauling high moisture corn directly to market, it is vital to deliver it as quickly as possible. Do not store grain in trucks, grain carts, combines, grain bins, or any non-aerated site for more than 4 to 6 hours. Swift and proper handling is also critical if you intend to dry your own corn. Corn should be dried to less than 15% moisture within 24 hours after harvest. High capacity, continuous flow driers can generally rapidly dry corn to 15 percent moisture or less, but in-bin drying or aeration systems are generally not capable of this goal, and thus, present serious management challenges for high moisture corn. Dried corn should also be aerated and cooled shortly thereafter as well. Fungal growth and associated aflatoxin development becomes dormant when grain moisture drops to about 12 percent, especially when grain temperatures decline to around 55 degrees F, so this should be your goal for long-term storage through the fall and winter.

For more information about aflatoxin, please refer to: Minimizing Aflatoxin in Corn