NDSU provides outlook for corn harvest, drying
According to U.S. Department of Agriculture’s National Agricultural Statistics Service, as of Sept.25, 36% of corn in North Dakota had reached maturity and 88% had dented. The near-term forecast is for continued warm temperatures, so most corn should reach or be near maturity, according to Ken Hellevang, North Dakota State University agricultural engineer and grain drying expert.
“There is considerable variation this year due to the challenging spring, variation in rainfall, planting date, maturity rating and growing degree days, so it is important to check each field,” says Hellevang.
The current forecast for October is slightly above normal temperatures and normal precipitation. The amount of drying in the field depends on parameters such as corn maturity, hybrid, moisture content, air temperature, relative humidity, solar radiation and wind speed. Iowa State University has an online corn dry-down calculator. It uses the location, initial moisture content and typical weather history to predict the dry-down rate.
Another predictor of the drying rate is potential evapotranspiration (PET-Penman), which is based on parameters similar to those that affect drying. Values for PET are available on the North Dakota Agricultural Weather Network website. Go to “Weather Data” and select the location and time period, and it will provide the estimated evaporation during that time period. About 1 inch of potential evapotranspiration results in about 4 percentage points of corn field drying.
Standing corn in the field may dry about 2.5-3.0 percentage points per week in North Dakota during October, assuming normal weather conditions, and about 1 percentage point per week during November. Corn at 35% moisture content on Oct. 1 might be expected to dry to about 20% to 25% by Nov. 1, Hellevang says. Very little drying occurs during November, so typically there is little benefit to waiting to harvest after late October. Therefore, corn moisture content at harvest likely will be in the 20% range this year.
Field drying normally is more economical until mid to late October in North Dakota, and mechanical high-temperature drying normally is more economical after that, Hellevang notes.
Natural-air and low-temperature drying are limited to an initial corn moisture content of about 20% to 21%. Even at that moisture content, air drying is limited in the northern states due to the colder outdoor temperatures in late October and November. The moisture-holding capacity of air is very small at temperatures below about 40 degrees Fahrenheit. Expect to store the wet corn over winter by cooling it to 20-30 degrees and drying in the spring when outside temperatures average above 40 degrees.
There are several types of dryers and options for high temperature corn drying. There are cross-flow dryers with and without corn turners and vacuum or heat reclaim cooling. There are also mixed-flow dryers and in-bin dryers. Each has specific features and benefits. Typical drying cost per point of moisture removed can be estimated by multiplying the propane cost per gallon by 0.02. For example, if propane is $1.50 per gallon, the propane cost for drying is about $0.03 per bushel per point of moisture removed.
Corn should be dried to about 15.5% moisture for storage over winter and about 13% to 14% if being stored into next summer. Cool the corn to 20-25 degrees for winter storage. Hellevang supports using temperature cables to assist with monitoring the corn, but technology does not replace management. He still recommends monitoring the corn moisture content, inspecting for insects and observing the corn quality.
Remember safety when working around grain. Protect yourself from grain dust with an N95 mask. Do not go into a grain bin while the grain is moving. It only takes a couple seconds to become helpless in flowing grain. Use the lock-out tag-out system to assure that you do not get hurt while working on grain drying and handling equipment.
For more information on corn drying and storage, search online for NDSU grain drying and storage.