Grain drying and storage FAQs

Due to the large amount of full season crop planted across much of South Dakota, and the high yield expectations, this column dealt with the anticipated drying and storage issues back in mid-September. Snow and rain has delayed harvest longer than expected, and farmers continue to deal with high moisture crops and the questions that go along with drying and storing them.

Rather than reinvent the wheel, I have summarized some information recently shared by Ken Hellevang, Professor and Extension Engineer at North Dakota State University.

• At what moisture content can I store corn (or other crops)? With aeration so the corn can be kept cool, it can be stored through the winter at moisture contents up to 23 percent. Without aeration, it is risky to store it for more than a few days. Wet grain, through respiration and microbial activity, produces heat, so the corn may not stay cool even if storaged at cold temperatures. The corn temperature should monitored and be prepared to move it if temperatures increase. The allowable storage time for corn at 20 percent moisture is about 90 days at 40 degrees, but is only 14 days at 70 degrees. Allowable storage times for corn can be obtained for various grain moisture levels and temperatures from the factsheet, ExEx1014, “Grain Drying Guidelines for a Wet Fall Harvest”: Allowable storage times for other crops can be estimated from this factsheet by comparing the recommended moisture contents of the crop in question to that of corn.

Aeration needs to be provided to cool corn that is piled on the ground. Wind driven air will go over the pile rather than through the grain. A one inch rain will increase the moisture content of the top foot of corn by about 9 percentage points. This will likely lead to spoiled grain unless it is very cold outside and the corn is rapidly dried.

• Will corn dry in the field? The rate of drying in the field will be extremely slow – likely only about one percentage point per week during November in North Dakota.

• Can corn be air dried in November? Natural air drying is inefficient at temperatures below about 40 degrees. It takes about 70 days to dry corn from 21% to 16% during November with an airflow rate of 1.0 cubic feet per minute per bushel (cfm/bu). Adding enough heat to warm the air 10 degrees only reduces the drying time to about 50 days and will approximately double drying cost. It is best to cool the corn to 20 to 30 degrees, store it over winter and dry it in the spring.

• Will a moisture meter accurately measure the moisture content of corn that is at 30 degrees? Moisture meters will generally not give accurate readings for kernel temperatures below about 40 degrees. To get an accurate reading, place the grain sample in a sealed container and allow it to warm to room temperature before taking the measurement. It is important to make a temperature adjustment to the meter reading based on the grain temperature unless the meter automatically measures the temperature and makes the adjustment. The adjustment may be several percentage points for grain that is not near room temperature (75 degrees).

For more information on grain drying and storage from Ken Hellevang, at NDSU, visit:

–SDSU Extension