A lot of southern corn production was hampered by wet conditions in 2013, which slowed maturation of the crop. In other years, there are dry conditions that push harvest sooner than expected. In both cases, management of drying and storage can make or break the quality of grain once it’s delivered to a buyer.
For example, if corn that was planted later than normal is harvested at a high moisture level, the grower will need to pay extra close attention to harvest method, drying and grain storage, says Matt Roberts, Purdue University Extension grain storage and drying specialist.
Samy Sadaka, University of Arkansas assistant professor and grain drying specialist, says increasing the temperature of the corn and/or increasing its moisture content decreases the safe storage period.
“In other words, the higher the temperature and/or the higher the moisture content, the higher the risk of the corn going out of condition and the shorter the time the corn should be stored,” he says.
“Simply put, it is safe to store corn up to 275 days if the corn temperature and moisture during the storage period remain at 60 degrees F and 15 percent moisture. However, it is not practical to assume that the corn temperature and moisture content will remain constant during the storage period.”
If corn is 17 percent at 60 degrees F, storage time is reduced to 88 days. At 19 percent, it drops to 39 days. A U of A grain storage chart (see Table 1) examines other maximum drying times at various temperatures and moisture contents.
For example, in this scenario, corn is harvested at 25 percent moisture content and immediately placed in a holding bin with a cooling fan. Corn is cooled from 70 degrees to 40 degrees in two days. The average storage temperature is 55 degrees.
The safe storage period corresponding to the corn temperature of 55 degrees and 25 percent moisture content is about 14 days.
Note that when corn reaches maturity late in the season, field dry-down is slower due to cooler air temperatures. Grain storage specialists say growers should screen grain prior to drying to help prevent foreign material and broken kernel fragments, or fines, from blocking air flow essential to uniform grain drying and storage.
“I would recommend that corn always be cleaned with a screen cleaner before it is placed in the bin,” says Richard Stroshine, Purdue agricultural engineering professor and grain drying specialist. “Fines tend to accumulate in the center of the bin, and even with a grain spreader there can be areas where fines accumulate.
“A centrifugal grain spreader could create a ‘ring’ around the center of the bin where there are higher fines concentrations. It happened to us one year during a field trial when a centrifugal spreader was being used in a bin on one of the Purdue farms.”
Sadaka says farmers may need to harvest lower quality grain — 1 or 2 points lower than the normal 14 percent to 15 percent. This could help reduce mold situations.
Coring the bin after filling can help reduce concentrations of broken kernels and fine material. This involves removing up to 10 percent of the total bin capacity.
“The presence of broken kernels, stalks and cobs in a grain bin can restrict airflow,” Roberts says. “Even with state-of-the-art grain spreaders, broken kernels and foreign material tend to accumulate in or near the center of bins.
“Coring can be accomplished by removing several loads of grain from the bin. This will also help to level the top of the grain mass. Air finds the path of least resistance, and the coring and leveling should eliminate or reduce the higher airflow resistance in the center of the bin, so the bin will be aerated more evenly.”
Stroshine says managers using high-temperature dryers need to be especially careful since these systems are particularly hard on kernels.
“If kernel temperatures get too high during high-temperature drying and there is rapid moisture removal followed by rapid cooling, the severity of kernel stress cracking will increase, and this will increase the likelihood of breakage during subsequent handling,” he says.