Drying and Storing Corn in 2009

This crop year has been full of surprises and it's not over yet. I hate to say it but do you remember 1992? Most farmers would like to forget the harvest of 1992. Corn way above normal harvest moistures, corn that was frozen, running corn through the drier twice and moisture rebound are all just a faint memory. Dust off your notes because it looks like here we go again. Many factors have converged to bring us to this point. A wet spring, a cool summer, wetter than normal growing conditions and an early frost have all brought us to the point we are today. We have what we have as far as yield and harvest moisture. Complaining is not going to help, so how do we deal with this highly abnormal corn harvest situation.

Combining

Since some of the corn will not be mature or higher in moisture than normal, you have to adjust your combine to minimize damage of this fragile corn. Reduce the cylinder speed and open up the concave to minimize the damage to the corn kernels. The kernels on higher moisture or immature corn will be more prone to mechanical damage than in a normal year. Try to get as clean a sample as possible in the field because fines will be a recurring problem as we proceed through the drying, aerating and long-term storage aspects of an on-farm grain system.

• reduce cylinder speed & open concaves
• leave fines in the field
• not much field drying occurs at this time of year

Clean Screens

Check interior drier screens daily this year to prevent material buildup. This buildup on the screen will affect airflow and a reduction in airflow will reduce throughput. Dryer fires can be caused by this buildup of material.

• clean interior perforated screens daily

Drying Temperatures

Higher than normal moisture contents will make you want to consider higher plenum temperatures to maintain dryer capacity. However, if corn is not increasing in test weight through the drying process your drying temperature is too high. Drop your plenum temperatures in 5Co increments and see if test weight increases. Corn at ½ milk line will caramelize easily in the dryer due to the high sugar content and extended time in the dryer. Lower plenum temperatures will help. Kernel to kernel moisture variability will affect all drier types. Going through the drier, all kernels will be reduced in moisture by roughly the same amount but not down to the same level. Kernels that are wetter to start will still be wetter than the dryer kernels when they exit the drier. This can be managed in storage with adequate aeration. Keep kernel temperatures below 50oC to 60oC or 120oF to 140oF. Kernel temperature is not the same as your plenum temperature. Corn as it dries will approach the plenum temperature but rarely reaches it.

• higher drying temperatures usually result in lower grain quality
• reduce drying temperatures to maintain or increase test weight
• monitor immature corn for caramelization
• kernel to kernel moisture content will vary both before and after drying
• good aeration in storage should bring wetter and drier kernels to near the same moisture content
• keep kernel temperatures below 50oC to 60oC or 120oF to 140oF
• consider two-stage drying - field moisture to 17% or 18% and finish drying through the winter
• two stage drying will allow the drying season to proceed

Test Weight

Test weight should increase during the drying process. Typically we expect a one pound / bushel increase in test weight per 4 points removal, or 0.25 lb per bushel increase in test weight per point of moisture removal. High drying temperatures will cause moisture to leave quickly and can plump the kernels. Fewer plumped kernels fit into the ½ litre measure, lowering test weight. Plenum temperatures of 95oC or 200oF or above make this problem worse. Lower drying temperature down to 70oC to 80oC or 160oF to 180oF to reduce this problem. Very immature corn may have little if any increase in test weight when dried in a high temperature dryer, even at low plenum temperatures.

• normally expect 0.25 lb / bushel increase per point moisture removed
• drop drying temperatures in 5Co or 10Fo increments and note test weight
• immature corn may have little if any test weight increase through drying

Moisture Rebound

A number of operators experienced moisture rebound or bounce in 1992. Corn that was in the field actually went up after extended periods of damp weather. The more immature the corn was, the more this moisture "bounce" seemed to occur. At the drier, farmers saw moisture contents of "dry" corn bounce up two points or more after cooling. One potential reason is that the moisture in the kernels had not migrated to the outside of the kernel. After some time has passed, this moisture does move to the outside of the kernel, and the corn is wetter than you thought. Farmers drying this season's corn are again experiencing some moisture rebound.

• watch corn for moisture rebound and dry accordingly

Moisture Testing Hot Corn

Electronic moisture testers will underestimate the moisture content of hot grain which has not reached equilibrium by anywhere from 1 to 2 percentage points. To get an accurate reading of the moisture content of hot corn, let it cool slowly in a sealed container, like a freezer bag, before testing.

• allow hot corn to cool in a sealed container before testing moisture
• moisture test corn frequently this year

Final Moisture Content

With high and variable grain moisture this year, consider drying the corn to a slightly lower moisture content to prevent surprises. Some producers are going to 14.5% and some as low as 14%. We learned in 1992 that corn harvested in the high 30's or even low 40's does not keep as well as corn harvested under 30% moisture content.

• consider drying down to 14% or 14.5% moisture content
• keeping ability of 2009 corn will be lower than in normal years
• consider drying to 18% + aerate and keep cool now and finish drying later

Stress Cracks

Stress cracks are internal fractures that occur in corn kernels which are caused by thermal shock. Stress cracks are not caused by the combining process or by augers and other conveying operations. Stress cracks are caused when hot corn is exposed to cold air. Stress cracks are fine cracks in the endosperm of the kernel which is located just below the surface. Some stress cracks are produced during field drying but the level of cracking can increase significantly during post harvest handling. Rapid drying and cooling rates are dominant factors in stress crack development. Stress cracks can be easily observed by spreading corn on a light board or light table, or on a flashlight with a lip around the lens. The light passing through the corn kernels will be refracted. You will see distinct light and dark areas within individual kernels. The line between the light and dark area is the stress crack, which is a failure plane. Some kernels may even have more than one stress crack. Stress cracked kernels appear whole, but in moving or dropping that corn it will break apart along the stress line. Stress cracked corn will produce more broken kernels every time it is handled.

• try to avoid hitting hot corn with cold air
• consider coolaeration which involves dropping corn hot out of a drier and cooling it down slowly in the storage bin
• hot corn can be dropped slightly above the final target moisture content (1 to 1.5 points) out of the drier

Take out Fines

Fines will be more of a problem this year. Corn that is higher in moisture content is harder to thresh and as a result more fines and broken kernels are produced. You all want to keep as many as are allowed in the corn because "I can get paid for them"! This year, fines should be avoided at all costs. The fines will complicate all aspects of drying, aerating and storing this corn crop. Fines and broken kernels are small bits that fill the void spaces between corn kernels in the drier and storage bins. In a drier and in a storage bin fines will restrict air flow. The air takes the easiest way through the grain and that's usually the area with little if any fines. The area with fines in the drier doesn't dry as quickly as the rest of the column and in a bin the area with the fines does not get cooled down with aeration as quickly, if at all. So we have fines material that may be wetter than the corn and it won't get aerated as quickly in the bin. The result will be spoilage in storage.

• screen out fines at many points in the system
• fines cause airflow problems
• Sawtooth Grain Beetle, Rusty Grain Beetle and Grain Mites are all broken kernel and dockage feeders
• stored grain insects feed and breed rapidly in dockage
• fungal feeding insects will arrive first
• broken kernels are more prone to fungal development

Core Your Storage Bins

Corn is going to break easily during harvest, drying and handling. Removing fines will help get you through this year. However, there will still be fines going into the bin. They will concentrate near the centre of the bin or end up in a ring somewhere in the bin. In sufficient concentrations the fines can prevent air from moving though those parts of the bin. Without air flow spoilage could result. Coring the bin will remove material from the centre of the bin which is usually the highest concentration of fines. Take out three loads and clean that grain. You can then put these loads back into the bin. You have removed most of the fines and air flow restriction will be reduced. A less desirable approach would be to remove a few loads and put them back in the same bin without cleaning. This doesn't remove the fines but redistributes them in the centre part of the bin. Hopefully they would pose less of a problem for air flow.

• core bins after filling or while filling
• clean corn that is removed and put back into bin
• less desirable option is to remove 3 loads and return to same bin without cleaning

Maintenance Aeration

Watch your bins carefully as we head towards and through the winter. Check your bins routinely and aerate them to maintain corn temperature fairly close to average outside temperatures, within 5Co. On your routine checks of the bin, turn the fan on and stick your head inside the bin and take a sniff. If you smell anything out of the ordinary, investigate further and take action as needed. Corn that is not completely mature does not keep as well as mature corn. This means you have to be even a better grain storage steward this year.

• aerate routinely to prevent convective air movement
• Keep grain temperature + 5Co of average outside temperature
• Use your nose to pick up off-odours
• Use you eyes to look for emerging problems

Figure 1. The 2009 corn crop will test the skills of all who are operating driers.

Figure 2. Leave as many of the fines in the field as possible this year. Fines will complicate all aspects of good drying and good aeration.

Figure 3. Corn will likely not dry down much in the field from here on. Listen to what's working and what's not in the 2009 drying front.