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Serving: IA
combine in cornfield at harvest
KEY INDICATOR: Test weight is a predictor of the storage quality for corn, and corn is coming out of fields at lower-than-normal test weight this fall.

Wide range in crop quality this fall

Variability in corn and soybeans coming out of Iowa fields this fall requires management.

This year’s corn and soybean crops require special attention for harvesting, handling and storage. Some corn and soybeans were planted early, and many fields were planted considerably later than normal due to the wet spring. Agronomists and grain handling specialists are advising farmers to pay attention to the quality of grain coming out of fields this fall and manage it accordingly. There’s a wide range of maturities and moisture contents.

“The 2019 planting and growing season had periods of both stress and favorable crop growth. The big issue this fall is variability — in yield, test weight, grain moisture and quality,” says Charlie Hurburgh, Iowa State University Extension grain management specialist. “You need to isolate your grain as much as possible, keep the lower-quality grain separate from the higher-quality grain right away at harvest — before you put it in the bin. I would say you should keep it separate pretty much according to planting date.”

The first frost this fall nipped Iowa the weekend of Oct. 11-13. For much of Iowa’s corn and soybeans, this frost was cold enough to stop the growth. The later-planted corn, especially corn planted in June, will have a lower test weight. Corn that reached black layer by first frost wasn’t affected as much, he notes.

Guidelines for handling, drying, storage

Hurburgh provides the following information and recommendations for handling this year’s corn and soybean harvest. Also, ISU Extension plant pathologist Alison Robinson offers information about ear molds that are showing up on corn in some fields this fall.

Corn quality concerns. Normal to very late planting guarantees a wide range in corn maturity and harvest moisture. Test weight, a good indicator of maturity, will probably average 54 to 55 pounds per bushel this year, less than the long-term average of 56 to 58 pounds. Lower test weight means more breakage in handling, shorter storage life and often higher drying costs per unit of water removed. On a weight basis, feed value and digestibility doesn’t decline significantly until test weights fall below the mid-40s. Farmers should check the test weights from each field and hybrid. Sell the lightest corn first. 

Test weight should increase about 0.2 pound per bushel per percent of moisture removed; increases less than that indicate immaturity. Early death of corn plants from frost typically creates low test weight grain that doesn’t increase much during drying. The detrimental effect of low-test weight is primarily on storage and handling. More fines will be created in handling, which increase storage issues by restricting airflow.

Feed value. As long as the low-test weight grain is formulated by weight and not volume, the feed value isn’t greatly reduced. On a weight basis, ethanol yields should not be affected unless there has been spoilage.

Variable grain quality means more variability in storage. Try to even out moisture going into dryers by not mixing grain from areas of fields with large differences in quality. Dryers will not even out such variable corn. Grain elevators will have more difficulty controlling uniformity than farmers who are drying on the farm, because the quality of corn in deliveries to grain elevators cannot be controlled.

Watch for corn ear mold

There have been reports of mold damage on ears in the field, so it is important to scout fields. This year, penicillium ear rot appears more prevalent than usual in central Iowa, along with fusarium ear rot. Most ear rots are associated with insect damage to the kernels. Before you harvest fields, scout the fields where insect activity was high.

Fusarium on an ear of corn and Penicillium on an ear of corn
WATCH FOR EAR MOLDS: Ears of corn show fusarium (left) and penicillium (right).

Other molds that have been observed include trichoderma, cladosporium and gibberella. The Crop Protection Network has a helpful publication that describes ear rots, their symptoms and signs. 

Moldy ears also bring a risk of mycotoxins and their negative health effects for consumers and livestock. Not all fungi produce mycotoxins. Fusarium ear rot may produce fumonisins in affected grain and penicillium ear rot poses a risk for ochratoxin A (OTA) production. The U.S. Food and Drug Administration has set guidance levels for the total level of fumonisins in livestock feed, which reflect the sensitivity of different species to this group of mycotoxins.

FDA doesn’t have limits or guidance for levels of OTA in grain and animal feed. Negative health production impacts have been noted, especially for swine and poultry consuming feed contaminated with OTA. Mycotoxin resources are available through the Iowa Grain Quality Initiative and from the Crop Protection Network mentioned above.

Safe storage

Grain management at harvest is particularly important this year. The table below shows the generally accepted storage life of corn and soybeans at varying moisture and temperature conditions. At the end of the allowable storage time, grain will have lost about 0.5% of weight and will have increases in damaged kernels enough to reduce its grade by one number, which generally would trigger damage discounts in the market as well.

Maximum storage time (months) for corn, soybeans table

With the expectation of lower test weights even in fully mature grain, these storage times should be reduced. Experiences from previous low-test weight, high-moisture years suggest that at 52 to 53 pounds per bushel, the storage life of corn is about 50% of the numbers in the table.

Variability plays a big role in storage life because if there are pockets of wetter (and likely lighter) grain, those pockets will behave as wetter grain would, not the dry average. This is not a good year to hold wet grain before drying, even for short periods. A load of 24% corn left on a truck for a day could lose half its storage life in that day, more if it were immature and low-test weight. Additionally, from a mycotoxin perspective, fumonisin levels can increase in the time between harvest and drying; minimizing wet-holding time is critical to quality and safety maintenance.

Don’t hold wet grain long

The key at-harvest activities you should follow are cooling the grain as fast as possible and drying as rapidly as drying systems will allow. The air dewpoint is a good measure of how cold the grain can be made with given air conditions. Low dewpoint days are valuable in getting warmer grain out of the field or out of dryers, and cooling it down to safer temperatures in the 40s.

Grain with field mold already present is particularly vulnerable to further spoilage if drying is not done quickly. Grain in bin dryers that use intermediate heat levels (90 to 120 degrees) can experience further mold development and potentially mycotoxin increases if filled beyond what can be dried in one to two days.

The ability to measure the temperature of grain in bins will be critical this year. There are carbon dioxide testers that have promise in detecting mold growth without having cables in the bin.

Finally, always remove the center core of grain from bins, as quickly after harvest as possible. This takes out the fines and foreign material that are sure to be storage issues later in the year. Also, air diverts around the foreign material, which prevents cooling. Mycotoxins are often higher in fines and broken or damaged kernels, so a secondary impact of removing this center core may be improved quality and fewer mycotoxin issues in the remaining grain.

Tips for handling soybeans 

Expect more wet soybeans (greater than 13% moisture) coming out of fields this fall because Iowa did not have the usual week of warm, low-humidity weather that in other years takes soybeans to 10% moisture or below. However, the sporadic periods of warm weather in September and early October probably prevented the very wet soybeans that had been expected. The exception to this could be with very late planted fields, or with large rains or snows that keep fields and plants wet. For detailed information on drying soybeans visit ISU Extension

In general, try to dry soybeans with air or low-heat dryers. There is significant fire risk when drying soybeans in continuous-flow dryers, or with high-heat, in-the-bin dryers. Bin-stirring machines will remove hulls and filter them to the bottom.

Frost before maturity (plant and pod still green) will reduce yield and will result in green, high-moisture soybeans. Green soybeans are a problem for processors because the processors have to refine the oil more intensively to remove the chlorophyll that creates greenness. Significant oil losses result. 

Frost-damaged beans

In handling, keep in mind that most moisture meters, except the newer 150 MHz meters used by many elevators, will read mixtures containing green or immature oblong soybeans at 1% to 2% lower moisture than they actually are. Best action to take with frost-damaged beans is to aerate them for several weeks before marketing. Moisture will fall, and the greenness will become less intense, sometimes to the point of not classifying as damage. 

Soybeans this year are shorter in height and have less closure of the rows. This has led to more of the late-season weed emergence, which in turn, will result in an increased potential for foreign material in the grain tank when you harvest the beans. The shorter bean plants that have podding lower in the canopy will mean more dirt showing up as foreign material in the harvested grain, as farmers attempt to recover as much of those beans in the lower-growing pods as possible.

Expect lower-protein beans

Foreign material is a percentage basis weight reduction for soybeans, which is not a real penalty other than increased shipping cost of the foreign material. In storage, however, the whole pods will typically roll to the edge, and the fine material will stay in the center of the bin. As with corn, remove the center core of soybean grain in the bin as soon after harvest as possible. One strategy is to heap the beans in the bin when you fill it, then remove enough to return the surface to level.

You can expect lower protein than normal in the 2019 soybeans. September rains added pods to late-planted soybeans, but their development time was short. Typically, protein is low when crop development is slow or incomplete. Oil content may increase, however, to partially offset the loss in protein.

 

 

 

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