Using Weather-Damaged Corn as Forage - UNL CropWatch, July 12, 2012

Using Weather-Damaged Corn as Forage - UNL CropWatch, July 12, 2012

July 12, 2012

Drought-stressed corn

In some areas yields from drought-stressed, rainfed corn may be particularly low and growers are looking at alternative forage uses for their crop.


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The expanding drought, as well as hail, wind, heat, and other factors, may lead to extremely low corn yields in some fields this year. Often much forage value still remains in this low- and no-grain corn. Silage, green chop, hay, and grazing all are potential options for capturing its value. However, harvest costs can be high, especially when yield per acre is low, so carefully evaluate the economics of any salvage operation.

Preliminary Considerations

Before deciding to harvest your crop as forage, consider these points:

  • If grain prices remain high, grain yield may not need to be very high to justify selecting grain harvest over forage harvest.
  • Sometimes leaving the corn residue can result in increased yield next year and that increase may provide more value than that resulting from forage use. See NebGuide G1846, Harvesting Crop Residues for information on evaluating your situation.
  • Check labels of all chemicals applied to be sure they are cleared for forage use and that the minimum harvest interval has been met.
  • Check with the USDA Farm Service Agency and your crop insurer to maintain compliance with farm programs and crop insurance requirements.
  • Nitrate concentrations can reach toxic levels in weather-damaged corn. The harvest method can affect the nitrate, a particular concern when its being fed to livestock. Leaving a tall stubble (8 or more inches) will reduce nitrate risk but note eliminate it. Choose the harvest method accordingly.

Silage

Silage may be the safest method of harvest as fermentation usually (but not always) reduces nitrate levels and risk. Yield is about one ton per acre of silage for each harvested foot of earless corn plant (not counting the tassel). Feeding value is about 70% to 80% of well-eared corn silage. Corn with some grain (less than 50 bushels) tends to produce about one ton of silage for every five bushels of grain with a feed value about 80 to 90% of regular corn silage.

Harvest timing is critical with silage to ensure the correct moisture for proper fermentation. Plants probably are about 80% moisture now and the desired moisture level for silage is about 65%. Plants with any green leaves usually are too wet to chop for silage. For proper moisture, most leaves may need to be dead before chopping. The stalk and ear hold amazingly high water concentrations. For corn with no grain, even if all leaves are dead, the whole plant (and silage) moisture can be 70% if the stalk is still green and alive. Once plants actually die they can rapidly dry down.

There are several ways to reduce moisture content.

  • If corn has pollinated, delay silage harvest until all chances of increased biomass tonnage have passed or plants naturally dry down to appropriate moisture levels.
  • Corn can be windrowed and allowed to partially dry before chopping.
  • Excessively wet material can be blended with drier feeds such as ground hay, cracked grain, or dried distillers grains. However, this can take a lot of material — about 500 lb of grain or hay to reduce each ton of chopped corn with 85% moisture down to 70% moisture.
  • Silage inoculants may improve fermentation and preservation of drought-damaged silage.

Green Chop

Green chop minimizes waste but may be the most dangerous way to salvage corn. If present, nitrates will start to change into nitrites (about 10 times as deadly) as green chop begins to heat. Chop and immediately feed only an amount that animals will clean up in one feeding. Chop and feed two or three times per day instead of providing excess feed from a single chopping. If any green chop remains two hours after feeding, clean out bunks. Never feed green chop held overnight because nitrites can be exceptionally high. Be sure to allow plenty of bunk space (36 inches per cow is recommended) so boss cows don’t overeat and timid cows can get their share.

Hay

Hay may be the most difficult method of mechanical harvest, especially if ears have started to form – the stalk and especially the ears will be slow and difficult to dry. If possible, use a crimper when windrowing. Unlike with silage, nitrate levels do not decrease in hay after it is baled. Some of the nitrate risk can be reduced by cutting to leave a tall stubble, about 8 inches. Tall stubble also will elevate the windrow off the ground, allowing air to circulate better through the forage and aid in drying.

Grazing

Challenges with grazing include acidosis risk for cattle not accustomed to grain if ears have started to fill (smart cows will selectively graze ears), waste from excessive trampling, availability of drinking water, perimeter fencing, and nitrates. Reduce acidosis risk by feeding increasing amounts of grain similar to feedlot step-up rations before turning into standing corn that has much ear development.

Reduce waste by strip-grazing with at least two or three moves per week; daily is best. Back fences are not needed because regrowth is not expected. Water can be hauled in as with winter corn stalks or lanes might be constructed with electric fence to guide animals back to water sites that are nearby. If strip grazing, animals can walk back over previously grazed areas since back fences aren't needed.

Perimeter fences can be built using the same fencing as for winter stalks. Cows are likely to respect such fencing but inexperienced calves may not remain where desired. To better control calves, use a double strand of electric wire and/or a more visible barrier such as electric polyrope or polytape. Animals not already experienced with electric fences may need some exposure and training before moving them to a corn field.

Nitrates usually are not a problem with grazing since the highest concentration is in the stem base, the plant part least likely to be consumed. Risk increases, though, if animals are forced to “clean-up” a strip before moving to fresh feed and when corn plants are short (probably less than 3 to 4 feet tall) with small, palatable stem bases. Tests for nitrate concentration (whole plant and just the bottom 8 inches of the stem base) can be made prior to grazing to assess risk. If nitrate levels are risky, the hazard can be reduced by offering enough desirable forage to discourage consumption of hazardous plant parts as a major component of diet. Also, delaying grazing until plants more fully mature often lowers nitrate risk.

NebGuide G1865, The Use and Pricing of Drought-Stressed Corn, offers additional information.

Windrow Grazing

This method includes cutting as you would for hay and then grazing the windrows rather than baling them. It eliminates the cost of baling, transporting bales, feeding bales, and maybe hauling manure. It also eliminates any flexibility in feeding location and may reduce opportunities to sell the corn forage.

Windrowing tends to preserve forage quality better than allowing plants to stand. Usually it is easier to strip graze windrows than standing corn because building fences and estimating strip size are easier. Snow cover rarely causes problems if animals already know the windrows are there. They will use their hooves and face to push snow aside to access the windrow. Thick ice, however, can cause a significant barrier. Follow appropriate management recommendations listed earlier for hay and grazing for best utilization and safety.

Bruce Anderson
Extension Forage Specialist
Tom Dorn
Extension Educator, Lancaster County