South Dakota Ag Connection - Consider Alternatives for Harvesting Drought-Stressed Corn as Forage

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Consider Alternatives for Harvesting Drought-Stressed Corn as Forage
South Dakota Ag Connection - 08/18/2021

Drought conditions across North Dakota have created major issues for livestock and crop producers.

Many are facing poor grazing conditions, reduced hay production, limited stored forages and anticipated poor grain yields. Producers have begun harvesting corn for forage instead of grain.

Drought-stressed corn will vary in forage quality based on grain fill, plant height and maturity across fields. Limited grain fill means the forage will contain less starch, greater crude protein and fiber with decreased energy content, compared with grain-filled corn silage. Producers have several alternative methods to harvesting drought-stressed corn that can help them with limited forage supplies.

"Before harvesting corn for forage, be sure to talk with your crop insurance person to determine if the field can be harvested as a forage crop and maintain compliance with U.S. Department of Agriculture farm program provisions and crop insurance requirements," says Zac Carlson, North Dakota State University Extension beef cattle specialist.

"Additionally, check the labels of any herbicides and insecticides applied to the cornfields and make sure those chemicals are cleared for grazing, feeding or haying and the minimum harvest interval has been met."

See pages 109 to 112 of the NDSU publication "2021 North Dakota Weed Control Guide" (www.ag.ndsu.edu/weeds/weed-control-guides ) for information on restrictions for grazing, feeding and haying crops treated with herbicides.

One of the major concerns with harvesting drought-stressed corn is the level of nitrates, which accumulate primarily in the lower one-third of the stalk. Raising the cutter bar may lower the amount of nitrate in forage; however, this strategy is not always possible with drought-stressed plants. If properly ensiled, corn silage or baleage can reduce the concentration of nitrates by 20% to 50%.

"However, this does not guarantee that the forage will contain 'safe' levels of nitrates, and the ensiled feed should be tested for nitrates before feeding," says Janna Block, Extension livestock systems specialist at NDSU's Hettinger Research Extension Center.

See the NDSU publication "Nitrate Poisoning of Livestock" (https://www.ag.ndsu.edu/publications/livestock/nitrate-poisoning-of-livestock ) for more information about elevated concentrations of nitrates in feedstuffs.

Grazing drought-stressed standing corn can be done successfully with some additional management. Grazing can reduce costs associated with mechanically harvesting corn but does require additional labor for fencing, watering and monitoring cattle. Harvest efficiency also will be reduced, compared with mechanical harvesting, due to forage losses from trampling.

Here are some basic rules of thumb for producers grazing standing corn:

- Prior to grazing cornstalks, producers should estimate the amount of grain in the field to determine if excessive corn is present. If grain production exceeds 8 to 10 bushels per acre, increased management will be necessary to avoid digestive issues and founder. Some potential options in this scenario include limiting access by strip grazing, providing good-quality forage to grazing animals and using an ionophore.

- Make sure the animals become adapted to corn before turning them out to graze corn stalks. Start with 2 to 3 pounds daily and move up the desired level of grain consumption during a 10-day period before turnout.

- Stock cattle lightly to allow them to selectively graze upper portions of plant parts that are lower in nitrates. Do not force cattle to eat lower portions of stalks.

- Do not turn hungry cattle out to graze. Provide good-quality hay for two to three days so cattle don't overeat.

- Begin grazing lower nitrate fields and gradually step cattle up to higher nitrate fields. This will allow the microbes in the rumen that degrade nitrates to increase in population and handle greater concentrations of nitrates.

- If drought stress has limited grain fill in corn, cattle may need to be provided with an energy supplement. This can reduce the risk of nitrate toxicity by supplying additional energy to the rumen microbes to help convert nitrate into ammonia.

- Carefully consider the class of cattle allowed to graze cornstalks. Cattle new to eating corn (calves or yearlings) may take more time before they actively seek corn, while cows with experience grazing corn will look for grain and ears immediately when turned out. Consider grazing calves, yearlings or cull cows on fields to clean up some of the corn before turning out pregnant cows.

Producers struggling with limited access to silage harvest equipment or custom harvesting crews and no nearby market for silage might consider cutting and baling corn as hay or baleage. If drought-stressed corn is going to be hayed, target the moisture content to be less than 20% before baling.

Drought-stressed short corn is ideal for haying because of a shorter wilting period and reduced volume for baling; however, it carries an increased risk of elevated nitrate levels.

Submitting a sample for nitrate analysis before harvest may be beneficial.

Samples must be representative of the field. A minimum of 15 plants should be collected at the same height as planned for harvest. Plants should be chopped to 1-inch lengths and mixed, then placed in a plastic bag and sent to a lab for analysis.

If corn is near normal height, grazing or harvesting as silage may be a better option. To improve the wilting process, the hay should be processed mechanically or crimped but it still may require seven to 10 days to cure properly.

Leaving the bottom 8 to 10 inches of the corn stalk if possible not only helps reduce the nitrate content of the hay but also allows air to flow underneath the windrow, aiding in the wilting process.

"Excessive moisture can lead to mold development, lowering the feeding value, or worse, spontaneous combustion," cautions Miranda Meehan, Extension livestock environmental stewardship specialist.

Unlike ensiling, harvesting corn as hay will not reduce the nitrate concentration so be sure to test the hay before feeding to livestock. If the particle size of hay or baleage is not reduced before feeding, cattle will not consume portions of the corn stalk, leading to forage losses as waste. The stalk is approximately one-third of the corn plant, so producers who do not tub grind bales before feeding can expect approximately 20% losses at feeding.

Ensiling corn as baleage requires additional management. Unlike silage, baleage should be harvested between 45% and 55% moisture. Excessive moisture will increase the risk of undesirable clostridial fermentation, and baleage that is too dry will not ensile properly.

Due to a lower targeted moisture content compared with corn silage and the large particle size of the baled forage, the rate and extent of fermentation may be limited. Using net wrap reduces the risk of corn stalks tearing holes in the plastic. Ensure the final thickness of the plastic wrap is between 6 and 8 millimeters.

If oxygen enters the bale, the forage will mold and not ensile properly. Be sure to wrap the bales in plastic within 12 hours of baling to limit additional oxygen from accessing the bale. Allow a minimum of 28 to 36 days for proper ensiling before feeding to livestock.

Depending on the amount of grain harvested with the corn, hay or baleage can be priced similarly to drought-stressed corn silage as long as producers account for the forage losses.

Crop producers with failed corn are encouraged to list the available forage for grazing or harvesting on the NDSU FeedList (https://www.ag.ndsu.edu/feedlist ) and/or on the Department of Agriculture's Hay Hotline and interactive map (www.nd.gov/ndda ) to connect with livestock producers looking for feed.

See the publication "What is the Value of a Standing Corn Crop for Silage?" and the corn silage decision tool at www.ndsu.edu/agriculture/ag-hub/corn-silage-decision-tool for more information.

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