Harvesting drought-stressed corn for silage

During drought conditions, aside from areas where plants are barren (with no pollination or ear development) and have little green tissue remaining, it is often best to delay corn silage harvest as long as possible to allow for maximum development of the kernels and total dry matter.

Check ear development

Inspect the ears and assess the grain’s status to help determine the optimal harvest timing.

• Fields with plants that have some grain development should be left for as long as possible to allow the grain to further develop.
• If rainfall is received, that grain will continue to fill, increasing dry matter and improving silage quality.
• If pollination was unsuccessful and ears have no kernels, harvest should occur as soon as the plant moisture is appropriate for storage.

The forage quality of drought-stressed corn silage is expected to be variable because of variation in plant height, maturity, and grain fill within a field. Expect greater starch production with increased grain fill.

If there is little to no grain, expect higher levels of crude protein and fiber content, but decreased energy content, compared to corn silage containing grain. It is important to test corn silage for nutrient content, as rations may need to be adjusted compared to corn silage in a more typical year.

Harvest moisture

Test the moisture level of corn silage before and during chopping. Silage moisture is a crucial factor in the ensiling process, and the moisture content of drought-stressed corn can be misleading. Even if the corn looks fired up and dried out, it may still contain over 70% moisture.

When testing for moisture, it’s essential to get a representative sample from the field. A Koster tester or microwave oven can provide an accurate estimate of the moisture level of the silage.

 Test often because silage that is too wet or too dry will have storage issues.

• Silage chopped too wet can become clostridial, and nutrients can seep from storage structures.
• Silage that is too dry will not pack well, increasing the potential for air pockets, mold, and storage losses.
  • It is possible to add moisture to dry corn silage, but it is usually not feasible, as it takes large amounts of water to increase moisture. For example, it takes 7 gallons of water per 1 ton of silage to raise the moisture level by 1%.

The recommended moisture levels for the different storage options of corn silage are:

• 65-70% for bunkers
• 60-70% for bags
• 60-65% for upright stave silos
• 55-60% for upright oxygen-limiting silos
• 40-55% for baleage

Test for nitrates

Nitrates taken up by plants are normally incorporated into amino acids, the building blocks of proteins. The conversion of nitrates to amino acids usually occurs in green leaf tissue. Drought conditions can cause nitrates to accumulate in the plants, especially in the lower one-third of the stalk.

Nitrate concentrations in drought-stressed corn

• Leaves: 64 ppm nitrate-nitrogen
• Ears: 17 ppm nitrate-nitrogen
• Upper third of stalk: 153 ppm nitrate-nitrogen
• Middle third of stalk: 803 ppm nitrate-nitrogen
• Lower third of stalk: 5524 ppm nitrate-nitrogen
• Whole plant: 978 ppm nitrate-nitrogen

Raising the cutting deck to a height of 10 to 12 inches to avoid the stalks that are highest in nitrates will decrease the nitrates in the silage, but also decrease tonnage. The whole-plant nitrate concentration should be factored into the decision regarding cutting height.

Harvest should also be delayed a minimum of three days following a rainfall event, as a flush of nitrates can enter the plant, temporarily increasing nitrate concentrations.

If ensiled properly, one-third to one-half of the nitrates will be converted and released as a gas. Test the silage during feedout to ensure you’re not feeding unsafe nitrate levels, taking into account the nitrate level in the corn silage and the proportion of corn silage in the ration.

Green chopping drought-stressed corn is not recommended, as nitrates will likely be high without fermentation.

Chopping length also plays a role in the ensiling process. The theoretical length of cut for processed corn silage is 3/4 inch, and if not processed, the length should be 1/4 to 1/2 inch.

If harvesting corn silage that is drier than recommended, decreasing the cutting size may help with packing.

Using an inoculant can also increase the chances of successful fermentation. With reduced yields, it is critical to preserve the forage we do have.

Watch for silo gas

The nitrate-nitrogen released as a gas during fermentation includes various nitrogen oxide gases that are toxic to humans and livestock. These gases are heavier than air and will accumulate above the silage in a silo, where they can flow down the chute, into the silo room, and out through the silo juice drain. Some of these lethal gases are colorless and odorless.

Always use extreme caution around silos and have an emergency action plan in place.

Baling corn dry is challenging

When stacking or baling drought-stressed corn as dry hay, make sure to dry down to less than 20% moisture to prevent storage issues. This can be nearly impossible to do without ideal drying conditions.

Since this material isn’t ensiled, it is especially important to test for high nitrates.

Baleage is a better alternative to baling corn dry, as it excludes oxygen and will ensile if dense bales are made and wrapped properly. For bale silage, it is best to bale at 40-55% moisture and wrap with a minimum of 6 millimeters of plastic (about 7-8 wraps).

Check pesticide labels

Before harvesting drought-stressed corn for forage, be sure to check the labels of any pesticides used in the crop. Be sure to follow the pre-harvest intervals listed on the label before harvest.

Contact your crop insurance agent

For insured crops, be sure to contact your crop insurance agent before harvesting or before changes are made to the crop to ensure coverage.