Options for Drought Damaged Corn Fields
Corn that has been affected by drought can be used as a feed for cattle. Before harvesting the drought damaged corn field for something other than the grain, check with your crop insurance person to determine what needs to be considered to make sure that the field can be put up as a forage crop and still receive any insurance that is possible.
The drought damaged corn plant will likely contain nitrates. Data indicates that the nitrates reside in the bottom 6 to 8 inches of the stalk. Use management strategies to reduce any possible cattle losses due to high nitrates in feed.
A drought damaged corn field can be salvaged as corn silage. Harvesting the drought damaged corn field as silage will reduce nitrates by 30 to 60 percent. To reduce the nitrates through the ensiling process, allow the silage to go through the 21-day fermentation process before opening the bunker to feed. Ideal moisture content of the silage for packing into a bunker is 65% (35% dry matter), with a range of 62 to 68 percent moisture. This is critical when making silage. If the silage is to wet, there will be excessive seeping and spoilage and proper fermentation will not occur. If the silage is to dry, then it will be difficult to pack and make the anaerobic (with oxygen) conditions necessary for the fermentation process.
It is difficult to determine when to chop a drought damaged corn field for silage. The chop material when it is green may be as high as 80% moisture, which is too wet to pack into a bunker. At this moisture content, let it continue to dry in the field. An extra step in making silage would be to windrow the field and let it wilt in the field until the desired moisture content is achieved for chopping and packing into the bunker.
To determine the moisture of the standing crop, select some stalks and cut them at the same height that the chopper will be set. Cut the stalks into small pieces (about ¾ to 1 inch in lenght) using a cleaver or heavy knife, mix the sample and then analyze the sample for dry matter using the microwave. Take a sample from some of the chopped material, weigh the sample then dry it down in a microwave. Reweigh the sample to determine the moisture. Microwave slowly so as not to "burn" the sample. Microwave and weigh until there is no change in weight of the sample after microwaving. This process requires a scale that can accurately weigh small amounts of material and changes in weight due to water. Most producers are not set up to test moisture using this method.
There is a "quick" method of estimating time to harvest a drought damaged corn field: the "squeeze test".
- Select a few stalks (like described in the previous paragraph) and chop them into pieces about the same size that the silage chopper would using a heavy knife or cleaver. Also, you could chop a round of the field with a silage chopper and sample the chopped material. Grab a hand full of the chopped material and squeeze it for 30 seconds.
- If the juices drip easily from the material, then it is too wet. In this situation, wait to chop in a couple of days or test again in a couple of days.
- If the sample doesn't drip any juices from the squeezed material, then slowly open your hand.
- If the stalk material remains compacted and doesn't fall apart or quickly expand back , the moisture level is acceptable for ensiling.
- If your hand is not wet and the stalk material falls apart when you open your hand, the material is too dry to ensile.
If the chopped silage is too wet:
- Stop chopping and allow the field to dry.
- OR -
- Add whole corn, dried distillers grains, or ground dry forage.
To avoid the nitrates, the chopper head could be set to leave an 8 inch stubble. This will result in a reduction in yield. The ensiling process will reduce nitrate 30 to 60 percent, so a compromise is leaving a 6 inch stubble.
Droughted corn silage will be 85% to 95% the energy value of regular corn silage depending on the number of ears on the stalk. The protein content can be slightly greater than regular corn silage.
Before feeding, sample and test for moisture, energy (TDN), crude protein, and nitrates.
Pricing drought corn silage is a bit of a challenge. Rule of thumb has been that each ton of 65% moisture corn silage in the bunker is priced at 9 to 10 times price of a bushel of corn (normal, well-eared corn). Pricing the standing crop is a little more difficult to determine. Below are two ways some have priced it in the field.
- Ton price is 5 times price of a bushel of corn (earless corn)
- Ton price is 6 to 7 times price of a bushel of corn (low grain corn - less than 100 bu/A).
It is hard to estimate the amount of silage that will be produced in a corn field that has been droughted out. The National Corn Handbook estimates the tonnage of a drought damaged corn field is related to the corn yield if the field were allowed to be harvested. For each 5 bu/acre corn yield results in a ton of corn silage per acre. If the droughted corn field were going to yield 15 bu/acre it would produce 3 tons of corn silage per acre.
Here are two sources of added information you might use.
- Estimating Corn and Sorghum Silage Value (UNL Extension Historical Archives: NebGuide G74-99)
- NebGuide: The Use and Pricing of Drought-Stressed Corn (PDF version, 1MB)
The droughted corn field could be salvaged as green chop. The field is chopped daily and fed daily. Set the chopper head to leave at least an 8 inch stubble to avoid the high concentration of nitrates residing in the base of the stalk. Nitrates will be a concern. Do not allow the green chop to heat in the wagon. This will cause nitrates to be converted to nitrites and nitrites are 10x more toxic than nitrates. Observe cattle frequently while they are eating the green chop.
The droughted corn field can be salvaged as hay. Nitrates are still a concern and consider leaving an 8 inch stubble as a major portion resides in the bottom part of the stalk. One of the challenges is to get the hay dried down enough to make a good bale. Leaving an 8 inch stubble will allow air movement around the underneath side of the windrow close to the ground to help the drying process. Crimping the stems will help in the drying process.
Before feeding, take a sample and test for moisture, energy (TDN), crude protein, and nitrates.
Grazing the droughted corn field is a way to extend the grazing season. Introduce livestock slowly to this new forage by feeding them hay before turning in to reduce the chances of digestive problems. Nitrates are still a possible problem so don't force cattle to consume the bottom part of the stalk. Acidosis could be a concern depending of the amount of ear development. Adapt cows and access may need to be limited depending on the amount of ear development and grain.
Avoid losses due to trampling by cross-fencing and allowing cattle only enough feed for a couple of days of grazing. A watering source or system will need to be developed.
Windrow the droughted field and leave windrows in the field for winter grazing. Nitrates are still a concern and consider leaving an 8 inch stubble as a major portion resides in the bottom part of the stalk. Leaving an 8 inch stubble will allow air movement around the underneath side of the windrow close to the ground to help the drying process. Nitrates can still be a concern, so fill cattle up with a forage low in nitrates before allowing access to the windrows. Acidosis could be a concern depending on the amount of ear development. Adapt cows and access may need to be limited depending on the amount of ear development and grain.
When feeding the windrows, fence off enough for a couple of days feeding to avoid wasting a lot of the forage. A watering source or system will need to be developed.
Rick Rasby, Beef Specialist, University of Nebraska
Bruce Anderson, Forage and Pasture Management Specialist, University of Nebraska