Producers Must Weigh Issues in Baling, Ensiling Corn

BROOKINGS, S.D. -- Producers have two main options for harvesting drought-stressed corn: baling it as hay or ensiling it to make silage.

South Dakota State University Extension Crops Specialist Bob Hall said an SDSU Extension publication discusses those alternatives. Extension Extra 4017,"Harvesting and Feeding Drought-Stressed Corn," is available through county Extension offices. Or find it online at the SDSU Extension drought Web site, http://sdces.sdstate.edu/drought/.

The publication also discusses grazing or green chopping corn, but SDSU does not recommend these methods because of the potential for toxic levels of nitrates in drought-stressed corn. Nitrates can accumulate in plants when there is a large amount of nitrate in the soil and some factor such as drought interferes with normal plant growth.

If producers are willing to accept the risk of high nitrate levels and choose to graze or green chop drought-stressed corn, SDSU Extension recommends producers use great caution if giving the feed to young, pregnant or nursing animals. In all cases make sure animals have a supplemental source of energy such as grain. Energy from the grain helps convert nitrate to ammonia in the rumen, reducing the threat of nitrate poisoning.

Baling corn is less desirable than ensiling, since the fermentation process of ensiling reduces nitrate levels. However, baling is sometimes more practical for several reasons: corn harvesting equipment is sometimes hard to use on short corn; direct cut short corn will be wet and will seep once ensiled; and yields won't be great enough to obtain the compaction necessary to have proper fermentation in making silage.

If cutting corn for hay rather than silage, a mower-conditioner can be used to get a lower level of cut. However, producers should keep in mind that if the stalk is cut low there's increased risk of high nitrate levels, which are greater in the lower region of the plant.

The hay curing process does not reduce nitrate levels, as the fermentation process of making silage does. Drought-stressed corn used as hay should be tested for nitrate. Use a core sampler to test 18 to 20 bales per field.

Producers who choose to bale corn may have difficulty getting the crop dry.

Ensiling forage, because of the fermentation process, can dissipate anywhere from one-fifth to two-thirds of the nitrate accumulated in the plant. Purdue University studies showed that ensiling corn forage reduced nitrate concentrations by about one-third.

Feeding trials also show that corn silage made from plants with no ears or partially filled ears had 65 to 80 percent of the value of normal corn silage on a dry matter basis when comparing feed efficiency, milk production and growth rate.

It's important to wait at least three weeks before feeding silage made from drought-stressed corn, since fermentation takes 14 to 21 days for completion.

Moisture content of 60 to 65 percent is best, and the minimum moisture content recommended for ensiling corn high in nitrate is 55 percent -- less than that can reduce fermentation so that there is less breakdown of nitrate. Moisture content of higher than 70 percent can result in seepage losses and may yield foul-smelling, unpalatable silage.

To estimate moisture content of silage use a quick "grab test" if a more method of determining moisture isn't available. Take a handful of finely cut plant material and squeeze it as tightly as possible for 90 seconds. Then release your grip and note the condition of the plant material in your palm:

If the juice runs freely or shows between the fingers, the crop contains 75 to 85 percent moisture.
If the ball holds its shape and the hand is moist, the material contains 70 to 75 percent moisture.
If the ball expands slowly and no dampness appears on the hand, the material contains 60 to 70 percent moisture.
If the ball springs out in the opening hand, the crop contains less than 60 percent moisture.

Purdue University studies have shown that the addition of 20 pounds of limestone per ton of silage going into the silo can further reduce nitrate levels.

Once it has been ensiled and fermented, be sure to sample the silage for a nitrate analysis. Take care to obtain a representative sample by taking samples for three or four days, mixing the samples and then sending one sample for analysis. Refrigerate all samples and try to get the sample to a laboratory as soon as possible after taking your last sample. Ask your county Extension educator for more information about sampling.

Contact: Bob Hall, (605) 688-4760

** For links to other sites showcasing SDSU's work in teaching, research, and Extension, visit http://sdces.sdstate.edu.

Lance Nixon, Editor
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-4653
Lance_Nixon@sdstate.edu