The alkali treatment of crop residue is a practice that could transcend drought management, said Dave Combs, a nutrition professor at the University of Wisconsin – Madison.
In his presentation at the Midwest Forage Symposium earlier this year, he stated that as corn yields increase the biomass per acre also increases.
With more corn grown for ethanol, Combs indicated the premise of using both the remaining distillers grains and fiber has its merits.
Citing the USDA, he said the six states in the Corn Belt produce 132 million metric tons or nearly 68 percent of the nation’s corn stover.
As mentioned, this is not a new concept. The alkali treatment of crop residues has been tried with calcium, sodium hydroxide and ammonia.
According to Combs, calcium or lime wins out because it is not as caustic as ammonia and more environmentally compatible than sodium hydroxide. It is also relatively economical at $20 to $30 per ton.
It is important to distinguish the different forms of lime. First, there is limestone or calcium carbonate.
Using combustion at 1800ºF, limestone is converted to quicklime or calcium oxide. Adding water to quicklime converts it to hydrated lime or calcium hydroxide.
Limestone cannot be used to treat corn stover, as it has no effect on fiber digestibility, Combs said.
However, quicklime and hydrated lime are both sold for this purpose as Stovercal O and Stovercal H, respectively.
Since quicklime reacts with water to form hydrated lime, Combs warned that many safety issues arise with its use.
“You need to be careful in how you handle it,” he said, noting it should be stored in a dry location.
When making a slurry, the quicklime should slowly be added to a large volume of water to avoid boiling or the rupture of containers.
Workers should take plenty of precaution, as quicklime dust will cause severe irritation or burning of the eyes, skin, respiratory and GI tract.
It is very reactive with water, including perspiration on the skin and moisture in tissues in the lungs and esophagus.
Eye protection is needed and contact lenses should not be worn. If contact is made, use soap and water to remove the dust.
“Calcium hydroxide is much safer and easier to work with,” Combs said.
The process
“There is no exact formula in terms of processes,” Combs said.
When treating the stover on the farm, the stover should be chopped at 3 to 6 inches to reduce the particle size and increase surface area. A tub grinder could also be used to shorten the particle length.
Either quicklime and water or hydrated lime should be added and enough water to make 50 percent dry matter feedstock.
It should be stored in a silage bag or bunker for at least seven days prior to feeding to allow the full reaction to take place.
To apply treatment in the field, begin by windrowing the stover. Apply the lime to the windrow and follow behind with water.
Then use a field chopper to pick it up off the field. Combs warned the dust during chopping could be dangerous and safety precautions should be taken.
For 1,000 pounds, the recipe would be 950 pounds dry matter corn stover, 50 pounds lime and 1,000 pounds water.
“To treat 50 tons of 90 percent dry matter stover, you need 10,600 gallons of water,” Combs said. “You’re not going to do it with a garden hose.”
Considerations for the process should include how to grind the stover, if quicklime or hydrated lime will be used, how much lime is needed to achieve 5 percent calcium application and how much water is needed to achieve a 50 percent dry matter.
Feed applications
Lime-treated corn stover can be used in cattle feed as a replacement for corn grain or forage.
Studies at Iowa State University and the University of Nebraska show lime treatment significantly improves the digestibility of corn stover and cobs.
Another study compared three feedlot diets. The control diet contained dry rolled corn at 46 percent of the dry matter content and roughage at 10 percent of the dry matter.
The second diet fed untreated corn stover at 25 percent of the dry matter, removing the roughage and 15 percent dry rolled corn.
The third diet was similar to the second but fed treated corn stover at 25 percent.
There was no significant difference of fiber digestibility between the control and untreated stover diets, but the treated stover diet had 68 percent NDF digestibility, compared to the control diet at 44 percent.
Jim Russell, a professor of animal science at Iowa State, looked into creating corn replacement feed for feedlots at 2-to-1 distillers grains to treated stover.
A diet with dry matter percentages at 35 percent corn grain, 20 percent treated stover, 40 percent distillers grains and 5 percent supplement was compared to a diet with 70 percent corn grain, 5 percent untreated stover, 20 percent distillers grains and 5 percent supplement.
Both groups of steers maintained a good rate of gain: 3.84 pounds per day on the replacement feed compared to 3.9 on the corn ration.
Since the replacement feed reduced corn fed by 30 bushels, returns per steer increased from $90 on the corn ration to $118 on the replacement ration.
Feeding trials in Nebraska replaced 10 to 15 percent units of corn with treated stover and saw equal performance in average daily gain, feed-gain, carcass weight and percent choice as compared to the control diet.
“In terms of beef cattle performance, this seems to be working very, very well,” Combs said.
For growing cattle, lime-treated stover can replace a significant amount of corn grain, especially if fed with distillers grains.
It can be fed to yearlings through finishing. A 2-to-1 ratio of distillers grains and treated stover can replace up to half of the ground corn in feedlot diets.
About 10 to 15 percent units of corn grain can be replaced with lime-treated stover without affecting dry matter intake, average daily gain or feed efficiency in background and finishing diets.
If considering this option, Combs said to think through the treatment process to have a tub grinder or chopper, an adequate water supply and bunkers or bags for storage.
Also, remember to take safety precautions when handling quicklime. 
PHOTO
It’s no surprise that farmers are rekindling an old idea of stretching their feed supplies further. The alkali treatment of crop residue is a practice that could transcend drought management.Photo by staff.
