Editor’s note: The following was written by Mary Drewnoski, University of Nebraska Extension beef systems specialist, for the university’s UNL Beef website on Nov. 1.
Ammoniation can be used to make low-quality forages, like corn residue, have digestibility and protein content that is the equivalent of — or slightly better than — grass hay.
Ammoniation of corn residue is relatively easy (although working with anhydrous ammonia can be dangerous and proper safety precautions must be taken).
To ammoniate residue, the bales will be stacked together and the outside covered with plastic. To prepare an area to ammoniate the bales, set aside a spot that will accommodate the stack of bales plus an additional 5 to 6 feet around all four sides. Scrape the ground and push the dirt to the sides of the area where the bales will be stacked. The dirt will be used to seal the plastic covering the stack around the edges.
Gather bales into stacked rows. If using round bales, stack in a pyramid (i.e. three bales on the base, two bales on the second level) leaving a couple of inches between pyramids for the ammonia to filter around the bales.
Cover the entire stack with one sheet of 6 to 8 millimeter black plastic. If the plastic is 40 x 100 feet, you will be able to cover 10 to 12 pyramids in a row.
Make sure the edges of plastic on the ground are sealed with the loose soil to prevent leaking of ammonia. Any holes in the plastic should be patched using duct-tape to prevent loss of ammonia.
If the stack was arranged in pyramids (three-bale base, two bales on top) 14 bales long, there would be a total of 84 bales. Assuming each bale weighed 1,200 pounds, there would be 50.4 tons of residue.
If the residue was 90 percent dry matter, there would be 42.8 tons (50.4 tons x 0.85 = 42.8 tons) of dry matter (DM). You will want to add 60 pounds of anhydrous ammonia per ton of dry forage (3 percent).
For this example, 2,724 pounds of anhydrous ammonia (42.8 tons DM x 60 lbs. = 2,568 lbs.) would be needed.
Remember, the ammoniation process is temperature dependent and occurs faster at higher environmental temperatures. This is why ammoniation of straw harvested in the summer works so well.
However, this does not mean that it can’t be done successfully even in late fall after corn residue is harvested. Corn residue has been successfully ammoniated starting in early November.
When ammoniating during cooler ambient temperature, the key is to leave the stack sealed longer. At a temperature of 86°F or higher, leave the stack sealed for seven days. At temperatures of 60° to 86°F, leave it sealed for two to four weeks. When temperatures are below 60°F, keep it sealed for four to eight weeks.
Black plastic is recommended, as it collects heat from the sun and will make the temperature in the stack warmer than ambient temperature, helping the reaction.
When finished, it is a good practice to open the plastic and let the stack breath for 24 hours before feeding.
Determining the cost
Anhydrous ammonia priced at $500 per ton would be 25 cents per pound. It is suggested that you use 60 pounds of anhydrous per ton of dry matter.
If your residue was 85 percent DM, you would need to add 51 pounds of anhydrous per ton of residue, therefore, the cost of the anhydrous would be $13 per ton (as-fed).
The plastic will cost about $7 per ton, and if labor was $3 per ton with machinery costs at $2 per ton, then the total ammoniation estimated cost, not including the residue, would be $25/ton.
Right now in parts of the Midwest, corn residue is being sold for around $60/ton, which would make the total cost of ammoniated residue around $85/ton.
What about waste?
We recently conducted a study to look at waste when corn residue bales were fed to cows using a round bale feeder, similar to how hay is often fed.
Conventionally harvested (raked and baled) corn residue had about 22 percent waste when ammoniated and fed this way. Corn residue that was harvested by turning off the spreader and baling the tailings had only 16 percent waste. This reduction in waste is because cobs appear to respond well to ammoniation and are much more palatable after being treated.
Using the same type of hay feeders, bale waste for grass hay would be around 14 percent. So, the price of ammoniated conventional residue consumed would be $104/ton or $120/ton of DM (again assuming 85 percent DM).
If medium quality hay was $95/ton, the price of the hay consumed would be $108/ton, and at 88 percent DM, this would equal $122/ton of DM.
What is the feeding value?
The energy content of ammoniated corn residue is around 55 percent TDN, and the crude protein is about 9 percent. That is equivalent to, if not better than, “fair to good” grass hay.
Given current anhydrous ammonia prices, if corn residue can be purchased for $34 ton less than the price of grass hay, you may want to consider ammoniating corn residue.
Ammoniation can transform baled corn residue into forage that meets the energy and protein needs of a dry cow without supplementation. The value of ammoniation will depend on the availability and cost of other forages and anhydrous.
But remember anhydrous ammonia can be dangerous and proper safety precautions must be taken.