Crop residue has value in the field. Harvest wisely!
By: Kevin Gould, Dennis Pennington and Paul Kamp, Michigan State University Extension
Recent growing seasons have created needs for additional forage and feed stock in the United States. In addition, since 2007, significant acres have been diverted from forage production to grain production. Crop residues have bridged the gap in many situations as livestock producers are “learning on the fly” how to harvest, store, and feed crop residues.
The key emphasis has been targeting corn stover in the mid-west. As crop yields grow, so does the available stover fraction. In many cases, harvesting a percentage (30-50 percent) can increase productivity in the cropping system. For this reason alone, it can be beneficial to livestock and crop producers to work on agreements for corn stover harvest in the rotation.
The key challenge with fall harvest is the stover moisture content. Dry stover is generally only harvested in the upper-mid west from Oct. 1- Dec. 1 and the harvest window may close quickly. Dry stover can be harvested with good quality product up to 25 percent moisture. Above those levels, we begin to see spoilage and fermentation of the stover depending on the climate conditions and storage method.
Harvesting wet corn stover is an excellent option to increase feed quality and palatability but does come with additional cost. Moisture levels can be 30-50 percent and bales should be tightly wrapped in plastic to allow for fermentation to occur over four to eight weeks. Fermentation will be slowed as ambient temperatures decline into the fall. Wrapping systems generally cost $8-10 per wet ton depending on bale size, transportation distance, number of bales, etc.
If the stover biomass is harvested and aggregated as feedstock for a cellulosic ethanol or biomass refinery operation, ash and dirt inclusion rate is important. Any biomass refinery technology would prefer the lowest possible levels of dirt in the incoming feedstock. Traditional methods of raking and mowing typically generate more than 10 percent ash content in the baled feedstock. New chopping and windrowing equipment designed for industrial scale harvesting, baling, and collection can achieve dirt and ash inclusion rates as low as 7 percent, with much of that being structural ash, part of the plant biomass. Some biomass refinery technologies capture the plant nutrients, such as potassium and phosphorus, which can be returned to the soil as a nutrient supplement. Here is document from Iowa State University addressing the ash content of harvested corn stover.
Recent work with the New Holland “Corn Rower Head” has increased options for harvesting and storing corn stover. This YouTube video helps show how this new equipment harvests grain and windrows the stover all in one pass at the 2015 Michigan State University harvest trial. Stover can then be baled without raking, which helps reduce ash levels in the stover.
If you are considering corn stover to harvest to fill a gap in your feeding system or biomass harvest for ethanol production, be sure your equipment is ready for the field ahead of time so you can hit a fairly narrow harvest window. Remember, you should only plan to remove 30-50 percent of the corn stover from the field. Some residue needs to be left for wind/water erosion protection and to build or maintain soil organic matter levels.