September 25, 2009
Selling Stover May Cost You More Than you Get
An area farmer told me that he recently received an offer to buy his corn residue for as much as $20 a ton or $60 an acre for a three-ton harvest. For a quarter section, he could receive $9600. At first glance, it looks like he could get paid for what appears to be waste material – crop residue, but let’s think about the value of that residue.
Potential Nutrient Loss
First, this residue contains nutrients that feed subsequent crops. We can determine that value by knowing the amount of residue produced, the nutrient concentration of the residue and the current commercial nutrient replacement costs.
The amount of crop residue produced is related to grain production. Approximately 1 ton of crop residue (at 10% moisture) is produced with 40 bushels of corn or grain sorghum (56 lb/bu at 15.5%), 30 bushels of soybean, and 20 bushels of wheat.
The concentration of nutrients in crop residue varies with the season, management practices, time of harvest, and location. In addition, crop residue components differ in nutrient concentration, with most elements concentrated more in leaves and husks than in stalks. The typical nutrient content for corn or sorghum is about 17 lb nitrogen, 4 lb P2O5, 50 lb K2O, and 3 lb sulfur per ton of dry harvested residue.
Using current fertilizer prices, these nutrients have a value of $36/ton of residue. The potassium (K) portion of that is $26. Since our soils are naturally high in potassium, let’s just say we’d replace only 38% of the potassium for $10 making our nutrient replacement cost $20/ton. Assuming 3 tons of residue are removed, the cost of replacing nutrients is $60/acre.
Potential Moisture Loss
We also can calculate the value of residue in moisture savings. Research results from Garden City, Kan. showed water loss due to evapotranspiration was 4.3 inches greater under irrigated conditions where all residue was removed than in a comparable field that still had its residue. Variable costs associated with pumping this additional water would be about $4/ acre inch or a total of $17.20 per acre. (You can calculate this with a handy spreadsheet calculator found at http://water.unl.edu/reduceneed.) The trade-off of not pumping this additional water would be a significant loss in yield.
Simon VanDonk, Extension Specialist at the West Central Research Station in North Platte, conducted small plot residue removal trials on no-till. He saw a 25 bushel reduction in limited irrigated corn yield when the previous soybean crop residue was removed. Steve Melvin, UNL Extension Educator at Curtis, saw a 10 bushel reduction in a similar study when the previous wheat crop residue was removed. These figures can be reduced somewhat if some residue remains.
If you consider both nutrient loss and moisture loss, the cost to replace the residue now exceeds the benefit of selling it.
In addition, residue traps snow for moisture accumulation. On the negative side, residue removal could lead to soil compaction from baling and removal of residue, reduced soil organic matter and soil biological activity, and increase potential for water and wind erosion on unprotected soils.
For more detailed information, including a chart to calculate the total value of residue, see Harvesting Crop Residues (UNL NebGuide G1846).
Related USDA ARS Research articles include:
How Much Corn Stover can a Corn Grower Pick? — looks at the environmental aspects of residue removal.
In Producing Ethanol, Some Cornstalks Should be Left in the Field — looks at the loss of soil organic matter from residue removal
Extension Educator, Hamilton County
Extension Soils Specialist, Lincoln