Putting a Value on Corn Stover
Following a grain harvest, corn stover is harvested in Wisconsin to the extent that we see in some other states. Perhaps this is a good thing given the conservation benefits and the fact we harvest much more corn silage than other regions. However, from time to time the question is raised regarding the value of corn stover harvested and/or sold off the field as bedding (most common) or feed. It’s difficult to come-up with a solid answer. Here’s why......
It’s always been proper to start with nutrient value, but never more so than with current fertilizer prices. Corn stover contains nitrogen (N), phosphorus (as P2O5), and potassium (as K2O). From a fertilizer replacement standpoint, the P2O5 and K2O are the important ones. Most sources peg equivalent P2O5 removal at about 4.5 lbs. per dry matter ton. The amount of K2O removed is the problematic number for a couple of reasons. First, there is double the concentration of K2O in the leaves compared to the stalks. The actual concentration of K2O removed in the stover bales will be dependent on the relative percentage of leaves and stalks harvested. Second, K2O is very soluble and readily leaches out of dead plant material. This means that both the elapsed time between grain and stover harvest along with the amount of rainfall will have an impact on actual K2O removed in the plant material.
The range of equivalent P2O5 and K2O concentrations reported in corn stover varies depending on the source and author. The range in these values along with a commonly reported value is shown in Table 1. Using the common value as a reasonable estimate, the fertilizer replacement value of corn stover can be made.
Keep in mind that the $22.00 figure is for 100 percent dry matter. Like the K2O concentration, moisture content will also vary. If bales are 25 percent moisture, this reduces the fertilizer value to $16.50 per ton as harvested, or to $8.25 for a 1000 lb. bale.
Soil Organic Matter:
Removing corn residue will have a negative impact on maintaining or improving soil organic matter. It is difficult to put an economic value on soil physical properties, although such estimates do exist and are typically reported at about $0.30 per ton of corn stover removed. For a single year, removing corn residue will likely have an immeasurable impact. If done routinely for consecutive years, the long term effects will be significant because increasing soil organic matter percentage is difficult once it has been reduced.
Erosion and runoff:
The importance of crop residue to reduce soil erosion and runoff is well documented. Obviously the impact that removing corn stover will have on soil and nutrient runoff will vary from field to field. It makes sense that fields prone to erosion because of steep slopes are not the best candidates for removing crop residue cover. There is generally no attempt to place a monetary value on the stover because of potential soil loss. If this is a concern, find a different field.
For more information contact Mike Rankin