By Paul Gross
Don’t sell yourself short when determining the nutrient value of wheat straw.
As wheat harvest continues, the question always comes up regarding the value of wheat straw sold out of the field. From a pure fertilizer standpoint, wheat straw contains very little in terms of phosphorus (P2O5), but moderate amounts of nitrogen (N) and potassium (K2O). According to the Michigan State University Extension Bulletin E-2904, “Nutrient Recommendations for Field Crops in Michigan,” the actual amounts of N, P2O5 and K2O contained in a ton of wheat straw are 13, 3.3 and 23 pounds, respectively. Actual nutrient content can vary based upon environmental conditions during the growing season and after the grain is harvested as well as soil nutrient supply, so if one really wants to know the actual value, straw analysis can be conducted by any lab that processes plant samples.
How much is that straw worth from a nutrient perspective? Well, it obviously depends upon the current market value of nutrients. Using today’s prices, a pound of N, P2O5 and K2O costs $0.65, $0.52 and $0.55, respectively. Thus, a ton of straw will contain $22.91 worth of nutrients. Again, this number can be variable, but it gives you a starting point for your own economic analysis.
It’s always best if prices are determined on a “per ton” basis rather than “per acre” basis. This takes the guess work out of determining actual yield. Average wheat straw yields are about 1.5 tons per acre. However, exceptional wheat can yield over two tons per acre or yields can be one ton if stubble is cut high or wheat yield was poor.
The seller has to determine how much profit over the cost of fertilizer is reasonable and put a value on the organic material that is leaving their farm. Farmers should consider planting cover crops or applying manure to replace this organic material. The buyer must consider the harvest costs which vary based on harvest method.