If you have excess dairy manure or are providing manure to a neighboring farmer supplying you with forage, it’s important to know a ballpark figure of what that manure is actually worth.
The University of Minnesota (U of M) has developed an on-line manure value calculator that helps you determine values, based on the type of manure you have available and its nutrient content, says Melissa Wilson, a U of M Extension soil specialist. (The calculator also can be used for beef, swine and poultry manure.)
To calculate the value of manure, you’ll need to determine the nutrient content of the manure and how much manure you are applying. For example, total nutrients in 1,000 gallons of liquid dairy manure might contain 33 lb of total nitrogen, 13 lb of total phosphorus (as P2O5) and 31 lb of total potassium (as K20).
However, not all of these nutrients from dairy manure are available in the first year. A more typical availability would be 18 lb of N, 10 lb of P205 and 28 of K20. If you are applying 9,000 gallons per acre, the applied rate would be 162-90-252.
The U of M calculator allows you to insert fertilizer prices. This winter, that might 35¢/lb of N, 56¢/lb of P205, and 43¢/lb of K20. So the total gross value of the manure would come to $215/acre. From that, you’ll need to subtract the cost of application, which might range from 1 - 2¢/gal. If your application cost is 1.5¢/gal, the cost to apply 9,000 gallons per acre would be $135. The net value of the manure, then, would be $80/acre.
The U of M manure value calculator allows you to fine tune these numbers for a variety of factors. You can access the manure value calculator here.