|With rising fertilizer prices, strategic application of manure can save you money.
The earthy smell of manure is often jokingly called the smell of money. With skyrocketing fertilizer prices, that is now literally true.
Once a break-even proposition whose value barely covered application costs, manure has crossed over into a potential profit center for many dairies. It can now be used to offset commercial fertilizer purchases for your own land or as a sales opportunity to crop-farming neighbors.
Over the past decade, fertilizer prices have continually ratcheted up. But they exploded this year as oil shot past $140/barrel and a hungry world drove demand for nitrogen (N), phosphorus (P) and potassium (K) through the roof.
The University of Minnesota (U of M) has developed an easy-to-use spreadsheet that can help you determine the value of manure. It allows you to enter your own values for the amounts of N, P and K you want to apply per acre.
Bob Koehler, a U of M Extension specialist who helped develop the spreadsheet, worked up an example for Dairy Today. He plugged in current fertilizer prices. He assumed the manure would be used on ground to be planted to corn, with a nutrient need of 140 lb. of N, 45 lb. of P and 40 lb. of K.
With 55% N available the first year from dairy manure, the program calculated that Koehler needed to apply 10,200 gal./acre. He also plugged in anhydrous ammonia at $945/ton (58¢/unit), diammonium phosphate at $1,085/ton (95¢/unit after subtracting N value) and potash at $875/ton (73¢/unit). Manure application costs were pegged at 1.25¢/gal.
The spreadsheet calculated that using manure rather than commercial fertilizer netted $4.49/1,000 gal. of manure, or $46/acre. A 1-million-gallon basin would fertilize 98 acres and net $4,485 above application costs.
The key to using
the spreadsheet, though, is plugging in the actual nutrient analysis of your manure. It can vary widely, depending on rations fed and the way manure is managed and stored. "The difference between farms can be like night and day,” says Roy Brodhagen of AgSource Cooperative Services in Bonduel, Wis.
Some large dairies he works with have two or three different treatment systems, depending on how they manage youngstock, dry cows and lactating cows. To ensure accurate application rates, these dairies are testing manure from each area.
Samples from liquid manure should be pulled after several hours of agitation, so you likely won't agitate simply to get a sample. From a practical standpoint, you'll agitate, pull samples and then spread.
Most testing labs can get results back in two days. But that's still too long when custom manure haulers are itching to empty pits and move on to the next job. So retaining records year-to-year is essential. "You need to develop a track record over a number of years,” Koehler says.
With current fertilizer costs, ap-plication accuracy is also critical. You don't want to underapply and short crops and yields. But you also don't want to overapply and waste manure—a precious resource.
- November 2008