With commercial fertilizer prices soaring, some corn growers may consider bartering their corn for manure from the neighboring hog farm they fought against locating there some months back. Manure is “the other fertilizer” and its value has increased as prices for N, P, & K have doubled in price over the past several years. If you have a source of manure in the neighborhood, that livestock producer may become your best friend.

Liquid swine manure used to be a commodity that had more cost than value, but with increased value of its components, the attitude toward manure has changed. That is the contention of Minnesota Extension economist William Lazarus and Extension specialists Robert Koehler and Mindy Spiehs in their research on the changing economics for manure. They say, “The increasing price of commercial fertilizer has heightened interest in the use of livestock manure for supplying crop nutrients and has significantly increased the value of manure as a nutrient source.” The first step is determining the value of the manure.

The basic challenge is to relate the manure components to the value of the commercial fertilizer they would replace, and the researchers provide a worksheet to accomplish that. Unfortunately, the manure is going to have a different ratio of elements than the dry bulk fertilizer you had spread on the field last year. While the greatest impact will be in the first year, there will be some carryover benefits to the second year, and even some savings on application and benefits related to tillage and weed control. The key to success according to the Minnesota specialists is to maximize nutrient utilization efficiency, by not wasting available nutrients and only placing a value on the nutrients that will be used by the crop as well as not placing a value on the nutrients which a soil test indicates will not be required.

Expectations may be that manure may be applied at concentrations less than what is needed, with commercial fertilizer blended to achieve the target of a soil test. Other choices may be an application at the maximum phosphate rate, with nitrogen and potash supplied from a commercial dealer. Application costs will be higher per acre, when lower rates are applied.

The Minnesota researchers calculated the economic benefits and published them in their research, however, readily acknowledge that commercial fertilizer prices have substantially changed since the research began, along with the value of the grain being produced on the land where the manure was applied. Both of those factors will change the economic outcome.

Economic tests were taken on 47 sites over a three year period where liquid swine manure was being applied. Nitrogen averaged 43 lbs per 1,000 gallons and phosphate averaged 18 lbs, but there were wide variations. Applications were made primarily to corn ground, but also to beans and alfalfa fields, and some with varying crop rotations. From 2005 to 2007 the application rate declined from 5,723 gallons per acre to 4,975 gallons per acre, with costs from 1 cent to 1.28 cents per gallon.

Based on 2008 prices for commercial fertilizer, the Minnesota researchers calculated a per acre manure value of $54 in 2006 and $44 in 2007, with the best case scenario at a $101 per acre manure contribution over the three years of application.

Summary:
Manure has long been used as a fertilizer for crops needing N, P, & K, but erratic nutrient ratios caused it to give way to commercial fertilizers. However, the recent doubling of fertilizer costs has caused some farmers with available supplies of livestock manure to consider using it to reduce the cost of commercial fertilizer. Research has demonstrated the success of doing that, and potentially saving substantial investments in fertilizer costs.