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Manure revisited

When hog prices crashed in December 1998, cynical humorists joked that the manure was worth more than the hogs.

That grim humor still applies today. Fortunately, hog prices have rebounded. Today the skyrocketing price of commercial fertilizer is the factor that has raised manure's stock. This spring, analysts expect the price of anhydrous ammonia to hover around $400/ton, double that of spring 2000.

Renewed interest. “Now that commercial fertilizer costs so much more, people think more of manure as a nutrient source than before,” says Bahman Eghball, a USDA-ARS soil scientist based in Lincoln, NE.

In some areas, neighboring farmers of hog operations, concerned about excessive manure production, have rallied against livestock expansion. However, the spike in nitrogen prices may cause some opponents to reevaluate their position, says Jim Gerwing, South Dakota State University extension soil scientist.

“Some farmers who didn't want hog barns built by their land may realize that they could get some value out of the manure,” Gerwing says.

Typically, hog operations with excessive manure for their land base have given it away. “But as fertilizer prices increase, you may even see some people interested in paying for manure,” Gerwing says.

Savings plus consistent yields. In some cases, manure's fertility value has keyed livestock expansion. Manure was a main reason why John Helvig, Truman, MN, built two 600-head custom finishing barns in 2000. These joined six of his own hog finishing barns that he uses in his 550-sow farrow-to-finish unit.

Each year, Helvig incorporates between 3,500 and 4,000 gal. of hog manure from his finishing barns on 500 to 600 acres. Because this is about 40% of his cropland, his fields receive manure every two to three years. Occasionally, he will apply a pop-up application of 3 to 5 gal./acre of 10-34-0 fertilizer on manured soils to promote early plant growth. But as a rule, soils receiving manure the previous fall have sufficient yearlong fertility.

“With manure, we can reduce our fertilizer costs down to basically nothing,” Helvig says. “Yields also seem to be more consistent with manure. I can grow 170 bu./acre corn more consistently on manured ground compared to fields with commercial fertilizer.”

Even before fertilizer prices began spiking last year, Helvig figured manure saved him between $45 and $50/acre in commercial fertilizer bills. He figures that fertilizer price increases will widen his savings.

Manure also was a perk when Donald Rudolph, Trimont, MN, constructed three 600-head finishing barns in 1995. He custom finishes 9,000 hogs annually.

“It's definitely a bonus, especially with high anhydrous ammonia costs,” he says. “Manure has been a more constant value than the hog market has been.”

Rudolph estimates that, besides consistently saving him $30 to $40/acre in fertilizer costs, the manure boosts corn yields 15 to 20% above commercial fertilizer, and around 10% on soybeans.

What's in this stuff? You've probably heard that milk is the perfect food for humans. Well, that's how corn views manure. In six out of seven University of Minnesota trials during the mid-1990s, swine manure outyielded an equivalent rate of commercial fertilizer by an average of 7 bu./acre.

“For whatever reason, you could see the difference between corn fertilized with manure versus commercial fertilizer,” says Gyles Randall, a University of Minnesota soil scientist. “The corn with manure was taller and had a darker, denser canopy. There's something about hog manure that corn seems to like.”

Manure contains the standard fare of nitrogen (N), phosphorus (P) and potassium (K) that commercial fertilizer contains. For example, 1,000 gal. of finishing barn manure typically contains 50 to 60 lbs. of total N, Gerwing says. Of this, 70% is typically available to corn the first year.

“Thus, if you have 35 lbs./acre of available N the first year, you can gain 105 lbs. of N just by injecting 3,000 gal./acre of manure the first year,” Gerwing says. “If N prices are $0.30/lb., you can save $30 to $35/acre on N.”

Besides N, manure also contains abundant P and K. Each 1,000 gal. of finishing barn manure contains 39 lbs. of P205 and 29 lbs. of K2O. “The monetary values are $0.29/lb. of P205 and $0.13/lb. of K20,” says Randall. “If growers are low on P and K, manure takes on added value,” he says.

Manure contains some intangibles you won't find in commercial fertilizer. “With manure, you add the kitchen sink,” Randall says. “There may be some ingredients that stimulate microorganisms. Manure may also release N more slowly than commercial fertilizer. This gives season-long availability to the corn plant.”

Manure also contains carbon, which greatly boosts soil quality, says Doug Karlen, research soil scientist with the National Soil Tilth Laboratory in Ames, IA.

“If the soil has a good carbon level, it promotes aggregation of the soil and water use efficiency. If soil loses its carbon, it will lose that aggregate stability because it forms crusts more frequently.”

Gerwing explains that these perks also encourage a better rooting environment for the plant. “Ultimately, this means better crop production,” he says.

So why not use it? Manure is harder to manage than commercial fertilizer. “When you compare manure to urea fertilizer, which has a guaranteed analysis, there is more variability,” says John Sawyer, an Iowa State University soil fertility specialist.

The variability can make it difficult to apply the correct rate. That's particularly true when farmers have not properly stirred manure before application. “N deficiencies have occurred with manure due to nonuniform mixing,” Gerwing says.

Volatilization also complicates applications. “Nearly half of the available N can volatilize because it is in the ammonia form,” Gerwing says. “If we don't incorporate the manure within a few hours, much of the ammonia disappears, and we lose a major chunk of its value.”

Transportation difficulties also have dimmed manure's potential. Remember how that quarter of land next to your barn used to be the most productive? That's because it likely served as a dumping ground for manure. Meanwhile, other fields that could have utilized the manure received none.

However, technology has eased these worries. Manure injection units prevent nutrient loss by injecting manure in the soils. Recent improvements with manure applicators also help ensure the correct application rate, as does good manure sampling and testing (see “Metering manure,” page 72). Meanwhile, hose reel attachments also have helped solve transportation headaches.

“The new hose reel systems can pump liquid manure up to two miles away without hauling it on the road,” Gerwing says.

Farmers also may have storage facilities that ensure ample supplies for uniform field application, says Keith Kelling, University of Wisconsin extension soil scientist. “Having enough manure to make an even application can improve a person's confidence,” he says.

Manure applications still pose more headaches than do commercial fertilizer applications. Odor is still a concern.

“We live in a fairly hog-dense county, and it takes communication to apply manure,” Helvig says. “We try to contact our neighbors before we apply. As with anything, there are challenges, but that's no different than if you apply anhydrous ammonia. Manure is an asset, not a liability.”

Short supply. If you're thinking about substituting manure for commercial N this spring, you may not be able to obtain the manure.

“At this winter's meetings, I'd hear from producers who said manure was in short supply,” Randall says.

Spring applications may also have a downside. “You could face headaches with wet soils and compaction,” Randall explains.

One possible drawback of using more manure on environmentally sensitive lands is P runoff. “Although you can't apply too much P with manure agronomically, you can environmentally,” Randall says. “Erosion from surface runoff can cause elevated levels of P in environmentally sensitive areas.”

In the future, policy makers could enact regulations to limit hog manure applications next to areas such as lakes and streams. “The crystal ball indicates that's where we'll be going,” Randall says.

Despite concerns like these, commercial fertilizer price increases could provide a gradual reliance back on well-managed manure applications, Karlen says. Before the advent of commercial fertilizer, manure was the main source of plant nutrients.

“I realize we won't see every farm go to a mixed crop/livestock operation,” Karlen says. “But maybe partnerships will form between crop and livestock farmers. Maybe a farmer with animals that produce more manure than his land will accept will partner with a neighbor who doesn't have animals. That's my vision of future agriculture. We look at managing the land resource in an optimum way.”

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