Minnesota farmers have a new source of local, renewable fertilizer. No, it's not manure — but it once was.

North American Fertilizer, Benson, MN, conditions and sells about 85,000 tons/year of ash fertilizer derived from incinerated turkey manure.

The ashes are generated at nearby Fibrominn, the nation's first electricity plant powered by poultry litter. The 55-megawatt plant, located in the center of Minnesota's turkey-growing region, burns half a million tons of poultry manure a year, along with wood and other biomass.

There are about 140 biomass power facilities in the U.S., according to the federal government, and the number is growing. As biomass power expands, large quantities of ash byproduct will become available, says Al Doering, a scientist with Minnesota's Agricultural Utilization Research Institute, which is working on biomass-use challenges. Ash characteristics vary by the feedstock and combustion method, but many ashes are excellent sources of phosphorus (P) and potassium (K), Doering says.

Fibrominn ashes supply enough nutrients to fertilize more than 120,000 acres of cropland, says Steve Miller, North American Fertilizer (NAF) manager. The warm ashes — which look like fine, gray sand — are conveyed from the power plant directly to the fertilizer plant next door, where they are sprayed with water for better handling, screened and stored indoors.

Combustion consumes the nitrogen and organic matter in the manure, but all the minerals remain, Miller says. NAF Fertilizer is sold on a guaranteed analysis of 6% available phosphate and 4% available potash (0-6-4). However, the total amount of P and K in the ashes is actually about 50% higher than what is readily available to plants, says Brent Emch, of Cargill, which markets NAF Fertilizer. Those nutrients break down in the soil and become available over time, providing additional value.

NAF Fertilizer also supplies micronutrients, including 1% sulfur and 0.05% zinc. “We are finding corn yields responding to sulfur fertilization more frequently, even on medium- and fine-textured soils,” says University of Minnesota Soil Scientist Jeff Vetsch.

In a replicated trial at Waseca, MN, in 2008, Vetsch tested two rates of turkey litter ash on corn: a low rate supplying 80 lbs. of total P/acre and a higher rate supplying 240 lbs. total P. “At the higher rate, there was no yield difference between ash and commercial fertilizer,” Vetsch says.

The ash is applied with the same spinner spreader rigs used for dry bulk fertilizer. It's marketed through a network of about a dozen fertilizer retailers within a 200-mile radius of the NAF plant.

Brad Aaseth, manager of Bird Island Soil Service Center, Bird Island, MN, has handled NAF fertilizer for three seasons, spreading it on about 48,000 acres of corn, sugar beet and alfalfa ground. “The last two years we've sold out of it.”

Aaseth sells NAF fertilizer at a small discount to commercial dry fertilizer, and he says it's a good value for farmers. As for performance, “We've seen no agronomic advantage or disadvantage to ash fertilizer compared to conventional fertilizer,” Aaseth says. “We're a local cooperative. We handle the product because it's a good fit for our growers.”

NAF FERTILIZER AT A GLANCE

Source: Incinerated poultry litter

Guaranteed analysis: 0-6-4-1(S); 0.05 (Zn)

pH: about 14

Relative salt index: 30-45

Application method: Spinner spreader

Application rate, corn: 1,400-2,000 lbs./acre

Application timing: Fall preferred