Composting manure easier to transport, boosts carbon

Battling the bull’s-eye | Composting reduces water content, boosts nitrogen

Farmers applied manure on six percent of cropland in Manitoba in 2010, five percent in Alberta and three percent in Saskatchewan, according to Statistics Canada.

The low numbers didn’t surprise Agriculture Canada researcher Frank Larney.

The specialist in composting and soil reclamation said they are similar to figures in the last agriculture census, which illustrates the point: “We didn’t spread it around enough.”

He said the low percentage in Saskatchewan can be attributed to the province’s large farms and fewer livestock.

Quebec, which has less farmland and more integrated crop and livestock operations, was the highest at 44 percent.

Larney told a manure management update meeting in Lethbridge Jan. 14 that half of Canadian farms applied some form of manure to their land in 2010. In Western Canada, it broke down to 50 percent in Alberta, 48 percent in British Columbia, 47 percent in Manitoba and 36 percent in Saskatchewan.

However, the low number of acres that received manure shows it wasn’t spread too far.

Larney calls it “the bull’s-eye effect,” which is the tendency to spread manure in higher concentrations closer to the source because it is too expensive to haul it farther.

“Basically we need to spread it around a bit. So instead of that land that’s just one kilometre from the feedlot source, which already probably has high soil N and P, we need to transport it out there further afield.”

A perfect nutrient loop involves crops that are fed to livestock, with the resulting manure spread on land for use by the subsequent crop.

“In actuality, it’s not that simple or straightforward,” Larney said, because many nutrients for intensive livestock operations are imported and not all of them leave the operation in the form of livestock or meat.

Compost is one way to close the nutrient loop. It reduces both water content and volume and concentrates nitrogen and phosphorus.

One tonne of fresh manure can be reduced to 210 kilograms of compost, making it more economical to move.

“When it comes to a haulage scenario of moving nutrients further afield from source, composting has the advantage there over fresh manure,” he said.

“It’s more economical to haul N and P as compost instead of fresh manure, and that helps close that nutrient loop.”

Larney said manure composting has been increasing in the livestock industry since the mid-1990s.

Statistically, it is difficult to determine the size of any increase because the wording of census questions differed between 2005 and 2010 and the answers don’t provide an apples to apples comparison.

Larney’s field research on irrigated cropland near Vauxhall, Alta., showed compost application increased soil carbon levels in crop rotation studies.

“Soil organic carbon is the integrator of soil quality,” he said.

“Basically, if you can bring it up, improve the levels in your surface, you’re going to maintain your soil quality and make your soil more sustainable for future cropping.”

Soil organic carbon increased 17.8 percent on land to which compost was applied in Larney’s 12-year study.

He also studied compost effects on well site reclamation and found soil benefits were still evident 10 years after application.

Composting eliminates pathogens, parasites and weed seeds and stabilizes nutrients so they are slowly released in soil. Disadvantages include carbon and nitrogen losses and greenhouse gas emissions.

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