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A report from the AgTech Centre

Organic nutrients put life back into native grassland

Fertilizer in any form, but particularly manure and compost, can provide a tangible production boost to native range yields, says an Alberta AgTech Centre engineer.

Native southern Alberta grassland that had been seriously depleted of topsoil and nutrients responded well to five years of application of compost, feedlot and liquid hog manure, as well as commercial fertilizer applied in the form of ammonium nitrate, says Lawrence Papworth, project engineer with the Lethbridge-based centre. Based on soil test recommendations, the plots received from 40 to 120 pounds of actual nitrogen per acre.

Over the various growing seasons, however, the organic fertilizer - manure and compost - provided the most consistent response. Blends of ammonium nitrate and urea produced respectable yields under more average moisture conditions, but in dry years plots receiving manure and compost had the best performance.

In a joint project with the Foothills Forage Association (FFA), the AgTech Centre applied the manure and fertilizer each year over a five-year period ending in 2002. Since then, the site has been monitored, not only to evaluate forage yield, but also to determine the economic benefit in terms of value of beef produced per acre.

"It indicates that fertilizing native grass pasture can make economic sense," says Dennis Laughton, FFA agronomist. "Most producers wouldn't apply treatments every year, but it may be needed if the goal is also to replenish soil organic material on a site."

The FFA project on re-established native range east of Nanton showed consistent improved yield, and more pounds of beef per acre on plots treated with manure and compost.

"Initially, we saw the biggest bang for the buck on plots treated with commercial fertilizer," says Laughton. "But over the longer term the organic treatments were the most productive."

In yield terms, manure and compost treatments produced from about 1,180 pounds to nearly 2,600 pounds of dry matter per acre depending on the year. That translated to between $40 and $269 worth of beef per acre after subtracting the value of fertilizer.

On the chemical fertilizer side, yields ranged from about 840 to a high of 2,600 pounds of dry matter per acre. Value of beef per acre ranged from a low of $8 to a high of $265 per acre after subtracting fertilizer cost.

"Treatments were repeated in each of the five years," says Laughton. "With commercial fertilizer we saw our highest production and returns in the first two years and then a decline after that. With organic nutrients yields and returns were more consistent over the five years.

For example, in 2001, which was a second year of drought, the economic return from fertilized pasture averaged about $8 per acre, while the manure and compost plots had a return of $44 per acre.

Yields on plots receiving no added nutrients over the five years averaged about 670 pounds of dry matter per acre, with an average economic return of about $64 per acre.

"We suspect the big difference in adding manure and compost is that it helps build soil organic matter which helps retain moisture," says Laughton. "Plants also develop a large root mass which is better able to make use of available moisture."

Even though fertilizer and manure is no longer being applied, FFA continues to monitor pasture yield to assess the long-term benefit of the treatment.

AgTech Centre is part of AAFRD's Technical Services Division and has a mandate to support all aspects of agricultural sustainability.

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