Phosphorus Balance Not A Province-Wide Problem

“It is legitimate to be concerned about phosphorus surpluses on a field-by-field, farm-by-farm and community-by-community basis.”

– DON FLATEN, U OF M

How much livestock can Manitoba handle? Don Flaten has the numbers.

Exactly 598,802,395 nursing and weaner pigs. Or 48,780,488 grower and finisher pigs. Or 7,142,857 calves less than a year old. Or 6,060,606 steers a year or older.

That’s the number of animals, arranged by species, you’d need to generate enough manure to supply all of Manitoba’s crop requirements for phosphorus.

Based solely on phosphorus, Manitoba could theoretically afford to increase its livestock numbers by five or six times without causing excessive soil nutrient buildup and exceeding plants’ ability to remove it, says Flaten.

Of course, the figures are meaningless and Flaten knows it. You’d never have that many animals to produce that amount of phosphorus.

It’s a popular view in some quarters that Manitoba is producing a mountain of livestock manure and its cropland is overflowing with manure nutrients.

ISOLATED PROBLEM

But the figures show that, generally speaking, Manitoba does not have a problem with surplus soil phosphorus, said Flaten, a University of Manitoba soil scientist.

That said, there are places in the province where phosphorus from livestock manure is a potential issue, he said following a presentation to the recent Manitoba Agronomists Conference.

“It is legitimate to be concerned about phosphorus surpluses on a field-by-field, farm-by-farm and community-by-community basis. And that’s really where our emphasis needs to be.”

In his presentation, Flaten dispelled the notion that phosphorus buildup from livestock manure poses a clear and present danger to the environment.

In fact, the application of phosphorus and its removal by crops is nearly in balance, said Flaten, who also chairs the National Centre for Livestock and the Environment.

Manitoba farmers apply 114,000 tonnes of phosphorus as a synthetic fertilizer annually to their fields. They also apply 17,000 tonnes of phosphorus in the form of livestock manure, of which pig manure comprises between 5,000 and 7,000 tonnes. (The value of the phosphorus in livestock manure is between $20 million and $25 million.)

In turn, crops take up 101,000 tonnes of soil phosphorus annually, leaving an imbalance of 30,000 tonnes.

IMBALANCE SMALL

Spread over agro-Manitoba, the amount is minimal. But there are areas, mainly in south-central and southeastern Manitoba municipalities with heavy livestock concentrations, where phosphorus is a concern, Flaten outlined in his presentation.

Two southeastern municipalities in the heart of Manitoba’s livestock alley stand out. In the Rural Municipality of La Broquerie, soil phosphorus concentrations are 84.8 per cent above balance, according to the data. Phosphorus in Hanover is 21.8 per cent above balance.

Ste. Anne, a neighbouring municipality, is below balance by only 0.53 per cent.

Regulations requiring setbacks for manure applications may increase pressure on available land. Up to 59 per cent of the land in La Broquerie could become unavailable for large livestock operations because of setbacks, according to a 2001 study.

Municipalities with high phosphorus concentrations have a “challenging situation” because the ability to haul large volumes of manure long distances is limited, said Flaten.

Some options might be: treating manure to separate the phosphorus and employing feeding strategies to reduce phosphorus in livestock rations, he said.

Flaten emphasized that balancing nutrient input with removal is critical to prevent buildup in the soil.

But it’s important to focus on surplus areas and not to jump to false conclusions about a province-wide problem, he said. [email protected]

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