FARM MANAGEMENT
NOT ALL SOILS SHOULD BE MANAGED THE SAME WAY By Lillian Schaer
CONTRIBUTOR
U
sing best management practices (BMPs) to manage phosphorus losses on-farm may not be enough, suggests leading phosphorus and water quality expert Dr. Merrin Macrae. Instead, using targeted phosphorus management zones tailored to geographic areas and soil conditions could yield better results. This is particularly the case for Lake Erie,
where agriculture is a source of phosphorus that contributes to water quality issues. “We’ve been applying BMPs in the watershed, but things aren’t getting better fast enough so we need to be strategic and use the practices that have the best effect depending on where we live,” she says during a presentation at the North American Manure Expo this summer. “There are different things farmers can do to reduce phosphorus losses from their farms, with some more effective than others.” It’s generally recognized there is no one prac-
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tice—the so-called silver bullet—that will solve all phosphorus issues for every grower, so prevailing agronomic advice has long promoted the idea of stacking BMPs or doing as many as possible for maximum benefit. Macrae says that may not always be the most economical approach, especially if the anticipated outcome isn’t clear. “What we’re really trying to do is optimize BMP selection by being strategic,” she says. “You may only be able to do one BMP, so you want to make sure what you choose is the best for your situation and that it will have a really good effect.” That means accounting for climate variability, differences in the landscape, tile drainage levels and how land is used. Those differences can extend right into a specific watershed, such as Lake Erie, where the northeast gets more snow and has longer snow cover than the southwestern areas, and soils vary from flat clay to sloping loam. This impacts how water and phosphorus move across fields and through the soil, with both surface and sub-surface runoff contributing to losses. When monitoring three sites in the watershed over eight years (Londesborough, Ont., Ilderton, Ont., and Essex, Ont.), Macrae and her team noted differences in how water runs off and what its phosphorus concentrations are, depending on the site’s location, its climate and soil types.
WHAT IT MEANS FOR GROWERS Reduce soil phosphorus
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This can decrease phosphorus loss in both surface and subsurface runoff. Keep levels to what’s agronomically appropriate, but avoid overapplying, and figure out ways to spread manure out over more fields. According to Macrae, getting soil phosphorus down to what is needed W W W.MILKPRODUCER.CA
