Soil School: Do your soil a favour — put forage in the rotation

Photo: Pat Lynch

More organic matter, fewer weed seeds and insect pests, and a nitrogen credit: that’s what farmers get when they put forage in the rotation, says independent agronomist Pat Lynch.

From better soil health to higher yields, the benefits of forage — especially alfalfa — is a story that Lynch promotes passionately. On this episode of the RealAgriculture Soil School, Lynch joins host Bernard Tobin to make his pitch for farmers to plant more forage.

Lynch says alfalfa brings numerous soil health benefits to a field, including increased organic matter. He notes that University of Guelph research indicates that soil organic carbon levels increase after only two years of alfalfa in the rotation.

Weed control is another chapter in the forage story. Lynch says herbicide resistant weeds such as waterhemp and Canada fleabane are becoming monumental problems across North America. “The thing with waterhemp is it’s an annual and it’ll germinate in the springtime. You put that field in alfalfa for a couple of years, those seeds are going to germinate and they’re gone.” The same strategy can be employed to stamp out resistant fleabane, says Lynch.

Pests are also on the forage hit list.  Lynch points out that forages can help defend against corn rootworm, a pest that growers wrestle with across North America. “If you take corn out for one year, and put alfalfa in, that gets rid of the corn rootworm. There are so many different ways that forages, especially alfalfa, benefit soil health.” (Story continues after the video.)

Fertility is Lynch’s favourite part of the forage story. He notes that many U.S. states through the Midwest give alfalfa up to a 190 pound N credit for the next crop. “A good stand of alfalfa is at least 150 pounds, maybe 160, 170 pounds. So when you factor in the current value of nitrogen, you’re looking at $200 an acre of nitrogen credit.” If growers follow that alfalfa with corn they’re also likely realizing a 10 percent bump in corn yield, he adds.

There’s also a nitrogen credit produced by the alfalfa’s roots breaking down and releasing nutrients. “You can get probably a 25 to 30 pound nitrogen credit for the second year after alfalfa,” says Lynch.

To wrap up the video, Lynch shares one crucial tip for growers to help them better manage forage stands: “Don’t leave the alfalfa down so long…. There’s no bragging rights for whoever’s got the oldest alfalfa.” He notes that many growers tend to harvest alfalfa fields for longer periods to offset seed costs, but that argument doesn’t make sense from a cost or soil health health perspective. If growers leave a forage field for three years they’re paying about $40/ac per year for seed. That’s a fraction of what it costs to plant an acre of corn.

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