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Skip the nurse crop for alfalfa establishment

By: Lyndsey Smith

April 30, 2021

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When establishing alfalfa there’s a key decision to make: should the forage be under-seeded to an annual crop?

Sometimes called a companion or nurse crop, experts say that instead, the annual crop acts more like competition than a companion.

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Ashley Knapton, dairy strategic account manager with Corteva, says that a nurse crop draws on similar resources as the hay field and there’s only so much water and nutrients to go around.

“Last year in eastern Ontario is a prime example. We are going to see sub par hay fields [this year] because they faced higher drought stress in the establishing year with that nurse crop, and that nurse crop didn’t even really provide that much yield to make it worthwhile,” she says.

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Another consideration is that a nurse crop can hide some issues, including leafhoppers that could blow in, or poor germination of the forage seedlings.

Alfalfa or any perennial forage fields are going to be sticking around for several years — leave the competition out of it and let the alfalfa win the race with ease, Knapton says.

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Peter Johnson, resident agronomist for RealAgriculture, agrees.

“A ‘nurse crop’ does NOT nurse the under seeding; it competes with it,” he says.

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It is true that the companion crop offers some weed suppression, stopping some weed species from going to seed, and a cut of oat/pea baleage in the establishment year seems like a positive.

“To the alfalfa plant, though, the companion crop was the weed. And most of the time that just means less alfalfa established moving forward,” Johnson says.

Johnson adds that some growers are discovering that the better job done at establishing the forage crop means those weeds are cut in the first harvest, and are less of an issue than first thought.

Seeding with a companion crop also makes seeding depth more difficult. The oat and pea crop needs to go into moisture, which might be 1.5” deep, but alfalfa seed needs to say shallow — at a half-inch deep or less. You can’t hit both right in the same pass.

“If growers really need that early forage, I understand why they under seed. Plus there are years where getting the alfalfa to establish can be a challenge, and oat peas are almost “never fail.” However, if you want a three-year stand, you are always way ahead of direct seeding.

“Control the weeds, keep on top of leafhopper, harvest big hays yields moving forward. And grow cereal rye after your silage to fill that early forage need,” Johnson adds.