How much yield potential do we lose planting after May 1?


It’s mid-April and a huge part of Western Canada, Ontario, and the northern U.S. is digging out after a late winter blast of snow, freezing rain, and ice. As May looms large in the next 14 days, we have to ask — when should we start to panic about a late planting season?

May 1st matters because research consistently shows that earlier planting and seeding offers the greatest yield potential, right? Well, as with many agronomic questions, the answer is “It depends.”

Peter Johnson, resident RealAgriculture agronomist, explains that yes, in Ontario we generally lose a bushel of corn, per acre, per day for every day past May 1st the crop goes in the ground. For soybeans, it’s .3 of a bushel, per acre, per day. A similar rule-of-thumb holds true for the west — in southern Alberta, for example, each day past May 1 that canola stays in the bag costs 1.7% of yield potential (see list below). But those numbers come with a caveat.

“That bushel-per-acre-per-day loss only holds true if conditions were fit to plant on May 1. In years where I can’t plant on May the 1st, that doesn’t mean I can’t get an awesome canola yield by planting on May 15th,” Johnson says, it all depends on the weather that happens after seeding and planting.

If Mother Nature smiles upon us with good weather and timely rains, there’s no reason why that May 15 canola can’t out-yield what you seeded April 20 the year before, Johnson says.

Johnson says the data supporting the advantages of an early planting date is absolutely real, but you have to take a step back and look at conditions overall, and then hope the weather cooperates

So, there you have it. The calendar matters, but soil conditions and the weather forecast matter more. Best thing to do in a late year? Be ready to go when the ground is fit!

Listen to the full discussion from the April 16 edition of RealAg Radio, here:

Example: Approximate crop yield decline for each day seeding date is delayed after May 1 (in southern Alberta, under irrigation)*

Barley – malt: 1.20%
Barley – grain: 1.3%
Wheat – hard red spring: 0.8%
Wheat – CPS: 1%
Wheat – durum: 1.3%
Canola: 1.7%
Flax: 0.6%
*Source: Alberta Agriculture and Forestry

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