Wheat School: Avoiding fertilizer injury in dry conditions


Although we don’t quite know what the moisture situation is going to be like for seeding across the Prairies, we do know one thing: if it’s dry, there are certain things we’re really going to have to watch out for this spring.

One of those items on the watch list is fertilizer injury of seed.

Jeremy Boychyn, agronomy research extension specialist with the Alberta Wheat and Barley Commissions, says one of the biggest thing to be knowledgeable about is your seedbed utilization (SBU)* and the salt index of the fertilizers that you’re using.

“Then you can make that assessment of how much fertilizer in a normal moisture year you should be putting down. And then if you’re heading into very dry seeding conditions, you’re going to want to reduce those rates of what goes down with the seed by half,” he explains in this Wheat School episode.

There are two main types of injury, says Boychyn: ammonia toxicity and salt injury. Although they play a little different, they are going to mainly have the same effect.

“Ammonia toxicity is when urea breaks down in the soil, it releases ammonia, and that ammonia can be toxic to the seed. Under drought conditions, there’s less hydrogen ions in the soil to turn that ammonia into ammonium and higher risk of seed injury,” says Boychyn. “When it comes to salt injury, that’s really a factor of the salt index of the fertilizer. The higher the salt index — and you can easily find the salt index of a variety of different fertilizers online — the higher risk of fertilizer injury to those seedlings. What happens is the high salt fertilizers actually pull moisture from the seed towards that fertilizer pearl, so instead of that seed imbibing, its actually being desiccated by the osmotic pressure that’s pulling from the fertilizer pearl.”

The key is to be knowledgeable before the crop goes into the ground, because when it comes to these types of injury, if you’re seeing it, it’s already too late.

Check out the full Wheat School episode with Boychyn, below:

  • SBU (expressed as a per cent) is the width of spread divided by the row spacing, multiplied by 100

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