Soil testers are no stranger to phosphorus — especially if you farm across the prairies.

Haley Tetreault, agronomy extension specialist with Sask Wheat Development Commission, says that second to moisture deficits, phosphorus deficiencies in soil is high on the list when it comes to looking at yield robbers. As we sit in the middle of January, it’s a great time to really look at your planning.

“If we look at phos in soil tests over say three, four, five years, we want to look at that trend and see which way that trend is going,” Tetreault explains. “It’s not something that you can just look at one year, because say you are limited to seed placement of phos. So on a cereal year, it’s not a big deal. You can maximize your phos up to 5o lbs in your seed row. But in your canola year, often times if you are limited to seed placement, you are out 25 lbs, so that’s your seed safe right there, and you are definitely having an export of phos in that year.”

(Editor’s note: the 50 lb actual rate is based on monoammonium phosphate, knife openers with a one-inch spread, nine inch row spacing, and good to excellent soil moisture, in western Canada. Always consider the 4Rs for phosphorus when planning your fertilizer applications.)

A way to be able to try to limit the potential of any deficiencies, is to look both into your previous records, and into your future crop plans. That way, if you are limited to how you can put phosphorus into the soil, you can maximize your potential in a cereal year. However, Tetreault says looking at other ways you can incorporate your phosphorus is going to be key as well.

By planning your long-term phosphorus goals, Tetreault explains you will be able to really see what is going on in your soil — which is so incredibly important to achieving agronomic success.

“It’s the first thing I’m looking at when I’m looking at a soil test, is that phos level. It tends to be a deficiency in 70 per cent of the soil tests I’ve looked at. It’s definitely a limiting factor. So planning and watching that trend over time is really important,” she says, adding to make sure that the soil samples are taken from the same GPS points each year to ensure consistency.

Tetreault notes that while you are creating these initial records, go as far back as you can to get the best sense of where your soil trends are at.

Want to hear more? Listen to Tetreault’s full discussion on the t0pic during this Q&A!

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