Canola School: The importance of soil testing in a drought year
Soil sampling and having a fertility plan in place might be even more important after a drought year. There’s a good chance that the fertilizer applied in the spring wasn’t used up by crops.
Where yields were lower than anticipated, it’s a good idea to get into the field, and see what’s left in terms of soil nutrients, says Warren Ward, agronomy specialist at Canola Council of Canada in this episode of the Canola School.
“The way I like to look at it is that it’s really part of that broader 4R management plan,” says Ward. Placing fertilizer at the right rate, from the right source, at the right time, and in the right place all make up for a responsible and efficient fertilizer strategy.
When talking about fertilizer, and the conditions over the past year, Ward says it’s really about the right rate when it comes to planning for next year, and fall is a great time to get out and do some soil testing.
Once soil temperatures have reached 10 degrees celsius, the soil microbial activity responsible for a lot of nutrient turnover has slowed, making it the optimal time to get an accurate nutrient reading for what would be available in the spring. Ward says that ideally, soil testing should happen as close to freeze-up as possible.
“Make sure you’re talking to your agronomy professional and getting in there to get some fields done this year,” says Ward, but keep in mind that testing objectives are going to vary a bit for everybody.
An average indication, using a composite sample avoiding high or low spots in the field is one way to get that nutrient snapshot, to calculate fertilizer rates with next year’s yield goal in mind.
“That’s what our right rate is going to be for next year is the difference between that soil test level, and the amount you’ll need to achieve your yield target,” says Ward. A more in-depth look at nutrient levels, say for zone management and variable rate applications, means sampling each zone for nutrient differences throughout the field.
The other “R’s” are important too, says Ward, and thinking about the right source, recommends to stay away from products that have nitrate in them, as it can be subject to more loss. Of course the right place is in the soil, but with the dry conditions, Ward says that getting soil to close after a banded application might mean going deeper when applying, or waiting until spring for soil conditions to be better.
He adds that enhanced efficiency fertilizer or in-season top-dressing can also be a part of the plan next year for success, if spring application isn’t an option or rates need to be cut back due to excess nitrates.
“A colleague of mine made a comment that really stuck with me: ‘you can’t manage what you don’t measure,’ which makes a lot of sense with regards to nutrients,” says Ward. “If we’re not measuring what’s left there in the soil right now, to figure out that right rate for next year is just a guessing game.”
Finally, Ward mentions that any acres managed by a 4R accredited agronomist can be included in the 4R Nutrient Management Program through Fertilizer Canada.