Reading soil tests key for proper nutrient use

The devil is in the details when it comes to nutrient application, 
meaning there is no silver bullet, just lots of hard work

If you’re planning on going somewhere, it’s best to know where you are starting from before you head out.

The same can be said of soil fertility.

According to Brian Hefty of Ag PhD, too many producers make assumptions about soil health and nutrients when deciding what inputs to use on their field crops.

“Soil tests, this is super important,” Hefty told producers at the recent CropConnect Conference in Winnipeg. “You’ve got to do them and you need to know how to read them.”

While you can get advice from agronomists or rely on outside experts, Hefty said achieving high yields demands close attention to nutrient levels and a personal investment of time.

“Anything you’re going to invest millions in, shouldn’t you know a little something about it?” he asked.

It’s a sentiment echoed by Dave Franzen, a soil expert at North Dakota State University.

Recent trials on nitrogen application in corn yielded unexpected results at that institution, making a case for split nitrogen application. But without soil testing, producers won’t be able to tell which applications made at what times will give them the best results, Franzen said.

“Soil tests are very important,” he stressed. “There’s a wide range every year in the residual soil nitrate after the wintertime, or after the previous crop, so just because you grew soybeans or field peas it doesn’t automatically mean that you’re going to get 30 or 40 pounds of residual.”

But while nitrogen levels are crucial, Hefty adds that they can’t be viewed in isolation, nor can other nutrients be ignored.

From the Grainews website: Frozen soils: Life under the soil

Potassium, he said, is sometimes overlooked in the nutrient matrix because it is often recorded at relatively high natural levels, even if that natural potassium is in the form of feldspar.

“Feldspar is a rock. How quickly does rock break down and become available for your crops? Not tremendously quickly,” he said.

Knowing how soil pH interacts with nutrients is also key, but unless soil tests are being done, Hefty said producers won’t know what pH they’re starting from.

“In our high-pH soils we’ve got excess calcium — excess calcium combines with phosphate to form calcium phosphate, calcium phosphate is insoluble in water and plants can’t suck it up, so you just wasted a bunch of money,” he said. “It will be out there, but maybe for your kids or your grandkids.”

To put it bluntly, not knowing your soil pH will waste fertilizer and wasted fertilizer means wasted nutrients and wasted money.

It can also waste water.

As plants begin to search for missing nutrients, they suck up more and more water, the expert said.

“So in effect, if you don’t have the right balance and the right amount of fertility in the soil, you just made your crop a water waster,” he said.

While it may seem daunting, Hefty said it only takes a few hours to learn how to read a soil test and begin the process of tailoring nutrients, regardless of what crop you’re growing.

“Everyone is always looking for a silver bullet — if I just do this everything will be fantastic. But it doesn’t work that way,” he said. “It’s about focusing on the details, doing a hundred small things.”

About the author

Reporter

Shannon VanRaes is a journalist and photojournalist at the Manitoba Co-operator. She also writes a weekly urban affairs column for Metro Winnipeg, and has previously reported for the Winnipeg Sun, Outwords Magazine and the Portage Daily Graphic.

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