Soil nutrients are in deficit after 2016

Consider the toll 2016’s big crop took on NPKS when planning for 2017 fertility

Make sure you have a late fall or early spring soil test as a guide to plant your 2017 crop fertility program. After the 2016 growing season, this is even more important than usual, says Rigas Karamanos, a long-time soil specialists who is now a senior agronomist for Koch Fertilizer Canada.

Karamanos says his message isn’t about selling more fertilizer, it is simply a fact once you look at how much fertilizer was applied in 2016 and how much was removed or was lost.

“While it wasn’t the ideal harvest season in many parts of Western Canada the fact is farmers produced a very large crop and the amount of nutrients removed was at near record levels,” says Karamanos.

Just with nitrogen in particular, Karamanos estimates the crop removed (or other losses) about 54,000 more tonnes in 2016 than was applied. That represents a 31 pound per acre nitrogen deficit across Western Canada.

“The bottom line, based on the numbers, is that farmers have 31 pounds less nitrogen per acre in the soil heading into this spring than they did in 2016,” says Karamanos. “So if you’re not a regular soil tester and tend just to assume there is a certain amount of nitrogen in the soil ahead of seeding, the fact is that this year there is less.”

These figures may not apply to every acre, and there is some mineralization of nitrogen even over winter. “So with that over winter mineralization farmers may be looking at a deficit of 20 pounds of nitrogen rather than 31 pounds, but the point is that overall across Western Canada there is a deficit.”

For the past number of years, Karamanos has calculated a Nutrient Balance Sheet for Western Canada. Drawing on a number of sources he looks at how much fertilizer was applied. Looking at yield data estimates, as well as weather, he can estimate how much fertilizer was removed during the growing season. This allows him to produce a nutrient balance sheet.

His figures show western Canadian farmers applied about 1.940 million tonnes of nitrogen, while crop removal or losses used 1.993 million tonnes, leaving a rounded-off deficit of 54,000 tonnes.

There are also deficits for phosphorus — about 356,000 tonnes; potassium — about 427,000 tonnes; and sulphur — about 15,000 tonnes.

The big crop was the main factor in nitrogen removal, but excessive moisture also takes a toll.

“Particularly in areas of southeast Saskatchewan and southwest Manitoba where some soils were saturated,” says Karamanos. “Each day when the pores of the soil are full of water, we lose anywhere from one to four pounds of nitrogen per acre, depending on temperature. And most of it is lost in a process called denitrification, as a gas to the atmosphere. So weather and moisture conditions are also a factor.”

Karamanos refers to phosphorus as the forgotten macronutrient. While there are generally good phosphorus reserves in the soil, the bank account is being drawn down.

“These big crops of canola are a good example,” he says. “A 60 bushel canola crop, for example, removes about 54 pounds of phosphorus (about 0.9 pounds for each bushel). And how many farmers are applying 54 pounds of phosphorus?”

The challenge with phosphorus is appling enough fertilizer without crop injury. A lot depends on fertilizer placement and seed bed utilization, he says. With a one inch spread on fertilizer on 10-inch row spacing that represents 10 per cent seed bed utilization. Under that circumstance the farmer can safely apply up to 30 pounds — perhaps even 35 pounds — of phosphorus with the seed. The rest has to go somewhere else.

“Even if you can get phosphorus placed one inch to the side and one inch below the seed, that’s adequate spacing and you can pretty well apply as much phosphorus as the you want,” says Karamanos.

He warns against broadcast-applying phosphorus, as it can easily be carried off fields by runoff and rain. Make sure phosphorus is incorporated. If you are applying more than can be safely applied in the seed row, look at banding, or using more of the space between seed rows.

“Farmers need to be cognisant of the fact there is a nutrient deficiency after the 2016 growing season, and obtaining a soil test ahead of the 2017 seeding season is highly recommended,” he says.

About the author

Field Editor

Lee Hart is editor of Cattleman’s Corner based in Calgary.

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