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Most common fertility questions

Rigas Karamonos answers the fertilizer questions he’s hearing from farmers

At CropConnect in Manitoba in February, Dr. Rigas Karamanos gave his 868th presentation to farmers. He’s been counting. And, he said, it’s the 35th time he’s been asked to give a talk on “contemporary fertility issues.” He used his time on the CropConnect agenda to talk about the issues he hears farmers raising.

Fertilizing for higher yields

Farmers want to know if fertilizing for higher grain protein makes sense. First, Karamanos says, you have to make sure it’s both economically and agronomically viable. “If so, what would be the appropriate rates, time of application and nitrogen products?”

Without the right weather and soil test conditions, additional nitrogen won’t contribute much to increased yield. Based on research Karamanos published in 2005, he said, “We found soil test and growing season precipitation explain 78 per cent of the yield increase due to nitrogen application.”

However, nitrogen is important when it comes to protein. “The nitrogen fertility contributes 70 per cent, and the cultivar, only three per cent towards it,” Karamanos said.

Applying nitrogen at the right time can make the difference between increasing yield or increasing protein. “If you’re going after yield, you have to attempt to apply before what is called the ‘first node being visible’ in wheat.”

“Any nitrogen you start applying later on is going to go to protein. Of course you’re got to look at the price of the premium… Most of the time it doesn’t pay to do that.”

When plants need nutrients

In experiments done by Karamanos when he worked for Westco Fertilizer, “No matter when we seeded,” he said, “maximum utilization of nitrogen occurred at the six-leaf stage of canola.”

During that time, he said, “the crop was picking up anywhere between 6.9 and nine pounds of nitrogen per acre per day.” When you multiply that rate by seven days in a week, that’s 42 to 54 pounds per week. “That’s a lot of nitrogen taken up in that particular week.”

The table shows average plant nutrient uptake for canola, wheat and barley, six to seven weeks after seeding.

If you are going to top-dress, “it has to occur prior to the six-leaf stage.”

“It’s not really something I would recommend as a practice, but if you are in a situation and the sky has opened, well, then, you have a chance to go back and make up for that extra yield potential.” If it remains dry, you’ve saved yourself some fertilizer. “But that’s not the way someone should be planning to farm.”

Corn as an exception

Corn is an exception in terms of top-dressing. “When it comes to corn, there are three stages that are critical in terms of nitrogen uptake.” These are: the first 40 days; mid-season; and late season, which is also important for high yields.

“Side banding is something that is critical to apply fertilizer for corn.”

It doesn’t make economic or environmental sense to apply all of the nitrogen required for corn at seeding.

Boron on canola

Karamanos has spoken about boron at several farm meetings lately.

“I think there is a lot of wasteful uses of boron.” While there are times when boron is needed, such as on sandy soils, or in alfalfa, Karamanos thinks it is often overrated. While he has heard farmers say that boron works like Viagra to give crops strength, most of the time, Karamanos doesn’t see benefits.

Fertilizer strategies

Karamanos outlined three fertilizer strategies.

  1. Sufficiency: Farmers using this strategy “fertilize only when there is a good chance for a yield response.”
  2. Build and maintain: In this case, “the strategy is to maintain the soil test at a certain level.” With this strategy, “to build phosphorus by one pound you need anywhere between 12 and 28 pounds per acre of P2O5. So you better have a good phosphorus program.” To build potassium by one pound, he says, “you need eight to 16 pounds per acre of K2O.” While this strategy will enhance your soil and build your soil tests for future years, “build and maintain is not a cheap proposition.”
  3. BCSR: This is the base-cation saturation ratio. This method was developed back in the 40s. Karamanos explained that proponents believe an “ideal” soil needs an ideal ratio of cations. Karamanos believes that the initial experiments behind this method “were neither well-designed, nor well-interpreted by today’s standards.” Karamanos told participants that the BCSR method is based on faulty methodology that would cause producers to strive for an artificially high level of calcium in the soil and an artificially low level of potassium. “Using this system will mean that you apply a heck of a lot more potassium that you need, with a low probability of getting a higher yield.”

These days, he said, “people want to go faster.” With more acres and better equipment, “they want to be going 15 miles as hour. Not 4.5 or five.”

Karamanos has heard from farmers who are raising their mid-row banders from 2.5 to three inches in the soil to higher levels so they can increase ground speed and decrease wear and tear. Obviously, this is not ideal.

“Deep banding,” he said, “still remains the gold standard.”

About the author

Editor

Leeann Minogue is the editor of Grainews.

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