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Evaluate your fertility plan for 2014

Entering the 2013 growing season, untapped nutrients were allegedly left in the soil from the 2012 drought. Spring floods dashed hopes to use nitrogen (N) from 2012 in 2013. Yet most areas were able to produce adequate yields, even with summer turning dry. So what will this year bring?

Peter Scharf, Extension nutrient-management specialist at the University of Missouri, doesn’t foresee any major concerns with soil fertility. He expects phosphorus (P), potassium (K), and lime management to remain the same.

“It’ll probably be about the same as most years. I don’t see any reason to do anything drastically different this year,” says Scharf.

An exception is if you experienced yields less than three fourths of normal. In those instances, there may be potential to lower P and K rates, as it’s likely the crop didn’t use all of the nutrients applied for last year, says Scharf. He believes there is potential for some N-depleted soils based on heavy spring precipitation over large areas of the Midwest.

“I’m a little hesitant saying that, as I didn’t see a lot of evidence of it while flying around in June and July,” he says. “When you get depletion one year, it affects your balance the next year. That’s especially true when you’re going from corn into wheat or corn again.”

He’s concerned about the soils in the Midwest that received around 16 inches or more of rain between April and June, including most of Iowa, Illinois, Missouri, Indiana, and Wisconsin.

Prevented Planting
The Farm Service Agency reported 8.3 million acres were filed as prevented planting. “If you applied P and K last fall or spring and then filed prevent planting on those acres, you can treat it as though you fertilized it in 2014,” says Scharf.

However, if you applied N last year and filed prevented planting, it’s a whole different story. It’s very difficult to know how much of that N is still around.

“You could do a pretty good job of identifying and crediting how much with plant-based diagnostics, like the GreenSeeker sensor or Minolta chlorophyll meter,” says Scharf. “Soil tests are less reliable, but they can still be useful.”

If you want to do a preseason soil test to identify if any N is left, you need to test at least 2 feet deep, says Scharf.

If you filed for prevented planting and then planted cover crops, you’re not alone. However, Scharf doesn’t have a recommendation for what you should do, other than to keep your management plan the same.

“I would not change my fertility management if I was in the early years of doing cover cropping until I had clear evidence of what’s changed, in which direction,” says Scharf.

Moving forward

Scharf’s main fertility message for corn is to make sure you don’t run short on N in a wet year. 

“How to do that is not necessarily straightforward and easy. If you get a lot of rain, make sure you check your fields,” he says. If you have a visual indication of a shortage, in an appreciable area of the field, he recommends applying more N, if possible. 

Kyle Freeman, senior manager for new product development at The Mosaic Company, wants you to consider how much P and K you have applied in the past years. He suggests looking back over two years to consider what has been applied and what has been removed by the crop. You should also consider if you are in a maintenance program or in a program that builds up soil nutrient levels. 

“There’s still an opportunity for you to keep in mind what your nutritional balance was on your farm and to make appropriate plans for 2014,” says Freeman.

If you’re questioning what you should be applying, Freeman recommends a soil test – prior to planting – to evaluate fertility needs.

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