When it comes to getting maximum yields, nitrogen is still king.
“Nitrogen is the most important nutrient when it comes to providing yield responses,” said agronomist Rigas Karamanos.
In a study conducted in 2000 that looked at how barley yields responded to various nutrients, nitrogen increased yields by almost 60 bushels per acre — over six times more than any other nutrient, said Karamanos, who spoke at FarmTech in late January.
“You can see why we always focus on nitrogen, because it does provide the maximum yield.”
But like any other nutrient, the availability of nitrogen in the soil depends on the potential losses, which can occur through volatilization (or loss from the soil surface), denitrification (or loss from the root zone), and leaching (which is movement below the root zone).
Typical nitrogen loss in the soil is about 50 per cent, said federal bioeconomist Elwin Smith.
“Essentially, half the nitrogen you apply could be accounted for in the plant and the yield, but 50 per cent either goes back into gaseous nitrogen or some of it leaches,” he said.
And reducing that nitrogen loss will give you more bang for your buck when it comes time to purchase inputs.
“If the nitrogen isn’t being lost, it’s available for your plants to use,” said Smith. “So the biggest impact is you could get away with purchasing less nitrogen if you have less losses.”
Producers apply a high rate of nitrogen knowing that the plant won’t be able to use it all, he said.
“You have to apply that extra, but with more efficient use, you could apply less and save on your input costs,” said Smith.
“If you could increase the efficiency — even to 60 per cent — at a typical nitrogen application rate, you could be looking at saving $7 to $10 an acre without impacting your crop yield.”
Reducing nitrogen loss
But how can producers prevent these nitrogen losses in the soil?
The first step is to deep band the nitrogen — or place the nitrogen at least three inches deep.
“Deep banding fertilizer still remains the golden standard,” said Karamanos.
“But now what happens is we have people who want to go faster, so they shallow band. People are looking for operational efficiencies versus agronomic efficiencies.”
Many farmers assume they’re home free as long as the nitrogen is in the soil — but that’s not always the case.
“Although we still put fertilizer in the soil, shallow banding is not the same thing as deep banding,” he said.
“Because it’s shallow banded, there’s not enough soil to prevent gaseous losses. Shallow banding does result in higher losses.”
Secondly, if you’re going to shallow band or broadcast your nitrogen, consider using an enhanced-efficiency product, like products with polymer coatings or nitrification inhibitors, Karamanos suggested.
“It allows for increased uptake. That’s the key. And increased uptake means getting the same yield with less fertilizer or getting less losses,” he said.
“If you have the means of reducing the conversion of ammonia to nitrate, you can also minimize the gaseous losses as well as the leaching losses.
“That’s what nitrification inhibitors do.”
And finally, producers need to adhere to the 4R nutrient stewardship principles — applying the right rate of the right nutrient source at the right time and the right place.
“There’s not very much nutrient uptake at the early stages of the crop, so the crops need to have the nutrients at the right time — the time they require maximum uptake,” said Karamanos.
“During the first two or three weeks, there is hardly any uptake happening, and that’s where most of the losses occur.”
For wheat, about 75 per cent of nitrogen is taken in during the first quarter of the plant’s life, while maximum uptake in canola happens at the six-leaf stage, he said.
“If the early supplies are not adequate, we run into issues, and the crops may not realize their maximum yield potential.”
That starts with “knowing what’s in the soil beforehand,” said Smith.
“If you already have quite a bit of nitrogen available in the soil, you may not need as much applied nitrogen, and if you continue to apply high amounts, you’re likely to have higher losses,” he said.
“Targeting your nitrogen application to what the plants need and considering what’s available in the soil would be a good starting point, but there’s no silver bullet out there.”