Nitrogen fertilizer options for winter wheat
By Bruce Barker
Enhanced efficiency fertilizers provide additional ways to put down N.
Back in the days of ammonium nitrate (34-0-0) fertilizer, most winter wheat growers broadcast all of their N requirements in the spring, but with the banning of the product growers were left looking for other options. Some tried to manage urea (46-0-0) broadcast in the spring but were at risk of volatilization losses. Others moved to fall sideband or broadcast urea, but risked denitrification and leaching losses under waterlogged conditions. Enhanced efficiency fertilizers (EEF) are helping to improve N-use efficiency and reduce N losses.
“Enhanced efficiency fertilizers give farmers more N management options,” says research scientist Brian Beres with Agriculture and Agri-Food Canada in Lethbridge, Alta. “Our research suggests that split applications of N when combined with enhanced efficiency urea products with a urease or urease plus nitrification inhibitors can provide the highest yield and protein levels.”
Beres led a three-year study at five sites across Western Canada: Brandon, Man., Hallonquist (south of Swift Current), Sask., and Lethbridge and Lacombe, Alta. Two experiments were conducted to assess the impact of N fertilizer type and time of application on yield and protein content.
In the first experiment, urea, urea plus urease inhibitor (Agrotain), urea plus urease and nitrification inhibitor (Super U), polymer-coated urea (Environmentally Smart Nitrogen; ESN), and urea ammonium nitrate (28-0-0; UAN) were applied. Time of application treatments included 100 per cent side-band, 100 per cent spring-broadcast, and 50 per cent side-band plus 50 per cent spring-broadcast. Varieties compared included AC Radiant hard red winter wheat and CDC Ptarmigan soft white winter wheat.
The Agrotain and CDC Ptarmigan treatments were removed in Experiment 2 to allow for additional application methods of 100 per cent fall side-band, 50 per cent side-band plus 50 per cent late fall broadcast, 50 per cent side-band plus 50 per cent early spring broadcast, 50 per cent side-band plus 50 per cent mid-spring broadcast, and 50 per cent side-band plus 50 per cent late spring broadcast.
Experiment results: split applications stand out
Beres says the split applications of N usually provided the maximum yield and protein, particularly with Agrotain or SuperU. Results with these products were similar whether all applied with the seed, in a split application, or broadcast in-crop in the spring. The results were also consistent across all soil zones. Beres also adds their work indicates that yield benefits from split applications improve with moderate to high-yielding production environments. “In moderate to low-yielding environments, split applications would provide similar yield to all N side-banded at planting.”
Untreated UAN had the poorest yield. Urea and ESN also produced lower yield compared to Agrotain and SuperU treatments.
“To be fair, the ESN treatments where it is 100 per cent broadcast wouldn’t be recommended, because we know that the polymer coating doesn’t break down fast enough, or not at all, if stranded high in the thatch layer when applied late fall or in spring treatment timings; that means the N isn’t available early enough – we had to include those placement and timing options with ESN because it was a factorial study,” Beres says.
“And if you are side-banding all the N at seeding, it doesn’t make sense to use 100 per cent ESN because our previous research established a 1:1 blend with urea will produce the same results. By far, ESN provides the greatest benefit for farmers in terms of seedling safety with high rates of seedrow N. You can apply ESN, up to 90 kilograms N per hectare in the seed run, when single-shooting and not worry about seedling toxicity injury.”
EEF fertilizers provide options for individual farm management
The choice of how and when to apply fertilizer N comes down to individual farmer preference and risk. Ken Gross, Ducks Unlimited agronomist in Brandon, Man., says that in his area, more and more farmers are applying N in a split application, and a growing number are banding all their N in the fall.
“The message is getting out there that producers should have nitrogen available to the crop very early in the spring in order to maximize the yield potential. It can be hard to get on the land to broadcast urea because it is too wet and you miss that early application window, or it can be too dry and the urea just sits there on the surface,” Gross says. “The seed head is developed early in spring so having the nutrients available to grow as big and healthy a seed head as possible is a great strategy to maximize yield. Not all the N has to be down in spring, but some N must be available to the plant so it can grow the seed head to its max potential.”
Based on his research, Beres thinks that applying 50 per cent of N as urea or a blend of urea:ESN in a side-band at seeding, followed up with a spring broadcast of Agrotain or SuperU is a good option for growers. For some growers, the advantage of splitting applications is that it reduces the amount of N that needs to be handled and applied at seeding, when upwards of 200 pounds of product per acre is needed. That can speed seeding at a time when farmers are also trying to harvest other crops.
“Band a percentage you are comfortable with in the fall using urea or an enhanced efficiency form to mitigate over-winter losses, and then go in the spring with Agrotain or SuperU to top-dress the balance based on your expectations for yield that year as driven by precipitation to date. That gives you a little more flexibility in application methods and risk management,” Beres explains. “The final question would be the economics of EEF fertilizers and our analysis indicated split-applications with SuperU and Agrotain, or ESN in a seed row or banded in an equal ratio with urea all appear to pay for themselves.”
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