Getting winter wheat seeded is a juggle of equipment, people and inputs that leaves little room for delays. On top of that, fertilizer and seed safety is top of mind for growers, more so in winter wheat, and for two good reasons. Getting the crop seeded is a challenge in the fall, and accommodating the fertilizer needs of winter wheat requires a lot of thought.
Should the fertilizer be applied with the seed? Or banded? Should the entire amount be applied in the fall? Or should some be applied in the spring, timed to the winter wheat breaking dormancy and meeting those immediate demands of the growing plant? Will you be able to get out on the field in time? Will you be able to spare the time and equipment in the spring to top-dress?
Applying sufficient fertilizer with the seed in the fall comes down to a seed safety issue. Nitrogen levels are the biggest concern. All three Prairie provincial governments have guidelines for safe rates of fertilizer applied with seed (find them on provincial websites). These guidelines are the results of years of research and provide rates based on the crop, soil texture, soil moisture, width of seed row openers and row spacing.
By replacing some or all of the nitrogen applied with the seed with ESN (Environmentally Smart Nitrogen), a polymer-coated fertilizer product, farmers can put more fertilizer down with the seed without risking seed safety. Compared with traditional forms of fertilizer, ESN brings a number of benefits that should be considered along with the price difference.
“The advantages of ESN are numerous and stem from the polymer coating and how it manages the release of fertilizer in the soil,” says Ray Dowbenko, senior specialist, agronomic services at Agrium. “The coating acts to slow the reaction of the urea granule with moisture in the soil and in doing that, it diminishes the free ammonia and salt problems that can damage seed. Additionally, the slow release of nitrogen coincides better with the growing seedlings’ demand for nitrogen — particularly with winter wheat.”
Winter wheat and ESN
Winter wheat has traditionally been fertilized by first applying a low rate of nitrogen at seeding, then broadcasting more in the early spring. There were many reasons for this:
- Too much nitrogen at seeding was thought to reduce winter survival.
- Too much nitrogen in the fall could lead to losses due to leaching or denitrification.
- There can be cost savings from not having to broadcast nitrogen in the spring if the crop doesn’t survive the winter.
Applying ESN as all or part of the nitrogen requirement for winter wheat in the fall accomplishes a number of things. Firstly, the full rate of nitrogen can be applied with less risk of losses to leaching or denitrification. “The coating on the granule separates the seed from the fertilizer, and also reduces urea from reacting with moisture in the soil directly, acting as a barrier,” says Dowbenko. “Only when moisture crosses that barrier will the urea be able to react and release nitrogen.”
“Secondly, as the temperature in the soil drops heading into fall and winter, water movement into and nitrogen movement out of the granule is essentially at zero,” says Dowbenko. “Conversely, as the soil warms up in the spring and the winter wheat breaks dormancy, nitrogen will become available in the right place and at the right time for the crop to take the best advantage of it.”
Winter wheat is seeded into warm soils from late August to mid- September. “In a normal year, we would expect 30 to 40 percent of the nitrogen to become available to the crop before freeze-up,” says Dowbenko. “The rest will be locked up in the granule until spring.”
The theory is that when nitrogen is supplied at the time the crop demands it, nitrogen use efficiency is increased, resulting in increased yield potential. Using ESN may not be the answer for all winter wheat growers, but it does add another option.