To get the biggest bang for the buck out of nitrogen (N), band it in the soil as close to when the crop is going to need it as possible. That boils down to soil banding at time of spring seeding.
That is the general, overriding recommendation from two leading soil fertility specialists in Western Canada when asked about how to maximize nitrogen use efficiency. In general, banding in the spring just before or at seeding will reduce or eliminate the risk of nitrogen losses, and make nutrients available to the crop when it is needed.
However, that doesn’t mean there aren’t other effective options, say Rigas Karamanos, a long-time soil fertility specialist with Westco Fertilizers and now Viterra, and Cynthia Grant, a research scientist with Agriculture and Agri-Food Canada in Brandon, Man.
Banding, broadcasting, split-applications, and using delayed and slow release nitrogen products can all work under specific circumstances. What’s your timing, what are the soil moisture and temperature conditions, what form of nitrogen are you using, and what are your machinery or application limitations? These questions all factor in to what is right for your farm operation.
While application at time of seeding is recommended, many of you prefer fall application. In that case, Karamanos says the ammonium form of nitrogen is better than the nitrate form. Products such as anhydrous ammonia and urea are more suitable for fall banding than a nitrate product because they convert to ammonium and stay in the soil longer — if there isn’t high moisture. A nitrate liquid product is more at risk of being lost through denitrification or leaching.
For fall timing, Karamanos says it has long been viewed that late fall application of products is best, but his recent research showed banding nitrogen in mid-September, mid-October and early spring shows no significant difference in nitrogen loss between the three dates. There might be a greater risk of nitrogen being lost through denitrification if applied in mid-September if there is moisture. But on “well drained soil” there appeared to be no major difference.
Banding is preferred, as long as the nitrogen gets under a layer of soil. But how or exactly where it is banded isn’t a big issue, says Karamanos.
Nitrogen is very mobile in the soil, so it and the crop roots will find each other.
So as long as there is some separation between seed and nitrogen, the risk of crop injury or ability of roots to find nitrogen doesn’t appear to change much whether the fertilizer is placed below, to the side, above, or between the seed rows.
“Distance is not a big issue, and there appears to be no advantage to have nitrogen nearer or farther from the seed row,” says Karamanos. “Nitrogen is very mobile in the soil, and provided it is applied at the recommended rate, the crop will find it.”
With a liquid nitrate product, for example, provided there is at least one-eighth inch separation from the seed, he says research shows as much as 70 to 80 pounds of N can be placed in the seed row without crop injury. But a minimum one-eighth inch separation is important.
With a urea product for example, he has banded as much as 220 pounds of N at seeding, without injury, provided the fertilizer is a minimum one-inch below or to the side of the seed.
Split applications of nitrogen fertilizer have a limited fit, as far as Karamanos is concerned. He says research shows applying all fertilizer at time of seeding produces optimum yields and has the best economics. “Top dressing crops on the Prairies is a high risk proposition,” he says.
Wheat has to be top dressed before the four-leaf stage and canola before the six-leaf stage. And after top dressing, rain is needed to carry nitrogen into the soil.
Research comparing all spring-applied fertilizer to a split application show yields are about the same. “So if the yield is about the same, what is the benefit,” he says.
Karamanos does see a split-application working as an emergency treatment, where, in error, a low rate of fertilizer was put on at seeding and then the skies open and conditions are excellent, he says. “But as a planned practice it is high risk.”
The worst-case scenario for nitrogen loss is to apply a liquid nitrate product on a direct-seeded or zero-till field. Without some type of incorporation, the microorganisms will consume most of the nitrogen as it breaks down crop residue.
Broadcast fertilizer does have a fit with some crops such as forages and winter wheat, where banding or incorporation is not an option. One of the best combinations Karamanos has found for broadcasting nitrogen to forages, with minimal loss, is to use urea treated with Agrotain. In his research, ammonium nitrate worked about equally as well, but that product is no longer available.
Cynthia Grant advises that UAN fertilizer can also be used in forages, but recommends it be dribble band applied, rather than sprayed on the crop.
The key to applying the correct rate of any fertilizer, is the age old advice — follow a soil test recommendation, says Karamanos. He does caution there can be wide variation in how labs formulate recommendations. Make sure the lab you use calibrates a recommendation using a local database relevant to your area, he says.
And nitrogen use calculators are also useful for helping producers determine rates and fertilizer economics. Farmers can go to the
Internet and search for nitrogen use calculators for their province. Alberta has a program called AFFIRM, the Canola Council of Canada has an on-line calculator and Manitoba has a calculator that can be found through the Manitoba Agriculture website. The direct link is www.gov.mb.ca/agriculture/soil-water/nutrient/fnm04s00.html
SLOWING NITROGEN DOWN
Where do products such as Agrotain and Agrium’s ESN product have a fit? Agrotain, in liquid or now a new dry formulation, is a chemical treatment applied to urea or added to urea-ammonium nitrate (UAN). Agrotain slows the conversion of urea to ammonia, says Grant. It keeps urea in the urea form longer.
ESN (Environmentally Smart Nitrogen) is urea with a polymer coating. “ESN is urea in a plastic bag”, Grant says, putting it in simple terms. The coating is a physical barrier that opens up with warming temperatures and moisture, allows for controlled release of nitrogen into the soil.
Agrotain is a chemical inhibitor, which delays for about two weeks the activity of enzymes that breakdown nitrogen. ESN is a physical barrier, which slows the release of the nitrogen over more of the growing season.
Both Agrotain and ESN have a benefit when used as seed placed products to reduce the risk of seedling damage.
If fall banding, these products also have a good fit, delaying release of nitrogen until spring. They also works well in a broadcast application to fertilize winter wheat in the fall.
With the growing conditions and climate over most of Western Canada, Grant isn’t sure if the slow nitrogen release feature of ESN has widespread value. “Generally with our growing conditions we are dealing with dry conditions rather than too much moisture,” she says. “And losses of nitrogen through leaching and to the atmosphere are not that great with a conventional urea fertilizer. It is not that the product doesn’t work, it’s just that I’m not sure it is needed.”
Lee Hart is a field editor for Grainews in Calgary, Contact him at 403-592-1964 or by email at [email protected]