S – for Sep. 2, 2010

hould you be applying nitrogen when you plant your winter

wheat?

It turns out there’s no right

or wrong answer.

Twenty to 40 pounds of phosphorus with the seed is a no-brainer, says John Heard, a soil fertility specialist with Manitoba Agriculture, Food and Rural Initiatives (MAFRI). The nutrient is necessary for establishing a good crop in the fall better able to survive a tough Manitoba winter. It also helps winter wheat recover from winter injury in the spring.

But applying some or all of the nitrogen a winter wheat crop needs in the fall instead of the spring is less straightforward. There are possible risks, but potentially rewards. The outcome depends a lot on the weather.

NEW REGULATIONS

And there’s a new twist – provincial government restrictions. Starting next year a new Water Stewardship regulation prohibits Manitoba farmers from applying fertilizer before April 10. The goal is preventing nutrients from running off frozen fields. But some springs, including this one, many winter wheat fields are thawed before April 10 and ideally that’s when nitrogen should be applied.

According to Heard, nitrogen needs to go on winter wheat early, before the crop appears to be actively growing. Farmers need to dig up some of the plants to see if they are alive. Look for new white root shoots.

It’s usually more efficient to apply nitrogen in the spring closer to the time when the crop can use it. There’s a risk fall-applied nitrogen will be lost through denitrification (converting to a gas and escaping the soil), or leaching, especially if the fall is warm and moist.

Fall-applied nitrogen can be lost in the spring too because of wet conditions. Farmers can cut some of the risk in the fall by applying nitrogen in the ammonium form and mid-row or side banding it, Heard said.

But wet fields can also prevent farmers from applying nitrogen in the spring. And spring-applied nitrogen can also be lost or stranded if it’s too dry.

“You’re caught between a rock and a hard place,” Byron Irvin, a researcher with Agriculture and Agri-Food Canada at the Brandon Research Centre said.

CAN BE EFFECTIVE

His research shows fall-applied nitrogen can be effective, but there’s risk. During one wet year at a trial in Brandon fall-applied nitrogen was lost and the crop yield was cut 20 per cent, he said.

Irvin believes farmers in the Red River Valley are at the highest risk of losing fall-applied nitrogen because their fields are so often wet.

“I don’t have the data to suggest you should be using one of these protected nitrogen products there, but if I was farming there I probably would just do it because their risk of losing it is much higher than most of us (in the drier areas).”

Protected nitrogen fertilizers like ESN, Super Nitrogen and Agrotain cost more, but should be considered under higher-risk conditions.

“It’s like having insurance,” Irvin said. “If you’re living on a flood plain it’s maybe not a bad idea to have flood insurance.”

Some of the other advantages of fall-applied nitrogen, if it isn’t lost, include reduced application costs and sometimes cheaper nitrogen.

BREAK GREEN BRIDGE

A week or so before or after September 1 is the ideal time to sow winter wheat, said Pam de Rocquigny, MAFRI’s provincial cereals specialist. The goal is a crop that goes into winter at the three-leaf to tillering stage with good root and crown development.

To prevent wheat streak mosaic, a viral disease that can reduce winter wheat yields, the so-called green bridge needs to be broken at least two weeks before seeding, she said.

The virus is transmitted by wheat curl mite, which can’t live more than 10 days in the absence of living grassy plants. However, the mites can be spread from field to field by wind so the risk can’t be eliminated completely.

SHALLOW SEEDING

Don’t seed winter wheat deeper than a half inch, de Rocquigny said.

“The deeper you go the plant has to use that much more energy to get up and get the crown developed,” she said.

“Keep in mind that soils are cooler in the fall and with less evaporation off the surface light rains can soak into that top inch of soil and be accessed by the seed. As little as a third of an inch of rain is often enough to successfully establish winter wheat.”

Ideally winter wheat should be seeded into standing stubble. It catches snow insulating the soil preventing winterkill.

Seeding into “eligible stubble,” is also a prerequisite for insuring winter wheat through the Manitoba Agricultural Services Corporation (MASC).

STUBBLE RULES

MASC says to qualify for a Stage 1 indemnity, winter wheat can only be sown into one of the following stubbles: tame hay, tall fescue seed, canola, rapeseed, barley, wheat, oats, mixed grain, triticale, flax, mustard, fall rye, canaryseed, ryegrass seed, timothy seed, alfalfa seed, hemp, sunflowers, corn, borage, millet, corriander, sorghum, sudan grass, or buckwheat.

Winter wheat not sown into stubble is eligible for crop insurance coverage the following growing season if it survives the winter.

To qualify for crop insurance coverage winter wheat must be planted between Aug. 20 and Sept. 15. The extended seeding deadline, with reduced coverage, is Sept. 20.

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About the author

Reporter

Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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