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Fertilizing wheat? Know before you go

What a difference a few inches of snow can make.

A month ago, a lot of wheat farmers were wondering whether they'd have enough of a stand to justify spending the time and money on inputs like fertilizer once the crop started nearing the end of dormancy. Then, along came Mother Nature. A few snows -- one that brought in excess of a foot of snow to parts of the parched Plains, injected a new optimism for farmers like Wayne Jeardoe, who farms near Concordia in north-central Kansas. He was in Florida for 2013 Commodity Classic last week, but said his area's recent snowfall had him ready to roll when he returned to the farm.

"When I get home, I'll be putting on 20 pounds of nitrogen (per acre) and spraying my wheat," he said.

He's not alone. More farmers are looking at applying fertilizer especially since the snow fell on the wheat, a lot of which was in dire condition heading into dormancy last fall. But, applying fertilizer on your wheat heading into spring shouldn't be done without making sure you're not overdoing it, says Purdue University agronomist Shaun Casteel. Your fields may already have plenty of residual nitrogen there that's been locked up by the dry conditions and is just now ready to move to the crop.

"Wheat planted in the fall has an advantage in that it will accumulate some nitrogen prior to dormancy. Wheat's primary advantage is the established root system that can take up nitrogen in the early spring before corn is even planted," Casteel says.

While that's an advantage in the sheer volume of the nitrogen you'll likely need to apply, you'll need to make certain you're putting down the right amounts in the right spots in the field. That's where good, comprehensive soil testing comes in. But, what comprises "comprehensive?"

"Take surface samples from the tillage layer (4 to 8 inches) or the 1-foot soil depth. Take subsoil samples to a depth of 2 feet for determination of available NO3-N. If the field has been in no-till, reduce the sampling depth to the tillage layer," says Colorado State University agronomist Jessica Davis. "A good sample is a composite of 15 to 20 soil cores taken from an area uniform in soil type. This number of soil cores is especially important in sampling fields where P fertilizers were band applied in previous years. Sample areas with major differences in soil properties or management practices separately."

And, when you start sampling for carryover nitrogen levels, also consider the growth stage of the wheat plants. Once the crop's out of dormancy, it will likely start taking up those nutrients fairly quickly. So, make sure you're sampling at the right time.

"Most of the nitrogen remaining in the soil at the end of the season is a highly leachable form of nitrate. Nitrate is repelled by soil particles, so it moves downward with water," says Purdue University Extension agronomist James Camberato.

Adds Casteel: "Sampling wheat at the proper growth stage is important because the tissue concentration changes rapidly with growth during this time period. The only guidelines for adjusting nitrogen fertilization are at Feekes 5, which is an ideal time to fertilize from crop production and nitrogen efficiency standpoints. Unfortunately, this timing is risky in wet soils and is later than when many fertilize wheat."

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