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Corn+Soybean Digest

High Levels of Carryover Nitrogen Could Save Money for Ag Producers

Farmers whose yields have been thinned by drought conditions in recent years may find something valuable in their soil, but they’ll have to dig to find it, says Dave Mengel, Kansas State University Research and Extension soil fertility specialist.

"Producers should consider taking profile soil samples to test for available nitrogen in their soils," Mengel says. "We’re finding that many fields have high carryover levels of available nitrogen, and this reduces the amount of nitrogen that needs to be applied for their wheat crop this fall, sometimes by up to $20/acre or more."

A profile nitrogen (N) test should be taken to a depth of two feet, Mengel added. The samples must be taken before any N fertilizer is applied and before the crop is planted. If the samples are pulled after fertilizer has been applied, it will give misleading results, he explains.

A survey of profile N tests taken this summer in McPherson County has revealed carryover N levels of anywhere from 0 to 125 lbs./acre, says Dale Ladd, K-State Research and Extension agent in McPherson County.

"These are all based upon a 24-in. deep soil sample where I took 12-15 probes per field," Ladd says. "Sampling deep is hard work, and you may want to have a consultant or fieldman do the job. But it’ll be well worth the effort to have the information."

K-State is conducting a survey of profile N levels in Kansas this year, Mengel says. The survey is being conducted through the county Extension offices. Each office has been offered the opportunity to submit samples from up to 10 fields being planted to wheat in their county.

"We’re requesting both a 0-6 and 6-24 in. sample from each field," he explains. "Producers who have an interest in participating in this survey should contact their local county (or district) Extension office soon. Samples should be collected before fertilizer is applied and before the crop is planted. Since nitrate is dynamic in soils, the sample should either be air-dried or frozen immediately. Don’t leave the sample at field moisture levels in a warm location for more than a day before sending it in for analysis."

With the potential for higher than "normal" nitrate-N carry over in many fields, and high N fertilizer prices, the profile N test may well pay big dividends for Kansas wheat growers this fall.
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