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Take nitrogen stalk tests now

By Staff | Sep 18, 2016

DR. JIM FREDERICKS, outreach and education advisor for AgSource, based in Ellsowrth, calls up stalk testing data on his computer. Fredericks said within three weeks of corn reaching maturity, or black layer, is the prime time to take nitrogen stalk tests. The results, he said, will show producers how they did in managing their nitrogen during the growing season, so they any make any needed changes during the 2017 growing season.

ELLSWORTH – With close an estimated 29 percent of Iowa’s corn crop reaching black layer, according to the National Agricultural Stateistics Service on Tuesday, this is an ideal time for farmers to determine how well they did with their fertilizer program.

A nitrogen corn stalk test will reveal if there was too much or too little nitrogen in the field during the growing season.

According to Dr. Jim Fredericks, outreach and education advisor for AgSource Laboratories, in Ellsworth, the key time to test corn stalks within three weeks of corn reaching black layer, which is considered a mature crop and safe from frost.

“Black layering is already happening in some fields,” he said, “so the time to do the checking is now.”

During those three weeks, the stalk test will show if the crop had enough, too little, or excessive amounts of nitrogen.

“Black-layering is already happening, so the time to do the checking is now.” —Jim Fredericks AgSource outreach and education advisor

This knowledge, Fredericks said, “Won’t help with this year’s crop, but will let you know how you did and what to do next year.”

The economic impact of the test is big, he said, since fertilization is one of the most expensive inputs during the season.

The test can show, for example, if too much nitrogen was applied this year. If so, then perhaps less will be required for the next corn crop.

Fredericks said AgSource, at 1701 Detroit St., in Ellsworth, is one of several labs in the region where the corn stalks can be tested.

According to Bob Streit, an independent crop consultant, in Ames, other stalks can also be sent to Frontier Lab, in Clear Lake; Minnesota Labs, in Nevada (Iowa); Midwest, in Omaha, Nebraska; and Ward Labs, in Kearney, Nebraska.

Independent studies at Iowa State University and Purdue University both confirm the validity of the stalk testing, Fredericks said.

At the lab, the stalks are dried, ground and analyzed for nitrate concentrations in parts per million, or ppm. The results are shown in three categories.

1). Deficient: 0-700 ppm. Corn could habe yielded higher with additional N. The problem could have been application failures or just too little applied or applied to far ahead of planting.

This needs to be weighed against other factors such as weed control, low pH or compaction which can inhibit N uptake.

2). Adequate: 700 to 2,000 ppm. The goal is to consistently have field tests in this range. It shows successful N management and that profits are maximized in this respect.

3). Excess: 2,000 ppm or higher. More N was applied than was needed for corn growth. Aside from economic loss, it may indicate N loss into the environment. This information must be weighed against other factors including drought stress, which can result in an accumulation of excess N in the corn stalk.

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