Due to drought, much of the nitrogen fertilizer applied to corn last year was not used. Some producers may have hoped to use this nitrogen with another corn crop planted this year. This possibility looked reasonable all through the fall of 2012, but is questionable now. A small number of deep soil samples Scharf and others took this spring have revealed less nitrogen than expected.
Nitrate has moved down
"We found almost zero nitrate in the top foot, but about 20 pounds of nitrogen per acre as nitrate in the second foot and another 20 in the third foot," Scharf said. "In short, the nitrate has moved down, and it seems likely that a good bit has moved below 3 feet deep. I wouldn't take a credit for last year's nitrogen unless it was backed up by a deep soil test."
Soil tests to measure residual nitrogen are available through the MU Soil and Plant Testing Laboratory, through local extension centers or through commercial vendors. Before planting corn, farmers should take the time to get their soil tested.
For information on how to interpret soil test results, MU Extension guide G9177, "Preplant Nitrogen Test for Adjusting Corn Nitrogen Recommendations," is available for free download here.
Information also is available from Scharf here. Precipitation maps are available at the link for "N Watch 2013," a tracking tool begun in 2009 to help producers make assessments about nitrogen loss in certain regions of the state.
Source: University of Missouri Extension
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