Excessive rainfall can result in loss of fertilizer and soil nitrogen. This page tracks spring rainfall and identifies ‘danger areas’ that are on track to have widespread problems with N loss and deficiency. This is a serious production and environmental problem that I estimate cost Midwestern corn producers 1.5 billion bushels total from 2008 to 2010.
The final update for Nitrogen Watch 2011 was on July 4. After this time there is a low probability of major N loss due to high evapotranspiration and high rates of N uptake. Maps from this final update show our best estimate of locations that are likely to experience substantial N loss and N deficiency when all N was applied pre-plant. Most of the southern and eastern corn belt is at risk for N deficiency in 2011, including nearly all of Indiana, most of southern Illinois and Ohio, and smaller areas of southeast Iowa and northeast Missouri. Areas farther south are at lower risk due to widespread use of sidedress N applications. I have seen substantial N deficiencies in corn while driving through southeast Iowa, northwest Missouri, and western and southern Illinois this year.
Nitrogen watch for well- and moderately well-drained soils:
| Missouri | Midwest | |
| Jul 3 | Jul 3 |
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| Jun 27 | Jun 27 |
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| Jun 20 | Jun 20 |
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| Jun 12 | Jun 12 |
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| Jun 5 | Jun 5 |
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| May 30 | May 30 |
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| May 23 | May 23 |
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| May 16 | May 16 |
Nitrogen watch for poorly- and somewhat poorly-drained soils:
| Missouri | Midwest | |
| Jul 4 | Jul 4 |
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| Jun 27 | Jun 27 |
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| Jun 20 | Jun 20 |
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| Jun 13 | Jun 13 |
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| Jun 6 | Jun 6 |
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| May 30 | May 30 |
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| May 23 | May 23 |
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| May 16 | May 16 |