It was a couple weeks ago almost every corn field I saw looked about as perfect as it could. Then a little over a week ago parts of most corn fields had areas with corn turning yellow. That is a classic symptom of nitrogen deficiency. Does that mean the nitrogen we applied last fall or early this spring was lost? Jeff Vetch Scientist at the Southern Research and Outreach Center at Waseca said the nitrogen was likely just unavailable until we saw the warmer weather.

Temperatures during April and May were much cooler than normal. Microbes in warm soil convert the anhydrous ammonia which is not water soluble into nitrate nitrogen which is. That is the form that is available to the corn plant. In addition nitrogen that was available in the soluble form may have been in a band deeper in the soil than the corn roots.

Compounding the nitrogen situation was the growth stage of the corn. When corn has two to 4 leaf collars it transitions from nutrients coming from the seed to the developing nodal roots. That too limited the uptake of available nitrogen in the soil as that is the stage that much of the yellow corn was at last weekend when I took this picture. Fortunately with all the heat late last week and over the weekend the yellow corn is looking much better.

Talking with Jeff Vetch Scientist at the Southern Research and Outreach Center at Waseca he said corn with yellow stripes on the leaf is a symptom of sulfur deficiency which he has seen this spring too. Click on the link and listen to Jeff's comments on yellow corn.