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Corn fields throughout Minnesota usually look much better than they do today (June 13). It’s difficult to find the right words to provide a good description of the appearance. In general, corn having a light green color appears in the same field with corn that is darker green. The light corn has stripes running the length of the leaves. The veins are green while the interveinal areas are light green. Is this serious? Will yields suffer? What caused this condition? Will it improve? These are some of the many questions that corn growers and those who advise them are asking.

The striped corn can be the result of:

• nutrient deficiencies (nitrogen and/or sulfur)
• cool nights
• lack of sunshine
• cool daytime temperatures
• saturated soils
• all of the above

It’s important to realize that the stripes are the end result of one or more factors. Most, if not all, of these factors are beyond the control of the corn grower.

The role of plant nutrients.
If the photographs of nutrient deficiencies are examined, many would reach the conclusion that the corn is deficient in magnesium (Mg). Except for very acid sandy soils, however, a deficiency of Mg has not been documented in Minnesota. Therefore, a deficiency of Mg can be eliminated as a cause of the problem.

Corn grown on sandy soils without the addition of sulfur (S) to a fertilizer program will show the same symptoms (striping in the leaves). If S was not applied and the soils are sandy, the stripes could be caused by a shortage of this nutrient. Deficiencies of S will not appear where soils are not sandy. If a shortage of S is suspected, a broadcast application of 75 to 100 lb. per acre of 12-0-0-24 is suggested.

To make life more confusing, the striping can be the result of temporary shortages of nitrogen (N). If a sidedress application of fertilizer N was planned, sidedress as soon as soil conditions permit. Corn that is striped and growing on sandy soils can be deficient in both nitrogen and sulfur. It is not possible to separate deficiencies of N and S for sandy soils. For this uncertainty, broadcast and incorporate a combination of 46-0- and 21-0-0-24.

When thinking about the causes of the striping, the combination of cool nights, lack of sunshine, and saturated soils cannot be ignored. Prior to Saturday (6/12) and Sunday (6/13), there were few days with sunshine and warm temperatures. As a result, the corn was not going through a normal metabolism and photosynthesis was suffering. It’s logical to conclude that the striping was a consequence of these environmental conditions.

The warmer and drier days of this past weekend (6/12 and 6/13) and the forecast of drier weather should help. If the light green, striped corn persists, use the scorecard described in the previous newsletter to help determine if additional fertilizer N should be applied. An application of 40 to 50 lb. additional N per acre may certainly be justified. Hopefully, this wet weather pattern may change to something more typical of Minnesota.

There is a high probability that the striped, light green corn has not hurt yield potential if supplemental fertilizer N can be applied. Research conducted at the University of Nebraska leads to the conclusion that nitrogen fertilizer can be applied up to tasseling. Yields begin to decline if part of the fertilizer N needed is applied after silking.