Puny Corn Around the State

Corn May 23, 2017, Fayette County, KY, Corn at V3; 100 lb N/A applied at V1

Chad Lee, Director, Grain and Forage Center of Excellence, University of Kentucky

Farmers, crop scouts and county extension agents around Kentucky are reporting fields of corn that look yellow and/or striped and otherwise puny. A lot of these symptoms are most likely related to weather. Some have other problems.

1.          Saturated soils are causing some of these symptoms. The roots are not very big on young corn plants and soaked fields can cause rapid die-off of those small roots. Corn in these fields need some air (oxygen, more specifically). Until oxygen returns to the soil and new roots can grow, the corn will continue to look yellow. Some sunshine can help as well, after air has returned to the soil.

2.          Sidewall Compaction. When planting began this year, I expected numerous fields to have this problem. We have had limited calls on this issue. Sidewall compaction limits root growth. Those roots could stay stunted the entire season, causing major yield reductions. In other fields, the moisture actually helps roots break through. There are not any good management options now.

3.          Everything is fine… but the weather. The majority of the fields fall into this category. Soil pH is good; N, P, K, and Zn are adequate. There is no sign of soil compaction. Stands are uniform. Weeds are controlled. The plants are simply yellow, or striped, or purple, or all the above. In most of these cases, the young plants just need a little sun and warmth.

Corn May 19, 2017 Hardin County, Rye Cover Crop. Matt Adams, Extension ANR Agent

4.          There is something else wrong with the field. Insects, diseases and poor weed control (or poor cover crop removal) could all be competing with the young corn crop and causing yellow symptoms. All these scenarios assume that soil test values and/or fertilizer applied is adequate for optimal yields. If P, K, or Zn are not sufficient, then we could have problems there.

Corn less than V6 growth stage has taken up less than 8 pounds of N per acre on average. A very small dose of N could improve green color, but you need some sun and air in addition to the N to improve the color. By the time you get the sun an air, the N already in the soil should be available to help. These research fields follow category 3, where everything is fine but the weather.

We do have some research corn with sulfur (S) where one hybrid is showing a greener color with the S application. We have another 4 to 5 hybrids that do not show any darker green from the S application. Previous studies with sulfur have not resulted in consistent yield increases. But, with that one hybrid, you can see why someone would recommend S simply to reduce the headaches of looking at yellow corn. For other 4 to 5 hybrids, the headaches of looking at slightly yellow corn persist, even with sulfur.

So, the weather is affecting the color of the corn crop in every field. In most cases, we just need some sun and warm weather. But, proper scouting will help us know for certain if any other issues are present.

We will try to provide some updates as we go through this spring.