Agronomy Talk

Agronomy Update

NE Illinois and NW Indiana: Soybean Emergence Issues and Sulfur Deficiency in Corn

Published on Friday, May 30, 2014

Soybean Emergence Issues
A large amount of soybeans were planted throughout the area May 7-12. Unfortunately, on May 14 the weather turned unseasonably cool and wet, with daily high temperatures only reaching the 50s for four consecutive days. Some even woke up to snow on the ground May 16. 4” soil temperatures at 10 a.m. dipped below 50F across much of the area on May 17.

This cool, wet period presented emergence challenges due to multiple reasons. Excessive rainfall led to a crusted soil surface in some areas as beans were starting to emerge. The extended cool, wet period also promoted Pythium seedling blight and caused reduced stand. One of the most common causes of seedling injury and death I have seen in the last 10 days has been from pre-emergence application of PPO-inhibitor herbicides within a week prior to the cool, wet conditions. This class of chemistry includes popular products in the Authority, Valor and Sharpen families.

These are excellent weed control products in any soybean system, however crop safety can sometimes be a concern. The product labels of these herbicides contain crop tolerance statements such as “crop injury may occur under stressful growing conditions (e.g. extreme hot or cold weather, excessive moisture, high soil pH, etc.).” The conditions were stressful enough to slow plant growth and negatively impact the soybean’s ability to metabolize the herbicide. Some fields have had a combination of herbicide damage and Pythium seedling blight. These often can be difficult to diagnose from each other.

Early symptoms of PPO herbicide damage often include necrotic spots on the undersides of the cotyledons, as well as significant scarring of the hypocotyl arch area (“neck” or “crook”). Soybean seedlings will normally survive if their hypocotyl arch remains firm and healthy, and the cotyledons remain green. Seedling death will not occur unless a significant amount of scarring leads to brown, rotten tissue. Although the Escalate™ yield enhancement system helps protect against seedling fungal pathogens, no seed treatment is 100 percent bulletproof under extreme conditions.

If you have not yet done so, be sure to assess your soybeans fields for adequate population. Most agronomists agree that a consistent, uniform stand near 100,000 plants per acre is adequate for maximum yield under most conditions. 



Necrotic “spotting” of soybean cotyledons from a PPO-inhibitor herbicide followed by an extended cool, wet period.


Plant death resulting from the combination of Pythium seedling blighand a PPO-inhibitor herbicide followed by cool, wet conditions.

Sulfur Deficiency in Corn
Sulfur is an essential nutrient for crop production. Historically, however, sulfur has not been a common component of crop fertility programs. Sulfur has naturally been supplied through atmospheric deposition, manure application, and mineralization of organic matter. With less deposition from cleaner air and fewer livestock operations, natural sulfur supply has been reduced and mainly limited to mineralization. Under cool conditions, mineralization of organic matter is slow.
Recent data from Midwest states suggests a high yielding corn crop removes 15-20 lbs./A. of sulfur. Under normal conditions, every one percent organic matter will supply 2-3 lbs./A. of available sulfur annually. Therefore, a soil with four percent organic matter may only be able to supply about half of the sulfur required. Many growers have started to see benefits of adding sulfur to their crop fertility program. This week, I began seeing sulfur deficiency in corn. See picture below. Notice the “striping” appearance of the leaves from interveinal chlorosis as a result of sulfur deficiency.



   Sulfur deficiency symptoms in young plants on May 28, 2014. Notice the interveinal chlorosis.




If manure is not available, there are many effective fertilizers available to address sulfur needs. Some of the most common sources of granular sulfur in our area include calcium sulfate aka gypsum (0-0-0-16S), ammonium sulfate (21-0-0-24S), and MESZ (12-40-0-10S-1Zn). Check with your local fertilizer supplier for folilar nutrition products containing sulfur, as well as availability and pricing.

Nitrification Inhibitors for Sidedressing Nitrogen (N)
Many growers are or will be sidedressing corn shortly. One question we often get this time of year is, “Do I use a nitrification inhibitor?” As is often the case, it is not an easy answer. The probability of response depends on many factors including soil type, drainage, tillage, form of nitrogen (N) used, and weather.

Here is a list that will provide the greatest chances for crop response to a nitrification inhibitor:

--- Poorly drained soils - With poorly drained soils the chance of denitrification is higher, increasing N loss. Therefore applying an inhibitor can keep nitrogen in the ammonium form a little longer.

--- Sandy soils - Sandy soils or lighter soils increase the probability that nitrogen will be leached from the root zone so nitrification inhibitors often help in this situation.

--- No-till - Corn planted into no-till situations have generally seen the greatest response to nitrification inhibitors (especially preplant). Acccording to the National Corn Handbook, 82 percent of studies have shown a positive increase with an average yield bump of 13 percent.

--- Dribbling UAN or spreading urea on the surface - A certain percentage of UAN and urea can volatilize, especially if there is not a rainfall event soon after application. If UAN or urea is applied to the surface, you have a better chance of seeing a crop response with inhibitors.

--- Sidedress corn early - The earlier you sidedress corn the greater the probability of response. If your corn is at the V2-V3 stage, then N inhibitors have a greater chance of paying off since very little N has been taken up at this time. If you wait until the V5-V8 stage, corn will actively be taking up between 4-8 lbs of N per day and inhibitors probably won’t provide a return.




Heavy rainfall soon after application - Storms pop up all the time in Illinois and Indiana. If we get a heavy rainfall soon after application, the chance of seeing a crop response is greater. The opposite can be true, however. If we turn dry and N is kept in the upper portion of the soil profile (because of the inhibitor) there can be a yield loss.

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Chad Kalaher
Chad Kalaher>

Chad Kalaher

Beck’s Hybrids team sales agronomist for 22 counties in NE ¼ of IL and 7 counties in NW IN. Raised on grain and livestock farm in southern IL. B.S. Agronomy 1995 – University of Illinois, M.S. Weed Science 1997 – North Carolina State University. Previous positions in seed industry as researc

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Full biography

Beck’s Hybrids team sales agronomist for 22 counties in NE ¼ of IL and 7 counties in NW IN. Raised on grain and livestock farm in southern IL. B.S. Agronomy 1995 – University of Illinois, M.S. Weed Science 1997 – North Carolina State University. Previous positions in seed industry as research agronomist, district, and regional sales manager.


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