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Pioneer Talks Crops
Causes For Field-To-Field Yield Variation
GREG PFEFFER
DEXTER, MO.
Welcome to DuPont Pioneer Talks Crops. This information is provided by the Pioneer agronomist serving your community.
Corn harvest in the upper mid-south is now in full swing, and so far the yields coming in are well above average. Several growers have commented that it may be the best corn crop they have ever had. However, there are some growers who have noticed some of their fields may not be yielding like the rest. We have always received calls like this, and often times it is difficult to diagnose these issues at harvest, but there are some common themes that have emerged.
Nitrogen a Must
Nitrogen (N) management has been a major key to high yields this year. The best yielding fields are those that had a lot of N applied. This makes sense in a good production year. However, the best yielding fields not only had a lot of N applied, but also had good application timing. Late-season N application is quickly becoming a must for growers who are growing corn in the delta on lighter sands and heavier clays where nitrogen loss is more likely. This application method also works well in years where irrigation is heavy.
Several growers applied nitrogen two weeks prior to tassel this year in an attempt to provide better nitrogen utilization during critical growth stages. It appears to have paid off in a major way. This is because we had above-normal rainfall early in the production season that allowed preplant nitrogen to either leach or denitrify. Thus, the late-applied nitrogen would help “make up” for these early-season losses.
Watch for Disease
Disease pressure in corn is high this year, but the disease has set in fairly late in the production year. It appears that northern corn leaf blight is having some impact on corn yields on sensitive hybrids. Most of the leaf blight set in late enough to cause minimal yield loss, but in some hybrids more susceptible, the yield losses could be higher. Later-planted fields may not be as fortunate.
Soybeans look really good right now, but just like the corn, there appears to be a higher level of disease pressure. Sudden death syndrome, bacterial blight, and frogeye leaf spot are common diseases in soybeans right now. Frogeye leaf spot has become resistant to strobilurin fungicides, so this disease may be something to watch out for in the future. Be sure to choose varieties with stronger genetic tolerance to frogeye leaf spot for best results.
We have found some fields with soybean aphids this year as well. We are even seeing economic thresholds of this pest. The University of Missouri recommends treatment at the presence of 250 aphids per plant from R1-R5. It is not recommended to treat once R6 has been reached unless the crop is stressed. Insect pressure overall has been low, but continue to watch for insects in double crop soybeans.
Here’s to a safe and rewarding harvest! ∆
GREG PFEFFER: Agronomist for Pioneer, Dexter, Missouri
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