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Considerations for Corn Planted Under Wet Conditions

Recent rains have created very wet soil conditions throughout most of Kansas. Some corn remains to be planted (about 59 percent as of May 5th). Weekly and monthly precipitation summaries are presented in Figure 1. The Kansas Mesonet soil moisture network reflects the saturation at both the shallow (2 inch) and the subsoil (10 inch) depths (Figure 2).
 
Figure 1. Weekly precipitation summaries for May 3 – May 9 (upper panel) and monthly for April 1-30, 2019 (lower panel), for Kansas.
 
 
Figure 2. Soil moisture at 2 inches (upper panel) and 8 inches (lower panel) as of May 9, 2019 (KS Mesonet).
 
The forecast for the coming week is showing potential for drier conditions towards the end of the period, starting about Wednesday May 15 and continuing through Saturday May 18 (Figure 3). The concern will be whether soils will dry out rapidly enough for producers to plant their remaining corn acres and begin soybean planting in eastern and central Kansas.
 
 
Figure 3. 48-hour precipitation forecast. Upper panel, May 13-14; Lower panel, May 15-16.
 
What should producers expect if they plant corn into soils that are too wet, and what can they do to minimize any problems?
 
It is best, of course, to allow time for the soil to dry adequately before tillage or planting operations if at all possible. Wet conditions will make the soil more susceptible to compaction. Tilling some soils when they are too wet can produce large, persistent clods, complicate planting, reduce herbicide effectiveness, and destroy the seedbed. Also, compaction can occur in the seed furrow itself, restricting proper root development (also diminishing nutrient accessibility) and early plant growth.
 
If soils remain or become unusually wet after the corn has emerged, corn may look sickly for a while. Saturated soils inhibit root growth, leaf area expansion, and photosynthesis because of the lack of oxygen and cooler soil temperatures. Yellow leaves indicate a slowing of photosynthesis and plant growth. Leaves and sheaths may turn purple from accumulation of sugars if photosynthesis continues but growth is slowed. For further details on these points, check the companion article in this issue of the eUpdate: “Effect of standing water and saturated soils on corn growth and yield.”
 
If wet weather conditions persist for more than a week, corn emergence will be delayed and seedlings will be more vulnerable to the presence of insects and diseases. Uneven corn stands likely will be greater when planting in cold and wet soils. This situation will directly affect plant-to-plant uniformity (Figure 4), impacting potential yield.
 
Figure 4. Uneven corn stands.
 
Unfortunately, the longer 8 to 14-day outlook is for a wetter-than-normal pattern (Figure 5). This does not exclude dry days during the period, but even light amounts are likely to continue the problem. Warmer-than-normal temperatures and sunshine would allow for quicker drying of the soils.
 
Figure 5. 8-14 Day Outlook (May 17- May 23, 2019) issued May 9, 2019.