Ugly Corn About to Turn the Corner

The 2024 corn season has created some ugly cornfields around the state. Those fields are about to turn the corner if they have not already. Excessive water, cool temperatures, windy conditions, active slugs and bugs, sidewall compaction, weeds and more created many challenges for the corn planted, especially corn planted earlier. 

Most of the corn is somewhere between emergence and about waist high which can be anywhere from the V8 growth stage (which has eight fully emerged leaves) to about V12. At this time of this writing, about 20% of the corn acres are still in the bag. Perhaps another 10% or more needs planted again. 

Corn fields seem to be either excellent or very poor. For the very poor fields, either the plants are rather small (probably V4 or less) or the corn plants are all over the place. Some fields have corn that is nearly waist high, corn that is stunted and yellow and low areas where corn was completely killed from flooding. 

Saturated soils can cause corn plants to look yellow. Most of that yellowing is from root death and the inability of the plant to take up nitrogen. Those plants need oxygen back into the rooting zone to allow for new growth of roots. Once new roots are developed, the plants will start taking up nutrients again. Plants in these fields may take one to two weeks before they start to look better. 

Saturated soils can cause nitrogen losses, mostly from denitrification, when anaerobic microbes convert the nitrogen into gaseous forms lost to the atmosphere. That nitrogen loss usually is not as high as you would think. Three days of saturation are needed before microbes will be active enough to denitrify. 

Even in fields that have not been saturated, several nutrient deficiency symptoms are evident this year. Sulfur deficiency is more prevalent this year. Historically, visual sulfur deficiency does not translate to yield differences. However, some recent studies in Kentucky have showed yield increases to fertilizer sulfur. No more than 30 pounds of sulfur per acre should be used and foliar applications of sulfur are not effective. 

The earlier-planted corn had more problems with slugs, insects, and seedling diseases. Raul Villanueva wrote an article on slug management for the last Corn and Soybean Newsletter: https://graincrops.ca.uky.edu/sites/graincrops.ca.uky.edu/files/cornsoynewsletter2024vol06issue05_May_final_0.pdf Kiersten Wise wrote an article about seedling diseases in the same newsletter. 

The weather forecast suggests that corn will grow out of this ugly phase in most fields. Once corn gets to about the V6 or V7 growth stages, the plants will actively take up nutrients and start to look healthier. The stress of the weather on the corn before the V5 growth stage likely will have little impact on yield if the plant population has been maintained. 

For those 20% of acres that needs planting, farmers should stay with their selected hybrids and populations for most fields if the corn is planted before June 15. At this point, there is only one chance to get it right and farmers will not be able to replant. As much as possible avoid planting into wet conditions that create sidewall compaction. If done correctly, there is still an opportunity for respectable yields. The corn planted in June will grow very quickly. For example, from June 7, 2024, the weather forecasts that corn will emerge in 5 days in Daviess, Hardin and Boyle counties. The longer term forecast historically suggests that corn will speed through the growth stages thereafter. If there has been 3 or 4 weeks between burndown application and planting, expect to need to apply more herbicide. Consider soil residual herbicides, accounting for what was applied earlier and accounting for crop rotation restrictions.