Key Issues to Address at Corn Planting

Early planting is a well-known component of successful corn production, since environmental stress normally increases during the summer, reducing yield potential of late-plantings. However, rushing the process is likely to prompt issues that will limit or may even overwhelm the benefits of early planting. We often hurry to get our crop planted in the South because rainfall restricts days suitable for fieldwork during prime planting time. Although corn is an amazingly productive plant generally possessing high seedling vigor, stand variability or other issues will substantially limit yield potential. Corn stand issues are particularly troublesome because it’s growth habit and physiology afford little opportunity to compensate later in the season compared to other crops. Therefore, it is extremely critical to make sure you do a good job and plant when conditions are favorable.

One word that you consistently hear associated with successful corn planting and optimal productivity is “uniformity.”  Scientists, industry, and producers all agree, as new World Record corn producer David Hula states, “Even spacing and emergence are critical to high (corn) yields.” Many of our corn research efforts at Mississippi State have evaluated methods to improve uniformity and demonstrate that using the Corn Verification Program.  Our research evaluated potential impact of planter ground speed and seed metering system on stand variability.  The results showed corn grain yield was reduced 4.2 bu/acre for each mph increase in ground speed from 3 to 6 mph with a standard seed metering system in a John Deere planter.  Retrofitting a John Deere planter with a Precision Planting e-Set metering system increased corn yields an average of 5.9 bu/acre and improved crop response to increasing ground speed by 17%. Obviously, this data shows corn yields can be improved by slowing down, which allows your planter to more precisely space and deliver seed. Indirectly related to this, recent planting date research from MSU and Arkansas show the optimal planting time for irrigated corn productivity is considerably wider than typically perceived. Furthermore, because corn planting intentions are more modest this season, it won’t take as long to plant.  Assimilating this knowledge, we suggest you use a deliberate approach to achieve a high level of precision needed to optimize corn yield potential.

The second part of the “uniformity issue” is seedling emergence uniformity. Our data shows non-uniform emergence reduces corn yield about 30% for each leaf stage delay. The resultant yield reduction will vary depending upon the proportion of late-emerging plants, but definitely result in severe yield loss, which can be just as important as reduced plant population.  Last spring was a vivid example of how challenging conditions can lead to emergence variability and stand issues. Soil conditions, including temperature and moisture content, are the environmental factors critical to achieving a vigorous and healthy corn stand. Cool soil temperature will substantially hinder germination and growth, leading to considerable emergence variability and even distorted development. This retarded growth may allow other issues, including wet soils, seedling pathogens, insect pests, and herbicide injury to also hamper stand development much more than normal.  We also know all too well that soil saturation can limit aeration, kill seedlings, and restrict root development. Therefore, make sure morning soil temperature at a 2-inch soil depth is at least 55 degrees F, which should ensure healthier seedlings, quick germination (within two weeks), and uniform emergence.

Another significant threat to uniform corn stands is our growing population of glyphosate- and ALS-resistant Italian ryegrass throughout the Delta and other row crop producing areas.  Italian ryegrass is extremely competitive with young corn because it is rapidly growing during corn emergence and early development. Additionally, there are no practical herbicide options to control resistant Italian ryegrass after corn emergence. Thus, it is extremely important to completely control Italian ryegrass prior to corn emergence. If you have live Italian ryegrass at planting, you should apply paraquat (Gramoxone SL at 4 pt/acre or 2.67 pt/acre of a 3 lb/gallon paraquat formulation) tank-mixed with atrazine.  Atrazine will not only enhance the postemergence efficacy of paraquat, but it will also provide residual control, which should help limit regrowth and subsequent emergence.  We suggest using 1.5 pt/acre or slightly more atrazine tank-mixed with paraquat. This will allow additional atrazine to be applied postemergence for Palmer amaranth later in the season.