As a lot of our March-planted corn progresses through late vegetative stages nearing tassel, most of the Mississippi corn crop has not generally received any supplemental irrigation. This is a bit uncharacteristic, but certainly no cause for alarm. In fact, moderate or sporadic rainfall and negligible soil saturation during corn vegetative stages relative to normal should improve corn root development and potential productivity in our climate. However, as corn plant size increases, so does water demand, so we will likely face decisions on initiating irrigation soon.
This prompts much conversation about the proper time to initiate irrigation for corn. The simple answer is that irrigation should commence whenever soil moisture becomes limiting. We often see corn leaves start rolling or wilting the first week or more we go without rain and temperatures drastically climb into the upper 80’s, despite plentiful moisture in the soil. However, leaf wilt is not a very reliable indicator of genuine drought stress in our environment. Thus, the key factor to determine crop needs is to make a conscientious effort to evaluate soil moisture throughout the root zone. We should evaluate soil moisture availability using anything from simple methods to state-of-the-art soil moisture sensors to determine whether the crop actually needs more moisture and will respond in a manner that will ultimately enhance crop productivity. Corn root growth and depth increase tremendously during late vegetative stages, as plants develop approximately 75% of root mass. Soil moisture sensors we’ve monitored in numerous Mississippi corn fields confirm root activity progresses from about 12-inches to ultimately 36-inches deep or more during late vegetative stages, if soil compaction and soil saturation do not limit growth. Premature and unnecessary irrigation, which is often the tendency in our region, can definitely retard or delay this corn root development. Of course, excessive irrigation/rainfall and soil saturation will stunt plant growth, reduce corn yield potential and promote nitrogen loss as well. Link to Complete Article