As we near the end of May, our earliest planted corn in the state is approaching tassel (VT) and reproductive growth, and our latest planted corn is near the V5 growth stage. Top/Side-dress nitrogen applications are now on most producers’ minds and actively going out where we can apply in between rain events. A few things to keep in mind over the next few weeks.
How late can I apply nitrogen and see a benefit? Our general recommendation is to end all nitrogen applications on corn by the R1 growth stage or when silks begin to brown. At this point, the majority of the nitrogen needed for the crop to grow and develop has been taken up (around 80%), so applying large amounts of N at this time may not be utilized and will not likely increase yield.
When should I start top/side-dressing on corn? During the development of corn, ear initiation starts around the V5 growth stage (~12 inches tall). Nitrogen demand on corn also begins to ramp up at this time, therefore, it is common for the majority of nitrogen to be applied around the V5 growth stage. In high-yield situations (often irrigated), splitting nitrogen in multiple applications can help ensure that nitrogen use efficiency is improved, getting the fertilizer to the crop.
How much nitrogen does my corn need? In the Corn Production Guide, our fertilizer recommendations are based on the yield goal. The higher the intended yield goal is, the higher the nitrogen recommendation. A good rule of thumb is that around 1.1 lbs. of N per bushel of corn yield goal is needed. For example, you would need to apply 110 lbs. of N for a 100-bushel yield goal.
Irrigating Corn in SC: Corn is our most heavily irrigated row crop in South Carolina due to yield response from timely irrigation and risk mitigation. Water demand in corn increases from the V4-V5 growth stage until it peaks around tassel. As ear formation begins, water demand remains high and then tapers off at maturation. The key takeaway when irrigating corn is that water demand is greatest at tassel, so if you have the ability to irrigate and we are not receiving adequate rainfall during and around tassel/ear formation, irrigation is recommended. Water use at this time is around 2 inches per week. If we are not receiving rainfall, approximately 0.3 inches of water needs to be applied per day or 1 inch every 3-4 days to meet the demand.
