Corn grows relatively slowly early on, especially this season when cool, wet weather has dominated part of the Corn Belt. Sometimes corn at V3 to V5 looks like a spindly calf – it doesn't have its 'legs' yet, systems are still developing, and it looks awkward.
Dave Nanda, Director of Genetics and Technology for Seed Consultants, Inc., says that all that changes once the growing point is above ground and corn reaches about the V7 stage. This means seven leaf collars are exposed. By this time, the photosynthetic factory is set up to turn sunlight into products the plant can use to grow and grow quickly.
I've actually taken yardsticks set next to corn plants and literally noticed growth overnight. It's not just an old saying – it's true.
Nanda says this rapid growth phase is normal and will continue through the V10 leaf stage. That's why people often worry about getting sidedress N on in time while they can still get in the field, especially if they're in the middle of a wet spell. The corn can go from passable to impassable in a short period.
Rescue operations with high-clearance rigs to add nitrogen are available should that happen, or should you decide that even if N was applied, you have lost enough due to saturated soils that you want to add some more N to stay on the course toward top yield potential. Drops are usually recommended. The UAN solutions often applied at that stage can cause leaf burn if the solution directly contacts the leaves.
Some now have high-clearance rigs with coulters that reach down to the ground and directly inject nitrogen, avoiding such issues and making sure the N will get into the soil where the roots can get it, and that it won't volatilize before it can be utilized.
Don't be surprised if your corn takes off and grows quickly now, Nanda concludes. It's all part of the wonder of nature when it comes to how corn develops.