The delay in field work in most parts of Iowa will shorten the time between ammonia (NH3) application and corn planting. So, how soon can you plant corn after applying NH3? The key is having a soil separation between the ammonia zone and the seed.

Depth of injection is extremely important. Ammonia usually diffuses 2 1/2 to 3 inches from the point of injection. But, if wet soil causes the injection knife to seal the sides of the injection slot and limits diffusion of ammonia, ammonia may concentrate below the soil covering or seal. If this happens, and you place seed in the ammonia zone, the longer you wait between applying ammonia and planting corn, the less corn roots will be affected. No magic number of days of waiting will eliminate potential problems if seed is placed in the ammonia zone.

Ammonia injury is detected more frequently in dry weather, because roots are slow to develop and a portion of the root system is injured. You will first notice uneven emergence, slow growth of injured plants, and in dry soil, wilting plants. Browning of roots indicates root injury. In severe cases, dead roots will turn black, even back to the seed.

If you apply ammonia at the proper depth and achieve soil separation between the ammonia zone and seed, you can plant corn immediately after you apply ammonia.