Sidedressing NH3

Anhydrous Ammonia is a very good source of Nitrogen and also usually the cheapest form available. It is important to make sure you apply the NH3 properly to avoid injury issues.


NH3 is injected into the soil, and usually is the most concentrated within 4” or so of the knife track. In sandy soils or very dry field conditions the concentrated band will be larger because NH3 has a huge attraction to water, and it will move to find available soil water. If you run the knife too close to the rows, you could see root injury from the applicator knife, but there is an even greater risk of burning the roots of the plant from the NH3 itself. See the picture below of root “burn” from NH3.

Once the NH3 ties up with soil water, it moves with soil water to the plant roots and can be taken up and used without causing any injury problems.


Another way NH3 can cause injury is by burning the leaves above ground. In very wet soils the knife will seal the sidewalls so the NH3 cannot move into the soil profile. This will cause the NH3 to move back up the slot made by the knife and escape into the air. Not only will you loose the NH3 that you are applying, it will burn the leaves of the young corn plants. Usually the corn will recover, but the Nitrogen that escapes is lost and does not available for the plant later in the season when it needs it most. It’s always good to make sure soil conditions are good and that you are getting a good seal in the knife tracks when applying NH3.