Fall NH3: Three Tips for a Solid N Foundation

Harvest is wrapping up and tillage is underway. As soil temperatures are trending downward, many farmers will be starting to apply fall NH3. Nitrogen is critical to your crop’s growth, and as you make decisions for your 2016 crop, it’s important to ensure that this nutrient is around in-season when your crop needs it most. As you lay the foundation for your 2016 N program, be sure to consider these tips regarding timing, placement, and rate.


Fall NH3 is typically applied well before the seed hits the soil – between 6-7 months prior to the crop being planted the following spring. Nitrification slows once soil temperatures reach 50°F but doesn’t completely stop until the soil reaches between 36°F. Managing this window is challenging, but is very important to ensure a high percentage of fall NH3 is available when the corn plant demands both ammonium and nitrate to produce yield.

Many growers are using a stabilizer with their fall NH3 application, allowing them to apply fall NH3 earlier in the season. Putting a stabilizer with a fall NH3 application will protect the NH4+ from nitrification in the fall – in soils that are greater than 36-40°F. However, the more demand you put on the stabilizer in the fall, the shorter the window of protection you will have in the spring. Stabilizers add protection to maintaining NH4+ during early rain events and slow nitrification as soil temperatures increase. It’s important to make sure that nitrogen is available when the plant needs it. Therefore, whether using a stabilizer or not, waiting for soil temperatures at 50°F or less with a downward trend would be considered the best management practice.


Farmers today typically apply NH3 in one of two ways. Strip till NH3 application places the nitrogen 6- 8 inches below where the seed will be placed the following spring, applying NH3 in a band where the heart of the root system will be for the 2016 corn plant. The second application approach is to charge the entire soil profile with nitrogen. Regardless of your approach, you are applying a nitrogen foundation that you will build on throughout the year. It is important in both systems to have accuracy from knife to knife across the toolbar in all weather conditions to make sure your foundation is uniform throughout the field.

Most NH3 rate controllers used by farmers today rely on tank pressure to push product through the controller – to the manifolds – then to the knives. This can cause significant variance from knife to knife. 360 EQUI-FLOW keeps NH3 in liquid form under high pressure all the way to the knife, ensuring row-to-row accuracy and providing consistency across the base of your 2016 plan.


Whether applying your first nitrogen foundation for the 2016 crop in the fall or the spring, remember that approximately 75% of nitrogen is used after V10, and in-season conditions are unpredictable. Applying all of your nitrogen in the fall or early spring leaves your crop at risk of running out of N at a critical point in its growth. Be sure to leave some N in reserve for in-season application when you know more about your yield potential and the environmental impact on what you’ve already applied. If NH3 is part of your system, we would suggest a program of applying 50% of fall or spring NH3, 15-20% of weed and feed or planter application, leaving 30-35% for a late season N application once you’ve evaluated yield potential, loss, and mineralization or immobilization. When determining in-season application needs, use 360 SOILSCAN to get an accurate and real-time reading on your nitrate levels. From there, you can have the peace of mind to apply N when you need it at the proper rate.

Be sure to work with your agronomist to create the optimum nitrogen for your crop in 2016. And, if you’re applying NH3 in the spring, check out this blog to more information on spring NH3 best practices.