Fall nitrogen application gives corn growers an opportunity to manage fertilizer costs and take advantage of additional application windows, but proper timing and stabilization are essential to keeping nutrients available for the following growing season.
Nitrogen is one of the most important nutrients in corn production, yet it can be difficult to manage. Once applied, nitrogen responds to weather conditions, interacts with soil and can move out of the root zone before the crop needs it.
Ron Geis, technical field agronomist for Corteva Agriscience, said understanding how nitrogen changes in the soil is critical to minimizing nutrient loss. Geis has 42 years of experience working with agricultural retailers and farmers.
Nitrogen is applied in the ammonium form, which carries a positive electrical charge. Because soil particles generally have a negative charge, they attract and retain ammonium. However, soil bacteria convert ammonium into nitrate, which carries a negative charge and is more susceptible to movement through the soil.
Keeping nitrogen in the ammonium form longer can help growers retain the nutrient in the soil and reduce the risk of losses before the next corn crop can use it.
Two primary pathways for nitrogen loss are leaching and denitrification. Leaching occurs when nitrate moves through the soil with water, potentially carrying nitrogen below the crop's root zone and making it unavailable to plants.
Denitrification occurs when saturated soils become oxygen-deficient. Under these conditions, soil microorganisms use nitrate instead of oxygen during respiration, converting plant-available nitrogen into gaseous forms that are released into the atmosphere.
Heavy rainfall and saturated soil conditions can increase the risk of nitrogen losses through these processes.
Nitrogen stabilizers can help reduce these risks by slowing the conversion of ammonium to nitrate, extending the period during which nitrogen remains available in the soil.
Corteva Agriscience offers two nitrogen stabilization products. N-Serve nitrogen stabilizer is designed for use with anhydrous ammonia, while Instinct NXTGEN nitrogen stabilizer can be applied with urea, urea ammonium nitrate (UAN) or liquid manure.
Both products use Optinyte technology, which contains the active ingredient nitrapyrin. N-Serve has been available in the market for 50 years.
According to Geis, the products suppress the activity of bacteria responsible for converting ammonium into nitrate. Slowing this process during the fall and early spring can help protect nitrogen from leaching and denitrification before the crop needs it.
Application timing also plays an important role in fall nitrogen management. Geis said medium- to fine-textured soils are generally best suited for fall anhydrous ammonia applications when soil temperatures consistently remain below 40 degrees Fahrenheit and continue declining into winter.
Proper soil moisture is another important consideration. Soil that is too wet or too dry can create challenges for nitrogen application and retention.
Applying nitrogen prematurely, particularly without a stabilizer, can increase the risk of conversion to nitrate before the crop is ready to use it. This leaves nitrogen vulnerable to losses during rainfall and other unfavorable weather conditions.
Beyond nutrient retention, effective nitrogen management can have economic and environmental benefits. With nitrogen fertilizer investments often exceeding $100 per acre, reducing nutrient losses can help growers protect their input costs.
Keeping nitrogen in the field also reduces the potential for nitrate movement into groundwater and nitrogen losses to the atmosphere.
Geis said growers should approach fall nitrogen application as a risk management strategy. Understanding soil conditions, monitoring application timing and using appropriate stabilization products can help retain nitrogen for the following corn crop while supporting profitability and nutrient stewardship.
Source: Michigan Farm News, "Understanding nitrogen to improve fall-applied retention and ROI"