Fall Anhydrous Ammonia Applications

BY Dairyland Seed Agronomy Team

2024 Nutrient Management

Fall is a crucial time for anhydrous ammonia application, but understanding how soil conditions, particularly moisture levels, impact nitrogen (N) retention is essential for farmers and agricultural professionals. Applying ammonia when soil moisture is insufficient can lead to significant nitrogen loss, impacting crop nutrition and farm profitability.

Anhydrous ammonia, a concentrated nitrogen fertilizer, relies on soil moisture to convert into ammonium, which binds effectively with soil particles. This conversion is vital because ammonium is less prone to loss through volatilization or leaching. When ammonia is applied to moist soil, it reacts with water, creating a stable environment where nitrogen is retained for plant use. However, when soil is overly dry, this stabilization process is compromised.

Dry soils present a unique challenge. Anhydrous ammonia remains in a gaseous form longer without adequate moisture. This delay increases the risk of nitrogen escaping into the atmosphere, as the gaseous ammonia may not bind securely to the soil particles. Additionally, dry soils tend to have more significant air-filled pore spaces, which can facilitate the upward movement of ammonia gas, exacerbating nitrogen loss.

To minimize these risks, it is crucial to monitor soil moisture before application. Experts recommend delaying ammonia application if soils are extremely dry and waiting for sufficient rainfall to replenish moisture levels. A well-timed rain can help ensure that the ammonia will effectively convert and stabilize, ultimately preserving nitrogen for spring crop uptake.

Furthermore, soil temperature also plays a role in nitrogen management. The ideal time for application is when soil temperatures drop below 50°F and continue to decrease. This temperature threshold slows the activity of nitrifying bacteria, which convert ammonium into nitrate—a form that is more susceptible to leaching and denitrification.

By carefully managing soil moisture and temperature conditions, farmers can improve nitrogen use efficiency and reduce losses, enhancing crop performance and environmental sustainability. Making data-driven decisions and being aware of local soil and weather patterns can make a significant difference in the success of fall fertilizer applications.

For a deeper dive into soil and moisture considerations, read the full article here.