Risks of Applying Anhydrous to Dry Soils October 16, 2025 Facebook Twitter LinkedIn Email When soils are too dry, anhydrous ammonia (NH₃) cannot react with soil water to form stable ammonium (NH₄⁺), which can increase the risk of volatilization losses, crop injury, and uneven nitrogen distribution. Anhydrous ammonia must be injected below the soil surface where it reacts instantly with water to form NH₄⁺, which binds to the negatively charged soil. If this reaction can’t happen due to lack of soil moisture, then the NH₃ gas can escape. “The nose knows.” If you smell ammonia 24 hours after the application in that field you are having N loss. Losses are typically greatest in: Dry, coarse-textured soils (sands, loamy sands) Dry, heavy clays with large cracks or poor knife closure Fields tilled too coarsely, leaving large air gaps in the injection path Even a small percentage of loss can add up quickly. A 10% loss of 180 lb-N rate equals 18 lbs of N lost per acre. Roughly, $11 per acre at $0.60/lb N. If we continue to experience dry weather into the spring other risks include ammonia burn to seed/roots if band is placed too shallow or too close to the row. Uneven nitrogen distribution can also occur if ammonia gas moved in the soil before stabilizing. Management Strategies Check soil moisture at injection depth Grab a handful of soil from 6–8 inches. If it crumbles into dust, it’s too dry to seal well. If it forms a weak ball when squeezed, it’s likely adequate. Use correct depth and spacing Go deeper (7–8 inches) in coarse soils and maintain spacing to ensure soil closure. High-speed application increases loss risk in dry conditions. Consider timing & tillage If soil is too dry, consider delaying application until after rainfall improves moisture conditions. Tillage after an application can open further pathways for loss. Delay tillage until soil has received moisture and ammonia odor is gone. Use a nitrification inhibitor Adding a nitrification inhibitor, like N-Serve and Centuro, can further slow the conversation of NH₄⁺, to NO3-, protecting N through the winter and early spring. Supporting articles Fall Anhydrous Ammonia Applications: What to know about soil moisture — Iowa State Crops Extension Anhydrous Ammonia Application in Dry Soil — Iowa State Univ. Extension / Integrated Crop Management Related Items Fall Phosphorus Fertilizer Comparison: TSP, MAP, DAP & MES There is no single “best” fall broadcast phosphate — the correct choice depends on soil test P, whether you also want to deliver N/S and field erosion/leaching risk. Read the full story Fall-Applied Herbicides: Starting the Spring Clean Fields where weeds are managed in the fall are often the most weed free in the spring. Read the full story Consider Soil Moisture When Soil Sampling Accurate soil analyses is critical when making fertilizer recommendations. When soils are dry, some soil measurements may be inaccurate. Key points and lookouts are discussed in this article. Read the full story