Distribution of Applied Anhydrous Ammonia in Soils and Germination Hazard to Winter Wheat

Abstract

AbstractCurrent changes in residue management systems for winter wheat (Triticum aestivum L.) include anhydrous NH3 injection combined with herbicide application, planting, and other field operations. The feasibility of NH3 application during planting is dependent upon potential NH3 toxicity to germinating seeds. A laboratory experiment was conducted to study anhydrous NH3 movement in soils by injecting 124 and 180 mg N as NH3 into a Hollister clay (fine, mixed, thermic Pachic Paleustolls), Grant silt loam (fine‐silty, mixed, thermic Udic Argiustolls), and Norge clay loam (fine‐silty, mixed, thermic Udic Paleustolls) at 0.124 and 0.181 water (kg kg−1) contents. Soil samples were taken 1, 7, and 14 d after N application. Soil NH+4‐N and calculated NH3(aq) concentrations following NH3 injection generated a normal distribution curve with N concentrations highest near the injection point and decreasing with increasing distance. Calculated NH+4 diffusion coefficients decreased with time and water content and were soil dependent. Field studies were conducted in 1983 to determine the potential germination hazard from NH3 applied at 0, 56, 112, 168, 224, and 280 kg N ha−1 while planting, and in 1984 to winter wheat planted 0, 1, 3, 5, 6, and 7 d after applications of 0, 100, and 200 kg N ha−1. Stand counts, forage NO‐3‐N concentration, and yield were not influenced by NH3 applications during planting in 1983, but grain N concentration increased linearly up to 24.1 mg g−1 with 280 kg N ha−1. In the 1984 experiment, increasing NH3 rates did not decrease seedling stand, even though analysis of soil samples reflected increased soil pH and soil NH+4‐N concentration. Anhydrous NH3 placement at a sufficient distance from newly seeded rows will ensure the success of systems which include NH3 injection in conjunction with other field operations in residue management systems.