Laboratory Apparatus to Apply and Sample Anhydrous Ammonia in Bands

To describe how soil properties affect anhydrous ammonia (NH3) retention, more accurate laboratory methods are needed to apply anhydrous NH3in a line source (band) and sample the resulting NH3retention zone. We developed and tested a line‐source NH3applicator and a method for sampling the resulting NH3retention zone. The applicator has a system of flow control valves and a flow meter to regulate the rate of NH3flow to an injection needle. The needle is held stationary while NH3is injected into a box of soil. The box of soil moves on a platform whose speed can be varied to change the NH3application rate. The soil sampling method was to sequentially remove concentric cylindrical cores of increasing radii centered around the line of NH3injection. Ammonia was applied to two soils with different NH3retention capacities and the resulting NH3retention zones were sampled. Accurate NH3deliveries were possible with the system described. The coefficient of variation of the platform speed was <1%. The sampling method gave N recoveries that ranged between 95 to 99%. By using the concentric ring sampling method, ammoniacal‐N concentrations of duplicate retention zones at different distances from the injection line were not significantly different. Thus, the applicator and soil sampling method proved to be both accurate and precise for studying NH3retention zones in soil.