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Laboratory Apparatus to Apply and Sample Anhydrous Ammonia in Bands¹

ABSTRACT

To describe how soil properties affect anhydrous ammonia (NH₃) retention, more accurate laboratory methods are needed to apply anhydrous NH₃ in a line source (band) and sample the resulting NH₃ retention zone. We developed and tested a line-source NH₃ applicator and a method for sampling the resulting NH₃ retention zone. The applicator has a system of flow control valves and a flow meter to regulate the rate of NH₃ flow to an injection needle. The needle is held stationary while NH₃ is injected into a box of soil. The box of soil moves on a platform whose speed can be varied to change the NH₃ application rate. The soil sampling method was to sequentially remove concentric cylindrical cores of increasing radii centered around the line of NH₃ injection. Ammonia was applied to two soils with different NH₃ retention capacities and the resulting NH₃ retention zones were sampled. Accurate NH₃ deliveries 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 NH₃ retention zones in soil.

¹ Contribution no. 86-33-J, Agronomy Dep., Kansas Agric. Exp. Stn., Manhattan, KS 66506. Part of a dissertation submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree at Kansas State Univ. This study supported in part by grants from the Test and Demonstration Branch of the National Fertilizer Development Center of TVA and Dow Chemical Company.

² Graduate Research Assistant, Professor, and Associate Professor, respectively, Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506. Present address of senior author is: Fac. de. C. Agropecuarias, Univ. Nacional de Cordoba, cc 509, 5000 Cordoba, Argentina.

Received for publication August 23, 1985.