Distribution and Recovery of Nitrogen-15-labeled Liquid Anhydrous Ammonia Among Various Soil Fractions
1987
Norman, R. J. | Kurtz, L. T. | Stevenson, F. J.
Since liquid anhydrous ammonia (LAA) is a major N fertilizer, information was sought about the proportions of LAA that enter into various combinations in soils. Liquid anhydrous NH₃, labeled with ¹⁵N was injected into three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf) in the laboratory at a rate equivalent to a field application of 206 kg N ha⁻¹ in 76.2 cm knife-spacings. At 1, 7, 14, 28, 56, and 112 d after application, fertilizer N present in different soil fractions was determined in five concentric zones with radii of 0 to 1.5, 1.5 to 3.0, 3.0 to 4.5, 4.5 to 6.0, and 6.0 to 7.0 cm around the point of application. Depending on the soil, from 68 to 83% of the applied ¹⁵N was accounted for as (exchangeable NH⁺₄ + NO⁻₃ + NO⁻₂)-N by the 112th day following application, the remainder being accounted for as clay-fixed NH⁺₄ (1.9-4.9%), organic matter-fixed NH₃ (4.0-6.0%), and biologically immobilized organic N (3.9-9.3%). From 50 to 70% of the organic matter-fixed NH₃-N was released by hydrolysis with dilute KOH solution as compared to 10 to 15% for the immobilized N. Total recovery of ¹⁵N at 112 d ranged from 77% for the Cisne soil to about 97% for the Drummer and Blount soils. Lateral distributions and transformations of NH⁺₄ and NO⁻₃ and pH trends after LAA applications were similar to those reported by previous investigators.
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