Distribution and Recovery of Nitrogen-15-labeled Liquid Anhydrous Ammonia Among Various Soil Fractions1
- R. J. Norman,
- L. T. Kurtz and
- F. J. Stevenson2
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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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