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|Title:||Recovery of Nitrogen-15-Labeled Liquid Anhydrous Ammonia Applied to Soil|
|Author(s):||Norman, Richard James|
|Department / Program:||Agronomy|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Although liquid anhydrous ammonia (LAA) is the most extensively used nitrogen (N) fertilizer in U.S. and Illinois agriculture, knowledge concerning its transformations in soil is limited. The understanding of LAA transformations and the products it forms in soil are agronomically important because they ultimately determine the effectiveness and efficiency of LAA as a N fertilizer. The study of LAA transformations in soil has been severely hampered in the past by the lack of proper isotopic concentrations of ('15)N-labeled LAA required to carry out such research. Quantitative techniques for LAA application on a laboratory scale have also been difficult.
The objectives of the work reported were: (i) to develop a procedure for preparing LAA of a desired ('15)N concentration and a syringe for metering the LAA accurately into soil samples, (ii) to use the ('15)N-labeled LAA to investigate fertilizer N transformations in the LAA distribution band, and (iii) to investigate the extent and persistence of soil organic matter solubilization by LAA.
A procedure was developed for preparing LAA of a desired ('15)N concentration by reacting ('15)N-labeled ammonium sulfate with a 2 N sodium hydroxide solution. The resultant ('15)N-labeled ammonia (NH(,3)) gas was mixed with reagent grade anhydrous NH(,3) gas, and the mixture condensed into a collection vessel from which it was withdrawn, measured, and dispensed with a specially built syringe.
Three soil types were injected with ('15)N-labeled LAA in a manner designed to simulate field application. At prescribed time periods up to 112 days the soils were sectioned into concentric zones around the point of injection and the soil nitrogen fractionated. In general, most of the LAA was recovered as inorganic-N, although some soils rendered up to 26% of the LAA nonexchangeable via immobilization and fixation by soil organic matter and clay minerals. In most cases, there was more of the fertilizer N fixed by soil organic matter than by clay minerals. The fertilizer N fixed by soil organic matter always contained a substantially larger percentage of hydrolyzable-N than that immobilized indicating it is probably more mineralizable. A very small percentage of the organic matter was solubilized in the bands of the soils by the LAA, but it returned to original levels as the soil pH returned to normal.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.
|Date Available in IDEALS:||2014-12-16|