HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Young, J. L. Search for Related Content PubMed Articles by Young, J. L. Agricola Articles by Young, J. L.

Ammonia and Ammonium Reactions with Some Pacific Northwest Soils¹

ABSTRACT

Retention and fixation of NH₃ and NH₄⁺ by 76 horizon samples from 20 different Pacific Northwest soils were investigated using aqua and anhydrous NH₃, NH₄Cl, and different degassing and fixing conditions.

Retention of NH₃ by ammoniated air-dry samples was approximately 0.7 me. N per each me. of soil cation-exchange capacity. In the surface horizons, retention of NH₃ was roughly 0.3 and 2.6 me. N per 100g. of soil for each percent clay and organic carbon, respectively.

Ratios of "NH₃ retained by air-dry ammoniated samples" to "H₂O retained by the air-dry samples prior to ammoniation" ranged from 0.03 to 0.19 but were generally < 0.1.

As with expandable lattice minerals, vacuum degassing increased NH₃ retention substantially beyond that of free diffusion degassed samples open to moisture of the atmosphere. Loss of retained NH₃ by diffusion and/or water vapor displacement continued at a slow rate for many weeks and while total retention was decreasing, mineral-fixed values were generally increasing.

Infrared absorption patterns were completely dominated by the soil mineral fraction thereby nullifying possible determination of sites or functional groups reactive in NH₃ fixation. An absorption band peaking near 7µ appeared most closely correlated with mineral-fixed NH₄⁺.

Generally, three-fourths or more of the retained anhydrous NH₃ was KCl leachable. Of the fixed NH₃ (that not leachable with KCl) the major part was associated with the organic fraction except in most subsurface horizons of the recent silty alluvial and water-deposited silt soils wherein the major part was fixed by the mineral fraction.

Comparative NH₃/NH₄⁴ fixation revealed widely variable behavior, suggesting that a considerable gradation of mineral structures may be involved in soil NH₃/NH₄⁺ reactions and that a correspondingly broad range in availability of fixed NH₃/NH₄⁺ is to be expected. A number of the minerals giving significant fixation exhibited characteristics intermediate between specimen montmorillonites and vermiculites, implicating beidellitic and/or expanding vermiculite-like structures.

¹ Contribution of the Soil and Water Conservation Research Division, ARS, USDA, in cooperation with the Oregon Agr. Exp. Sta., Corvallis. Technical Paper No. 1711. Ore. Agr. Exp. Sta. Partial financial support from Phillips Petroleum Company and technical assistance of R. Cattani, L. Lee, B. McNeal, W. Wipper, and the Ore. State Univ. Statistics Lab are gratefully acknowledged.

² Chemist, Northwest Branch, SWCRD, ARS, USDA, Corvallis, Ore.

Received for publication September 18, 1963. Accepted for publication January 23, 1964.