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Regulation Mechanisms and Field Implications of Ammonia Bonding with Various Crystalline Salts
Author(s) -
Evangelou V. P.
Publication year - 1990
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1990.03615995005400020016x
Subject(s) - chemistry , solubility , inorganic chemistry , ammonia , urea , dissociation (chemistry) , ionic bonding , dissolution , metal , precipitation , adsorption , hydrogen bond , volatilisation , fourier transform infrared spectroscopy , infrared spectroscopy , ion , molecule , chemical engineering , organic chemistry , physics , meteorology , engineering
Ammonia volatilization following surface application of urea or inorganic NH 4 salts can be reduced by the addition of CaCl 2 , MgCl 2 , or MgSO 4 salts. The mechanisms for this phenomenon are reported to be: (i) precipitation of CO 2‐ 3 by Ca 2+ or Mg 2+ , preventing (NH 4 ) 2 CO 3 formation and (ii) Ca 2+ depression of soil pH by suppression of the dissociation of the CaCO 3 ‐Ca(OH) 2 buffer system. Using Fourier‐transform infrared (FTIR) spectroscopy, this study demonstrates that, for systems containing limited quantities of water (adsorbed water only), the CaCl 2 or MgCl 2 salts act as proton donors to NH 3 , forming stable M H 2 OOH·H 4 N·Cl 2 ( M = Ca or Mg) compounds. However, the ability of a metal cation to act as a proton donor is diminished when the cation‐anion bond increases in strength (ionic character of the bond is diminished while covalent character is increased). These findings are consistent with NH 3 ‐volatilization data reported in the literature. The present study shows, via a different mechanism, that Ca salts of low solubility (e.g., CaSO 4 ·2H 2 O) should not be effective in reducing NH 3 losses. On the other hand, Ca or Mg salts of high solubility ought to be effective in reducing NH 3 losses from surface‐applied urea or NH 4 fertilizers.