Ammonium fixation in relation to characteristics of some entisols and aridisols of Iraq
1987
Berigari, M.S. | Al-Any, F.M.S. | Umran, M.A. | Ibrahim, L.H. (Scientific Research Council, Baghdad (Iraq). Agriculture and Water Resources Research Centre, P.O. Box 2416)
Very limited information if any is available on the NH4+ fixing capacity or the parameters which affect this process in soils of Iraq. Thus, samples from two Calciorthid and four Torrifluvent soils were treated with a wide range (0.25-10.0) symmetry concentration of NH4Cl at (1:5) soil: solution. Six replicates from every addition were shaken 48 h then the bulk solution was centrifuge separated. One triplicate soil sediment was kept wet 72 h at 25 deg C while the second was allowed to dry 72 h at 50 deg C. Soluble and NaCl exchangeable NH4+ was determined by the Kjeldahl method, and the fixed NH4+ was taken as the difference between the amount added and the increase in the extractable NH4+ after equilibration. Fixed and exchangeable NH4+ increased under the wet and dry treatments with the increase in NH4Cl addition but at decreasing rates with concurrent CEC reductions upon drying. Fixation of NH4+ correlated positively with CEC, exchangeable NH4+ and organic matter and negatively with gypsum content but did not correlate significantly with soil pH, clay or CaCO3 content. Also the diagnostic XRD peak heights displayed inconsistent correlations with NH4+ fixation
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