Ammonia Volatilization from Surface Applications of Ammonium Compounds on Calcareous Soils: IV. Effect of Calcium Carbonate Content
1975
Fenn, L. B. | Kissel, D. E.
The purpose of this study was to determine the effect of soil CaCO₃ content on ammonia volatilization from surface applied ammonium compounds. Ammonia-nitrogen losses from surface-applied (NH₄)₂SO₄ increased rapidly to 6.1% soil CaCO₃, with slight NH₃ loss increases from 6.1 to 9.7% soil CaCO₃, and no NH₃ loss increase beyond 9.7% soil CaCO₃. Ammonium nitrate reached maximum NH₃-N loss at 1.3% soil CaCO₃ and 110 kg NH₄⁺-N/ha, with lower but still increasing losses of NH₃-N at 6.1% soil CaCO₃ and 550 kg NH₄⁺-N/ha. The acidity of the ammonium compounds caused a reduction in final soil pH at low CaCO₃ levels and high NH₄⁺-N application rates; but at 6.1% soil CaCO₃ and above, the pH values remained at 7.5 to 7.6. The effect of soil pH on NH₃-N losses was greater for NH₄NO₃ than for (NH₄)₂SO₄. For (NH₄)₂SO₄, the percent loss of NH₃-N below 1.3% soil CaCO₃ decreased as NH₄⁺-N application rates increased; but at 2.9% and above, NH₃-N losses were greatest at the highest rate of NH₄⁺-N application. In contrast, no reversal in NH₃-N losses were observed for NH₄NO₃ with increasing soil CaCO₃ content and NH₄⁺-N application rates. Multiple regression analysis of NH₃-N losses with respect to time, temperature, rate of NH₄⁺-N application, and soil CaCO₃ content resulted in two equations with correlation coefficients (R²) of 0.88 and 0.85.
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