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SOIL FERTILITY & PLANT NUTRITION

Temperature Quotients of Ammonia Emission of Different Nitrogen Sources Applied to Four Agricultural Soils

^a Soil and Water Science Dep., Tropical Research and Education Center, Univ. of Florida, 18905 SW 280th St., Homestead, FL 33031
^b USDA-ARS, 24106 N. Bunn Rd., Prosser, WA 99350

^* Corresponding author (yunli@mail.ifas.ufl.edu).

Emission of N as NH₃ is the primary gaseous loss of N from N sources applied to soils. Knowledge of NH₃ volatilization, however, in relation to temperature is incomplete. Soils used in this study were a Biscayne marl soil (BMS) and Krome gravelly loam (KGL) from Florida, and Quincy fine sand (QFS) and Warden silt loam (WSL) soils from Washington. These soils were amended with either KNO₃, NH₄NO₃, (NH₄)₂SO₄, or urea, and incubated at 11, 20, or 29°C under 20 or 80% field capacity (FC) soil water regimes. A change in the rate of NH₃ emission corresponding to a 9°C change in temperature is expressed as the temperature quotient (Q₉), which describes the temperature effect on rates of NH₃ volatilization. At 20°C, the cumulative NH₃ emission at 20% FC was up to 8.1-fold greater than that at 80% FC. The Q₉ values of NH₃ emission from the WSL soil were up to 10-fold greater than those from the other three soils amended with either (NH₄)₂SO₄ or NH₄NO₃. The Arrhenius activation energy (E_a) was about 188 J mol^–1 for the WSL soil but 42 J mol^–1 for the other soils. Volatilization from the WSL soil was highly temperature dependent. These results indicate that Q₉ and E_a could be used as indices for N management for crop production to minimize NH₃ emissions. Further research is needed, however, to verify the above relationships across a wide range of soils and agroclimatic regions.

Abbreviations: BMS, Biscayne marl soil • CAE, cumulative ammonia emission • FC, field capacity • IPAV, isothermal point of ammonia volatilization • KGL, Krome gravelly loam • QFS, Quincy fine sand • WSL, Warden silt loam