Date of Award:
5-1996
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Plants, Soils, and Climate
Department name when degree awarded
Plants, Soils and Biometeorology
Committee Chair(s)
Lynn M. Dudley
Committee
Lynn M. Dudley
Committee
John Stark
Committee
Dani Or
Abstract
An isotopic dilution method was used to test the effects of osmotic potential, (𝛹s), upon nitrification, ammonification, N-immobilization, and nitrous oxide production rates in soil at solute concentrations encountered in Penoyer soil. A nitrification potential assay was also performed to approximate maximum nitrification rates.
Nitrification potential rates in soil slurries exponentially declined in response to decreased osmotic potential. However, nitrification was independent of salt concentration at the ambient NH4+ concentrations of the soil. The differential response was attributed to the variable NH4+ substrate quantities. The effects of osmotic potential were secondary to NH4+ substrate levels in controlling nitrification rates. Ammonification rates declined exponentially as a function of decreased osmotic potential; however, the 33% reductions in ammonification rates were restricted to a range of osmotic potentials between 0 and -500 kPa. Ammonification rates were independent of osmotic potential at potentials between -500 and -1800 kPa. Immobilization rates of both NH4+ and NO3- declined exponentially as osmotic potential decreased. Absolute rates of NO3- immobilization exceeded those of NH4+ by a factor of 4, indicating that under NH4+ limited conditions, substantial NO3- assimilation occurred. However, the generalization that NH4+ is the preferred N source was in fact supported by the data, where immobilization rates relative to the respective pool sizes clearly favored NH4+ assimilation. Nitrous oxide production rates increased linearly as osmotic potential decreased. An NH4+ dependence indicated the evolved N2O was derived from nitrification rather than denitrification.
Checksum
966de3893cbcfbe2fd9fe9dfbc465d2a
Recommended Citation
Low, Andrew P., "The Effects of Osmotic Potential on Ammonification, Immobilization, Nitrous Oxide Production, and Nitrification Rates in Penoyer Soil" (1996). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 3764.
https://digitalcommons.usu.edu/etd/3764
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