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Thesis (M.S. - Agricultural Chemistry & Soils)--University of Arizona. / Bibliography: leaves 53-55.

Thesis (M.S. - Agricultural Chemistry and Soils)--University of Arizona. / Bibliography: leaves 106-129.

Thesis (M.Sc.)--University of Western Australia, 2006.

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The inputs and losses of nitrogen from Great Basin arid soils were studied using the acetylene reduction and 15N techniques. Filamentous blue-green algae were observed to be the predominant algal group in the soil crusts. The bacterial association with this group of algae suggest a phycosphere-like effect, thus allowing heterotrophic nitrogen fixation and denitrification to occur. Up to 17.5 mg N/100 g soil was found to have been fixed in surface soils (0 to 3 em) during a three week incubation period, while 45.9 mg N/100 g soil was fixed in a five week incubation period. Ammonium sulfate and ammonium sulfate plus plant material amendments reduced the gain in nitrogen by 41 to 100 percent. 15 + 15 - Fifty to sixty percent of the applied NH4-N and N0 3-N was denitrified during the first week of incubation while 70 to 80 percent of the NH 4-N was lost in a three- to five-week incubation period. These data suggest that a potential for heterotrophic nitrogen fixation exists, and under optimal conditions, significant gains in soil nitrogen may be achieved. However, in the presence of allelochemic agents, the potential gain in soil nitrogen may be reduced or inhibited. In addition, the denitrification potentials of these soils may also limit the input of nitrogen. The application of protein ( casein) to these soils resulted in an ammonification rate of 50 to 60 percent. 15 Fixed N2 indicated a 21 to 48.8 percent ammonification rate, thus suggesting that the mineraliztion of NH 4 was the rate limiting step for nitrogen loss. Ammonia volatilization accounted for less than a five percent nitrogen loss, regardless of experimental conditions. The inhibitory effects of plant material and litter extracts, and ''N-Serve" on heterotrophic nitrogen fixation has been assessed. The data suggest that the nitrogen fixing population is sensitive to the inhibitory effects of such agents .

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In der vorliegenden Arbeit werden die Möglichkeiten einer Nutzung thermal-infraroter Wellenlängen zur fernerkundlichen Erfassung/Quantifizierung von Bodenparametern vorgestellt. Die Studie basiert auf Bodenproben des Untersuchungsgebietes Mullewa, welches sich in einer semiariden Agrarregion im West-Australischen Weizengürtel befindet. Im Mittelpunkt der Arbeit steht die Bewertung des langwelligen Infrarots (LWIR), innerhalb des atmosphärischen Fensters zwischen 8 und 14 Mikrometer, bezüglich seines spektralen Potentials für die quantitative Ableitung des Ton- und Sandgehaltes sowie des Gehaltes an organischem Kohlenstoff (SOC). Zur Abschätzung der Effizienz wurden die Ergebnisse des LWIR einer Quantifizierung aus dem herkömmlich gebrauchten solar-reflektiven Wellenlängenbereichs zwischen 0,4 und 2,5 Mikrometer (VNIR-SWIR) gegenübergestellt. Mit verschiedenen Methoden der Laborspektroskopie wurden Bodenproben aus dem Untersuchungsgebiet im thermalen (Emissions-FTIR-Spektroskopie und direktional-hemisphärische Reflexions- (DHR) Spektroskopie)und im solar-reflektiven (Diffuse Reflexions-Spektroskopie) Wellenlängenbereich eingemessen und anschließend auf ihren Informationsgehalt hin untersucht. Die quantitative Modellierung der pedologischen Parameter aus den gemessenen spektralen Signaturen wurde mithilfe einer multivariaten Regressionsanalyse (Partial Least Squares Regression – PLSR) realisiert. Diese Grundlagenstudie konnte zeigen, dass die spektralen Voraussetzungen im LWIR für ein mögliches Monitoring der Bodenparameter mit thermalen Fernerkundungsdaten gegeben sind. Die Arbeit demonstriert darüber hinaus, dass für die Erfassung/Quantifizierung der Textur-Parameter (Sand- und Tongehalt) der relevante spektrale Informationsgehalt im LWIR deutlich höher ist als im VNIR-SWIR. / This study embraces the feasibility of using the thermal infrared wavelength region for future remote sensing applications to detect/quantify soil parameters. The research is based on soil samples from the semiarid agricultural area of Mullewa, located within the wheat belt of Western Australia. The main focus of this study is to assess the potential of the longwave infrared (LWIR), within the atmospheric window between 8 and 14 micrometer, to predict the content of sand, clay and organic carbon (SOC) in soils. The results are compared with predictions made with the traditionally used solar-reflective wavelength region (visible, VIS: 0.4 - 0.7 micrometer; near infrared, NIR: 0.7 - 1.1 micrometer; shortwave infrared, SWIR: 1.1 - 2.5 micrometer). Using laboratory spectroscopy, the Mullewa soil samples were measured, both in the thermal infrared (emission FTIR spectroscopy and directional hemispherical reflection (DHR) spectroscopy) and in the solar-reflective (diffuse reflection spectroscopy) wavelength region. This data was analyzed to determine the relevant content of information for the soil parameters. Multivariate regression analyses (partial least squares regression - PLSR) were used to quantitatively model the soil parameters from the spectral signatures. This basic research demonstrated that the spectral requirements in the LWIR are met for monitoring these soil parameters with thermal remote sensing instruments. Furthermore the study found that the relevant spectral information for the detection/quantification of the sand- and the clay content (textural parameters) is explicitly higher in the LWIR than in the VNIR-SWIR.