Losses of soil nitrogen that cannot be attributed to leaching or crop removal have been observed in many field experiments. Several mechanisms have been proposed to account for these losses. Perhaps the best known mechanism involves the process of microbial denitrification. Undoubtedly this process plays a major role in nitrogen loss but it does not seem to adequately account for many of the losses observed. A thorough understanding of other possible loss pathways has tremendous agricultural implications as well as being of interest from a purely scientific standpoint. It has long been accepted that nitrite is an intermediate in the biological oxidation of ammonium to nitrate. Because of the high reactivity of nitrous acid and the nitrite ion many investigators have proposed pathways involving them. Considering the diversity of possible reactions and products involving nitrite it is not surprising that numerous contradictions are found in the literature on this subject. The work reported here was an attempt to clarify the role of some of these pathways in the destruction of the nitrite ion in acid soils. The availability of a gas chromatograph and incubation equipment made the study feasible from a technical standpoint. Most of the data reported here were collected by the author in the late summer of 1961, using techniques developed over the previous year. Some data re included that were collected by Dr. Keith Justice in the summer of 1962 using these same methods.

Just twenty years have passed since the first papers were published on the application of chemical thermodynamics to the soil-water system (11, 14). Since then, soil physicists have used thermodynamics in an attempt to characterize and l earn more about this intricate system.

Nitrification, the process whereby ammonical-nitrogen (NH i+4 - N) is changed into nitrate- nitrogen (NO3-N), is one of the more important biochemical processes associated with agriculture. Nitrate appears to be the form of N that most crops can most readily utilize.

Changes in the energy status of water that occurred in Milville silt loam and in bean (Phaseolus vulgaris L.) plants growing on it , during two consecutive 6-day periods while being irrigated with saline solutions, were studied. Total soil water potential (Ψ soil) (measured with thermocouple psychrometers), matric-potential (Ψm) (measured with tensiometers) were considered. In leaf samples, the total water potential (leaf) and the osmotic potential (Ψπ)--after freezing-- were determined with thermocouple psychrometers; by difference, the pressure potential (Ψp) was obtained. There is no evidence of close relationship between changes taking place in the values of the leaf water potential (or its components) and changes that occur in the energy status of the soil solution. Also, there is a lack of close relationship between the concentration of the solutions added and the resulting water potentials in the soil solution. Results indicate that the soil water potential exerts increasing control of leaf water potential as it decreases. In addition, there is a smaller range of values of leaf water potentials when the saltier solutions (C and D) are used for irrigations. Also, the osmotic potential is higher in leaves of plants grown in pots watered with saltier water. High values of pressure potentials (Ψp)--low turgor-calculated for leaf samples, where no wilting symptoms were visible, suggest that there are differences among plant species with regard to the turgor level at which wilting occurs.

A consideration of the physical principles involved in evaporative drying of soil indicates that several physical processes might possibly limit the rate of evaporation. These include the rate of supply of energy to the site of evaporation, the rate of transfer of water vapor through the sample or through the atmosphere above the sample, and the rate of unsaturated flow of water to the soil surface or to the site of evaporation.

Relationship between soil moisture and the absorption of phosphorus and other nutrients.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19297号 / 工博第4094号 / 新制||工||1631(附属図書館) / 32299 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 米田 稔, 教授 伊藤 禎彦, 准教授 藤川 陽子 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

No description available.