No description available.

No description available.

Land application of domestic and industrial wastewaters provides an effective means of recycling water and its components into the ecosystem. Successful treatment by soil requires that wastewater is applied in quantities that both maintain infiltrative capacity of the soil and do not exceed the capacity of the soil-plant system to assimilate biological and chemical contaminants. Application of N-rich wastewaters requires that consideration be given to both the ability of the soil to transmit the hydraulic load and remove sufficient N to maintain groundwater quality standards. A textile wastewater containing high concentrations of organic N was spray-irrigated to tall fescue (Festuca arunindinacea) to determine optimum N application levels. Nitrogen balances were determined at each N level and and the potential for predicting the leaching component of the excess N applied was investigated. Historically on-site wastewater disposal systems (OSWDS) for treating septic tank effluent (STE) have been designed on a hydraulic loading basis with N pollution potential essentially ignored. Many soils have been deemed unsuitable for application of STE because of textural, water table, or landscape restrictions. The relations between soil properties, hydraulic performance of OSWDS, and N distribution around OSWDS are evaluated. Wastewater from a nylon processing plant was applied to 'Ky 31' tall fescue at total Kjeldahl nitrogen (TKN) levels of approximately 250, 430, and 1900 kg ha⁻¹ during 1982 and 1983. Fescue yield and N removal was comparable to agricultural yields at similar N application levels. Nitrogen balances indicate that plant uptake efficiency decreased with increasing organic N levels above the 250 kg ha⁻¹ level and that maximum uptake occurred at the 450 kg ha⁻¹ level. Most of the N not recovered in plant tissue mineralized rapidly to the nitrate NO₃⁻ form and leaching was noted during the winter and spring. This data is evaluated with quasi-transient analytical solution of the convection-dispersion equation. The movement of the solute center of mass is predicted on the basis of assumptions of piston flow as well as alternative assumptions of mixing via plate layer theory. Prediction of the location of the center of solute mass (α) provides a moving lagrangian coordinate solution around which dispersion of solute is calculated. The assumptions made about the sequence of evaporation and infiltration events significantly influence the prediction of α and hence the agreement between predicted and measured solute distribution. Both approaches give results which are within experimental error and provide a rational basis for predicting leaching losses and carry-over NO₃⁻ available to future crops. Prototype OSWDS with low pressure distribution installed in three clayey limestone-derived soils were dosed with STE at flux densities ranging from 0.4 to 3.6 cm d⁻¹ on a trench bottom area basis. Ponding was noted in OSWDS at all sites dosed at the 3.6 cm d⁻¹ flux due to both underlying hydraulic restrictions and resultant anaerobic conditions. It is concluded that clayey B horizons low in swelling clays but moderately well structured can be dosed at flux densities up to 2 cm d⁻¹ if low pressure distribution of STE is used. Nitrification was found to be quite limited in soils where effluent was ponded above a restrictive layer but occurred readily within 30 cm below trenches which were freely drained or had matric potentials of at least 40 cm of water. Ratios of NO₃⁻ to Cl⁻ indicate that only limited denitrification can be expected and that substantial NO₃⁻ does leach from below OSWDS in the direction of water flow. / Ph. D.

Lam Lai-yee. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 124-140). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.vii / Table of contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xiii / List of Plates --- p.xiv / Chapter CHAPTER ONE --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Background and ecological impact of hill fires in Hong Kong --- p.2 / Chapter 1.3 --- Conceptual framework of study --- p.4 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER TWO --- The study area / Chapter 2.1 --- Introduction --- p.14 / Chapter 2.2 --- Geographical setting of Hong Kong --- p.14 / Chapter 2.2.1 --- Climate of Hong Kong --- p.14 / Chapter 2.2.2 --- Geology of Hong Kong --- p.15 / Chapter 2.2.3 --- Soils of Hong Kong --- p.16 / Chapter 2.2.4 --- Vegetation of Hong Kong --- p.17 / Chapter 2.3 --- Site selection --- p.18 / Chapter 2.4 --- Grassy Hill --- p.20 / Chapter CHAPTER THREE --- Heating effect on the properties of ash / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Experimental design and methodology / Chapter 3.2.1 --- Selection of simulation heating --- p.26 / Chapter 3.2.2 --- "Heating intensity at 200°-600°C for 1,5 and 15 minutes" --- p.27 / Chapter 3.2.3 --- Field work --- p.27 / Chapter 3.2.4 --- Heating method --- p.28 / Chapter 3.2.5 --- Chemical analysis --- p.28 / Chapter 3.2.6 --- Analysis of data --- p.32 / Chapter 3.3 --- Results and Discussion / Chapter 3.3.1 --- Heating effect on ash weight and pH --- p.33 / Chapter 3.3.2 --- "Heating effect on ash organic C, N and P" --- p.33 / Chapter 3.3.3 --- Heating effect on ash available cations --- p.40 / Chapter 3.4 --- Conclusion --- p.42 / Chapter CHAPTER FOUR --- The effect of heat and ash on soil / Chapter 4.1 --- Introduction --- p.44 / Chapter 4.2 --- Methodology / Chapter 4.2.1 --- Field work --- p.48 / Chapter 4.2.2 --- Soil heating methods --- p.48 / Chapter 4.2.3 --- Chemical analysis --- p.49 / Chapter 4.2.4 --- Statistical analysis --- p.52 / Chapter 4.3 --- Results and Discussion / Chapter 4.3.1 --- The effect of heat and ash on soil pH --- p.53 / Chapter 4.3.2 --- "The effect of heat and ash on soil organic matter, N and P" --- p.55 / Chapter 4.3.3 --- The effect of heat and ash on soil cations --- p.62 / Chapter 4.4 --- Conclusion --- p.65 / Chapter CHAPTER FIVE --- Nitrogen and phosphorus mineralization after heating / Chapter 5.1 --- Introduction --- p.67 / Chapter 5.2 --- Methodology / Chapter 5.2.1 --- Heating and incubation method --- p.70 / Chapter 5.2.2 --- Laboratory methods --- p.72 / Chapter 5.2.3 --- Statistical analysis --- p.72 / Chapter 5.3 --- Results and discussion / Chapter 5.3.1 --- Temporal changes of N mineralization in heated bare soils --- p.72 / Chapter 5.3.2 --- The effect of ash on N mineralization --- p.78 / Chapter 5.3.3 --- Comparison of N mineralization with other studies --- p.79 / Chapter 5.3.4 --- Temporal changes of P mineralization in the heated bare soils --- p.81 / Chapter 5.3.5 --- The effect of ash on P mineralization --- p.83 / Chapter 5.3.6 --- Comparison of P mineralization to other studies --- p.84 / Chapter 5.4 --- Conclusion --- p.85 / Chapter CHAPTER SIX --- Vertical movement of mineral N in ash-covered soil columns / Chapter 6.1 --- Introduction --- p.87 / Chapter 6.2 --- Methodology / Chapter 6.2.1 --- Package of soil columns --- p.89 / Chapter 6.2.2 --- Water addition and extraction of pore water --- p.90 / Chapter 6.2.3 --- Statistical analysis --- p.92 / Chapter 6.3 --- Results and Discussion / Chapter 6.3.1 --- Mineral N in the pore water --- p.92 / Chapter 6.3.2 --- The effect of ash on mineral N in pore water --- p.97 / Chapter 6.3.3 --- The leaching loss of mineral N --- p.98 / Chapter 6.3.4 --- Comparisons with other studies --- p.103 / Chapter 6.4 --- Conclusion --- p.105 / Chapter CHAPTER SEVEN --- Integrative discussion / Chapter 7.1 --- Summary of major findings --- p.107 / Chapter 7.2 --- Clarifying some misconceptions about the effect of fire --- p.110 / Chapter 7.3 --- Estimated losses of N and P from heating --- p.112 / Chapter 7.4 --- Nutrient supplying capacity of soils after heating --- p.115 / Chapter 7.5 --- Why are repeatedly burnt areas reduced to grassland? --- p.118 / Chapter 7.6 --- Implication on the restoration of fire-affected areas --- p.119 / Chapter 7.7 --- Limitations of the study --- p.121 / Chapter 7.8 --- Suggestions for future research --- p.122 / References --- p.124 / Appendices --- p.141

Liu Wing Ting. / Thesis submitted in: November 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 141-156). / Abstracts in English and Chinese. / Abstract (English) --- p.i / Abstract (Chinese) --- p.iii / Acknowledgments --- p.v / List of Tables --- p.vii / List of Figures --- p.ix / List of Plates --- p.x / List of Appendices --- p.xi / Chapter CHAPTER 1 --- INTRODUCTION / Chapter 1.1 --- Urban ecological environment and the urban parks in Hong Kong --- p.1 / Chapter 1.2 --- Conceptual framework of the study --- p.4 / Chapter 1.3 --- Objectives of the study --- p.9 / Chapter 1.4 --- Scope of the study --- p.10 / Chapter 1.5 --- Significance of the study --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter CHAPTER 2 --- LITERATURE REVIEW / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- Urban parks and urban soils --- p.13 / Chapter 2.3 --- Urban soils: properties and problems --- p.14 / Chapter 2.3.1 --- Overseas studies about urban soils --- p.15 / Chapter 2.3.2 --- Urban soils in Hong Kong --- p.16 / Chapter 2.4 --- Nitrogen dynamics --- p.22 / Chapter 2.4.1 --- The internal N cycle and N transformations in soil --- p.22 / Chapter 2.4.2 --- Factors affecting nitrogen dynamics in soil --- p.24 / Chapter (i) --- "Soil moisture and temperature, seasonality and spatial variation" --- p.24 / Chapter (ii) --- Soil pH and texture --- p.26 / Chapter (iii) --- Litter quality and C:N ratio --- p.26 / Chapter (iv) --- Disturbance --- p.27 / Chapter (v) --- Fertilizer input and management intensity --- p.27 / Chapter 2.4.3 --- N dynamics in urban areas --- p.28 / Chapter 2.4.4 --- Research of N dynamics in Hong Kong --- p.29 / Chapter 2.5 --- Phosphorus dynamics --- p.30 / Chapter 2.5.1 --- Gains and losses of P from soil system --- p.30 / Chapter 2.5.2 --- Forms and transformations of phosphorus in soil --- p.31 / Chapter 2.5.3 --- Factors affecting P dynamics in soil --- p.34 / Chapter (i) --- Fluctuations of soil moisture --- p.34 / Chapter (ii) --- Liming and pH adjustment --- p.34 / Chapter (iii) --- Cultivation and management intensity --- p.35 / Chapter (iv) --- Vegetation cover and disturbances --- p.35 / Chapter 2.5.4 --- P dynamics in urban areas --- p.36 / Chapter CHAPTER 3 --- STUDY AREA / Chapter 3.1 --- General situation of Hong Kong and the study locations --- p.37 / Chapter 3.2 --- Background of the two parks: Kowloon Park and Tin Shui Wai Park --- p.40 / Chapter 3.3 --- Climate --- p.43 / Chapter 3.4 --- Park vegetation --- p.45 / Chapter 3.5 --- Park soils --- p.47 / Chapter 3.6 --- Park management and horticultural routines --- p.47 / Chapter CHAPTER 4 --- BASELINE STUDY OF URBAN PARK SOIL PROPERTIES / Chapter 4.1 --- Introduction --- p.52 / Chapter 4.2 --- Methodology --- p.54 / Chapter 4.2.1 --- Sampling --- p.54 / Chapter 4.2.2 --- Soil texture --- p.55 / Chapter 4.2.3 --- Soil reaction --- p.55 / Chapter 4.2.4 --- Total Kjeldahl nitrogen (TKN) --- p.55 / Chapter 4.2.5 --- Mineral nitrogen (ammonium and nitrate nitrogen) --- p.55 / Chapter 4.2.6 --- Total phosphorus --- p.56 / Chapter 4.2.7 --- Available phosphorus --- p.56 / Chapter 4.2.8 --- Organic carbon --- p.56 / Chapter 4.2.9 --- "Exchangeable cations (K, Na, Ca, Mg)" --- p.57 / Chapter 4.2.10 --- Carbon: nitrogen ratio and carbon: phosphorus ratio --- p.57 / Chapter 4.3 --- Statistical analysis --- p.57 / Chapter 4.4 --- Results --- p.58 / Chapter 4.4.1 --- Texture --- p.58 / Chapter 4.4.2 --- Soil pH --- p.58 / Chapter 4.4.3 --- Organic matter --- p.59 / Chapter 4.4.4 --- Total Kjeldahl nitrogen and C:N ratio --- p.60 / Chapter 4.4.5 --- Ammonium nitrogen and nitrate nitrogen --- p.61 / Chapter 4.4.6 --- Total phosphorus and C:P ratio --- p.62 / Chapter 4.4.7 --- Available phosphorus --- p.64 / Chapter 4.4.8 --- Exchangeable cations --- p.65 / Chapter 4.5 --- Discussion --- p.66 / Chapter 4.5.1 --- Park soils under different vegetation covers --- p.67 / Chapter 4.5.2 --- Duration of park management and influence of land use outside the parks --- p.72 / Chapter 4.5.3 --- Quality of substrates in Kowloon Park and Tin Shui Wai Park --- p.76 / Chapter 4.5.4 --- C:N ratio and C:P ratio --- p.83 / Chapter 4.6 --- Conclusion --- p.84 / Chapter CHAPTER 5 --- NITROGEN DYNAMICS OF URBAN PARK SOILS / Chapter 5.1 --- Introduction --- p.87 / Chapter 5.2 --- Methodology --- p.89 / Chapter 5.2.1 --- In situ incubation --- p.89 / Chapter 5.2.2 --- "Determination of N mineralization, leaching and uptake" --- p.91 / Chapter 5.3 --- Results --- p.94 / Chapter 5.3.1 --- "Net ammonification, NH4-N leaching and uptake" --- p.94 / Chapter 5.3.2 --- "Net nitrification, NO3-N leaching and uptake" --- p.95 / Chapter 5.3.3 --- "Net N mineralization, N leaching and uptake" --- p.96 / Chapter 5.4 --- Discussion --- p.97 / Chapter 5.4.1 --- Nitrogen mineralization and immobilization --- p.98 / Chapter 5.4.2 --- Comparison with other studies --- p.100 / Chapter 5.4.3 --- Nitrogen leaching and uptake --- p.103 / Chapter 5.5 --- Conclusion --- p.108 / Chapter CHAPTER 6 --- PHOSPHORUS DYNAMICS OF URBAN PARK SOILS / Chapter 6.1 --- Introduction --- p.110 / Chapter 6.2 --- Methodology --- p.112 / Chapter 6.3 --- Results --- p.113 / Chapter 6.4 --- Discussion --- p.115 / Chapter 6.4.1 --- Phosphorus mineralization and immobilization --- p.115 / Chapter 6.4.2 --- Phosphorus leaching and uptake --- p.118 / Chapter 6.4.3 --- Comparison with other studies --- p.120 / Chapter 6.5 --- Conclusion --- p.122 / Chapter CHAPTER 7 --- CONCLUSION / Chapter 7.1 --- Summary of findings --- p.124 / Chapter 7.2 --- Implications of the study --- p.128 / Chapter 7.2.1 --- Chemical characteristics of urban park soils and their relationship to management --- p.128 / Chapter 7.2.2 --- Management practices for different vegetation types and species --- p.133 / Chapter 7.3 --- Limitations of the study --- p.136 / Chapter 7.4 --- Suggestions for future study --- p.139 / REFERENCES --- p.141 / APPENDICES --- p.157

Chan, Wing Shing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 201-222). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (in Chinese) --- p.iv / Acknowledgements --- p.vi / Table of contents --- p.viii / List of tables --- p.xii / List of figures --- p.xiv / List of plates --- p.xvi / Chapter Chapter One --- Introduction / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research background --- p.2 / Chapter 1.3 --- Conceptual framework --- p.6 / Chapter 1.4 --- Objectives of the study --- p.10 / Chapter 1.5 --- Significance of the study --- p.11 / Chapter 1.6 --- Organization of the thesis --- p.12 / Chapter Chapter Two --- Literature Review / Chapter 2.1 --- Land degradation: an overview --- p.14 / Chapter 2.2 --- Land degradation in Hong Kong --- p.17 / Chapter 2.3 --- Ecological rehabilitation --- p.20 / Chapter 2.4 --- Role of plantation in ecological rehabilitation --- p.22 / Chapter 2.5 --- Reforestation history in Hong Kong and species selection --- p.25 / Chapter 2.6 --- Nutrient requirements of native species --- p.31 / Chapter 2.7 --- The geology and soils of Hong Kong --- p.35 / Chapter 2.7.1 --- Geology --- p.35 / Chapter 2.7.2 --- Soils --- p.35 / Chapter 2.8 --- Greenhouse approach in nutrient requirement study --- p.37 / Chapter 2.9 --- Nitrogen mineralization --- p.38 / Chapter 2.10 --- Chlorophyll fluorescence --- p.40 / Chapter 2.11 --- Summary --- p.41 / Chapter Chapter Three --- Inherent Characteristics and Properties of Decomposed Granite and Fire-affected Soil / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Materials and methods --- p.42 / Chapter 3.2.1 --- Sources of soil and sampling --- p.43 / Chapter 3.2.2 --- Soil pre-treatment --- p.44 / Chapter 3.3 --- Laboratory analysis --- p.45 / Chapter 3.3.1 --- Reaction pH and conductivity --- p.45 / Chapter 3.3.2 --- Texture --- p.46 / Chapter 3.3.3 --- Organic carbon --- p.46 / Chapter 3.3.4 --- Total Kjeldahl nitrogen (TKN) --- p.47 / Chapter 3.3.5 --- Carbon: nitrogen ratio --- p.47 / Chapter 3.3.6 --- Total phosphorus (TP) --- p.47 / Chapter 3.3.7 --- Exchangeable Al and H --- p.48 / Chapter 3.3.8 --- "Exchangeable cations, base saturation percentage (BSP) and exchangeable Al percentage" --- p.48 / Chapter 3.4 --- Results and discussion --- p.49 / Chapter 3.4.1 --- Texture --- p.49 / Chapter 3.4.2 --- Reaction pH and conductivity --- p.49 / Chapter 3.4.3 --- "Soil organic matter, total Kjeldhal nitrogen and total phosphorus" --- p.51 / Chapter 3.4.4 --- Exchangeable cations --- p.52 / Chapter 3.4.5 --- DG as a representative soil of soil destruction sites --- p.54 / Chapter 3.4.6 --- FAS as a representative soil of vegetation disturbance sites --- p.56 / Chapter 3.5 --- Summary --- p.58 / Chapter Chapter Four --- Nitrogen Fluxes of Decomposed Granite and Fire-affected Soil Amended with Urea / Chapter 4.1 --- Introduction --- p.59 / Chapter 4.2 --- Materials and methods --- p.62 / Chapter 4.2.1 --- Experimental design --- p.62 / Chapter 4.2.2 --- Soil incubation and sampling --- p.63 / Chapter 4.2.3 --- Analysis of mineral nitrogen (NH4-N and NO3-N) --- p.64 / Chapter 4.2.4 --- Statistical analysis --- p.64 / Chapter 4.3 --- Results and discussion --- p.64 / Chapter 4.3.1 --- Variation of NH4-N in DG and FAS --- p.64 / Chapter 4.3.2 --- Variation of N03-N in DG and FAS --- p.68 / Chapter 4.3.3 --- Variation of mineral N in DG and FAS --- p.74 / Chapter 4.3.4 --- NH4-N fluxes in DG and FAS --- p.78 / Chapter 4.3.5 --- NO3-N fluxes in DG and FAS --- p.80 / Chapter 4.3.6 --- Mineral N fluxes in DG and FAS --- p.82 / Chapter 4.4 --- Summary --- p.86 / Chapter Chapter Five --- Growth Performance of Native Species in Decomposed Granite and Fire-affected Soil / Chapter 5.1 --- Introduction --- p.88 / Chapter 5.2 --- Materials and methods --- p.91 / Chapter 5.2.1 --- Experimental design --- p.91 / Chapter 5.2.2 --- Nitrogen treatments --- p.94 / Chapter 5.2.3 --- Post-planting care --- p.95 / Chapter 5.2.4 --- "Measurement of survival rate, height, basal diameter, aboveground biomass and foliar nitrogen" --- p.95 / Chapter 5.2.4.1 --- Survival rate --- p.96 / Chapter 5.2.4.2 --- Height and basal diameter --- p.96 / Chapter 5.2.4.3 --- Aboveground biomass --- p.96 / Chapter 5.2.4.4 --- Foliar sampling --- p.97 / Chapter 5.2.4.5 --- Determination of foliar nitrogen --- p.97 / Chapter 5.2.5 --- Statistical analysis --- p.97 / Chapter 5.3 --- Results and discussion --- p.98 / Chapter 5.3.1 --- Survival rate --- p.98 / Chapter 5.3.2 --- Height growth of species in DG --- p.105 / Chapter 5.3.3 --- Effect of nitrogen on species height growth in DG --- p.112 / Chapter 5.3.4 --- Height growth of species in FAS --- p.117 / Chapter 5.3.5 --- Effect of nitrogen on species height growth in FAS --- p.118 / Chapter 5.3.6 --- Effect of DG and FAS on species height growth --- p.120 / Chapter 5.3.7 --- Basal diameter growth of species in DG --- p.122 / Chapter 5.3.8 --- Effect of N on basal diameter growth of species in DG --- p.124 / Chapter 5.3.9 --- Basal diameter growth of species in FAS --- p.126 / Chapter 5.3.10 --- Effect of N on basal diameter growth of species in FAS --- p.127 / Chapter 5.3.11 --- Effect of DG and FAS on species basal diameter growth --- p.127 / Chapter 5.3.12 --- Overall height and basal diameter growth of species in DG . --- p.129 / Chapter 5.3.13 --- Overall height and basal diameter growth of species in FAS --- p.131 / Chapter 5.3.14 --- Aboveground biomass of species in DG --- p.133 / Chapter 5.3.15 --- Effect of N on aboveground biomass of species in DG --- p.135 / Chapter 5.3.16 --- Aboveground biomass production in FAS --- p.138 / Chapter 5.3.17 --- Effect of N on aboveground biomass of species in FAS --- p.139 / Chapter 5.3.18 --- Effect of DG and FAS on aboveground biomass of species --- p.141 / Chapter 5.3.19 --- Foliar nitrogen --- p.143 / Chapter 5.3.19.1 --- Foliar N of species grown in DG --- p.143 / Chapter 5.3.19.2 --- Effect of N amendment on foliar N of species in DG --- p.147 / Chapter 5.3.19.3 --- Foliar N of species in FAS --- p.149 / Chapter 5.3.19.4 --- Effect of N amendment on foliar N of species in FAS --- p.151 / Chapter 5.3.19.5 --- Effect of DG and FAS on the foliar N of species --- p.152 / Chapter 5.4 --- Summary --- p.155 / Chapter Chapter Six --- Photosynthetic Efficiency of Native Species / Chapter 6.1 --- Introduction --- p.158 / Chapter 6.2 --- Materials and methods --- p.160 / Chapter 6.2.1 --- Measurement of chlorophyll fluorescence --- p.160 / Chapter 6.2.2 --- Statistical analysis --- p.162 / Chapter 6.3 --- Results and discussion --- p.162 / Chapter 6.3.1 --- Photosynthetic efficiency of species in DG --- p.162 / Chapter 6.3.2 --- Photosynthetic efficiency of species in FAS --- p.170 / Chapter 6.3.3 --- Effect of DG and FAS on photosynthetic efficiency of Species --- p.172 / Chapter 6.4 --- Summary --- p.175 / Chapter Chapter Seven --- Conclusions / Chapter 7.1 --- Introduction --- p.178 / Chapter 7.2 --- Summary of major findings --- p.179 / Chapter 7.3 --- Implications of the study --- p.187 / Chapter 7.3.1 --- Species selection for the rehabilitation of soil destruction sites --- p.187 / Chapter 7.3.2 --- Species selection for the rehabilitation of vegetation disturbance sites --- p.191 / Chapter 7.3.3 --- Fertilization practice in different degraded lands --- p.193 / Chapter 7.3.4 --- The importance of soil test in ecological rehabilitation Planting --- p.195 / Chapter 7.4 --- Limitations of the study --- p.197 / Chapter 7.5 --- Suggestions for further study --- p.198 / References --- p.201 / Appendices --- p.223

"September 2001" / Bibliography: leaves 144-159. / xix, 159 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The two main aims of this study were: 1) to determine if the presence of Calcium carbonate in soil was the reason behind soils from Yorke Peninsula having relatively high OC (organic carbon) contents, given local farming practices, and 2) to determine the effect that the composition of the soils' OC has on the mineralisation rates. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy and Farming Systems, 2002

Rotating wheat with other crops is a common practice in the Willamette Valley of western Oregon. Depending upon previous crop and soil type, current N fertilizer recommendations for wheat in the Willamette Valley vary widely. Excessive fertilizer poses environmental risk, whereas lower N inputs than required by the crop represent economic losses to growers. Growers and their advisors face the challenge to minimize the environmental risk, and at the same time to maintain or increase economic returns. Questions are often raised concerning the efficient use of N fertilizer and accurately predicting the amount of N needed by wheat following different crops. The first study measured growth, N uptake and N use efficiency (NUE) of winter wheat grown after either a legume or oat for three years. In all three growing seasons, winter wheat showed higher biomass, N uptake and NUE when grown after a legume than after oat. The contribution of legume was evident before the wheat was fertilized in spring, indicating that legume N had mineralized in fall or winter. Contribution of soil N to wheat suggested that fertilizer N can be reduced by 44 kg N ha����� if a legume is grown previously. Nitrogen use efficiency estimated 50 to 70 days after N application by isotopic method (24 to 94%) was comparable with that estimated simply by difference (21 to 94%) at the same time. The second study predicted gross mineralization rates using analytical models. Comparable N mineralization was predicted by a model assuming remineralization and a model assuming no remineralization, suggesting that remineralization was negligible. In the spring, mineralization-immobilization turnover was at a lower pace than expected in both rotations. In two growing seasons, gross mineralization rates were higher where the previous crop was legume (0.37 to 0.74 kg����� ha����� day�����) as compared to where oat was grown previously (0.14 to 0.6 kg����� ha����� day). Negative net mineralization indicated that fertilizer N was immobilized in the oat-wheat rotation. The third study evaluated calibration and digestion techniques used to determine elemental concentration in grasses. Use of a dry ashed standard to calibrate the ICP spectrometer generated highly variable calibration curves and was not a viable calibration method. Good agreement was found between chemical and microwave digested standards. Dry ashing resulted in considerable S and Mn losses, whereas, perchloric acid digestion and microwave digestion showed similar results. Our study suggests that if routine analysis are to be performed for macro nutrients or involve trace level work, the best method is microwave digestion with chemical standard calibration of ICP spectrometer. / Graduation date: 1999

Winter wheat is commonly grown in rotation with leguminous and non-leguminous crops in the Willamette Valley. For agronomic, economic, and environmental reasons it is important to understand the influence of previous crops on availability of N and other nutrients. Objectives of this study were: (1) to evaluate the effects of long-term rotations on winter wheat response to N fertilizer, and (2) to evaluate the use of Plant Root Simulator���(PRS) probes for measuring soil N mineralization and N availability to winter wheat. Field experiments were conducted over three growing seasons in plots of `Stephens' soft white winter wheat at Hyslop farm. Plots receiving 0, 50, 100, 150 and 200 kg N ha����� at Feekes GS 4 were sampled to determine above ground N uptake, grain yield, and grain protein. In spring 1998, PRS probes were placed in 0 kg N ha����� plots and removed at one-week or two-week intervals. In autumn 1998, probes were placed in unfertilized plots and removed at 1-week, 4-week, and 8-week intervals. Probes measured the availability of NH������-N, NO������-N, K���, Ca�����, Mg�����, and P0��������-P. Grain yield and N uptake were greater for wheat following clover as compared to following oats. Three-year average fertilizer equivalent values calculated from N uptake and grain yield data were 44.5 kg N h����� and 49.0 kg N h�����, respectively. The similarity of these independent measurements suggest that differences in N availability were the primary reason for the rotation effect. PRS probes also detected rotational differences in N availability. Average N recovered by probes sampled at 1-week intervals indicated that there was 63% as much NO������-N available to wheat following oat as compared to clover. Wheat recovered 64% as much N following oats as compared to clover. This suggests that PRS probes are an effective method for predicting relative amounts of plant available N. PRS probes also detected rotational differences in plant available potassium. Agronomic responses are useful for assessing the availability of nutrients that are limiting plant growth. PRS probes, on the other hand, are effective for assessing the availability of both limiting and non-limiting nutrients. / Graduation date: 2000

Graduation date: 1996