Phosphorus (P) released in overland flow is related to P form, soil solution P concentration and the release rate of P from soil. Models relating soil test P (STP) to water soluble P (WSP) and the degree of P saturation (DPS) to STP are used in Virginia to estimate P loss potential. Typically the reservoir of biologically available P in eastern soils has been attributed to P sorbed onto surface sites of non-crystalline aluminum (Al) and iron (Fe) oxides, extractable in ammonium oxalate. More recently, soils with a long-term history of manure application have exhibited properties that indicate calcium (Ca) may also be limiting P, especially in soils impacted by poultry manure. Accurate estimation of P loss potential is critical for justification of long-term management approaches. To evaluate the accuracy of model estimation of P loss potential and P source, we evaluated the (i) soil chemical properties, (ii) soil solution equilibria, (iii) inorganic speciation, and (iv) P desorption capacity of soils impacted over a long period of time by poultry litter (broiler and layer), dairy manure and commercial fertilizer applications. Soil chemical properties were measured with various extractions, while soil solution was measured in samples equilibrated at field capacity. Inorganic material was analyzed using scanning electron microscopy with electron dispersive capacities. Phosphorus desorption capacity was determined by calculating the rate of P release into a 0.01 M NaCl batch reactor. Out of the said analysis, we found that Al and Ca were the primary soil chemical elements limiting soil test P extractability and release. Soils with a high P sorbing capacity (PSC), that were not yet saturated, retained the most total soil P over a 60 hr. batch release experiment. Phase diagrams show that all soils were supersaturated with respect to common Al-, and Fe â P minerals. Saturation indices calculated with Visual Minteq were correlated with the degree of P saturation, and suggested that as the DPS increased, formation of less soluble Ca -P minerals occurs. The soils found to be supersaturated with respect to tri-calcium phosphate (TCP) and octa-calcium (OCP) had the highest P release rate coefficients for both the first (k1) and second (k2) phases of release. Scanning electron microscopy with electron dispersive analysis (SEM-EDS) found that for some manure impacted soils, Al formed associations with P that are stable over a large soil to solution ratio. Additionally, it appears that as non-crystalline Al becomes saturated with P, Ca-P forms may act as an additional reservoir of P in soils with a long-term history of poultry manure application. / Master of Science

Archaeological sediment chemistry is a valuable but underutilized method for exploring the use of space in the past. It is based on the understanding that many human activities will impact the chemistry of the sediment upon which they are performed, either by introducing or causing depletion of chemical residues. Although sediment chemistry can provide valuable data on “invisible” activities and the ways that humans structure space, it has been underutilized in the Mediterranean to date. This dissertation comprises four articles, two of which propose new methodological approaches to chemical analysis and sample collection, and two of which are case studies demonstrating the value of sediment chemistry in diverse archaeological contexts. These studies use samples collected from sites in the Gediz River valley in western Turkey through the Central Lydia Archaeological Survey and the Kaymakçı Archaeological Project. Areas studied include a contemporary courtyard used regularly, an abandoned 20th century village, and a 2nd millennium BCE citadel (Kaymakçı). The first article directly compares the results of inductively coupled plasma mass spectrometry and wavelength dispersive x-ray fluorescence—the latter using two sample preparations, loose-powder and fusion-bead—to determine if the methods produce comparable data. The study demonstrates that these methods are statistically comparable, supporting the validity of a wider variety of analytical methods and therefore increasing the accessibility of the method. The second article presents an innovative multi-scalar sampling strategy designed for the citadel of Kaymakçı; analysis results demonstrate how different chemical datasets inform one another, and how each contributes to our understanding of the site. The third article is an ethnoarchaeological examination of a modern-day courtyard and demonstrates the ability of sediment chemistry to recognize both visible and invisible activity areas that help to reveal the taskscape and smellscape of the courtyard as experienced by its inhabitants. The fourth article presents a holistic sediment chemistry study of the citadel of Kaymakçı. In combination with data from geophysical survey and excavation, results suggest that social organization at the site was relatively heterarchical, in contrast to expectations for a citadel site in this region. / 2021-12-24T00:00:00Z

The legacy phosphorus (P) in the Eastern Shore of Virginia poses significant challenges for crop nutrition and water quality. Nutrient losses from row crop agriculture and poultry litter applications have potential to cause water quality impairments affecting the environment, aquaculture, and tourism industries. To address these concerns, this study investigated P management strategies across various scales. The first component of the study focused on optimizing edamame production in the context of high legacy soil P levels and harvest efficiency. Over three years, field experiments on Bojac sandy loam soil assessed the effects of different P fertilizer rates and legacy P levels on edamame yield, biomass, and P uptake. Results showed that short-season edamame in high legacy P soils had significantly more yield than long-season varieties. However, additional P fertilization was deemed unnecessary for soils with P concentrations above 21 kg P ha-1, as current edamame P recommendations exceed the crop's P removal needs. Moreover, mechanical harvesting efficiency was notably higher for short-statured edamame varieties (89.3%) compared to tall varieties, indicating their preference for improved harvesting. The second component examined the influence of agricultural lime on legacy P phases in the soil. Lime was applied at rates ranging from 0 to 2690 kg ha-1 to an acid sandy loam Ultisol (pH < 5.1). Using partial Hedley P fractionation, changes in water-soluble P, soil test P (Mehlich-1 extraction), and total soil P (nitric acid digest) were monitored. Although lime application significantly affected soil pH, calcium (Ca), and magnesium (Mg), it did not significantly alter the relative proportions of water-soluble and soil test P. This indicates that while lime can improve soil pH and nutrient availability, it does not substantially impact P phase distribution. The final study utilized historical water quality data from the Virginia Institute of Marine Sciences and GIS technology to analyze the impact of land use and land cover (LULC) on nitrogen (N) and P concentrations in 52 watersheds. Row crop LULC was significantly correlated with higher total nitrogen (TN) concentrations (p = 0.03), while forested LULC was linked to lower TN (p = 0.02) and nitrate-nitrite (NOx) concentrations (p = 0.05). Thirty-two out of 52 watersheds had mean total P concentrations exceeding 0.10 mg L-1, with stormflow conditions showing significantly higher total P concentrations and loadings compared to baseflow. Landscape-scale turbidity strongly correlated with elevated total P levels, emphasizing the role of particulate P transport. Baseflow samples also had higher ammonia (NH3) and NOx concentrations, but stormflow resulted in higher loadings. In conclusion, effective P management on the Eastern Shore requires a coordinated approach that addresses soil, crop, watershed, and landscape-scale factors in cooperation with multiple stakeholder groups. This study highlights the importance of optimizing agronomic practices and implementing targeted conservation strategies to mitigate nutrient and sediment losses, thereby improving both crop production and environmental quality. / Doctor of Philosophy / The Eastern Shore of Virginia has high levels of phosphorus (P) due to past farming and poultry litter use, which can have a major impact on both farming and water quality. To address high soil P, our study looked at different ways to manage P effectively. First, we studied how to grow edamame (a type of soybean) more efficiently in soils with different P levels. Over three years, we tested various P fertilizer amounts and found that fast-growing edamame plants grew better in soils with high P than long-season varieties. We also discovered that adding more P fertilizer was not necessary. Additionally, short-statured edamame varieties were easier to harvest mechanically and had better harvesting efficiency compared to taller varieties, making them ideal for mass production. Next, we explored how adding agricultural lime might change the way P is stored in soil. We applied lime at different amounts to very acidic sandy soil and measured its effects. Although lime improved soil pH and availability of certain nutrients, it did not significantly change how P was distributed in the soil. Finally, we used maps and water quality data to see how different land uses, like row crops and forests, affect P and nitrogen (N) levels in local streams. We found the areas with more row crops had higher N levels, while forested areas had lower levels. We noticed that rainy conditions led to higher P levels in streams compared to normal flow conditions because the P was attached to soil particles, suggesting that reducing soil erosion and nutrient runoff is crucial. In summary, managing P is essential for both better crop yields and cleaner water. This study provides important insights to land managers to improve agricultural practices and protect local waterways.

Headwater catchments play a large role in the storage and release of water and chemical constituents, thereby influencing downstream flows and water quality. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variation by using high temporal resolution, in situ sensors. However, despite these new technologies, there have been limited studies on installation approaches and their effects on sensor measurements. Accurate in situ monitoring is particularly important to capture catchment disturbance effects that may be highly dynamic over time (e.g., following storms) or limited in duration. For example, prescribed fire is a commonly applied forest management tool, but there remain questions regarding how this disturbance affects catchment soils and resultant stream water chemistry. Effective assessment of prescribed fire thus requires coupled monitoring of both soil properties and water chemistry. In this thesis, I addressed two linked objectives: i) assess the effects of commonly used protective housings on in situ sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I compared four different housing types (mesh, screen, holes, and open) using in situ specific conductance measurements over time and from salt tracer injections for discharge estimates. This study demonstrated substantial effects from some of the housing types evaluated, where flow resistance reduced water exchange between stream water and water in contact with the sensor. From these findings, I suggest that in situ water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I assessed prescribed fire effects on soil properties (particle size, aggregate stability, and chemistry), stream discharge, and fine-scale water chemistry dynamics. Findings demonstrated some significant differences following fire in soil properties (e.g., overall decrease in aggregate stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of DOC, turbidity, and nitrate) and discharge (increases in stage and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether the minor level of disturbance observed in this study results in any negative environmental impacts. / Master of Science / Headwater catchments (where precipitation first becomes streamflow) provide important aquatic habitat and regulate downstream water flows and chemistry. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variability by using high frequency, submerged water quality sensors. However, these new technologies present new, unique challenges, such as measurement errors that may be induced by different installation methodologies. Accurate measurements are particularly important to evaluate how changes in catchment conditions (e.g., soils, vegetation) impact local and downstream water quality. For example, prescribed fire is a commonly used forest management tool, but questions remain about how it affects catchment soils and headwater stream chemistry. Consequently, understanding the effects of this and other catchment disturbances requires coupled monitoring of both soil properties and water quality. In this thesis, I addressed two objectives: i) assess the effects of commonly used protective housings on water quality sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I demonstrated substantial effects from some of the housings evaluated and suggest that water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I demonstrated some significant effects of prescribed fire on soil properties (e.g. overall decrease in soil stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of dissolved organic matter, turbidity, and nitrate) and flow (increases in stream water levels and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether this minor level of disturbance causes any negative environmental impacts.

<p dir="ltr">Conservation agriculture has differential impact on the soil organic carbon (SOC) and total nitrogen (TN) storage. Thus, the study was conducted to investigate the long-term response of tillage and crop rotation on SOC and TN storage and their association with mineral fraction dynamics. The key findings of this research indicated that soil organic carbon (SOC) and total nitrogen (TN) storage were enhanced under no-tillage; however, SOC and TN storage showed no significant difference between intermediate tillage (chisel plow) and extreme tillage (moldboard plow). Similarly, the increase in carbon and nitrogen content at the plow depth of the tillage systems was attributed to particulate fractions, while the carbon and nitrogen associated with minerals were higher in no-till systems, regardless of soil depth.</p>

by Fung, Chun-hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 111-123). / Abstract --- p.i / Acknowledgments --- p.iii / List of Tables --- p.v / List of Figures --- p.vii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Reforestation in Hong Kong --- p.1 / Chapter 1.2 --- Conceptual framework of the study --- p.2 / Chapter 1.3 --- Objectives of the study --- p.5 / Chapter 1.4 --- Significance of the study --- p.6 / Chapter 1.5 --- Organization of the thesis --- p.6 / Chapter Chapter 2 --- Literature Review / Chapter 2.1 --- Vegetation and soils --- p.8 / Chapter 2.2 --- Trees and soil physical properties --- p.9 / Chapter 2.2.1 --- Aggregate stability --- p.9 / Chapter 2.2.2 --- Organic matter and aggregate stability --- p.10 / Chapter 2.2.3 --- Other factors affecting aggregate stability --- p.12 / Chapter 2.2.4 --- Reforestation and bulk density --- p.12 / Chapter 2.2.5 --- Reforestation and soil moisture --- p.13 / Chapter 2.3 --- Trees and soil chemical properties --- p.14 / Chapter 2.3.1 --- Exchangeable acidity --- p.14 / Chapter 2.3.2 --- Exchangeable acidity and cation exchange capacity --- p.15 / Chapter 2.3.3 --- Organic matter and cation exchange capacity --- p.15 / Chapter 2.3.4 --- Clay and cation exchange capacity --- p.16 / Chapter 2.3.5 --- Organic matter and nitrogen --- p.17 / Chapter 2.3.6 --- Organic matter and phosphorus --- p.18 / Chapter 2.4 --- Litter decomposition --- p.18 / Chapter 2.4.1 --- Factor affecting litter decomposition --- p.19 / Chapter 2.4.2 --- Effects of litter on soil nutrient reserve --- p.21 / Chapter Chapter 3 --- The Study Area / Chapter 3.1 --- Location --- p.23 / Chapter 3.2 --- Geology --- p.23 / Chapter 3.3 --- Soils --- p.25 / Chapter 3.4 --- Vegetation --- p.27 / Chapter 3.4.1 --- Reforestation since the mid-1980s --- p.27 / Chapter 3.4.2 --- Growth performance of the acacias --- p.28 / Chapter 3.4.3 --- Undergrowth of the acacia woodlands --- p.29 / Chapter Chapter 4 --- Effects on Soil Physical Properties / Chapter 4.1 --- Introduction --- p.31 / Chapter 4.2 --- Methodology --- p.33 / Chapter 4.2.1 --- Soil texture --- p.33 / Chapter 4.2.2 --- Bulk density and porosity --- p.33 / Chapter 4.2.3 --- Penetration resistance --- p.34 / Chapter 4.2.4 --- Aggregate stability --- p.34 / Chapter 4.2.5 --- Water characteristic curve --- p.35 / Chapter 4.2.6 --- Infiltration rate --- p.35 / Chapter 4.3 --- Statistical analysis --- p.35 / Chapter 4.4 --- Results --- p.36 / Chapter 4.4.1 --- Soil texture --- p.36 / Chapter 4.4.2 --- "Bulk density, porosity and penetration resistance" --- p.36 / Chapter 4.4.3 --- Aggregate stability --- p.38 / Chapter 4.4.4 --- Infiltration --- p.39 / Chapter 4.4.5 --- Water characteristic curve --- p.40 / Chapter 4.5 --- Discussion --- p.42 / Chapter 4.5.1 --- Inherent physical properties of granitic soil --- p.42 / Chapter 4.5.2 --- Effects of acacias on the aeration of granite soil --- p.44 / Chapter 4.5.3 --- Effects of acacias on the penetration resistance and aggregate stability of granitic soil --- p.46 / Chapter 4.5.4 --- Effects of acacias on the water transmission property of granitic soil --- p.47 / Chapter 4.5.5 --- Effects of acacias on the water retention property of granitic soil --- p.50 / Chapter 4.6 --- Conclusion --- p.52 / Chapter Chapter 5 --- Effects on Soil Chemical Properties / Chapter 5.1 --- Introduction --- p.54 / Chapter 5.2 --- Methodology --- p.55 / Chapter 5.2.1 --- Sampling --- p.55 / Chapter 5.2.2 --- Soil reaction and conductivity --- p.55 / Chapter 5.2.3 --- Organic carbon --- p.55 / Chapter 5.2.4 --- Total Kjeldahl nitrogen --- p.56 / Chapter 5.2.5 --- Total phosphorus --- p.56 / Chapter 5.2.6 --- "Exchangeable K, Ca, Mg and Na" --- p.56 / Chapter 5.2.7 --- Exchangeable A1 and H --- p.57 / Chapter 5.2.8 --- Carbon : nitrogen ratio --- p.57 / Chapter 5.3 --- Statistical analysis --- p.57 / Chapter 5.4 --- Results --- p.58 / Chapter 5.4.1 --- Conductivity --- p.58 / Chapter 5.4.2 --- Soil pH and exchangeable acidity --- p.58 / Chapter 5.4.3 --- Soil organic matter --- p.61 / Chapter 5.4.4 --- Total Kjeldahl nitrogen --- p.62 / Chapter 5.4.5 --- Total phosphorus --- p.63 / Chapter 5.4.6 --- "Exchangeable K, Ca, Mg and Na" --- p.64 / Chapter 5.5 --- Discussion --- p.67 / Chapter 5.5.1 --- Inherent chemical properties of granitic soil --- p.67 / Chapter 5.5.2 --- Effects of acacias on the acidity of granitic soil --- p.69 / Chapter 5.5.3 --- "Effects of acacias on the organic matter, total nitrogen and phosphorus of granitic soil" --- p.71 / Chapter 5.5.4 --- Effects of acacias on the exchangeable cations of granitic soil --- p.74 / Chapter 5.6 --- Conclusion --- p.76 / Chapter Chapter 6 --- Litter Decomposition / Chapter 6.1 --- Introduction --- p.78 / Chapter 6.2 --- Methodology --- p.79 / Chapter 6.2.1 --- Standing litter --- p.79 / Chapter 6.2.2 --- Litter decomposition --- p.80 / Chapter 6.2.3 --- Chemical analysis --- p.80 / Chapter 6.3 --- Statistical analysis --- p.81 / Chapter 6.4 --- Results --- p.81 / Chapter 6.4.1 --- Standing litter --- p.81 / Chapter 6.4.2 --- Chemical composition of fresh litters --- p.82 / Chapter 6.4.3 --- Cumulative dry weight loss of litters --- p.82 / Chapter 6.4.4 --- Cumulative weight loss of nutrients --- p.84 / Chapter 6.4.5 --- C : element ratios --- p.88 / Chapter 6.5 --- Discussion --- p.88 / Chapter 6.5.1 --- Litter decomposition --- p.88 / Chapter 6.5.2 --- Litter decomposition and soil organic matter --- p.93 / Chapter 6.5.3 --- Nutrient release patterns --- p.94 / Chapter 6 5 --- 4 Litter decomposition and soil nutrient reserves --- p.96 / Chapter 6.6 --- Conclusion --- p.98 / Chapter Chapter 7 --- Conclusion / Chapter 7.1 --- Summary of findings --- p.100 / Chapter 7.2 --- Implication of the study --- p.103 / Chapter 7.3 --- Limitations of the study --- p.106 / Chapter 7.4 --- Suggestion for future study --- p.108 / References --- p.111 / Appendice --- p.124

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

Thesis (MScAgric (Soil Science)--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: A number of chemical and physical features of Namibian soils in a 22 790 km2, two degree-square block between 17 – 19 oE and 22 – 23 oS in eastern central Namibia, had been investigated, and the fertility status established. In 80 % of samples the nitrate, nitrite, and sulfate concentrations of the saturated paste extract are 0 – 54.6 mg l-1 NO3 -, 0 – 24.7 mg l-1 NO2 -, and 5.4 – 20.9 mg l-1 SO4 2- respectively. In 90 % of samples the plantavailable phosphorus is below 12 mg kg-1, which is low for a soil under natural grassland, but in line with the prevailing semi-arid climate and low biomass production of the study area. In 80 % of samples the extractable calcium, magnesium, potassium, and sodium concentrations are 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolckg-1 K (51 – 213 mg kg-1 K) and 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) respectively, while the exchangeable calcium, magnesium, potassium, and sodium concentrations are 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0 – 0.13 cmolckg-1 Na respectively. The mean ± 1 standard deviation is 3.57 ± 3.57 cmolckg-1 for cation exchange capacity, 3.48 ± 3.61 for sum of exchangeable bases and 4.53 ± 4.39 for sum of extractable bases. The cation exchange capacity and the sum of exchangeable bases are virtually identical, which indicate the almost complete absence of exchangeable H+ and Al3+ in the soils of the study area, as expected from a semi-arid climate. None of the profiles were classified as saline or sodic. In 80 % of samples the plant-available iron, manganese, zinc and copper concentrations are 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0 – 1.80 mg kg-1 Zn and 0 – 4.0 mg kg-1 Cu respectively. Soil organic matter content of the study area soils ranges between 0.05 – 2.00 %, with most (80 % of samples) containing 0.25 – 1.20 % organic matter. This is considerably lower than values reported in literature, even for other southern African countries. The reason lies with the hot, semi-arid climate. The pH distribution is close to normal, with 80 % of samples having pH (H2O) of 5.54 – 8.18, namely moderately acid to moderately alkaline. Sand, silt and clay content of most (80 %) samples varies between 60.3 – 89.7 % sand, 4.6 – 25.2 % silt and 3.5 – 19.1 % clay. The soils of the study area are mainly sandy, sandy loam and loamy sand. In 80 % of samples the coarse sand fraction ranges from 3.5 – 34.5 %, the medium sand fraction from 20.5 – 37.3 %, the fine sand fraction from 38.7 – 54.5 % and the very fine sand fraction from 0.0 – 12.9 % of all sand. The fine sand fraction, thus, dominates, with very fine sand being least abundant. The topsoil contains relatively more coarse sand and less very fine sand than the subsoil. Instances of sealing, crusting and hardening occur sporadically in the study area. Cracking is only found in pans, while self-mulching is not evident. No highly instable soils were encountered in the study area. The water-holding capacity is generally low, with depth limitations in the western highlands, the Khomas Hochland, and texture limitations in the eastern Kalahari sands. The central area has soils with a somewhat better water-holding capacity, but it is still very low when compared to arable soils of temperate, sub-humid and humid zones elsewhere in southern Africa. Soil characteristics are perceptibly correlated with climate, parent material, topography, degree of dissection of the landscape and position in the landscape. The most obvious differences are between soils formed in schistose parent material of the Khomas Hochland in the west and those of the Kalahari sands in the east. The soils of the study area are unsuitable to marginally suitable for rainfed crop production, due to low iv fertility. The study area is climatologically unsuited for rainfed crop production, so the present major land use is extensive livestock production on large farms. The natural vegetation is well adapted to the prevailing conditions. The methodology followed to delineate terrain units, with a combination of procedures involving digital elevation data and satellite imagery, seems to work well in the Namibian landscape. This study thus served as a successful proof-of-concept for the methodology, which can in future be rolled out for the remainder of the country. The site and analytical information is available in digital format as spreadsheets and in a geographical information system, as well as in a variety of digital and printed maps. / AFRIKAANSE OPSOMMING: ‘n Aantal chemiese en fisiese eienskappe van Namibiese gronde in ‘n 22 790 km2, 1o x 2o blok tussen 17 – 19 o Oos en 22– 23 o Suid in oostelike sentraal-Namibië is ondersoek en die grondvrugbaarheidstatus bepaal. In 80 % van monsters is die nitraat-, nitriet- en sulfaatkonsentrasies van die versadigde pasta ekstrak 0.0 – 54.6 mg l-1 NO3 -, 0.0 – 24.7 mg l-1 NO2 -, en 5.4 – 20.9 mg l-1 SO4 2-onderskeidelik. In 90 % van monsters is die plant-beskikbare fosfor minder as 12 mg kg-1, wat laag is vir gronde onder natuurlike grasveld, maar dit is verklaarbaar deur die heersende semi-ariede klimaat en lae biomassa produksie in die studiegebied. In 80 % van monsters is die konsentrasies van ekstraheerbare kalsium, magnesium, kalium en natrium 0.61 – 5.73 cmolckg-1 Ca (122 – 1 146 mg kg-1 Ca), 0.12 – 2.28 cmolckg-1 Mg (15 – 278 mg kg-1 Mg), 0.13 – 0.54 cmolc kg-1 K (51 – 213 mg kg-1 K) en 0.05 – 0.38 cmolckg-1 Na (11 – 87 mg kg-1 Na) onderskeidelik, terwyl die uitruilbare kalsium, magnesium, kalium en natrium konsentrasies onderskeidelik 0.21 – 6.02 cmolckg-1 Ca, 0.12 – 2.01 cmolckg-1 Mg, 0.12 – 0.49 cmolckg-1 K and 0.0 – 0.13 cmolckg-1 Na is. Die gemiddelde ± 1 standaardafwyking is 3.57 ± 3.57 cmolckg-1 vir katioonuitruilvermoë, 3.48 ± 3.61 vir die som van uitruilbare basisse en 4.53 ± 4.39 vir die som van ekstraheerbare basisse. Die katioonuitruilvermoë en som van uitruilbare basisse is feitlik identies, wat ‘n feitlik algehele afwesigheid van uitruilbare H+ and Al3+ in die gronde van die studiegebied aandui, soos verwag word weens die semi-ariede klimaat. Geeneen van die profiele is geklassifiseer as soutbrak of natriumbrak nie. In 80 % van monsters is die plant-beskikbare yster, mangaan, sink en koper konsentrasies onderskeidelik 7.2 – 32.8 mg kg-1 Fe, 13.6 – 207.5 mg kg-1 Mn, 0.0 – 1.80 mg kg-1 Zn en 0.0 – 4.0 mg kg-1 Cu. Grond organiese material inhoud in die studiegebied wissel tussen 0.05 – 2.00 %, met 80 % van monsters wat 0.25 – 1.20 % organiese material bevat. Dit is aansienlik laer as die waardes gevind in literatuur, selfs vir ander Suider-Afrikaanse lande. Die oorsaak is die warm, semiariede klimaat. Die pH verspreiding is feitlik normaal, met 80 % van monsters wat pH (H2O) van 5.54 – 8.18 het, met ander woorde matig suur tot matig alkalies. Sand, slik en klei inhoud van die meeste (80 %) monsters varieer tussen 60.3 – 89.7 % sand, 4.6 – 25.2 % slik en 3.5 – 19.1 % klei. Die gronde van die studiegebied is hoofsaaklik sand, sand-leem en leem-sand. In 80 % van monsters beslaan die growwe sandfraksie 3.5 – 34.5 %, die medium sandfraksie 20.5 – 37.3 %, die fyn sandfraksie 38.7 – 54.5 % en die baie fyn sandfraksie 0.0 – 12.9 % van die totale sandfraksie. Die fyn sandfraksie is dus dominant, terwyl die baie fyn sandfraksie die skaarsste is. Die bogronde bevat relatief meer growwe sand en minder baie fyn sand as die ondergronde. Gevalle van verseëling, korsvorming en verharding kom sporadies in die studiegebied voor. Krake kom net in panne voor en self-omkering is nie opgemerk nie. Geen hoogsonstabiele gronde is in die studiegebied gevind nie. Die waterhouvermoë is in die algemeen laag, met dieptebeperkinge in die westelike hooglande, die Khomas Hochland, en tekstuurbeperkinge in die oostelike Kalahari sande. Die sentrale gedeelte het gronde met ‘n ietwat beter waterhouvermoë, maar dis steeds baie laag in vergelyking met akkerbougronde van gematigde, sub-humiede en humiede sones elders in Suider- Afrika. Grondeienskappe is ooglopend verwant aan klimaat, moedermateriale, topografie, graad van gebrokenheid van die landskap en posisie in die landskap. Die duidelikste verskille kom voor in die gronde wat van vi skisagtige moedermateriaal van die Khomas Hochland in die weste en dié wat in die Kalahari sande in die ooste gevorm het. Die gronde van die studiegebied is ongeskik tot marginaal geskik vir droëland akkerbou, weens die lae vrugbaarheid. Aangesien die studiegebied klimatologies ongeskik is vir droëland akkerbou, is die huidige hoof landgebruik ekstensiewe veeproduksie op groot plase. Die natuurlike plantegroei is goed by die heersende omstandighede aangepas. Die metodiek wat gevolg is om terreineenhede af te baken, wat ‘n kombinasie van prosedures met digitale hoogtedata en satellietbeelde is, blyk goed te werk vir die Namibiese landskap. Hierdie studie dien dus as ‘n suksesvolle bewys-van-konsep van die metodiek, wat in die toekoms uitgebrei kan word na die res van die land. Die veld- en ontledingsinligting is beskikbaar in digitale formaat, in ‘n geografiese inligtingstelsel en ‘n verskeidenheid digitale- en gedrukte kaarte.

Thesis (MScAgric)--University of Stellenbosch, 1955. / No Abstract Available

A preocupação com a contaminação por metais reflete na busca de metodologias de recuperação de solos. O objetivo deste trabalho foi compreender os mecanismos de formação e oxidação dos sulfetos em solos e propor uma metodologia de imobilização de metais pela formação de sulfeto insolúvel e posterior fitoextração. Três experimentos foram conduzidos em solos contaminados com Cd e Zn. O primeiro teve como objetivo definir a concentração de (NH4)2S necessária para a formação dos sulfetos metálicos. Os resultados confirmam que a adição de sulfeto reduz a disponibilidade de Cd e Zn em Argissolos Vermelho-Amarelos distróficos e que concentrações de sulfetos superiores a 30 e 60 mmol kg-1, respectivamente para Cd e Zn, não melhora a capacidade de imobilização dos metais. O segundo experimento objetivou avaliar a influência da matéria orgânica, pH, tempo e ambiente na imobilização de Cd e Zn associado ao sulfeto. Foi demonstrado que a adição de matéria orgânica reduz a concentração de Cd solúvel e mantém o pH em faixa adequada às plantas. Para o Zn, a matéria orgânica não apresentou efeito significativo, prevalecendo o efeito do sulfeto. O aumento do pH, através da adição de carbonatos aumenta a imobilização do Cd e Zn em presença de sulfeto, influenciado pela formação dos respectivos hidróxidos. A exposição dos sulfetos metálicos a um ambiente oxidante reduz a imobilização de Cd e Zn devido à sua oxidação e consequente dissociação molecular. O terceiro experimento, desenvolvido em casa de vegetação, avaliou a disponibilidade de Cd e Zn e sua toxidez em Phaseolus vulgaris L. (feijão), utilizando a melhor dose de sulfeto com adição de matéria orgânica para obter maior eficiência na imobilização. A produção de massa seca da planta foi superior em solos que não continham sulfeto, o que indica fitotoxicidade. Concluímos que soluções de sulfeto podem ser utilizadas para imobilização temporária de Cd e Zn em solos contaminados, entretanto sua aplicação combinada à fitorremediação necessita de maiores estudos / The development of remediation of soil degraded areas methodologies reflects the concern with the metal contamination. The aim of this work was to understand the formation mechanisms and oxidation of sulfides in soils and propose a metal immobilization procedure by precipitation an insoluble sulfide and subsequent phytoextraction. Three experiments were conducted in contaminated soils with Cd and Zn. The first aimed to determine the (NH4)2S concentration necessary for the metallic sulfide formation. The results confirm that the sulfide addition reduces the Cd and Zn available in red-yellow dystrophic Argisoil and sulfide concentration above 30 and 60 mmol kg-1, respectively for Cd and Zn, not improve the metals immobilizations. The second experiment evaluated the organic matter, pH, time and atmosphere influence in the Cd- and Zn-sulfide immobilization. The addition of organic matter reduces the concentration of soluble Cd and maintaining the pH in adequate range for plants. For Zn, organic matter didn\'t show significant effect, prevailing the sulfide effect. The increase in pH by carbonates addition increases the Cd and Zn immobilizations in the sulfide presence. The exposure of metallic sulfide to an oxidizing atmosphere reduces Cd and Zn immobilization. The third experiment, developed in greenhouse, evaluated the Cd e Zn toxicity in Phaseolus vulgaris L. (bean) by using the best sulfide dose and addition of organic matter. The dry matter production was higher in soils without sulfide, indication phytotoxicity. We conclude that sulfide solutions can be used for Cd and Zn temporary immobilization in contaminated soils, however the application combined with phytoremediation needs further studies