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.

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

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

Com o objetivo de avaliar o uso de extratores de soluções do solo no auxílio ao manejo da fertirrigação e no controle da salinidade em solo cultivado com melão rendilhado, conduziu-se um estudo em ambiente protegido na área experimental do Departamento de Engenharia Rural da ESALQ/USP, localizado no município de Piracicaba, SP. Os tratamentos foram compostos da combinação de dois fatores: 6 níveis de salinidade inicial do solo (S1 = 1,0; S2 = 2,0; S3 = 3,0; S4 = 4,0; S5 = 5,0 e S6 = 6,0 dS m-1) e dois manejos de fertirrigação: tradicional e com controle da condutividade elétrica da solução do solo. O delineamento estatístico adotado foi o de blocos casualizados completos com 4 repetições, sendo os fatores estudados arranjados em um esquema fatorial de 6 x 2. A salinização inicial do solo se procedeu por meio da aplicação de soluções salinas preparadas a partir de fertilizantes, sendo que a quantidade de sais a ser adicionada foi determinada tomando por base uma curva de salinização artificial obtida previamente em laboratório. A condutividade elétrica da solução foi medida após o término de cada evento de irrigação, utilizando-se extratores com cápsulas porosas. Os resultados revelam que as produções total e comercial, além do peso médio total dos frutos foram significativamente reduzidos com o incremento dos níveis de salinidade do solo Os efeitos da salinidade do solo sobre a altura e o diâmetro das plantas foram mais severos durante o desenvolvimento vegetativo inicial do que no início da frutificação, o que sugere uma possível adaptação das plantas ao estresse salino ao longo do tempo. Embora não tenha sido possível se detectar diferenças expressivas causadas pelos dois tipos de manejo da fertirrigação no desenvolvimento ou na produção da cultura, o uso dos extratores de solução permitiu auxiliar no manejo da fertirrigação, mantendo os níveis desejados de salinidade da solução do solo ao longo do tempo. / A study was carried out under greenhouse conditions, at the experimental area of the Department of Rural Engineering of "Escola Superior de Agricultura Luiz de Queiroz-USP", Piracicaba, São Paulo State, Brazil, with the aim of evaluating ceramic cup samplers used to facilitate fertirrigation management and soil salinity control on a netmelon crop, was carried out The treatments comsisted of two combination factors: six level of initial soil salinity (S1 = 1.0, S2 = 2.0, S3 = 3.0, S4 = 4.0, S5 = 5.0 and S6 = 6.0 dS m-1) and two fertirrigation managements: the traditional and the control of eletrical conductivity of soil solucion. The statiscal test was in randomized blocks, with four replications, arranged in 6 x 2 factorial design. The initial soil salinity value was obtained by appling saline solutions of fertilizer salts using an artificial soil salinization curve obtained previously in laboratory. The electrical conductivity in soil solucion was measured after each irrigation using ceramic cup samplers. Results showed that both total and marketable fruit yield and total weight per fruit were significantly reduced by increase in soil salinity level. The soil salinity effects on plants height and stem diameter were more severe during early vegetative growth than in the beginning of fruit set. This suggests a possible plant adaptation to saline stress along the time. Although no differences were observed in case fertirrigation management treatments on plants development or yield, however the use of solution extractors helped in fertirrigation management because them permitted to keep soil solution salinity at desired level.

Os mecanismos que regulam o desenvolvimento de micorrizas arbusculares (MAs) em condições de baixo e alto nível de P ainda são desconhecidos. Tem sido proposto que proteínas secretadas no apoplasto das raízes podem ter papel importante na regulação de MAs. A análise comparativa do proteoma do fluido intercelular (FI) de raízes colonizadas por fungos micorrízicos arbusculares (FMAs) com o de raízes não-colonizadas, em condições de baixo e alto nível de P, poderia contribuir para a elucidação dos mecanismos que controlam o desenvolvimento das MAs, e foi o objetivo deste trabalho. Plântulas de cana-de-açúcar foram inoculadas com Glomus clarum, Glomus etunicatum ou Gigaspora rosea e cultivadas em substrato esterilizado contendo 20 ou 200 mg P kg -1 . Oito semanas após a inoculação, as plantas foram colhidas, e os seguintes parâmetros avaliados: matéria seca da parte aérea, acúmulo de nutrientes na parte aérea e colonização micorrízica intrarradicular. Os resultados mostraram que, em condições de alto P, a taxa de colonização intrarradicular por G. clarum e G. etunicatum foi menor do que no controle com baixo P. Para a análise comparativa do proteoma do FI das raízes, quantidades iguais de proteínas de plantas não-inoculadas ou inoculadas com G. clarum, em condições de baixo P ou alto P, foram separadas por eletroforese bidimensional em gel de poliacrilamida desnaturante. A análise dos proteomas do FI das raízes revelou a predominância de proteínas ácidas. Nos proteomas do FI de raízes de cana-de-açúcar, em condições de baixo P, foram detectadas 49 proteínas. Destas, 8,2% apresentaram acúmulo induzido e 10,2% acúmulo suprimido (³50%) no FI de raízes colonizadas por G. clarum, em relação ao controle não-inoculado. Desse total, 13 proteínas foram detectadas somente no FI de raízes de plantas inoculadas e representam micorrizinas putativas ou proteínas fúngicas extracelulares, induzidas em condições de baixo P. Nos proteomas do FI de raízes de cana-de-açúcar, em condições de alto P, foram detectadas 56 proteínas. Destas, 8,9% apresentaram acúmulo induzido e 16,1% acúmulo suprimido (³50%) no FI de raízes colonizadas por G. clarum, em relação ao controle não-inoculado. Desse total, 12 proteínas foram detectadas somente no FI de raízes de plantas inoculadas e representam micorrizinas putativas ou proteínas fúngicas extracelulares, induzidas em condições de alto P. Comparando-se os proteomas do FI de raízes de plantas não-inoculadas, em condições de baixo e alto P, foram detectadas 16 proteínas únicas de condições de baixo P e 24 proteínas únicas de condições de alto P. Comparando-se os proteomas do FI de raízes de plantas inoculadas com G. clarum, em condições de baixo e alto P, foram detectadas 12 proteínas únicas de condições de baixo P e 5 proteínas únicas de condições de alto P. Essas proteínas podem ter papéis importantes, diretos ou indiretos, no controle de MAs. A caracterização das proteínas com acúmulo diferencial no FI de raízes de cana-de-açúcar por espectrometria de massa e/ou seqüenciamento N-terminal poderá contribuir para definir suas possíveis funções nas MAs. / The mechanisms controlling arbuscular mycorrhizae (AM) development at different soil P concentrations are not understood. It has been proposed that proteins secreted in the root apoplast may have important roles in AM regulation. The analyses of the intercellular fluid (IF) proteome from sugarcane roots inoculated with arbuscular mycorrhizal fungi, grown at low or high P conditions, compared to the IF proteome from not-inoculated roots may contribute to the understanding of the mechanisms controlling AM development, and was the aim of this work. Sugarcane seedlings were inoculated with Glomus clarum, Glomus etunicatum or Gigaspora rosea, and grown in sterilized substrate containing 20 or 200 mg P kg -1 . Eight weeks after inoculation, the plants were harvested and the following parameters evaluated: shoot dry weight, nutrients in the shoots and intraradical fungal growth. The results showed that intraradical colonization by G. clarum and G. etunicatum at high P conditions was significantly lower than at low P. Equal amounts of proteins were used to compare the proteome from the IF of not-inoculated and G. clarum inoculated roots, at low and high P conditions, using 2D-PAGE. The proteome analyses revealed the predominance of acidic proteins in the IF of sugarcane. A total of 49 proteins were detected in the IF of sugarcane at low P soil concentration. From those, 8.2% were induced and 10.2% suppressed (³ 50%) in the IF of roots inoculated with G. clarum, as compared to not-inoculated controls. Thirteen proteins were detected only in the IF of mycorrhizal roots, and represent putative mycorrhizins or extracellular fungal proteins induced at low P conditions. A total of 56 proteins were detected in the IF of sugarcane at high P conditions. From those, 8.9% were induced and 16.1% suppressed (³ 50%) in the IF of roots inoculated with G. clarum, as compared to not-inoculated controls. Twelve proteins were detected only in the IF of mycorrhizal roots, and represent putative mycorrhizins or extracellular fungal proteins, induced at high P conditions. Comparing the proteomes from the IF of non-inoculated sugarcane roots at low and high P conditions, 16 proteins were detected only at low P conditions, whereas 24 proteins were detected only at high P conditions. Comparing the proteomes from the IF of sugarcane roots inoculated with G. clarum at low and high P conditions, 12 proteins were detected only at low P conditions, whereas 5 proteins were detected only at high P conditions. Those proteins may be, direct or indirectly, involved in the development and/or efficiency of AM. Further characterization of those proteins by mass spectrometry and/or N-terminal sequencing would contribute to the determinations of their possible functions in AM.

A agricultura de precisão (AP) depende do gerenciamento da variabilidade dos fatores que influenciam a produtividade agrícola. Seu principal produto de tomada de decisões são mapas que fornecem a variação de parâmetros do solo. Para obter mapas confiáveis há necessidade de coletar grande quantidade de amostras, resultando em custos elevados de aplicação da técnica. O presente estudo objetivou avaliar as particularidades de grades amostrais que visam à compreensão da distribuição espacial dos parâmetros químicos do solo, assim como propor uma metodologia de avaliação da fertilidade do solo. Para isto, foram testados diferentes instrumentos de coletas, tipo de amostras e metodologia de confecção de amostras. O estudo parte do pressuposto que o método tradicional de levantamento da fertilidade analisa diversos parâmetros quantificados em laboratórios para prescrição de recomendações agrícolas. Seu uso intensivo é limitado pelo custo, comprometendo a precisão da aplicação de insumos agrícolas. Desta maneira, o trabalho testou um método que visa quantificar atributos químicos do solo de baixo custo e estimar parâmetros ligados a prescrição agrícola e, assim, aumentar o número de amostras com menos número de parâmetros a serem analisados, ao invés de poucas amostras com muitos parâmetros. A metodologia apresentou resultados satisfatórios quanto à quantificação da necessidade de calagem. Para a maioria das áreas estudadas a necessidade de calagem estimada foi estatisticamente igual à necessidade de calagem calculada pelo método tradicional de análise de solo. A menor diferença apresentada pelas metodologias quanto a necessidade de calagem foi de 0,035 Mg ha1 e a maior diferença foi de 0,203 Mg ha1. / Precision agriculture (PA) management depends on the variability of the factors that influence agricultural productivity. Its main product decisions are based on maps that provide the variation of soil parameters. For reliable maps there is a need to collect large amount of samples, resulting in costly implementation of the technique. The present study aimed to evaluate the sampling grids particularities designed to understand the spatial distribution of soil chemical parameters, as well as propose a methodology for evaluation of soil fertility. We tested different instruments of soil collecting, type of samples and sample preparation methodology. The study assumes that the traditional method of fertility survey analyzes several parameters quantified in the laboratory for prescribing agricultural recommendations. Its use is limited by the cost-intensive, compromising the accuracy of the application of agricultural inputs. This way the work tested a method that aims quantify soil chemical attributes with low cost and estimate parameters related to the agricultural prescription, and so, increase the number of samples with less parameters to be analyzed instead of a few samples with many parameters. The methodology presented satisfactory results for quantification of lime requirement. For most of the areas studied the effects of limestone was statistically equal to the estimated lime requirement calculated by the traditional method of soil analysis. The smallest difference presented by the methodologies and the need for liming was 0.035 Mg ha1 and the biggest difference was 0.203 Mg ha1.