Made available in DSpace on 2014-06-11T19:29:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-28Bitstream added on 2014-06-13T19:59:37Z : No. of bitstreams: 1 soutofilho_sn_me_ilha.pdf: 641458 bytes, checksum: 709b438691b2ff769d4ebb432078dab1 (MD5) / Universidade Estadual Paulista (UNESP) / A utilização incorreta dos solos e a construção de barragens no meio rural vêm causando alterações nos mesmos, tornando-os menos produtivos, aumentando assim as áreas degradadas. Técnicas que visam à restauração ecológica de solos degradados têm sido investigadas. Neste sentido estudaram-se as alterações no ambiente edáfico de um solo decapitado, em recuperação, usando como indicador a variação de armazenagem de água no mesmo. O Latossolo de Cerrado está sob intervenção antrópica com técnicas para recuperação há sete anos, tendo sido utilizado uma espécie arbórea de cerrado, adubos verdes, lodo de esgoto e braquiária. O delineamento experimental utilizado foi em blocos casualizados com seis tratamentos e cinco repetições, o qual foi implantado em 2004, sendo os tratamentos: 1-Testemunha - solo exposto (sem manejo); 2-Espécie arbórea Gonçalo-alves (Astroniumfraxinifolium); 3-Gonçalo-alves+feijão-de-porco (Canavaliaensiformis);4-Gonçalo-alves+nabo forrageiro (Raphanussativus), até 2005 sendo substituído no ano de 2006 pela crotalária (Crotalariajuncea); 5-Gonçalo-alves+gramínea (Brachiariadecumbens)+lodo de esgoto (60 t ha-1, base seca). Estudou-se também a condição de vegetação nativa de Cerrado. As amostras de solo foram coletadas no ano de 2010, seis anos após a implantação do experimento. Em duas camadas do solo, de 0,00-0,05 e 0,05-0,10, foram estudados: retenção e a armazenagem de água no solo. Analisaram-se também, densidade, porosidade, textura e os atributos químicos nas camadas 0,00-0,05; 0,05-0,10; 0,10-0,20 e 0,20-0,40 m. Os resultados foram analisados efetuando-se a análise de variância e teste de Scoot-knott a 5 % de probabilidade para a comparação de médias. O tratamento Gonçalo-alves+Brachiariadecumbens+lodo de esgoto é o manejo mais indicado para a recuperação do solo degradado em estudo; a retenção de água no solo foi um bom indicador da sua recuperação / Incorrect use of land and construction of dams in rural areas have caused changes in them, making them less productive, thus increasing the degraded areas. Techniques aimed at ecological restoration of degraded soils have been investigated. In this sense, we studied the positive changes in the edaphic environment of a beheaded soil, recovering, using the water storage variation as indicator. The Savannah Oxisol is under human intervention techniques for recovery to seven years, having been used a Savanna tree species, green manure, sewage sludge and pasture. The experimental design was randomized blocks with six treatments and five replication, which was implemented in 2004 and the treatments were: 1-Control - bare soil (without management), 2-species tree- Astroniumfraxinifolium, 3 –A. fraxinifolium+Canavaliaensiformis, 4- A. fraxinifolium fodder Raphanussativus by 2005 was replaced in 2006 by Crotalaria juncea, 5- A.fraxinifolium+Brachiariadecumbens+sewage sludge (60 t ha-1, dry basis). We studied the condition of Savannah native vegetation. In two soil layers, from 0.00 to 0.05 and 0.05-0.10 were studied: retention and storage of water in the soil. We analyzed also, density, porosity, texture and chemical attributes of the layers from 0.00 to 0.05, 0.05-0.10, 0.10 to 0.20 and 0.20-0.40 m. The results were analyzed by performing the variance analysis and Scoot-Knott test at 5% probability to averages comparation. The treatment A. fraxinifolium+Brachiariadecumbens+sewage sludge management is the best for the degraded soil recovery under study. The water retention in the soil was a good indicator of recovery

This thesis addressed two main issues. First, using an inter-temporal optimisation framework, the thesis analysed the tradeoffs between short and long-term objectives of soil use that smallholder farmers’ face in their production decisions. Second, using econometric models that account for simultaneity of choices and plot level data, the thesis explored the determinants of soil fertility and soil conservation adoption decision behaviour of smallholder farmers in the Central highlands of Ethiopia. Four major conclusions are drawn from the optimization results. First, steady state optimal output and input levels under the dynamic decision rule are found to be significantly higher than the static solutions suggesting that the static decision rule is sub-optimal. Second, current soil nutrient inputs and conservation efforts are well above the requirements of the static solutions suggesting smallholder farmers consider some of the long-term (dynamic) costs of soil degradation. Third, current farmer practices involve net nitrogen extraction of 16.2 kg/ha from bottomlands and 56.7 kg/ha from slopping lands entailing a total soil user cost of Birr 255 per ha and Birr 928 per ha, respectively. This suggests that current smallholder farmer practices discount the future heavily and hence over exploit the soil resource stock. Fourth, a comparison of steady state dynamic solutions when nutrient stocks are the sole determinant of soil quality with a situation where both nutrient stocks and rooting depth impinge on soil quality confirm the main hypothesis that the socially optimal path of soil use also depends on the nature of soil degradation smallholder farmers face on their plots. The econometric analysis of soil fertility and soil conservation adoption confirmed that awareness of soil degradation, public assistance with sharing initial costs of constructing soil conservation structures, improved security of land tenure and farmers’ education and access to information on soil degradation were found essential for farmers to adopt soil fertility management practices and invest in soil conservation. On the other hand, improved small farmers’ access to short-term credit for the purchase of inorganic fertilizers present a disincentive for long-term conservation practices, an important trade off with serious policy implications. / Thesis (PhD (Environmental Economics))--University of Pretoria, 2007. / Agricultural Economics, Extension and Rural Development / unrestricted

The effects of 40 years of integrated field management on soil organic phosphorus and its forms was evaluated on a highly organic B.C. soil supporting high value vegetable crops. This project was undertaken to study the effects of cultivation on the soil content of organic phosphorus, as a predictor of overall degradation effects of the soil organic matter. Organic carbon, total nitrogen, soil pH and total and inorganic phosphorus were also evaluated, due to the strong relationship of organic P and these other soil chemical properties. The forms of organic P that were evaluated were the phytic acid, inositol polyphosphates and the soil biomass phosphorus. The biomass P was used as a predictor of the effects of cultivation on nucleic acids since the soil methods for nucleic acid determination were very complicated and time consuming. In this study, attempts were made to find a shorter soil analytical method for phytic acid, the largest pool of soil organic phosphorus. Due to chemical structure of phytic acid and its higher negative charge, it was believed that this molecule is highly stable in the soil environment due to its adsorption and/or precipitation on mineral surfaces through cation bridging at low soil pH particularly by Iron and Aluminium salts and hydrous oxides which bear pH-dependent positive charge or through P chermsorption, and hence its turnover rate due to cultivation could be used to predict the behaviour of the rest of soil organic P and hence the organic matter in the same soil environment. It was however realized that P analysis in soils was very cumbersome and there was a need for a shorter and precise quantitative analytical technique for this element in the soil. ³¹P NMR spectroscopy was thought to be the solution and its possibilities were evaluated in this project. Therefore the objectives of the study were; a) To determine the effects of 40 yrs of integrated field managements on organic P and its forms. b) To develop a shorter method for soil phytic acid analysis. c) To attempt the use of ³¹P NMR for qualitative and quantitative determinations of soil phytic acid. It was found that soil pH was significantly increased from pH 4.46 to 5.28 due to liming and the increased degree of organic matter decomposition. Total nitrogen was significantly decreased by 24% with larger significant decrease of 42% in the shallow organic cultivated soil site, and only 8% significant decrease in the highly organic, deeper cultivated soil site. The decline in soil nitrogen was attributed to mineralization of organic nitrogen followed by crop uptake and leaching losses. Organic carbon was significantly decreased by 22%. There was a 40% decrease in this organic carbon in the cultivated shallow organic cultivated soil site, but there was no significant effect of cultivation on organic carbon (hence the organic matter) in the highly organic deeper cultivated soil site. There was no significant effect of cultivation on the C/N ratio. However, the highly organic deeper soil site had significantly wider C/N ratio than the shallow organic cultivated soil site. This observation was attributed to the degree of decomposition of soil organic matter in the two sites. There was a significant 20% decrease in P total in the highly organic deeper cultivated soil site. There was no significant effect of cultivation on P total in the shallow organic cultivated soil site, however there were indications of 33% accumulation in total P in this soil site as determined by ignition method. There was 179% accumulation of inorganic P in the shallow organic cultivated soil site, but there was no significant effect of cultivation on inorganic P in the deeper highly organic soil cultivated site. Organic phosphorus was significantly decreased by 4 0 yrs of integrated field management by 31% on a soil basis and 25% on an ash free basis. The percentage of organic P in total soil P was significantly decreased from 66% to 45%. The C/orgnic P was increased significantly from 394 to 439. This reflected greater effects of cultivation on turnover of organic P than organic carbon in the organic matter and that P has a geological cycle which organic carbon does not have. The results further showed that before the field was placed under cultivation, the shallow organic soil site had a significantly larger amount (73%) of organic P in the soil total P. However cultivation had a significant decrease in organic P by 23% in the deeper highly organic soil cultivated site and 40% in the shallow organic cultivated soil site. The study soil sites started with same the amounts of biomass P (the most labile form of organic P) , however it was found that 40 years of cultivation had no significant effects on this biomass in the highly organic soil site, but there was a significant decrease in biomass P by 86% in the shallow organic cultivated soil site. Soil phytic acid, the largest pool of organic P was significantly decreased by 28% due to 40 yrs of integrated field management. Its turnover rate was found to be equal to the turnover rate of the other forms of organic P. It was however noted that the study soil sites started with same amount of phytic acid before the field was placed under cultivation. Phytic acid was significantly decreased due to cultivation in the shallow organic cultivated soil site by 35%, but there was no significant effect of cultivation on phytic acid in the highly organic cultivated soil site. Inositol polyphosphates were not significantly affected by 40 years of integrated management. This form of organic P was found to have the same turnover rate as the rest of soil organic P. The slower turnover rate of inositol polyphosphates assayed by the barium acetate precipitation method of McKercher and Anderson was attributed to methodology. In the present study, there were no significant differences in results obtained by various methods for total P determination except in a few cases where the ignition method was thought to have over-estimated total P. A tentative new method for phytic acid analysis was developed in the on-going research. This method was proposed to be applicable in all soils. However, further research is required to confirm the purity of the phytic acid determined by this method. ³¹P NMR spectroscopy showed potential possibility for qualitative and quantitative analysis of soil phytic acid. However, it was emphasized that care should be exercised particularly during sample concentration step. It was concluded that organic P and its forms, organic carbon, total nitrogen, soil pH and phytic acid were significantly decreased by 40 years of integrated field management more in the shallow organic cultivated soil sites than in the deeper highly organic soil sites. This observation was found very interesting and was in contrast to existing soil literature and further research was proposed in this direction to investigate this phenomenon. / Land and Food Systems, Faculty of / Graduate

No description available.

Pasture-based dairy farming is the major land use in the Tsitsikamma region of the Eastern Cape. Permanent kikuyu grass (Pennisetum clandestinum) dominates pastures in the region. Kikuyu pastures do not, however, provide adequate year-round quality feed for dairy cows. This has led to the use of annually sown pastures with perennial ryegrass (Lolium perenne) to provide winter forage. Soil degradation under this management has, however, become recognised as a major limitation. Soil quality and degradation under annual and permanent pasture in the region were evaluated in three separate studies. These were (i) an investigation of the extent of loss of soil organic matter and related soil microbial properties and aggregate stability under annual pastures, (ii) a comparison of soil physical properties under annual and permanent pastures and (iii) a survey of the nutrient status of soils and pasture herbage in the region. In the first study, four commercial dairy farms, situated on sites which represented the three main soil groups in the region were sampled, were taken from under permanent kikuyu pastures, annual ryegrass pastures and undisturbed native vegetation nearby. In comparison with undisturbed, native vegetation, soils under both annually cultivated and permanent pasture had gained soil organic matter on the sandy, low rainfall eastern end of the Tsitsikamma. By contrast, at the higher rainfall, finer-textured, western end, where the native vegetation consists of coastal forest, there was a loss of soil organic matter under both types of pasture. Despite this, soil organic C content was lower under annual ryegrass than permanent kikuyu pasture at all the sites reflecting the degrading effect of annual cultivation on soil organic matter. As a consequence, labile, K(2)S0(4) - extractable C, microbial biomass C, basal respiration, arginine ammonification, flourescein diacetate hydrolysis rates and aggregate stability were all less under annual ryegrass than permanent kikuyu pastures at all the sites. The effects of annual ryegrass and permanent kikuyu pastures on soil physical properties and root length density were compared with those of undisturbed native vegetation on the four experimental sites. Root density and the depth of rooting were much less under annual ryegrass than under kikuyu pastures or native vegetation. There was no consistent effect of improved pastures or pasture type on bulk density and total porosity or penetrometer resistance, although annual pasture soils generally had higher bulk densities and lower total porosities than those under native vegetation. There was a tendency for smaller saturated hydraulic conductivity and air permeability under ryegrass than kikuyu pastures, regardless of whether total porosity was higher or lower under ryegrass. This was attributed to annual cultivation and subsequent natural consolidation causing a decrease in pore continuity under ryegrass pastures. Penetrometer resistance values confirmed the presence of subsoil compacted layers at two annual ryegrass pasture sites. At one such site, subsoil tillage was effective in reducing penetrometer resistance and bulk density, increasing pore continuity (as evaluated by hydraulic conductivity and air permeability) and greatly increasing root density and rooting depth. The nutrient status of soil and herbage from annual ryegrass and permanent kikuyu pastures sampled from 40 dairy farms in the Tsitsikamma region were evaluated. Along with the decreased organic matter content, there was a decrease in soil pH and a loss of exchangeable cations under annual pastures. Large concentrations of extractable P and sometimes exchangeable K were measured in soils under both ryegrass and kikuyu pastures and it was concluded that the rates of applied P, and sometimes K, were often excessive (particularly under kikuyu). Various nutritional problems were also identified. These included the need for Ca supplementation, particularly under kikuyu, due to the low herbage Ca concentrations. The low Ca : P ratio measured in annual ryegrass pastures, and more particularly in kikuyu herbage, highlighted the low Ca content of herbage and also the tendency of kikuyu grass to accumulate large concentrations of P. The large K concentrations and high K : Ca +Mg ratios identified in pasture herbage suggest the potential for animal nutritional problems such as hypomagnesaemia. It was concluded that although kikuyu is an excellent pasture in terms of dry matter production it tends to be deficient in Ca (and sometimes Na) and can contain prohibitively high K levels, which are likely to induce Mg deficiencies in grazing animals. The micronutrient concentrations in herbage were generally adequate, although copper concentrations tended to be low suggesting that fertilizer applications and/or feed supplementation is required. It was concluded that annual conventional tillage results in a substantial loss of soil organic matter, soil microbial activity and aggregate stability under annual ryegrass pastures when compared to those under permanent kikuyu grass. This loss of soil organic matter can result in natural consolidation of the soil in the cultivated layer and exasperated through treading by the grazing cows. The annual cultivation can also lead to the formation of a subsoil compacted layer. Nonetheless, compaction can also occur under permanent pasture presumably due to treading damage. Careful management to avoid treading damage to pastures should be practised. In order to protect the organic matter status of annual pastures, direct drilling of such pastures should be seriously considered. In some cases, annual fertilizer P rates (and to lesser extent those of K) could be reduced considerably since the levels accumulated in the soils are excessive. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2002.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 125-136). Also available on the World Wide Web.

by Choi Chi Hoi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography: leaves 171-178. / ABSTRACT --- p.iii / ACKNOWLEDGMENTS --- p.v / TABLE OF CONTENT --- p.vi / LIST OF FIGURES --- p.x / LIST OF TABLES --- p.xii / LIST OF PHOTOS --- p.xiv / LIST OF APPENDICES --- p.xvi / Chapter I --- INTRODUCTION / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Objectives --- p.6 / Chapter 1.3 --- Uniqueness and Significance of the Study --- p.7 / Chapter 1.4 --- Some Key Concepts --- p.9 / Chapter 1.5 --- Organization of the Thesis --- p.11 / Chapter II --- THE STUDY AREA / Chapter 2.1 --- Selection of the Study Area --- p.12 / Chapter 2.2 --- The Physical and Socio-Economic Environment of the Deqing County --- p.17 / Chapter 2.2.1 --- Location --- p.17 / Chapter 2.2.2 --- Climate --- p.17 / Chapter 2.2.3 --- Geology and Landform --- p.18 / Chapter 2.2.4 --- Vegetation --- p.18 / Chapter 2.2.5 --- Population and Economic Activities --- p.19 / Chapter 2.2.6 --- History of Soil Erosion and Conservation --- p.21 / Chapter 2.3 --- The Shenchong Basin --- p.26 / Chapter 2.4 --- The Lichong Basin --- p.28 / Chapter 2.5 --- The Resource Base of Deqing --- p.30 / Chapter III --- METHODOLOGY --- p.34 / Chapter 3.1 --- Conceptual Considerations --- p.34 / Chapter 3.2 --- Land Degradation Processes --- p.35 / Chapter 3.2.1 --- Nutrient Loss from Hillslopes --- p.38 / Chapter 3.2.2 --- Iron Toxicity --- p.43 / Chapter 3.2.3 --- Properties and Nutrient Status of Rehabilitated Soils --- p.44 / Chapter 3.2.4 --- Methods of Chemical Analysis of Water and Soil Samples --- p.49 / Chapter 3.3 --- Cost-Benefit Analysis of Rehabilitation Measures --- p.50 / Chapter 3.4 --- Problems and Limitations --- p.54 / Chapter IV --- LAND DEGRADATION： PROCESSES AND PROBLEMS --- p.56 / Chapter 4.1 --- Landscape Changes in a Severely Eroded Granitic Area --- p.56 / Chapter 4.2 --- Land Degradation Processes 一 On-site Effects --- p.60 / Chapter 4.2.1 --- Soil Loss on the Hillsides --- p.60 / Chapter 4.2.2 --- Loss of productivity on the Hillsides --- p.64 / Chapter 4.3 --- Land Degradation Process - Off-Site Effects --- p.70 / Chapter 4.3.1 --- Burial of Agricultural Land Beneath Alluvial Fans --- p.70 / Chapter 4.3.2 --- Concentration of Dissolved Iron in Sub-surface Water --- p.74 / Chapter 4.4 --- Concluding Remarks --- p.78 / Chapter V --- COST-EFFECTIVENESS OF EROSION CONTROL MEASURES THEORETICAL CONSIDERATIONS --- p.80 / Chapter 5.1 --- Introduction --- p.80 / Chapter 5.2 --- Economic-Biophysical Management Linkages in the Shenchong Basin --- p.80 / Chapter 5.3 --- Range of Erosion Control/Land Use Options --- p.83 / Chapter 5.4 --- Methodology --- p.83 / Chapter 5.4.1 --- Data Sources --- p.85 / Chapter 5.4.2 --- Economic Valuation Techniques --- p.85 / Chapter 5.5 --- Cost-Effectiveness Evaluation of Erosion- Control Measures --- p.87 / Chapter 5.5.1 --- Option 1 - Hillsides are Maintained Under Dense Fern and Tree Cover and No Use is Permitted --- p.88 / Chapter 5.5.2 --- Option 2 : Slope - Maintaining Dense Vegetation Cover but Permitting Sustained Yield Harvesting of Fern for Fuel and Resin and Timber Production --- p.90 / Chapter 5.5.3 --- Option 3 : Slope - Building Terraces on Hillslopes --- p.92 / Chapter 5.5.4 --- Option 4 : Slope - No Erosion Control Measures --- p.94 / Chapter 5.5.5 --- Option 5 : Slope - Conversion from Fern and Woodland to Baji and Yu Gui Crops --- p.94 / Chapter 5.5.6 --- Option 6 - Small Check Dams Constructed to Control Gully Erosion --- p.94 / Chapter 5.5.7 --- Option 7 : Gully - Large Check Dams --- p.97 / Chapter 5.5.8 --- Option 8 : Gully - Biological Dams --- p.98 / Chapter 5.5.9 --- Option 9 : Gully - Infilling of Gullies --- p.99 / Chapter 5.5.10 --- Option 10 : gully - No Erosion Control --- p.100 / Chapter 5.6 --- Policy Implications --- p.100 / Chapter 5.7 --- Policy Optimization With Multiple-Objective Decision Modeling --- p.102 / Chapter VI --- REHABILITATION PROGRAM AT SHENCHONG AND LICHONG RECONSIDERED --- p.107 / Chapter 6.1 --- Introduction --- p.107 / Chapter 6.2 --- Land Rehabilitation at Shenchong --- p.107 / Chapter 6.3 --- Land Rehabilitation at Lichong --- p.111 / Chapter 6.4 --- Ecological Considerations --- p.119 / Chapter 6.5 --- Agricultural Considerations --- p.124 / Chapter 6.5.1 --- Chemical Soil Properties --- p.126 / Chapter 6.5.2 --- Physical Soil Property --- p.135 / Chapter 6.6 --- Economic Considerations --- p.143 / Chapter 6.6.1 --- Costs and Benefits of Rehabilitation Activities --- p.144 / Chapter 6.6.2 --- Sustainability of the Rehabilitation Programs --- p.146 / Chapter 6.6.3 --- Distribution of Costs and Benefits over Time --- p.148 / Chapter 6.7 --- Institutional Considerations --- p.151 / Chapter 6.7.1 --- Rural Economic Reform --- p.152 / Chapter 6.7.2 --- Institution Set-up of the Two Brigades --- p.153 / Chapter 6.7.3 --- Distribution of Cost and Benefits --- p.154 / Chapter 6.7.4 --- Risk Management --- p.155 / Chapter 6.7.5 --- Land Use Planning --- p.156 / Chapter 6.7.6 --- Motivation --- p.157 / Chapter 6.7.7 --- The Search for Solution --- p.159 / Chapter VII --- CONCLUSION --- p.162 / Chapter 7.1 --- Introduction --- p.162 / Chapter 7.2 --- Discussion --- p.166 / BIBLIOGRAPHY --- p.171 / APPENDICES --- p.179

Soil degradation is a complex process which may occur anywhere and at any time. It directly affects the physical, chemical and biological processes within the soil profile. Soil degradation can either be as a result of natural hazards or due to manmade actions, such as mismanagement on cropping patterns, soil preparation and cultivation practices. Regardless of how it is caused, soil degradation has strong negative effects on plant and soil productivity. Soil degradation can accelerate a series of processes such as erosion, compaction, loss of organic matter, loss of whole soil biota, surface sealing and contamination. This thesis presents the assessment of soil properties to improve our understanding of soil degradation on raised-bed orchards in the Vietnamese Mekong delta (MD). Measurements were made on 10 citrus plantations which had been established during a range of years from 1970 to 1998 at Hau Giang province. Soil sampling was made in the dry season of 2010 at two soil depths for each raised-bed to determine soil chemical and physical properties. The soil penetration resistance (PR) was periodically measured once a week together with soil sampling for moisture measurements during a period of 5 months. Analysis indicated the pH value of the soil was tending to decrease, nutrient imbalance and deficiency was developing, and the soil structure was deteriorating during the age since the raised-beds were originally constructed. Preventive and restorative measures need to be considered for restoring and retaining the quality of the soil and the ground water. These measures should consist of (1) neutralizing of excess acidity, (2) balancing of nutrients, (3) maintaining of soil organic matter, and (4) application of appropriate irrigation schedules. / Suy thoái đất là một tiến trình phức tạp xuất hiện ở mọi nơi, mọi lúc làm tác động trực tiếpđến các quá trình lý, hóa và sinh học trong phẫu diện đất. Nó có thể là kết quả của các hoạtđộng do tự nhiên hoặc do con người như sử dụng sai hoặc thực hành quản lý đất đai bất hợplý. Cho dù nguyên nhân thế nào chăng nữa, suy thoái đất cũng gây ra các ảnh hưởng bất lợinặng nề lên cây trồng và sức sản suất của đất. Suy thoái đất có thể thúc đẩy hàng loạt cácquá trình như là xói mòn, nén dẽ, mất vật liệu hữu cơ và sinh vật đất, đóng váng bề mặt vàô nhiễm. Luận văn này trình bày sự đánh giá về các đặc tính của đất để mở mang sự hiểubiết về suy thoái đất trên các vườn cây ăn trái ở đồng bằng sông Cửu Long. Thí nghiệmthực hiện trên 10 vườn cam quít với khoảng thời gian thành lập vườn từ 1970 đến 1998 tạitỉnh Hậu Giang. Mẫu đất được lấy vào mùa khô năm 2010 ở hai độ sâu cho mỗi vườn đểphân tích các chỉ tiêu lý hóa đất. Sức kháng xuyên của đất được đo định kỳ mỗi tuần kếthợp với lấy mẫu để xác định ẩm độ đất trong suốt khoảng thời gian 5 tháng. Kết quả phântích cho thấy pH đất có khuynh hướng giảm, sự thiếu và mất cân bằng dinh dưỡng đất ngàycàng lộ rõ, và cấu trúc đất đang xấu đi theo độ tuổi của vườn. Các biện pháp phòng ngừa vàphục hồi cần được quan tâm đối với việc phục hồi và duy trì chất lượng của đất và nướcngầm. Các biện pháp nên bao gồm (1) trung hòa độ chua đất, (2) cân bằng dinh dưỡng, (3)duy trì vật liệu hữu cơ trong đất, và (4) áp dụng chế độ tưới thích hợp. / <p>QC 20130909</p>

O projeto estudou a potencialidade de seqüestrar carbono em solos arenosos de Cerrado sob pastagens. O enfoque principal consistiu em deduzir quantas toneladas por hectare podem ser seqüestradas em função de um melhor manejo. Para tanto escolheram-se quatro pastagens com as mesmas características pedológicas, climáticas e topográficas, possibilitando explicar as diferenças nos estoques de carbono no solo por seus diferentes manejos e níveis de produtividade. As pastagens encontram-se na parte ocidental da bacia do rio Piracicaba (SP). Nessa região, as pastagens constituem o uso dominante da terra e são cultivadas principalmente em solos arenosos do tipo Neossolos Quartzarênicos (RQ). Após a fase de seleção, as quatro pastagens foram caracterizadas de acordo com os estoques de carbono no solo (0-50cm) e suas respectivas produtividades. A produtividade das pastagens foi determinada pelos seguintes parâmetros: (i) índice de área foliar (IAF), (ii) taxa de crescimento da biomassa vegetal, (iii) peso da biomassa vegetal e (iv) peso radicular. Investigou-se a correlação entre os estoques de carbono no solo e cada parâmetro de produtividade de cada pastagem estudada. Avaliou-se também o nível de produtividade em relação ao histórico de manejo do pasto. Os resultados indicam uma boa correlação entre a produtividade de pasto e seu estoque de carbono no solo. Especialmente o parâmetro de produtividade IAF revelou uma boa correlação com os estoques de carbono no solo (r = 0,97). O segundo objetivo do projeto era investigar a aplicabilidade de técnicas de sensoriamento remoto para mapear a potencialidade de seqüestrar carbono no solo. Para os fins da pesquisa, considerou-se que o pasto estudado que apresentou o maior estoque de carbono (e também maior produtividade) no solo possui o estoque máximo possível sob as condições climáticas, pedológicas e topográficas encontradas nas áreas de estudo. Calculou-se a diferença do estoque entre a pastagem com o maior estoque de carbono no solo e as três outras pastagens. A diferença no estoque representa a potencialidade de as pastagens estocarem mais carbono. O potencial de seqüestro de carbono total no pasto mais degradado (Descalvado) representa um aumento de 70,0% (22,41 Mg ha -1 ), de 30,8% (12,81 Mg ha -1 ) no pasto significativamente degradado (Bondade) e de 4,9% (7,7 Mg ha -1 ) no pasto moderadamente degradado (Barreiro Rico). Como as quatro pastagens só diferem no tipo de manejo no que se refere aos parâmetros determinantes da estocagem, as diferenças no estoque são diretamente ligadas ao manejo. O estoque de carbono no solo é uma informação subterrestre e portanto não pode ser investigado diretamente por bandas espectrais do espectro óptico, as quais não penetram a superfície terrestre. Portanto, como este projeto comprovou uma boa correlação entre a produtividade e os estoques de carbono no solo sob pastagens na região estudada, tentou-se mapear os estoques de carbono por meio das produtividades das pastagens. Para esse fim, estabeleceu-se uma classificação radiométrica de produtividade de pasto. Seis bandas do sensor ETM+, além do NDVI, (Normalized Difference Vegetation Index) foram processadas em todas as combinações de entrada possíveis (120) para duas classificações supervisionadas (Máxima Verossimilhança e Rede Neural Propagação Posterior). Para determinar quais são as melhores combinações de entradas de bandas para fins de discriminação da produtividade de pasto em diferentes níveis, usou-se uma matriz de erro. O melhor resultado, com a entrada das bandas B2 B5 B7 NDVI, revelou uma exatidão de 64,79% ao classificar corretamente duas classes de produtividade de pasto (alta/baixa). Essa exatidão foi considerada insuficiente. Entretanto, efetuou-se uma análise radiométrica das pastagens por espectro, que revelou uma melhor separabilidade espectral da produtividade no espectro do infravermelho médio do que no espectro visível ou infravermelho próximo. Foram realizadas também análises de regressão entre a reflectância das quatro pastagens para cada espectro e seus respectivos estoques de carbono, para investigar correlações diretas entre o comportamento espectral das pastagens e os estoques de carbono no solo. O espectro vermelho (r = 0,96 ) e infravermelho médio I (r = 0,944) possuem uma correlação significativa com o estoque de carbono no solo. Resumindo, conclui-se que existe uma boa correlação entre o manejo (produtividade) de pasto e o estoque de carbono no solo. Constatou-se que a imagem de satélite utilizada (Landsat 7) não tem uma resolução espacial/espectral suficiente para separar com uma exatidão adequada os diferentes níveis de produtividade de pasto. Entretanto, existe boa separabilidade dos diferentes níveis de produtividade no espectro infravermelho médio. A investigação da correlação direta entre o comportamento espectral das pastagens e o estoque de carbono obteve resultados significativos nos espectros de vermelho (630 – 690nm) e infravermelho médio I (1550 – 1750nm). Portanto, no âmbito do sensoriamento remoto, recomenda-se investigar se é possível mapear estoques de carbono no solo diretamente por meio da reflectância espectral das pastagens ou por meio do Índice de Área Foliar, que pode ser deduzido por meio do NDVI em imagens de satélite. / The project studied the potential for soil carbon sequestration in pastures growing on sandy soils in the Cerrado region and for the application of remote sensing techniques for estimating carbon sequestration levels. The main focus was deducing how many tons per hectare could be sequestered if better pasture management techniques were adopted. Four pastures with identical pedological, climate and topographical characteristics were chosen, so that the discrepancies in carbon stock levels in the soil could be interpreted in light of their different types of management and productivity levels. The pastures are located in the western part of the Piracicaba basin, in São Paulo State, Brazil. The dominant land use in this region is pasture on sandy soils, classified as Neossolos Quartzarênicos (RQ), according to Brazilian soil classification. After the selection phase, the four pastures were classified according to their soil carbon stocks (0-50cm layer) and their respective productivity levels. Pasture productivity was determined by the following parameters: (i) leaf area index (LAI), (ii) biomass growth rate, (iii) dry matter weight and (iv) root stocks. The correlation between soil carbon stocks and each of the productivity parameters was investigated. The productivity levels were also studied in relation to the pasture management history of each of the selected pastures. The results indicate a good correlation between the productivity level of the pastures and their carbon stocks in the soil. The LAI parameter showed a particularly good correlation with soil carbon stocks (r= 0,97). The second objective of the project was investigating the applicability of remote sensing techniques to map the potential for soil carbon sequestration. For the purposes of this study, the pasture with the highest soil carbon stocks (and higher productivity) was considered to represent the maximum stock possible under the climate, pedological and topography conditions found in the region of the study. The difference between the stock in the highest stock pasture and the three other pastures was calculated. This difference represents the potential for increasing carbon sequestration. The total soil carbon sequestration potential in the most degraded pasture (Descalvado) is equivalent to a 70,0% increase (22.41 Mg ha -1 ) from current levels. In the significantly degraded pasture (Bondade), the potential amounted to 30.08% (12.81 Mg ha -1 ) and to 4.9% (22.41Mg ha -1 ) in the moderately degraded pasture (Barreiro Rico). Since the only determinant parameter for soil carbon sequestration these pasture do not have in common is the type of management, the differences in stock levels are directly related to their type of management. Soil carbon stock levels are a subterraneous type of information, and thus cannot be examined through direct use of optical spectrum bands, which cannot go through the soil. Therefore, and taking into consideration that this study demonstrated a good correlation between productivity and soil carbon stocks in the pastures of the sample, the author attempted to map carbon stocks through pasture productivity. To this end, a radiometric classification of pasture productivity was established. Six spectral bands from the ETM+ satellite sensor and the Normalized Difference Vegetation Index (NDVI) were processed in all possible entry band combinations for two supervised classifications (Maximum Likelihood and Back Propagation). An error matrix was subsequently used to determine the best band combinations for distinguishing pasture productivity levels (two classes). The best result (B2 B5 B7 NDVI) revealed an overall accuracy of 64,79% in the classification of two classes of productivity, which is considered insufficient. Nevertheless, a spectrum radiometric analysis of the pastures was conducted, which showed better separability in the medium infrared spectrum than in the visible or near infrared spectrum. Regression analyses were performed between the reflectance of the four pastures under each spectrum and their respective soil carbon stocks levels, with the purpose of investigating whether there are any direct correlations between the spectral behavior of the pastures and the soil carbon stocks levels. The red (r=0.95) and middle infrared (r=0,944) spectra were demonstrated to have a significant correlation with soil carbon stocks. The author concludes that there is a good correlation between pasture management (productivity) and soil carbon stocks. It has also been determined that the satellite image used in this study (Landsat 7) does not have an adequate spacial and spectral resolution for accurately separating different productivity levels. However, good separability of productivity levels was shown in the middle infrared spectrum. The evaluation of a direct correlation between the spectral behavior of the pastures and their respective soil carbon stock levels obtained significant results in the red (690nm) and near infrared (1550- 1750nm) spectra. Therefore, it is recommended to investigate carbon soil stock mapping by remote sensing techniques directly through the spectral reflectance of pastures in the red and middle infrared spectra or indirectly through the LAI, which can be deduced through the NDVI in satellite images.

The urban sprawl cannot be any longer perceived as a solely esthetic and socioeconomic problem. The process of shift of population and activities from city centre to its fringe has significant environmental impacts as well. Typicaly, suburban areas are spatially and therefore energetically demanding, the landscape is being fragmented by their presence and the natural environment of organisms is severely modified or destroyed. Soil sealing and impervious surfaces lead to altered heat and moist regimes, infiltration rate and runoff. Soils at city fringe - usually very productive and valuable - are endangered by total loss of all of their functions, both environmental and agricultural. That is also the case of Prague surroundings, where high quality soils, which are supposed to be protected by the law, are irreversibly degraded by urban sprawl. Logistic regression model in this work has proved that commercial urban sprawl tends to occur in areas with a good logistic position and a level terrain. The awareness of factors, which are favorable for urban sprawl, can be utilized in future to make local planning more effective and prevent sealing of high-quality agricultural soils, which are currently built on. By sprawling on an agricultural land, Czech Republic loses its natural wealth and valuable...