A study on the performance of flexible pavements on mature soil subgrades

The country has witnessed tremendous increase in the vehicle population and increased axle loading pattern during the last decade, leaving its road network overstressed and leading to premature failure. The type of deterioration present in the pavement should be considered for determining whether it has a functional or structural deficiency, so that appropriate overlay type and design can be developed. Structural failure arises from the conditions that adversely affect the load carrying capability of the pavement structure. Inadequate thickness, cracking, distortion and disintegration cause structural deficiency. Functional deficiency arises when the pavement does not provide a smooth riding surface and comfort to the user. This can be due to poor surface friction and texture, hydro planning and splash from wheel path, rutting and excess surface distortion such as potholes, corrugation, faulting, blow up, settlement, heaves etc. Functional condition determines the level of service provided by the facility to its users at a particular time and also the Vehicle Operating Costs (VOC), thus influencing the national economy. Prediction of the pavement deterioration is helpful to assess the remaining effective service life (RSL) of the pavement structure on the basis of reduction in performance levels, and apply various alternative designs and rehabilitation strategies with a long range funding requirement for pavement preservation. In addition, they can predict the impact of treatment on the condition of the sections. The infrastructure prediction models can thus be classified into four groups, namely primary response models, structural performance models, functional performance models and damage models. The factors affecting the deterioration of the roads are very complex in nature and vary from place to place. Hence there is need to have a thorough study of the deterioration mechanism under varied climatic zones and soil conditions before arriving at a definite strategy of road improvement. Realizing the need for a detailed study involving all types of roads in the state with varying traffic and soil conditions, the present study has been attempted. This study attempts to identify the parameters that affect the performance of roads and to develop performance models suitable to Kerala conditions. A critical review of the various factors that contribute to the pavement performance has been presented based on the data collected from selected road stretches and also from five corporations of Kerala. These roads represent the urban conditions as well as National Highways, State Highways and Major District Roads in the sub urban and rural conditions. This research work is a pursuit towards a study of the road condition of Kerala with respect to varying soil, traffic and climatic conditions, periodic performance evaluation of selected roads of representative types and development of distress prediction models for roads of Kerala. In order to achieve this aim, the study is focused into 2 parts. The first part deals with the study of the pavement condition and subgrade soil properties of urban roads distributed in 5 Corporations of Kerala; namely Thiruvananthapuram, Kollam, Kochi, Thrissur and Kozhikode. From selected 44 roads, 68 homogeneous sections were studied. The data collected on the functional and structural condition of the surface include pavement distress in terms of cracks, potholes, rutting, raveling and pothole patching. The structural strength of the pavement was measured as rebound deflection using Benkelman Beam deflection studies. In order to collect the details of the pavement layers and find out the subgrade soil properties, trial pits were dug and the in-situ field density was found using the Sand Replacement Method. Laboratory investigations were carried out to find out the subgrade soil properties, soil classification, Atterberg limits, Optimum Moisture Content, Field Moisture Content and 4 days soaked CBR. The relative compaction in the field was also determined. The traffic details were also collected by conducting traffic volume count survey and axle load survey. From the data thus collected, the strength of the pavement was calculated which is a function of the layer coefficient and thickness and is represented as Structural Number (SN). This was further related to the CBR value of the soil and the Modified Structural Number (MSN) was found out. The condition of the pavement was represented in terms of the Pavement Condition Index (PCI) which is a function of the distress of the surface at the time of the investigation and calculated in the present study using deduct value method developed by U S Army Corps of Engineers. The influence of subgrade soil type and pavement condition on the relationship between MSN and rebound deflection was studied using appropriate plots for predominant types of soil and for classified value of Pavement Condition Index. The relationship will be helpful for practicing engineers to design the overlay thickness required for the pavement, without conducting the BBD test. Regression analysis using SPSS was done with various trials to find out the best fit relationship between the rebound deflection and CBR, and other soil properties for Gravel, Sand, Silt & Clay fractions. The second part of the study deals with periodic performance evaluation of selected road stretches representing National Highway (NH), State Highway (SH) and Major District Road (MDR), located in different geographical conditions and with varying traffic. 8 road sections divided into 15 homogeneous sections were selected for the study and 6 sets of continuous periodic data were collected. The periodic data collected include the functional and structural condition in terms of distress (pothole, pothole patch, cracks, rutting and raveling), skid resistance using a portable skid resistance pendulum, surface unevenness using Bump Integrator, texture depth using sand patch method and rebound deflection using Benkelman Beam. Baseline data of the study stretches were collected as one time data. Pavement history was obtained as secondary data. Pavement drainage characteristics were collected in terms of camber or cross slope using camber board (slope meter) for the carriage way and shoulders, availability of longitudinal side drain, presence of valley, terrain condition, soil moisture content, water table data, High Flood Level, rainfall data, land use and cross slope of the adjoining land. These data were used for finding out the drainage condition of the study stretches. Traffic studies were conducted, including classified volume count and axle load studies. From the field data thus collected, the progression of each parameter was plotted for all the study roads; and validated for their accuracy. Structural Number (SN) and Modified Structural Number (MSN) were calculated for the study stretches. Progression of the deflection, distress, unevenness, skid resistance and macro texture of the study roads were evaluated. Since the deterioration of the pavement is a complex phenomena contributed by all the above factors, pavement deterioration models were developed as non linear regression models, using SPSS with the periodic data collected for all the above road stretches. General models were developed for cracking progression, raveling progression, pothole progression and roughness progression using SPSS. A model for construction quality was also developed. Calibration of HDM–4 pavement deterioration models for local conditions was done using the data for Cracking, Raveling, Pothole and Roughness. Validation was done using the data collected in 2013. The application of HDM-4 to compare different maintenance and rehabilitation options were studied considering the deterioration parameters like cracking, pothole and raveling. The alternatives considered for analysis were base alternative with crack sealing and patching, overlay with 40 mm BC using ordinary bitumen, overlay with 40 mm BC using Natural Rubber Modified Bitumen and an overlay of Ultra Thin White Topping. Economic analysis of these options was done considering the Life Cycle Cost (LCC). The average speed that can be obtained by applying these options were also compared. The results were in favour of Ultra Thin White Topping over flexible pavements. Hence, Design Charts were also plotted for estimation of maximum wheel load stresses for different slab thickness under different soil conditions. The design charts showed the maximum stress for a particular slab thickness and different soil conditions incorporating different k values. These charts can be handy for a design engineer. Fuzzy rule based models developed for site specific conditions were compared with regression models developed using SPSS. The Riding Comfort Index (RCI) was calculated and correlated with unevenness to develop a relationship. Relationships were developed between Skid Number and Macro Texture of the pavement. The effort made through this research work will be helpful to highway engineers in understanding the behaviour of flexible pavements in Kerala conditions and for arriving at suitable maintenance and rehabilitation strategies. Key Words: Flexible Pavements – Performance Evaluation – Urban Roads – NH – SH and other roads – Performance Models – Deflection – Riding Comfort Index – Skid Resistance – Texture Depth – Unevenness – Ultra Thin White Topping

Microphytoplankton community structure in the North Eastern Arabian Sea during Winter Monsoon

The overall attempt of the study was aimed to understand the microphytoplankton community composition and its variations along a highly complex and dynamic marine ecosystem, the northern Arabian Sea. The data generated provides a first of its kind knowledge on the major primary producers of the region. There appears significant response among the microphytoplankton community structure towards the variations in the hydrographic conditions during the winter monsoon period. Interannually, variations were observed within the microphytoplankton community associated with the variability in temperature patterns and the intensity of convective mixing. Changing bloom pattern and dominating species among the phytoplankton community open new frontiers and vistas towards more intense study on the biological responses towards physical processes. The production of large amount of organic matter as a result of intense blooming of Noctiluca as well as diatoms aggregations augment the particulate organic substances in these ecosystem. This definitely influences the carbon dynamics of the northern Arabian Sea. Detailed investigations based on time series as well as trophodynamic studies are necessary to elucidate the carbon flux and associated impacts of winter-spring blooms in NEAS. Arabian sea is considered as one among the hotspot for carbon dynamics and the pioneering records on the major primary producers fuels carbon based export production studies and provides a platform for future research. Moreover upcoming researches based on satellite based remote sensing on productivity patterns utilizes these insitu observations and taxonomic data sets of phytoplankton for validation of bloom specific algorithm development and its implementation. Furthermore Saurashtra coast is considered as a major fishing zone of Indian EEZ. The studies on the phytoplankton in these regions provide valuable raw data for fishery prediction models and identifying fishing zones. With the Summary and Conclusion 177 baseline data obtained further trophodynamic studies can be initiated in the complex productive North Eastern Arabian Seas (NEAS) ecosystem that is still remaining unexplored.

Architecture and other Architectures: Mapping the Production of Insular Space in the Pearl River Delta (China) and Jakarta (Indonesia)

Globalization is widely regarded as the rise of the borderless world. However in practice, true globalization points rather to a “spatial logic” by which globalization is manifested locally in the shape of insular space. Globalization in this sense is not merely about the creation of physical fragmentation of space but also the creation of social disintegration. This study tries to proof that global processes also create various forms of insular space leading also to specific social implications. In order to examine the problem this study looks at two cases: China’s Pearl River Delta (PRD) and Jakarta in Indonesia. The PRD case reveals three forms of insular space namely the modular, concealed and the hierarchical. The modular points to the form of enclosed factories where workers are vulnerable for human-right violations due to the absent of public control. The concealed refers to the production of insular space by subtle discrimination against certain social groups in urban space. And the hierarchical points to a production of insular space that is formed by an imbalanced population flow. The Jakarta case attempts to show more types of insularity in relation to the complexity of a mega-city which is shaped by a culture of exclusion. Those are dormant and hollow insularity. The dormant refers to the genesis of insular– radical – community from a culture of resistance. The last type, the hollow, points to the process of making a “pseudo community” where sense of community is not really developed as well as weak social relationship with its surrounding. Although global process creates various expressions of territorial insularization, however, this study finds that the “line of flight” is always present, where the border of insularity is crossed. The PRD’s produces vernacular modernization done by peasants which is less likely to be controlled by the politics of insularization. In Jakarta, the culture of insularization causes urban informalities that have no space, neither spatially nor socially; hence their state of ephemerality continues as a tactic of place-making. This study argues that these crossings possess the potential for reconciling venue to defuse the power of insularity.

Cereal/legume rotation effects on rhizosphere bacterial community structure in West African soils

The increased use of cereal/legume crop rotation has been advocated as a strategy to increase cereal yields of subsistence farmers in West Africa, and is believed to promote changes in the rhizosphere that enhance early plant growth. In this study we investigated the microbial diversity of the rhizoplane from seedlings grown in two soils previously planted to cereal or legume from experimental plots in Gaya, Niger, and Kaboli, Togo. Soils from these legume rotation and continuous cereal plots were placed into containers and sown in a growth chamber with maize (Zea mays L.), millet (Pennisetum glaucum L.), sorghum (Sorghum bicolor L. Moench.), cowpea (Vigna unguiculata L.) or groundnut (Arachis hypogaea L.). At 7 and 14 days after sowing, 16S rDNA profiles of the eubacterial and ammoniaoxidizing communities from the rhizoplane and bulk soil were generated using denaturing gradient gel electrophoresis (DGGE). Community profiles were subjected to peak fitting analyses to quantify the DNA band position and intensities, after which these data were compared using correspondence and principal components analysis. The data showed that cropping system had a highly significant effect on community structure (p <0.005), irrespective of plant species or sampling time. Continuous cereal-soil grown plants had highly similar rhizoplane communities across crop species and sites, whereas communities from the rotation soil showed greater variability and clustered with respect to plant species. Analyses of the ammonia-oxidizing communities provided no evidence of any effects of plant species or management history on ammonia oxidizers in soil from Kaboli, but there were large shifts with respect to this group of bacteria in soils from Gaya. The results of these analyses show that crop rotation can cause significant shifts in rhizosphere bacterial communities.

Migration and Spatial Development

This is an empirical study with theoretical interpretation and elaboration simultaneously on the migration process and the related spatial development in contemporary China. In so doing, there is always a combination of series of studies of the modernization of the migrants themselves with accumulation of forms of capital and changes of lebenswelt (life world) as well as the regions of their origins by the effective use of the gained resources from outgoing migration and remigration. With great efforts made to put the issues together for analysis, the author has taken three approaches to the study based on the political and economic institutional arrangements, the field work data and the elaboration of respective findings. First, as the analytical parts of the institutional changes, which have gone through the whole research, many of the policies from state level to townships involved in the migration, remigration and spatial development have been interpreted with Chinese political and cultural insight. The making of these, as the means of understanding the contexts of macro level and micro level cases is served as key linkages between scholarly imagination and social reality. Indeed most of the discussions made to explain the phenomena such as the sudden upsurge of migration flows, the emergence of three generations, the strong and weak trends of remigration as well as the related spatial development planning, etc are mainly due to the domination, at least the impact of governments decision-making in spite of growing market functioning in often operative manners. Secondly, case studies of the effects of migration and remigration are carried out between the years of 1995 and 2005 in the costal urban regions as designations and the interior rural regions as origins. Conducted mainly by the author, the cases drawn in the research focus on the process of migration with an accumulation of forms of capital away from home and the effective use of the resources flowing back to home areas. As a result, ways of accumulation and utilization of the economic, social and cultural capital are described and interpreted in terms of the development and modernization of both the migrants themselves and the regions where they come out from or move to in the future. Thirdly, in accordance with the findings generated from the cases, the author proposes in the final chapter an important argumentation as conclusion that the duel social-economic structure will inevitably be broken up and reformulated with flows of migrants and forms of capital they possess as types of future spatial development that will be put into practice. With scenarios and all the other conclusions worked out in the end, the research concludes that the pluralistic spatial development in the condition of constant space flows between regions can be a decisive line of thinking in the process of urbanization, industrialization and modernization in the long run in the future. Since this is an exploratory study of the past and present, the author has left some space open for academic debates and put forward suggestions on the inclusion of future research before implementing policies necessary for migration associated spatial practice and development.

Segregation unter Stagnationsbedingungen

Anlass der Untersuchung sind Verstärkungen von strukturwandel- und globalisierungsbedingten Wandlungen unter Schrumpfungs- und Stagnationsbedingungen. Denn Stagnations- und Schrumpfungstendenzen in einer Region sind selektiv, sie begünstigen über verschiedene Mechanismen Polarisierungen und Marginalisierungen: Die allgemeine Entspannung am Wohnungsmarkt hat erhöhte Mobilität und damit sozialräumliche Segregierungen und Polarisierungen der Wohnungsversorgung zur Folge. Leerstände und ausbleibende Investitionen begünstigen Polarisierungen von baulich-räumlichen Qualitäten. Diese beiden Entwicklungen überlagern sich im Stadtraum und verstärken sich gegenseitig. Dabei verbessert sich die Wohnungsversorgung in den benachteiligten Quartieren kaum, so die Ausgangshypothesen. Die Untersuchung fragt nach den Wirkungen des Nebeneinanders von Wachstums-, Stagnations- und Schrumpfungserscheinungen auf unterschiedlichen Maßstabsebenen, dem Zusammenspiel von sozialstrukturellen und qualitativen Veränderungen der baulich-räumlichen Gegebenheiten in den Quartieren sowie in innerstädtischer Differenzierung. Dabei interessieren besonders die Einflüsse eines regional entspannten Wohnungsmarktes und dessen Folgen für die Verwertungsstrategien im Wohnungsbestand auf Segregationsprozesse und die Wohnungsversorgung. Als Fallbeispiel der Untersuchung dient die Stadt Kassel. Der sozialräumliche Fokus liegt auf drei Typen benachteiligter Quartiere: Neben den in der aktuellen Diskussion zumeist betrachteten gründerzeitlichen Arbeiterquartieren und den Großsiedlungen der 1960/70er Jahre wurden auch die peripheren Geschosswohnungsbausiedlungen der 1950er/60er Jahre in die Untersuchung einbezogen, um den unterschiedlichen Rahmenbedingungen und Wirkungen in den Quartierstypen auf die Spur zu kommen und damit letztlich Grundlagen für stadtentwicklungspolitische Strategien zu erarbeiten. Die kleinräumigen Analysen von sozialräumlicher und baulich-räumlicher Struktur sowie zur Wohnungsversorgung deckten Parallelen und gegenläufige Entwicklungen zwischen den unterschiedlichen Quartierstypen auf; es ergaben sich verschiedene Anhaltspunkte zur Erhärtung der Ausgangsthesen. So wurde z.B. deutlich, dass sich unter den Marktbedingungen stagnierender Städte die Wohnflächenversorgung in den benachteiligten Quartieren kaum verbessert. Hierin zeigt sich ein entscheidender Unterschied zu stark schrumpfenden Städten, in denen sich die Versorgungslage (fast) durchgängig verbessert. Wohnungsmarktbarrieren wirken offensichtlich unter Stagnationsbedingungen für bestimmte Bevölkerungsgruppen weiter. Da sich ihre Wirkung aber für weitere Kreise der Bevölkerung abschwächt, verschärfen sich sozialräumliche Konzentrationen. Vor allem aber wurden Überlagerung und gegenseitige Verstärkung dieser sozialräumlichen mit baulich-räumlichen Polarisierungen deutlich, die vor allem aus stadträumlich konzentrierten Investitionen in den Gebäude- und Wohnungsbestand resultieren. Letztlich zeigt sich damit, dass regulierende Eingriffe nicht nur im Rahmen des Umbaus und der Erneuerung der Quartiere erforderlich sind, sondern insbesondere auch in den Wohnungsmarkt und dies auch bei entspannter regionaler Marktlage. Andernfalls ist weder eine angemessene Wohnungsversorgung aller Bevölkerungsgruppen noch der Zusammenhalt der Stadt(Gesellschaft) zu gewährleisten. Dabei ist die Stadtpolitik permanent mit der Gleichzeitigkeit von (wirtschaftlicher) Standortpolitik und sozialer Stadtentwicklung konfrontiert, die sie im Sinne einer nachhaltigen Entwicklung gegeneinander und miteinander abwägen muss.

Nutrient cycling and nutrient use efficiency in urban and peri-urban agriculture of Kabul, Afghanistan

Like elsewhere also in Kabul, Afghanistan urban and peri-urban agriculture (UPA) has often been accused of being resource inefficient and unsustainable causing negatives externalities to community health and to the surroundings. These arise from the inappropriate management and use of agricultural inputs, including often pesticides and inter-city wastes containing heavy metal residues and pathogens. To address these concerns, parallel studies with the aims of quantification of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) horizontal and vertical fluxes; the assessment of heavy metal and pathogen contaminations of UPA produce, and an economic analysis of cereal, vegetable and grape production systems conducted for two years in UPA of Kabul from April 2008 to October 2009. The results of the studies from these three UPA diverse production systems can be abridged as follows: Biennial net balances in vegetable production systems were positive for N (80 kg ha-1 ), P (75 kg ha-1) and C (3,927 kg ha-1), negative for K (-205 kg ha-1), whereas in cereal production systems biennial horizontal balances were positive for P (20 kg ha-1 ) and C (4,900 kg ha-1) negative for N (-155 kg ha-1) and K (-355 kg ha-1) and in vineyards corresponding values were highly positive for N (295 kg ha-1), P (235 kg ha-1), C (3,362 kg ha-1) and slightly positive for K (5 kg ha-1). Regardless of N and C gaseous emissions, yearly leaching losses of N and P in selected vegetable gardens varied from 70 - 205 kg N ha-1 and 5 - 10 kg P ha-1. Manure and irrigation water contributed on average 12 - 79% to total Inputs of N, P, K and C, 10 - 53% to total inputs of C in the gardens and fields. The elevated levels of heavy metal and pathogen loads on fresh UPA vegetables reflected contamination from increasing traffic in the city, deposits of the past decades of war, lacking collection and treatment of raw inter-city wastes which call for solutions to protect consumer and producer health and increase reliability of UPA productions. A cost-revenue analysis of all inputs and outputs of cereal, vegetable and grapes production systems over two years showed substantial differences in net UPA household income. To confirm these results, more detailed studies are needed, but tailoring and managing the optimal application of inputs to crop needs will significantly enhance farmer’s better revenues as will as environmental and produce quality.

Agricultural practices and horizontal nutrient balances in urban gardens and the alternative use of urban agricultural land in Khartoum, Sudan

The surge in the urban population evident in most developing countries is a worldwide phenomenon, and often the result of drought, conflicts, poverty and the lack of education opportunities. In parallel with the growth of the cities is the growing need for food which leads to the burgeoning expansion of urban and peri-urban agriculture (UPA). In this context, urban agriculture (UA) contributes significantly to supplying local markets with both vegetable and animal produce. As an income generating activity, UA also contributes to the livelihoods of poor urban dwellers. In order to evaluate the nutrient status of urban soils in relation to garden management, this study assessed nutrient fluxes (inputs and outputs) in gardens on urban Gerif soils on the banks of the River Nile in Khartoum, the capital city of Sudan. To achieve this objective, a preliminary baseline survey was carried out to describe the structure of the existing garden systems. In cooperation with the author of another PhD thesis (Ms. Ishtiag Abdalla), alternative uses of cow dung in brick making kilns in urban Khartoum were assessed; and the socio-economic criteria of the brick kiln owners or agents, economical and plant nutritional value of animal dung and the gaseous emission related to brick making activities were assessed. A total of 40 household heads were interviewed using a semi-structured questionnaire to collect information on demographic, socio-economic and migratory characteristics of the household members, the gardening systems used and the problems encountered in urban gardening. Based on the results of this survey, gardens were divided into three groups: mixed vegetable-fodder gardens, mixed vegetable-subsistence livestock gardens and pure vegetable gardens. The results revealed that UA is the exclusive domain of men, 80% of them non-native to Khartoum. The harvested produce in all gardens was market oriented and represented the main source of income for 83% of the gardeners. Fast growing leafy vegetables such as Jew’s mallow (Corchorous olitorius L.), purslane (Portulaca oleracea L.) and rocket (Eruca sativa Mill.) were the dominant cultivated species. Most of the gardens (95%) were continuously cultivated throughout the year without any fallow period, unless they were flooded. Gardeners were not generally aware of the importance of crop diversity, which may help them overcome the strongly fluctuating market prices for their produce and thereby strengthen the contributions of UA to the overall productivity of the city. To measure nutrient fluxes, four gardens were selected and their nutrients inputs and outputs flows were monitored. In each garden, all plots were monitored for quantification of nutrient inputs and outputs. To determine soil chemical fertility parameters in each of the studied gardens, soil samples were taken from three selected plots at the beginning of the study in October 2007 (gardens L1, L2 and H1) and in April 2008 (garden H2) and at the end of the study period in March 2010. Additional soil sampling occurred in May 2009 to assess changes in the soil nutrient status after the River Nile flood of 2008 had receded. Samples of rain and irrigation water (river and well-water) were analyzed for nitrogen (N), phosphorus (P), potassium (K) and carbon (C) content to determine their nutrient inputs. Catchment traps were installed to quantify the sediment yield from the River Nile flood. To quantify the nutrient inputs of sediments, samples were analyzed for N, P, K and organic carbon (Corg) content, cation exchange capacity (CEC) and the particle size distribution. The total nutrient inputs were calculated by multiplying the sediment nutrient content by total sediment deposits on individual gardens. Nutrient output in the form of harvested yield was quantified at harvest of each crop. Plant samples from each field were dried, and analyzed for their N, P, K and Corg content. Cumulative leaching losses of mineral N and P were estimated in a single plot in garden L1 from December 1st 2008 to July 1st 2009 using 12 ion exchange resins cartridges. Nutrients were extracted and analyzed for nitrate (NO3--N), ammonium (NH4+-N) and phosphate PO4-3-P. Changes in soil nutrient balance were assessed as inputs minus outputs. The results showed that across gardens, soil N and P concentrations increased from 2007 to 2009, while particle size distribution remained unchanged. Sediment loads and their respective contents of N, P and Corg decreased significantly (P < 0.05) from the gardens of the downstream lowlands (L1 and L2) to the gardens of the upstream highlands (H1 and H2). No significant difference was found in K deposits. None of the gardens received organic fertilizers and the only mineral fertilizer applied was urea (46-0-0). This equaled 29, 30, 54, and 67% of total N inputs to gardens L1, L2, H1, and H2, respectively. Sediment deposits of the River Nile floods contributed on average 67, 94, 6 and 42% to the total N, P, K and C inputs in lowland gardens and 33, 86, 4 and 37% of total N, P, K and C inputs in highland gardens. Irrigation water and rainfall contributed substantially to K inputs representing 96, 92, 94 and 96% of total K influxes in garden L1, L2, H1 and H2, respectively. Following the same order, total annual DM yields in the gardens were 26, 18, 16 and 1.8 t ha-1. Annual leaching losses were estimated to be 0.02 kg NH4+-N ha-1 (SE = 0.004), 0.03 kg NO3--N ha-1 (SE = 0.002) and 0.005 kg PO4-3-P ha-1 (SE = 0.0007). Differences between nutrient inputs and outputs indicated negative nutrient balances for P and K and positive balances of N and C for all gardens. The negative balances in P and K call for adoptions of new agricultural techniques such as regular manure additions or mulching which may enhance the soil organic matter status. A quantification of fluxes not measured in our study such as N2-fixation, dry deposition and gaseous emissions of C and N would be necessary to comprehensively assess the sustainability of these intensive gardening systems. The second part of the survey dealt with the brick making kilns. A total of 50 brick kiln owners/or agents were interviewed from July to August 2009, using a semi-structured questionnaire. The data collected included general information such as age, family size, education, land ownership, number of kilns managed and/or owned, number of months that kilns were in operation, quantity of inputs (cow dung and fuel wood) used, prices of inputs and products across the production season. Information related to the share value of the land on which the kilns were built and annual income for urban farmers and annual returns from dung for the animal raisers was also collected. Using descriptive statistics, budget calculation and Gini coefficient, the results indicated that renting the land to brick making kilns yields a 5-fold higher return than the rent for agriculture. Gini coefficient showed that the kiln owners had a more equal income distribution compared to farmers. To estimate emission of greenhouse gases (GHGs) and losses of N, P, K, Corg and DM from cow dung when used in brick making, samples of cow dung (loose and compacted) were collected from different kilns and analyzed for their N, P, K and Corg content. The procedure modified by the Intergovernmental Panel on Climate Change (IPCC, 1994) was used to estimate the gaseous emissions of cow dung and fuel wood. The amount of deforested wood was estimated according to the default values for wood density given by Dixon et al. (1991) and the expansion ratio for branches and small trees given by Brown et al. (1989). The data showed the monetary value of added N and P from cow dung was lower than for mineral fertilizers. Annual consumption of compacted dung (381 t DM) as biomass fuel by far exceeded the consumption of fuel wood (36 t DM). Gaseous emissions from cow dung and fuel wood were dominated by CO2, CO and CH4. Considering that Gerif land in urban Khartoum supports a multifunctional land use system, efficient use of natural resources (forest, dung, land and water) will enhance the sustainability of the UA and brick making activities. Adoption of new kilns with higher energy efficiency will reduce the amount of biomass fuels (cow dung and wood) used the amount of GHGs emitted and the threat to the few remaining forests.

Effects of grassland conversion and tillage intensities on soil microbial biomass, residues and community structure

Agricultural intensification has a strong impact on level of soil organic matter (SOM), microbial biomass stocks and microbial community structure in agro-ecosystems. The size of the microbial necromass C pool could be about 40 times that of the living microbial biomass C pool in soils. Due to the specificity, amino sugar analysis gives more important information on the relative contribution of fungal and bacterial residues to C sequestration potential of soils. Meanwhile, the relationship between microbial biomass and microbial necromass in soil and its ecological significance on SOM are not fully understood and likely to be very complex in grassland soils. This thesis focuses on the effects of tillage, grassland conversion intensities and fertilisation on microbial biomass, residues and community structure. The combined analyses of microbial biomass and residue formation of both fungi and bacteria provided a unique opportunity to study the effect of tillage, grassland conversion and fertilisation on soil microbial dynamics. In top soil at 0-30 cm layer, a reduction in tillage intensity by the GRT and NT treatments increased the accumulation of saprotrophic fungi in comparison with the MBT treatment. In contrast, the GRT and NT treatments promoted AMF at the expense of saprotrophic fungi in the bottom soil layer at 30-40 cm depth. The negative relationship between the ergosterol to microbial biomass C ratio and the fungal C to bacterial C ratio points to the importance of the relationship between saprotrophic fungi and biotrophic AMF for tillage-induced changes in microbial turnover of SOC. One-season cultivation of winter wheat with two tillage events led to a significant loss in SOC and microbial biomass C stocks at 0-40 cm depth in comparison with the permanent grassland, even 5 years after the tillage event. However, the tillage induced loss in microbial biomass C was roughly 40% less in the long-term than in the short-term of the current experiment, indicating a recovery process during grassland restoration. In general, mould board tillage and grassland conversion to maize monoculture promoted saprotrophic fungi at the expense of biotrophic AMF and bacteria compared to undisturbed grassland soils. Slurry application promoted bacterial residues as indicated by the decreases in both, the ergosterol to microbial biomass C ratio and the fungal C to bacterial C ratio. In addition, the lost microbial functional diversity due to tillage and maize monoculture was restored by slurry application both in arable and grassland soils. I conclude that the microbial biomass C/S ratio can be used as an additional indicator for a shift in microbial community. The strong relationships between microbial biomass and necromass indices points to the importance of saprotrophic fungi and biotrophic AMF for agricultural management induced effects on microbial turnover and ecosystem C storage. Quantitative information on exact biomass estimates of these two important fungal groups in soil is inevitably necessary to understand their different roles in SOM dynamics.

Finding Spaces for Urban Food Production – Matching Spatial and Stakeholder Analysis with Urban Agriculture Approaches in the Urban Renewal Area of Dortmund-Hörde, Germany

Using the case of an economically declined neighbourhood in the post-industrial German Ruhr Area (sometimes characterized as Germany’s “Rust Belt”), we analyse, describe and conclude how urban agriculture can be used as a catalyst to stimulate and support urban renewal and regeneration, especially from a socio-cultural perspective. Using the methodological framework of participatory action research, and linking bottom-up and top-down planning approaches, a project path was developed to include the population affected and foster individual responsibility for their district, as well as to strengthen inhabitants and stakeholder groups in a permanent collective stewardship for the individual forms of urban agriculture developed and implemented. On a more abstract level, the research carried out can be characterized as a form of action research with an intended transgression of the boundaries between research, planning, design, and implementation. We conclude that by synchronously combining those four domains with intense feedback loops, synergies for the academic knowledge on the potential performance of urban agriculture in terms of sustainable development, as well as the benefits for the case-study area and the interests of individual urban gardeners can be achieved.

Local food security initiatives: systemic limitations in Vancouver, Canada

This paper approaches the topic of urban/community gardening not through the lens of urban theory per se but in light of basic farming realities such as growing season and land availability. Food security comprises availability and affordability. In the context of North American and Western European societies, only food affordability normally merits public discourse. In practice, governments have little or no means to change food affordability, in view of prevailing capitalistic free-market structures. In the current wave of popular exuberance, civic politicians and others have promoted the belief that community gardening could be the pathway to produce affordable food. The formidable obstacles to this pursuit include the availability of (low-cost) land within the highly-densified city limit, insufficient ambient temperature and water supply during the growing season and the contemporary structure of society. Overcoming these fundamental hurdles carries significant negative environmental and economic consequences.

“La Felicidad incluye a todos”. La construcción de un barrio mezclado en Bogotá.

El trabajo se enmarca en las discusiones relacionadas con segregación espacial, segregación social y construcción de barrios mezclados. Específicamente, selecciona el caso de La Felicidad: ciudad parque en Bogotá como un ejemplo que sirve para analizar las políticas públicas enfocadas en disminuir la segregación residencial en la ciudad a partir de la construcción de un vecindario que está compuesto por vivienda de interés social y vivienda regular. A partir de métodos cuantitativos y cualitativos se analiza cómo esta funcionando esta propuesta urbana.

Representaciones sociales hegemónicas y polémicas en el contexto de identidad rural [TC]

El objetivo de este estudio es conocer las representaciones de lo rural y lo urbano con el intento de comprender cómo miembros de una comunidad rural se posicionan frente a la estructura social y simbólica hegemónicamente urbana. Se obtuvo el conjunto de datos a través de entrevistas a 200 integrantes de una comunidad rural, contemplando los siguientes núcleos de información: motivaciones para éxodo/permanencia en el territorio, experiencia de prejuicios, estereotipos atribuidos al grupo rural, y valores endo/exo-grupales. Los resultados referentes a las motivaciones para el éxodo o permanencia en el campo revelaron el predominio del proyecto de vida vinculado a lo rural. Los clásicos estereotipos de roceiros, bobos y caipiras fueran identificados como la imagen social del hombre del campo, elementos que producen el escenario conflictivo estratégico a la elaboración de representaciones defensivas, siendo el endogrupo rural asociado a valores positivos, y la ciudad, a significados negativamente valorizados. Se discute el imaginario grupal como campo de fuerzas en el que se elaboran representaciones polémicas en respuesta a la hegemonía urbana.