Selective Sweeps in Cattle Genomes in Response to the Influence of Urbanization and Environmental Contamination.

A genomic study was conducted to identify the effects of urbanization and environmental contaminants with heavy metals on selection footprints in dairy cattle populations reared in the megacity of Bengaluru, South India. Dairy cattle reared along the rural-urban interface of Bengaluru with/without access to roughage from public lakeshores were selected. The genotyped animals were subjected to the cross-population-extended haplotype homozygosity (XP-EHH) methodology to infer selection sweeps caused by urbanization (rural, mixed, and urban) and environmental contamination with cadmium and lead. We postulated that social-ecological challenges contribute to mechanisms of natural selection. A number of selection sweeps were identified when comparing the genomes of cattle located in rural, mixed, or urban regions. The largest effects were identified on BTA21, displaying pronounced peaks for selection sweeps for all three urbanization levels (urban_vs_rural, urban_vs_mixed and rural_vs_mixed). Selection sweeps are located in chromosomal segments in close proximity to the genes lrand rab interactor 3 (RIN3), solute carrier family 24 member 4 (SLC24A4), tetraspanin 3 (TSPAN3), and proline-serine-threonine phosphatase interacting protein 1 (PSTPIP1). Functional enrichment analyses of the selection sweeps for all three comparisons revealed a number of gene ontology (GO) and KEGG terms, which were associated with reproduction, metabolism, and cell signaling-related functional mechanisms. Likewise, a number of the chromosomal segments under selection were observed when creating cattle groups according to cadmium and lead contaminations. Stronger and more intense positive selection sweeps were observed for the cadmium contaminated group, i.e., signals of selection on BTA 16 and BTA19 in close proximity to genes regulating the somatotropic axis (growth factor receptor bound protein 2 (GRB2) and cell ion exchange (chloride voltage-gated channel 6 (CLCN6)). A few novel, so far uncharacterized genes, mostly with effects on immune physiology, were identified. The lead contaminated group revealed sweeps which were annotated with genes involved in carcass traits (TNNC2, SLC12A5, and GABRA4), milk yield (HTR1D, SLCO3A1, TEK, and OPCML), reproduction (GABRA4), hypoxia/stress response (OPRD1 and KDR), cell adhesion (PCDHGC3), inflammatory response (ADORA2A), and immune defense mechanism (ALCAM). Thus, the findings from this study provide a deeper insight into the genomic regions under selection under the effects of urbanization and environmental contamination.

Telecoupled urban demand from West African cities causes social-ecological land use transformation in Saharan oases.

Little is known about the long-distance telecoupling effects of urban food demands on land use changes (LUCs) in remote oases of the Southern Sahara. Using the example of two typical oasis settlements on Mont Bagzam in the southern Aϊr Mountains of Niger which are linked to regional and global markets by an unpaved road since 2015, this study aimed at analyzing time trajectories of LUCs and related changing agricultural production patterns. LUCs were quantified for 1955 to 2022 using GIS-based mapping of agriculture and natural vegetation based on historical aerial photographs, CORONA and multi-spectral satellite images, and high resolution drone-based surveys. The results show a major increment in actively used agricultural land in the 850 ha watershed of the two oases from 11 ha in 1955 to 13 ha in 2003 and 68 ha in 2022 as well as the addition of 92 irrigation wells to 16 existing ones between 2003 and 2022. LUCs and evapotranspiration calculated from climatic data of a local weather station allowed to estimate changes of irrigation water needs in the selected watershed. While annual precipitation averages only 214 mm, local reference evapotranspiration may reach 1,476 mm year-1. Therefore, the additional annual irrigation water needs for the newly established fields between 2003 and 2022 cultivated to cash crops rose by 696 million l. To detect LUC effects on soil quality, soil samples of onion and garlic fields of different ages were collected employing a false-time-series approach. Results reveal increasing soil pH and salt concentrations and falling ground water tables, which reflects a negative water balance and ground water extraction above recharge levels. Our study provides evidence that the newly established telecoupled production systems on Mont Bagzam threaten the sustainability of existing local agricultural production and related livelihoods of agro-pastoralists.

Monitoring rural-urban transformation in the coastal region of Rabat-Sale-Kenitra, Morocco.

Worldwide urbanization drives rural-urban transformation (RUT) which has major consequences in many countries of the Global South where there is an urgent need to better understand and manage the underlying processes and consequences for ecosystem services. To fill existing knowledge gaps on the extent and time course of RUT in Morocco, this study focused on (i) analyzing the spatial patterns of rural-urban transformation in the Rabat-Sale-Kenitra (RSK) region from 1972 to 2020, (ii) identifying key mechanisms of change, and (iii) defining the main driving forces behind the spatial transformation patterns. To this end, we processed data of the Landsat free archive, historical grayscale Corona images, and nighttime lights datasets on Google Earth Engine (GEE) using machine learning classifiers and LandTrendr spectral-temporal segmentation algorithms. With an overall accuracy (OA) ranging from 88-95%, the results revealed that during the study period the RSK region experienced a 473% growth of horizontal built-up reflected in an area increase from 63.4 km2 to 299.9 km2. The main changes occurred along the Kenitra-Rabat-Temara axis and in central cities connected to the main road network. The horizontal expansion of large and medium-sized cities led to the formation of a Rural-Urban Interface (RUI) on the outskirts. The urban sprawl of some cities has affected the surrounding rural lands within the RUI. Environmental, social, economic, and political forces have interacted in shaping the changes in rural-urban landscapes.

Rurbanity: a concept for the interdisciplinary study of rural-urban transformation.

Along with climate change, population growth, and overexploitation of natural resources, urbanisation is among the major global challenges of our time. It is a nexus where many of the world's grand challenges intersect, and thus key to sustainable development. The widespread understanding of urbanisation as a successive and unidirectional transformation of landscapes and societies from a rural to an urban state is increasingly questioned. Examples from around the globe show that 'the rural' and 'the urban' are not only highly interdependent, but actually coexist and often merge in the same space or livelihood strategy. Our concept of rurbanity provides an integrated theoretical framework which overcomes the rural-urban divide and can be operationalised for empirical research. Rurbanity is the next stringent step following the gradual widening of previous concepts from urban-centred approaches through the emphasis on urban peripheries to attempts of abolishing any distinction of a rural environment and acknowledging the highly dynamic nature of globalising urbanisation. Building on complex systems theory and assemblage thinking, our concept explores complementary aspects of the distinct epistemic worldviews dominating the natural and social sciences. Within this theoretical frame, we derive four analytical dimensions as entry points for empirical research: Endowments and Place, Flows and Connectivity, Institutions and Behaviour, and Lifestyles and Livelihoods. Two examples illustrate how these dimensions apply, interact, and together lead to a comprehensive, insightful understanding of rurban phenomena. Such understanding can be an effective starting point for assessing potential contributions of rurbanity to long-term global sustainability.

A spatio-temporal dataset on food flows for four West African cities.

Gaining insight into the food sourcing practices of cities is important to understand their resilience to climate change, economic crisis, as well as pandemics affecting food supply and security. To fill existing knowledge gaps in this area food flow data were collected in four West African cities - Bamako (Mali), Bamenda (Cameroon), Ouagadougou (Burkina Faso), and Tamale (Ghana). The data cover, depending on the city, road, rail, boat, and air traffic. Surveys were conducted for one week on average during the peak harvest, lean, and rainy seasons, resulting in a dataset of over 100,000 entries for 46 unprocessed food commodities. The data collected includes information on the key types of transportation used, quantity, source, and destination of the food flows. The data were used to delineate urban foodsheds and to identify city-specific factors constraining rural-urban linkages. The data can also be employed to inform academic and policy discussions on urban food system sustainability, to validate other datasets, and to plan humanitarian aid and food security interventions.

Showcasing the multifaceted aspects of agricultural transformation: The example of mountain oases in Oman.

In the Anthropocene the consequences of land-use transformation on ecosystem services are of growing concern, particularly in fragile areas of mountain agriculture that often represent high nature-value farmland. This study uses a decadal repeated survey approach to analyse the effects of modernisation on oasis systems in the Jabal Al Akhdar region of northern Oman. This rugged mountain region at the north-eastern tip of the Arabian Peninsula experiences a growing influx of regional and international tourists since the opening of a modern highway 15 years ago. In 2007, at the onset of transformation processes, a survey was conducted with all households (HH) located in three major settlements along the 1000-m-altitude gradient of the Wadi Muaydin watershed. The survey was repeated in 2018, including all remaining HH of the three settlements. This longitudinal approach allowed studying the consequences of social-ecological transformation processes on crop and livestock husbandry, agricultural labour use, product marketing, and perception of the region's future by its local residents. Though the village inhabitants are aging and declining in numbers, they still adhere to agriculture, largely because of tradition and identity. Fallowing and abandoning farmland increased over the investigated time span but was paralleled by increased application of agrochemicals and animal manure on fields, purchase of roughage and concentrate feeds for small ruminants, concentration on cash crop and meat production for sale, and increased employment of migrant workers. These indicators of modernisation of oasis agriculture are accompanied by predominantly pessimistic views on future prospects of oasis farming. Commonly perceived problems are shortage of irrigation water and profound societal change. Against these challenges, value chain generation and direct marketing opportunities for local agricultural produce are seen as prerequisites to keep the high nature-value farmland of these mountain oases alive.

Phenotypic and genetic diversity of domestic yak (Bos grunniens) in high-altitude rangelands of Gilgit-Baltistan, Pakistan.

Due to climate change, irrigated agriculture may become restricted in the mountain valleys in northern Pakistan in the future. Hence, the importance of yak (Bos grunniens) keeping in the mountain ranges as risk-mitigating strategy for mountain dwellers will potentially increase. However, little is known about the current status of the domestic yak in this region. We therefore used phenotypic characteristics and 13 microsatellite loci to determine the phenotypic differences and the level of genetic differentiation between populations of six valleys. Larger body measures and partially different physical appearance were observed in Shimshal and Khaplu yaks, especially when compared with yaks in the Chapurson valley. Overall, the mean observed heterozygosity was similar to the mean expected heterozygosity. Average genetic diversity was highest in the Hopar population and lowest in the Haramosh population. A low FIS value indicated that individuals were less related than expected under a model of random mating. Three distinct genetic clusters were found for the six yak populations under study. Genetic distances were largest between Shimshal and Khaplu populations, and lowest between populations of Phandar and Hopar. It is concluded that yaks of Shimshal, Khaplu and Haramosh valleys were genetically distinct from yak populations in Chapurson, Hopar and Phandar valleys, indicating that the free-range conditions and pastoral yak rearing system in the region have preserved the underlying genetic diversity of the yak populations.

Seasonal Variations in Voluntary Intake and ApparentDigestibility of Forages by Goats in the Chinese Altai Mountains.

Forage availability and quality directly impact animal performance, ultimately affecting productivity and health. This study aimed to understand the interaction between qualitative and quantitative vegetation availability and feed intake of goats on alpine pastures in the Chinese Altai Mountains. The daily grazing routes of three goats from a local herding family were monitored with GPS devices set at a logging rate of 64 s during spring and the early and late summer season in 2013 and 2014. The quantity and quality of vegetation along their grazing routes was determined, and the amount of feces excreted was measured in a total of five goats per season for the indirect determination of the animals' feed intake. The grazing routes were longer in spring than in summer, leading to larger grazing areas visited in spring. Vegetation on offer ranged from 980 to 2400 kg dry mass per hectare and was similar in the spring and summer seasons but higher in 2013 than in 2014. Feed consumption of forage and nutrients did not significantly differ between seasons and years, respectively, suggesting that the goats' nutrient intake was not restricted by interannual variability of forage on offer. Regular monitoring of animal numbers and of vegetation quantity and quality on the mountain rangelands can help responsible government agencies to estimate forage offtake of small ruminants in order to timely adjust grazing pressure in the study region.

Spatial patterns of urbanising landscapes in the North Indian Punjab show features predicted by fractal theory.

Understanding and governing human settlement patterns is a major challenge of the urban age. While rural settlements emerge as parts of agricultural landscapes, cities typically evolve in economically strategic locations, and over time form hierarchical systems of cities. Purposeful planning and the collective, self-organized behavior of the inhabitants interact in the development of regional settlement patterns. Since self-organizing systems often produce fractal patterns in nature, this study combines approaches of land use science, city ranking, and urban planning under a fractal theory framework, to analyze the settlement system of the Indian Punjab. Scaling levels were defined by discontinuities in the size distribution of built-up areas (Global Urban Footprint), which correlated to population-based classifications (r = 0.9591). Self-similarity across scales was supported by geo-statistical similarity (p < 0.05) of distances and angles between settlements of successive classes, and the overall fractal dimension of DB = 1.95. When compared to a modeled Sierpinski Carpet, more than 50% of the settlements met the fractal geometry rules at larger scales. The spatial distribution of small villages, however, deviated, indicating a scale-related shift in organizing principles. Explicitly acknowledging cross-scale relations and self-organisation in regional planning policies may lead to more sustainable settlement structures that are in harmony with natural system properties.

Agro-ecological landuse transformation in oasis systems of Al Jabal Al Akhdar, northern Oman.

The millenia-old oasis systems in the Western Hajar Mountains of Northern Oman have received widespread attention as models of sustainable irrigated agriculture in hyperarid Arabia. Given Oman's rampant urbanization, growing scarcity of water and skilled labour, we quantified chances in water use, land use, and land cover between 2007 and 2018 using a rare time-series approach of detailed GIS-based crop mapping. Results from satellite image analysis and comprehensive ground truthing showed that urban areas grew from 206 ha in 2009 to 230 ha in 2014 and 252 ha in 2018. Throughout this decade, irrigated areas in backyards and front-house gardens of the town, planted largely to tree crops and vegetables, increased from 13.5 to 23.3 ha. Between 2007 and 2018 the actively used area of the studied oasis systems declined by 2.0% and the share of perennial crops without underplanting by 5.1%, while land under agroforestry increased by 2.1% and fallow land by 3.5%. Rising water demand of the sprawling town Sayh Qatanah led to terraces of Al 'Ayn and Ash Sharayjah now being partly irrigated with treated wastewater which accelerated the abandonment of the old settlement structures. The labour- and water use efficiency-driven transformation of the Al Jabal Al Akhdar oasis agriculture into increasingly market-oriented landuse systems questions its function as example of sustainable, bio-cultural heritage of Arabia.

Soil microbial properties of subalpine steppe soils at different grazing intensities in the Chinese Altai Mountains.

Long-term provision of ecosystem services by grasslands is threatened by increasing stocking densities. The functions of grassland ecosystems depend on a mutual relationship between aboveground and belowground biota. While the effects of increasing stocking density on plant biomass are well studied, little is known about its impact on soil microbial properties. To fill this knowledge gap a grazing experiment was conducted on a summer pasture in the Chinese Altai Mountains during the summers of 2014 and 2015 using a randomized block design with stocking densities of 0, 8, 16, and 24 sheep ha-1 replicated four times. After two summer grazing periods (each 56 days), topsoil samples (1-7 cm) were taken in September 2015 and analyzed for major physical, chemical, and microbial soil properties. Except for the metabolic quotient (qCO2; p < 0.05), the examined soil properties remained unaffected by the increasing stocking densities, likely due to high spatial variability. The qCO2 declined from 13.5 mg CO2-C g-1 microbial biomass C d-1 at zero grazing to 12.2 mg CO2-C g-1 microbial biomass C d-1 at a stocking density of 24 sheep ha-1. Low values of qCO2 indicate an aged and dormant microbial community that diverts less soil organic carbon (SOC) to catabolic processes within their cells, characteristic for C limiting conditions. The aboveground biomass affected by grazing intensity correlated positively with SOC (rs = 0.60, p = 0.015) and ergosterol (rs = 0.76, p = 0.001) pointing indirectly to the effect of stocking density. Additionally to the relatively high values of qCO2, highest values of SOC (39.2 mg g-1 soil), ergosterol (6.01 µg g-1 soil), and basal respiration (10.7 µg g-1 soil d-1) were observed at a stocking density of 8 sheep ha-1 indicating that a low grazing intensity is recommendable to avoid soil degradation.

Arthropod Communities in Urban Agricultural Production Systems under Different Irrigation Sources in the Northern Region of Ghana.

Urban and peri-urban agricultural (UPA) production systems in West African countries do not only mitigate food and financial insecurity, they may also foster biodiversity of arthropods and partly compensate for structural losses of natural environments. However, management practices in UPA systems like irrigation may also contribute to disturbances in arthropod ecology. To fill knowledge gaps in the relationships between UPA management and arthropod populations, we compared arthropods species across different irrigation sources in Tamale. During a 72-h sampling period, 14,226 arthropods were caught with pitfall traps and pan traps from 36 fields. These specimens comprised 13 orders, 103 families, 264 genera, and 329 taxa (243 identified species, 86 unidentified species) and categorized into five feeding guilds (carnivores, decomposers, herbivores, omnivores, and pollinators). Species richness, species accumulation curves, and diversity functions (richness, evenness, and dispersion) were calculated to characterize the arthropod community. Non-metric multidimensional scaling was applied to examine structural similarity of arthropod communities among sites. To account for the effects of soil-related data, we furthermore applied a redundancy analysis. Arthropods grouped according to the irrigation water source, whereby the dipterans were most dominant under wastewater conditions. Here, particularly the eye gnat, Hippelates pusio, a disease-causing vector for humans, accounted for the dipterans. The occurrence of three alien ant species suggested community shifts through invasive species, while the occurrence of seven ant species (at least one ant species occurred under each water source) that form mutualistic relationships with aphids highlighted future risks of aphid pest outbreak. Future studies on these taxa should specifically target their ecological and economic effects and potential countermeasures.

Structure and composition of field margin vegetation in the rural-urban interface of Bengaluru, India: a case study on an unexplored dimension of agroecosystems.

Field margin vegetation (FMV) refers to the plant community in the interface between agriculture and natural environments. Substantial work has been carried out on the management of field margins in European countries with the aim of conserving field-level biodiversity and enhancing agronomic benefits. India, instead, is lagging behind in the assessment of FMV and formulating subsequent management strategies for biodiversity conservation at the field boundaries. This study is a first step to better understand the structural and functional dimensions of field margin vegetation along an agricultural transformation gradient near the megacity of Bengaluru, India. Empirical field studies along with the detection of vegetation change using remote sensing and geo-informatics technique were used to record information on field margin vegetation. The phytosociological study, revealed a total of 81 species, comprising 29 species of trees, 21 shrubs and 31 herbs at the field margins of six selected villages of northern Bengaluru. Randomly selected 355 field boundaries were delineated from high-resolution Worldview 3 images for the year 2018 and from Google Earth images for the year 2004-2005. The FMV area was around to 85.40 ha in 2004-2005 but declined to 76.69 ha in 2017-2018. The survey also indicated that local farmers have in-depth ecological knowledge on the importance of FMV in ensuring a sustainable flow of resources within the agricultural landscape. The results demonstrate that rural and transition zones of the study area have higher dominance of planted tree species on the margins, whereas urban zone exhibits comparatively uniform dominance for all species. Our study also highlights the need for conservation of FMV to ensure agroecosystem health as a prerequisite for sustainable socioecological development.

The explanatory power of silent comics: An assessment in the context of knowledge transfer and agricultural extension to rural communities in southwestern Madagascar.

The distribution of silent comic illustrations can facilitate the communication and transfer of scientific recommendations about sustainable land management (SLM) to local communities in countries where many people are illiterate. However, since there are cross-cultural differences in "visual languages", visualization styles need to be carefully selected as well as locals' comprehension of the illustrated recommendation evaluated systematically. Three agricultural recommendations were chosen for comic-style illustrations, distributed to six communities in the Mahafaly region of southwestern Madagascar and evaluated using a three-step, interdependent approach. The silent comics illustrated (i) composting of manure and its application to improve soil fertility; (ii) cautious utilization of succulent silver thicket as supplementary forage; and (iii) sustainable harvesting practices of wild yam. Results revealed that general understandability strongly depended on the community that was surveyed and on the environmental subject that was illustrated. We found a strong relationship between the general understandability of comics and the divergence that exist in communities' socio-economic structure. Education level was an important factor that explained a better understanding of respondents for the comic illustrating compost production, but not for comics that illustrated sustainable usage of silver thicket and wild yam harvest. Willingness to follow the recommended practice was impaired when respondents valued no change to the improved technique compared to the common one. Effects of respondents' socio-economic characteristics on the implementation of the recommended practice could not be clarified within this study due to the small subset of data. Based on the evaluation of recurring comments made by respondents and interviewers, we conclude that comics can be a useful communication tool to increase locals' awareness and comprehension for SLM practices. This, however, requires that drawing details used to facilitate farmers' ability to adopt a point-of-view inside the comic story are used thoughtfully as they might interfere with the central message.

Is the push-pull paradigm useful to explain rural-urban migration? A case study in Uttarakhand, India.

The present study explored the motivation of rural-urban migrants who moved from the Himalaya foothills of Uttarakhand to its capital city, Dehradun. A survey of 100 migrant families reported their socio-economic profile before and after migration, personal and general reasons for migration, problems in the village and in the city, and perception of push- and pull factors. A remote sensing-based analysis of land cover and forest changes was conducted for two villages of the migrants' origin, aiming to link the reasons for migration to land cover changes. This was contextualised by reported large scale changes in forest cover. Major reasons for migration mentioned in this study were education, employment opportunities with the associated income, and facilities. These were perceived as both, push and pull factors, whereas environmental factors ranked very low. Declining environment or agriculture were never mentioned spontaneously as personal reason, and only occasionally as a presumed general reason for migration, but were frequently confirmed as a major problem in the village. Thus, although such problems existed, they seemed not a major driver of rural-urban migration. For most of the respondents their migration resulted in a profound change of livelihoods and significantly improved their socio-economic situation. Land and forest cover around the chosen villages fluctuated by up to 15% with a trend to increasing forest cover in recent years. At the district and state scales, forest cover was rather stable. These results question the narrative of deforestation and environmental degradation in the Himalayas as major push-factors for rural-urban migration in Uttarakhand. Even if environmental constraints were felt, it was rather the differences in socio-economic opportunities (education, employment, facilities) that drove people to migrate to the city. Regarding the push-pull paradigm, we conclude that scenarios of external conditions under which people migrate cannot be evaluated without taking the migrants' attitudes and choices into account.

Effects of Water Quality and Post-Harvest Handling on Microbiological Contamination of Lettuce at Urban and Peri-Urban Locations of Ouagadougou, Burkina Faso.

Vegetable production in urban gardens of Ouagadougou contributes to food security, but water for irrigation is often of low quality. This is particularly acute if irrigation water is taken from wastewater polluted channels. This study aimed at (i) verifying to what degree irrigation water quality is correlated with contamination of lettuce with Escherichia coli, total coliforms, and Salmonella spp., and (ii) assessing effects of post-harvest handling on pathogen development during the trade chain. We tested pathogen removal efficiency on lettuce by applying post-harvest washing. Irrigation water of production areas in Ouagadougou (n = 10) showed a mean E. coli load of 2.1 × 105 CFU 100 mL-1. In 60% of the cases, irrigation water did not meet the standards of the World Health Organization (WHO) for safe irrigation water, and in 30% of the cases, irrigation water was contaminated with Salmonella spp. Loads of total coliforms on lettuce leaves ranged from 2.9 × 10³ CFU g-1 to 1.3 × 106 CFU g-1, while E. coli averaged 1.1 × 10² CFU g-1. Results on post-harvest handling revealed that microbial loads increased along the trade chain. Overall, half of all lettuce samples (n = 60) were tested positively for Salmonella spp. The experiment showed that appropriate post-harvest handling could prevent the increase of total coliforms.

Author Correction: Effects of biochar, waste water irrigation and fertilization on soil properties in West African urban agriculture.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Agronomic benefits of biochar as a soil amendment after its use as waste water filtration medium.

In many water-scarce countries, waste water is used for irrigation which poses a health risk to farmers and consumers. At the same time, it delivers nutrients to the farming systems. In this study, we tested the hypotheses that biochar can be used as a filter medium for waste water treatment to reduce pathogen loads. At the same time, the biochar is becoming enriched with nutrients and therefore can act as a fertilizer for soil amendment. We used biochar as a filter medium for the filtration of raw waste water and compared the agronomic effects of this "filterchar" (FC) and the untreated biochar (BC) in a greenhouse pot trial on spring wheat biomass production on an acidic sandy soil from Niger. The biochar filter showed the same removal of pathogens as a common sand filter (1.4 log units on average). We did not observe a nutrient accumulation in FC compared to untreated BC. Instead, P, Mg and K were reduced during filtration while N content remained unchanged. Nevertheless, higher biomass (Triticum L. Spp.) production in BC (+72%) and FC (+37%) treatments (20 t ha-1), compared with the unamended control, were found. There were no significant differences in aboveground biomass production between BC and FC. Soil available P content was increased by BC (+106%) and FC (+52%) application. Besides, mineral nitrogen content was reduced in BC treated soil and to a lesser extent when FC was used. This may be explained by reduced sorption affinity for mineral nitrogen compounds on FC surfaces. Although the nutrients provided by FC decreased, due to leaching in the filter, it still yielded higher biomass than the unamended control.

Effects of biochar, waste water irrigation and fertilization on soil properties in West African urban agriculture.

In large areas of sub-Saharan Africa crop production must cope with low soil fertility. To increase soil fertility, the application of biochar (charred biomass) has been suggested. In urban areas, untreated waste water is widely used for irrigation because it is a nutrient-rich year-round water source. Uncertainty exists regarding the interactions between soil properties, biochar, waste water and fertilization over time. The aims of this study were to determine these interactions in two typical sandy, soil organic carbon (SOC) and nutrient depleted soils under urban vegetable production in Tamale (Ghana) and Ouagadougou (Burkina Faso) over two years. The addition of biochar at 2 kg m-2 made from rice husks and corn cobs initially doubled SOC stocks but SOC losses of 35% occurred thereafter. Both biochar types had no effect on soil pH, phosphorous availability and effective cation exchange capacity (CEC) but rice husk biochar retained nitrogen (N). Irrigation with domestic waste water increased soil pH and exchangeable sodium over time. Inorganic fertilization alone acidified soils, increased available phosphorous and decreased base saturation. Organic fertilization increased SOC, N and CEC. The results from both locations demonstrate that the effects of biochar and waste water were less pronounced than reported elsewhere.

Effects of waste water irrigation on soil properties and soil fauna of spinach fields in a West African urban vegetable production system.

The usage of inadequately processed industrial waste water (WW) can lead to strong soil alkalinity and soil salinization of agricultural fields with negative consequences on soil properties and biota. Gypsum as a soil amendment to saline-sodic soils is widely used in agricultural fields to improve their soil physical, chemical and hence biological properties. This study aimed at analysing the effects of intensive WW irrigation on the structure and composition of soil-dwelling arthropods on spinach fields (Spinacia oleracea L.) in a West African urban vegetable production system. We used gypsum as a soil amendment with the potential to alleviate soil chemical stress resulting in a potentially positive impact on soil arthropods. A total of 32 plots were established that showed a gradient in soil pH ranging from slight to strong soil alkalinity and that were irrigated with WW (n = 12) or clean water (CW; n = 20), including eight plots into which gypsum was incorporated. Our study revealed a high tolerance of soil-dwelling arthropods for alkaline soils, but spinach fields with increased soil electrical conductivity (EC) showed a reduced abundance of Hymenoptera, Diptera and Auchenorrhyncha. Arthropod abundance was positively related to a dense spinach cover that in turn was not affected by WW irrigation or soil properties. Gypsum application reduced soil pH but increased soil EC. WW irrigation and related soil pH affected arthropod composition in the investigated spinach fields which may lead to negative effects on agronomical important arthropod groups such as pollinators and predators.