College of Agricultural and Environmental Sciences (CAES)
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Browsing College of Agricultural and Environmental Sciences (CAES) by Subject "Aboveground biomass"
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ItemAgroforestry practices for enhancing food security and climate change resilience in Rajaf county, South Sudan(Makerere University, 2019-10-18) Mayele, Joseph MayindoAgroforestry (AF) is being practiced traditionally as a sustainable land- use option, in many agro-ecological zones of Sub-Saharan Africa. Agroforestry is important as incorporating trees and shrubs in food crop systems can help address food insecurity issues and reduce vulnerability of agricultural systems to climate change. The purpose of this study was to investigate the current agroforestry practices and their relevance to enhancing food security and climate change resilience among rural communities in Rajaf County. Household surveys using structured and semi-structured questionnaires, Key informants interviews (KIIs) and Focused Group Discussions (FGDs) were used as tools to collect survey data in which 332 household respondents were sampled and interviewed. Results indicated that most people practiced agrisilvicultural and agrisilvopastoral AF systems with scattered trees on farms, boundary plantings, homegardens, and woodlots as their on-farm arrangements. While goats and chicken were most reported domestic animals; sorghum, beans, groundnuts, cassava, maize, and simsim were the most reported food crops. The most preferred tree species were Mangifera indica, Azadiractha indica, Balanites aegyptiaca, Mahogany spp, Acacia spp, etc for distinguished uses. Over 350 trees were inventoried by non-destructive methods through systematically established line transects and circular sample plots. The tree species parameters (DBH, H & CR) were measured and used to determine their diversity, abundance and carbon sequestration potentials. It was found that average DBH of trees in AF farms was 12.68cm with a minimum and maximum DBH of 5.0 cm and 62.9 cm respectively. Densities for respective species were calculated and above-ground biomass (AGB) equations or models were then used to generate results to estimate carbon sequestration potential of AGB. Chave 2014 was taken as the baseline model to compare among the other models used and select the best fitting model for computation of aboveground carbon (AGC). From the calculated AGB, it is revealed that most carbon sequestration stock accrued from boundary planting (183.1 tons/ha), homegardens spp (142.5 tons/ha), scattered trees in farms (132.2 tons/ha). Tree diversity was not uniform as few species are found in other AF sites although there was abundance of some species such as citrus spp, Mangifera indica, Psidium guajava, Acacia spp and Tectona grandis. The values of Shannon diversity indices varied among the sites: Kolye west (2.211), Gumbo (1.726), Kolye East (2.268) and Tokiman Island (1.699). Agroforestry practices have the potential to food security and climate change because it holds more components as compared to conventional Agriculture and Forestry, resulting into diversified alternative sources despite its intensive labour requirements i.e there is always a secured next component in case of failure of one component. Therefore, farmers should be encouraged to practice AF that results to food availability and accessibility.
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ItemPerformance of subsurface flow constructed wetlands in domestic wastewater treatment and their potential in increasing greenhouse gas emissions at Bugolobi, Kampala( 2016-12) Ddibya, RonaldUganda is grappling with public health and eutrophication challenges of its water bodies, owing to persistence of microbial pathogens, excess nutrients and organic matter contents in domestic and industrial wastewater effluents. In addition, the country is also faced with emerging climate change challenges as a result of increasing greenhouse gas emissions (especially carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from several sources, such as industrial activities and natural processes taking place in various ecosystems, such as wetlands. The overall objective of this study was to assess the performance of horizontal (HF) and vertical (VF) subsurface flow (SSF) constructed wetlands (CWs) (planted with Cyperus papyrus) in domestic wastewater treatment and their potential as Carbon and Nitrogen sinks in increasing greenhouse gas (GHG) emissions. The system was operated under batch hydraulic loading in Kampala, Bugolobi. Both HF and VF CWs exhibited high efficiency for remediation of organic matter (OM), nitrogen (N), phosphorus (P) and faecal coliforms in effluent pollution loads. Notably, the higher percentage reduction was observed in the VF CWs, probably attributable to optimal oxygen supply within the system. Moreover, the VF CWs were most important for the removal of faecal coliforms (99.7%), 5-day biological oxygen demand (85.5%), total suspended solids (77.2%), ammonium-nitrogen (71.3%), chemical oxygen demand (67%), total nitrogen (55.9%), total phosphorus (55.9%) and ortho-phosphate (53.7%). The highest recorded mean CH4 flux (in mg CH4-C m-2 h-1) was 38.3 ± 3.3 in unplanted HF, compared to (3.3 ± 0.4), and recorded in planted VF CWs. However, CO2 fluxes (mg CO2-C m-2 h-1) were significantly higher (P < 0.05) in planted CWs, with no significant difference (P > 0.05) between the planted HF (2213.5 ± 122.4) and VF (2272.8 ± 191.0) CWs. The CO2 flux attained in the planted CWs was attributable to presence of roots and rhizomes for which their exudates in the planted beds, may have increased microbial activity which eventually could have increased CO2 emission rates. However, N2O fluxes were relatively low and their variations were insignificant (P > 0.05) in all treatments. Nevertheless, the unplanted HF mesocosms registered the highest N2O fluxes of 0.24 ± 0.07 mg N2O-N m-2 h-1 differing to the planted HF, unplanted VF and planted VF treatment systems that registered N2O fluxes of 0.19 ± 0.05, 0.07 ± 0.02 and 0.08 ± 0.02 mg N2O-N m-2 h-1 respectively. Low N2O fluxes, could be attributed to the inhibition of denitrification under aerobic conditions, which on the other hand promoted nitrification, particularly in the planted CWs. The VF systems according to the observations, have shown low CH4 and N2O emissions, therefore making them an appropriate technological option for low carbon development targets concerning sanitation and wastewater management in Uganda. On the other hand, harvesting of the above ground biomass (AGB) removed 19.6% and 17.5% N and 23.8% and 25% P of the total N and P from planted VF and HF CWs respectively. Further, this would imply that SSF CWs are significant removal routes for nutrients, i.e., nitrogen and phosphorus and indeed, significantly more removal was recorded in the VF wetland systems planted with Cyperus papyrus. Therefore, SSF CWs are recommended for adoption, as suitable and less costly technology that may be used for interventions at local levels, to increase the adaptation and resilience of receiving environments through lessening the impact of intermittent and pulse pollution loads from wastewater treatment plants (WWTPs).