Performance of Twelve Mass Transfer Based Reference Evapotranspiration Models under Humid Climate

Reference evapotranspiration is very important parameter in the hydrological, agricultural and environmental studies and is accurately estimated by the FAO Penman-Monteith equation (FAO-PM) under different climatic conditions. However, due to data requirement of the FAO-PM equation, there is a need to investigate the applicability of alternative ETo equations under limited data. The objectives of this study were to evaluate twelve mass transfer based reference evapotranspiration equations and determine the impact of ETo equation on long term water management sustainability in Tanzania and Kenya. The results showed that the Albrecht, Brockamp-Wenner, Dalto, Meyer, Rohwer and Oudin ETo equations systematically overestimated the daily ETo at all weather stations with relative errors that varied from 34% to 94% relative to the FAO-PM ETo estimates. The Penman, Mahringer, Trabert, and the Romanenko equations performed best across Tanzania and the South Western Kenya with root mean squared errors ranging from 0.98 to 1.48 mm/day, which are relatively high and mean bias error (MBE) varying from −0.33 to 0.02 mm/day and the absolute mean error (AME) from 0.79 to 1.16 mm/day. For sustainable water management, the Trabert equation could be adopted at Songea, the Mahringer equation at Tabora, the Dalton and/or the Rohwer equations at Eldoret, the Romanenko equation at Dodoma, Songea and Eldoret. However, regional calibration of the most performing equation could improve water management at regional level

Modeling sludge accumulation rates in lined pit latrines in slum areas of Kampala City, Uganda

Disposal of faecal sludge particularly in slum areas is a difficult undertaking given the lack of space and resources. Inaccurate prediction of sludge accumulation rates (SAR) in pit latrines leads to unplanned pit latrine emptying. Given that the users and owners cannot afford the conventional emptying techniques frequently, inappropriate methods such as open defecation and emptying into storm drainages are employed which consequently contribute to environmental and health-related challenges. The main objective of this study was to develop a predictive model for sludge accumulation rates in lined pit latrines in slum areas of Kampala so as to guide routine management of pit latrines. This mathematical model was developed using a mass balance approach with a sample space of 55 lined pits. The developed model gave an average sludge accumulation rate of 81±25 litres/person/year with an efficiency of 0.52 and adjusted R2 value of 0.50. The model was found to be sufficient and most suited for rental and public pit latrines given their bigger percentage in the slums. Further studies should include geo-physical characterization of soil and drainage of pit latrine sites so as to improve model accuracy.Keywords: Faecal, sludge accumulation rates, slum areas, lined pit latrine

Transforming Corn Stover to Useful Transport Fuel Blends in Resource-Limited Settings

Development of local technologies is crucial to the sustainable energy agenda in resource-limited countries and the world. Strengthening local green technologies and promoting local utilization will reduce carbon emissions that could be generated during transportation and delivery of green products from one country to another. In this paper we developed bio-oil/diesel blends using a low-tech pyrolysis system designed for smallholder farmers in developing countries and tested their appropriateness for diesel engines using standard ASTM methods. Corn stover retrieved from smallholder farmers in Gayaza, Uganda were pyrolyzed in a batch rocket stove reactor at 350 °C and liquid bio-oil harvested. Bio-oil chemical composition was analyzed by Gas Chromatography equipped with Flame Ionization Detector (GC-FID). Bio-oil/diesel emulsions in ternary concentrations 5%, 10% and 20% bio-oil weight were developed with 1% concentration of sorbitan monolaurate as an emulsifier. The bio-oil/diesel emulsions and distillates had property ranges: specific gravities at 15 °C 827.4–830.7 kg m−3, specific gravities at 20 °C 823.9–827.2 kg m−3, kinematic viscosities at 40 °C 3.01–3.22 mm2/s, initial boiling points 140–160 °C, final boiling points 354–368 °C, and calculated cetane indexes 56.80–57.63. These properties of the bio-oil/diesel blends and their distillates compare well with standard transportation diesel fuel. The emulsion distillates meet the standard requirements for automotive diesel in East Africa

Contextual investigation of factors affecting sludge accumulation rates in lined pit latrines within Kampala slum areas, Uganda

Pit latrines in slums areas of Uganda fill up faster than might be expected from some estimates owing to inappropriate use and failure to consider critical factors affecting sludge accumulation rates at the planning, design and construction stages. This study sought to investigate factors affecting filling rates of lined pit latrines in slum areas of Kampala with the goal of contributing to accurate planning, design, construction, emptying and overall maintenance. Fifty-five pit latrines were selected from the five divisions of Kampala city using stratified random sampling. Data collected included: number of users, frequency of emptying, years taken since last emptying, type of non-faecal materials deposited, cross-sectional dimensions of the pit, rate of sludge degradation and geo-physical factors of pit location. Methods used were: field surveys, questionnaires and key informant interviews plus on-site depth measurement. Mass loss tests to investigate the rate of sludge degradation were carried out in the laboratory at moisture content levels similar to those in pit latrines. Sludge accumulation rates were calculated using volume of sludge in the pit, number of users and time taken since last emptying. Statistical analyses included correlation and one-way ANOVA. Results revealed that number of users and type of material deposited in the pit latrines, especially non-faecal matter, had a significant (p < 0.05) effect on sludge accumulation rate. Public pit latrines with a higher number of users had lower sludge accumulation rates and this was attributed to greater degradation taking place and greater restriction on entry of non-faecal matter. The rate of sludge degradation was higher at 90–100% than 80–90% moisture content, due to better degradation conditions. Tighter restrictions on non-faecal material deposition into pit latrines are recommended to reduce filling rates of pit latrines in slum areas.Keywords: sludge accumulation rates, slum areas, faecal matter, degradation, lined pit latrine

Improving Maize Shelling Operation Using Motorized Mobile Shellers: <em>A Step towards Reducing Postharvest Losses in Low Developing Countries</em>

Maize shelling is still a challenge in low developing countries with more efforts required to advance this operation. In Uganda, motorized immobile maize shellers have been fabricated locally to enhance the shelling operation. However, their performance has not elated the farmers. The unsatisfactory performance is a result of these shellers being fabricated by local artisan with finite understanding of the maize grain characteristics and operation factors to optimize maize shelling. In addition, farmers in these countries have a deficiency of power to operate the motorized maize shellers available. Transportation of these motorized maize shellers is also still a challenge and it imposes an extra cost to the farmers hence reducing their profits from maize growing. In this chapter, we reviewed maize shelling process in low developing countries particularly the categories of maize shelling, maize sheller design requirements, use of equations to design sheller parts, modification of the motorized maize shellers and case studies on the mobile maize shellers, comparing them with immobile maize shellers. The study concluded that on addition to other sheller performance attributes, motorized mobile maize shellers can solve transportation challenges associated with motorized immobile maize shellers

Stomatal and Canopy Resistance, Plant Physiological Parameters, Evapotranspiration and other Surface Energy Fluxes of Phragmites-dominated Riparian Plant Community in the Platte River Basin, Nebraska, USA

Effective water balance analyses require the knowledge of water use rates of riparian zones. Riparian zones usually consist of a variety of vegetation species that have specific transpiration rates. This mosaic of vegetation presents a challenge of how to improve the accuracy to estimate the evaporative fluxes of the riparian zone. The challenge is compounded by the fact that riparian zones are often exposed to large fluctuations in environmental forcing throughout the growing season. Our study presents a robust methodology to measure total evapotranspiration (ETa) and to estimate the growing season transpiration (TRP) for individual vegetation species within a riparian zone through extensive field campaigns conducted in 2009 and 2010. With the espousal of the measured data for individual species, including coverage, stomatal resistance, photosynthetic photon flux density, canopy light interception, leaf area index, plant height, and other within and above-canopy biophysical properties, we scaled up stomatal resistance to canopy resistance to quantify TRT rates of individual specie. The evaporation rates from the riparian zone were also quantified. We developed mixed riparian vegetation evapotranspiration crop coefficients and transpiration crop coefficients for individual species. The total ETa from mixed plant community was 679 mm in 2009 and 982 mm in 2010. In 2009, the seasonal total daytime transpiration for phragmites, cottonwood, and peach-leaf willow were 483, 522 and 431 mm, respectively, and the values for 2010 were higher 550, 655 and 496 mm, respectively. The transpiration was influenced by vegetation phenology (especially increase in LAI and leaf aging) and strongly correlated to irradiance. The average evaporation rate of the riparian zone was 0.81 mm/day in 2009 and 1.7 mm/day in 2010. The seasonal total daytime evaporation was 150 mm in 2009 and 312 mm in 2010. The presence of flood water on the surface and warmer seasonal average temperatures contributed to the high evaporation rates observed in the 2010 growing season

APPLICATION OF GIS AND GEOGRAPHICALLY WEIGHTED REGRESSION TO EVALUATE THE SPATIAL NON‐STATIONARITY RELATIONSHIPS BETWEEN PRECIPITATION VS. IRRIGATED AND RAINFED MAIZE AND SOYBEAN YIELDS

Understanding the relationship between the spatial distribution of precipitation and crop yields on large scales (i.e., county, state, regional) while accounting for the spatial non‐stationarity can help managers to better evaluate the long‐term trends in agricultural productivity to make better assessments in food security, policy decisions, resource assessments, land and water resources enhancement, and management decisions. A relatively new technique, geographically weighted regression (GWR), has the ability to account for spatial non‐stationarity with space. While its application is growing in other scientific disciplines (i.e., social sciences), the application of this new technique in agricultural settings has not been practiced. The geographic information system (GIS), along with two different statistical techniques [GWR and conventional ordinary least square regression (OLS)], was utilized to analyze the relationships between various precipitation categories and irrigated and rainfed maize and soybean yields for all 93 counties in Nebraska from 1996 to 2008. Precipitation was spatially interpolated in ArcGIS using a spline interpolation technique with zonal statistics. Both measured and GWR‐ and OLS‐predicted yields were correlated to spatially interpolated annual (January 1 to December 31), seasonal (May 1 to September 30), and monthly (May, June, July, August, and September) precipitation for each county. Statewide average annual precipitation in Nebraska from 1996 to 2008 was 564 mm, with a maximum of 762 mm and minimum of 300 mm. Mean precipitation decreased gradually from May to September during the growing season. County average yields followed the same temporal trends as precipitation. When the OLS regression model was used, there was a general trend of linear correlation between observed yield and long‐term average mean annual total precipitation with a varying coefficient of determination (R2). For rainfed crops, 67% of the variability in mean yield was explained by the mean annual precipitation. About 23% and 17% of the variability in mean yield was explained by mean annual precipitation for irrigated maize and soybean, respectively. However, the performance of the GWR technique in predicting the yields from spatially interpolated precipitation for irrigated and rainfed maize and soybean was significantly better than the performance of the OLS model. For both rainfed maize and soybean, 77% to 80% of the variation in yield was explained by the mean annual precipitation alone. For irrigated crops, 42% of the variation in the yield was explained by the mean annual precipitation. For rainfed crops, there was a strong correlation between seasonal precipitation and yield, with R2 values of 0.73 and 0.76 for maize and soybean, respectively. The mean annual total precipitation was a better predictor of rainfed maize yield than rainfed soybean yield. On a statewide average, July precipitation as a predictor had the greatest correlation with yields of both maize and soybean. June, July, and August precipitation had greater impact on maize yield than on soybean under rainfed conditions due to more sensitivity of maize to water stress than soybean. For irrigated yields, July precipitation had more impact on soybean yield than on maize. The performance of the GWR technique was superior to the OLS model in analyzing the relationship between yield and precipitation. The superiority of the GWR technique to OLS is mainly due to its ability to account for the impact of spatial non‐stationarity on the precipitation vs. yield relationships

Occurrence and survival of pathogens at different sludge depths in unlined pit latrines in Kampala slums

Occurrence and survival of pathogens in faecal sludge was investigated in unlined  pit latrines at varying depths in peri-urban areas of Kampala city, Uganda. A total of 55 unlined pit latrines, 7 private and 8 rental unlined pit latrines were sampled in thefirst and second phases (representing the rainy season) and 40 pits in the third  phase (representing dry season), and analysed for indicator organisms and  pathogens from 4 pit latrine sludge layers, at depths of 0, 0.5, 1.0 and 1.5 m,  following APHA standard methods. Physico-chemical parameters of the faecal  sludge were also measured. Three sampling phases were  undertaken to determine the effect of seasonal variation. Results indicate that the mean temperature and pH were 25.4 ± 1.14°C and 8.0 ± 1.5, respectively; and moisture content increased with pit sludge depth, except between Depths 3 and 4. Average moisture content was 86.3 ± 3%. The measured parameters varied significantly (P &gt; 0.05) between seasons. The mean reduction in total coliforms, thermo-tolerant coliforms, E. coli, and faecal enterococci with sludge depth was significant at all depths (P &lt; 0.05), but the least significant difference was not significant at depth levels of 1.0 m and 1.5 m. Salmonella was only detected at the top layer of faecal sludge in 60% of Phase 2 samples and in only 20% of the samples in Phase 3. About 200–4 100 eggs/g of strongyles were found in 98% of the samples and 100–1 600 eggs/g of ascarids in 55% of the samples. Temperature, pH and moisture content did not show a significant correlation with observed reductions of indicators and pathogens. With extrapolation of the generated regression models, a pit of 8 m can be recommended for reduction of bacteria. It is recommended that protective field gear be used during pit emptying and that faecal sludge treatment should be done to reduce pathogens before disposal into the environment.Keywords: pathogens, indicator organisms, faecal sludge, unlined pit latrine, water contaminatio

Performance evaluation and optimization of the maize shelling operation of the multi-purpose farm vehicle

Small-scale farmers register high postharvest losses partly due to failure to carry out primary processing operations. Most of the maize shellers on the Ugandan market lead to high percentage of broken maize grains thus raising the risk of aflatoxin infection during storage. In this study, the operation of an existing maize sheller on the market with a shelling speed of 870 rpm for maize at 13 % moisture content was tested. The main objective of this study therefore was twofold; (i) to develop and evaluate a maize sheller and (ii) to optimize the multi-purpose vehicle shelling operation. The improved maize sheller was designed, fabricated, evaluated and optimized using a factorial experiment with shelling speed and moisture content as the main effects at three levels. Analysis of Variance was done using R-studio. A cost-benefit analysis of the shelling technology was conducted. The obtained results showed that a reduction in moisture content and an increase in shelling speed increased the shelling efficiency, the grain damage percentage, output capacity and the cleaning efficiency. The optimum moisture content and the shelling speed of the multi-purpose vehicle maize shelling were 13% and 896 rpm respectively. Except the shelling efficiency, the results of the modified maize sheller were significantly different (p&lt;0.05) from those of the market sheller. The payback period was 1.37 years while the benefit-cost ratio was 1.07. The optimized maize shelling operation of the multi-purpose vehicle is therefore economically viable