Theses and Dissertations Collection

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    Assessment of irrigation systems’ performance and sustainability in Burundi
    (Sokoine University of Agriculture, 2022) Manirakiza, Prosper
    Irrigated agriculture has a crucial role to play in enhancing food security; hence, irrigation expansion would significantly increase agricultural production, improving household income and reduce food insecurity and poverty levels among smallholder farmers. However, majority of irrigation schemes developed in Burundi have performed below their potential. Evaluation of the performance of an irrigation schemes is essential in knowing whether water availability meets or exceeds demand. In Burundi, these evaluations are limited. This study aimed to assess the irrigation systems’ performance and sustainability in Burundi with a case study of Kidwebezi Irrigation Scheme. Specifically, this study intended (i) to evaluate the performance of the irrigation structures, (ii) to assess the water delivery performance using technical indicators and (iii) framers’ knowledge and to assess the effect of Irrigators’ Association on the performance of Kidwebezi Irrigation scheme with the target of evaluating the existing operation rules and proposing alternative options for further improvement. In this study, a float method was used for determining the flow rate. The CROPWAT Penman-Monteith method was used to determine the reference crop evapotranspiration, the combination of Food and Agriculture Organization (FAO) CROPWAT 8.0 simulation software and the CLIMWAT 2.0 tool was used to calculate the crop water requirement (CWR) of the paddy. Field observations (state of a structure) and physical work were used to evaluate the performance of the irrigation structures. Based on the technical performance indicators such as efficiency, adequacy, dependability, equity and water productivity, the performance of water delivery was assessed. A social economic survey (farmer interviews, focus group discussions and key informants) was undertaken to assess financial self-sufficiency, fee collection and relative water costs of the scheme. Results for the performance evaluation of irrigation structures showed that 84.15%were still functioning. On the physical condition part, the findings showed that the intake was working at 80%; canals network was operational at 80% while command area development was functioning at 88%. For the conveyance efficiency, the results indicate that 82.48%, 80.40% and 66.38% of water conveyed reached the destined farm for lined main canal, lined secondary canal and unlined secondary canal, respectively. The total net irrigation and total gross irrigation were 342.2 mm and 760.4 mm. The study results showed that the irrigation system was good in terms of adequacy and poor in terms of efficiency while it was fair to both dependability and equity. Moreover, the results for the assessment of effect of Irrigators’ Association with regard to financial viability and sustainability of the scheme were found to be encouraging. The results showed that the effectiveness of fee collection (EFC) was 87.77%, the financial self-sufficiency (FSS) was 3.11 with an average relative water cost of 0.05 and 97.75% of the scheme were still irrigated. The results from farmer interviews, focus group discussions and key informant showed that the uncontrolled paddy farming expansion, lack of updated irrigation knowledge and technologies and low efficiency on water use are the main causes of low yields of paddy in the Kidwebezi Irrigation Scheme.
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    Effects of integrating deficit irrigation and carbonate foliar fertilizer application into the system of rice intensification
    (Sokoine University of Agriculture, 2021) Aseru, Gloria
    Introduction Rice plays a key role in food availability and the economy of Tanzania. However, the rice yield gap of over 87% indicates that there are challenges of inadequate management practices for enhancing its production. In literature, there are recommendations on the use of the System of Rice Intensification (SRI) as one of the means to enhance rice yield by improving water productivity. Further, deficit irrigation is profound in increasing water productivity while having minimal or no impact on yield. Other studies have emphasized the use of the conventional fertilizers, while recent developments have recommended the use of foliar fertilizers at the various growth stages in order to enhance rice productivity.Individually, deficit irrigation, SRI and foliar fertilizer application have proved to be effective in enhancing rice yield and water productivity. However, the information on their combined effects is limitedly known. Therefore, a study was conducted to assess the effects of integrating deficit irrigation and carbonate foliar fertilizer (Lithovit) application into the System of Rice Intensification (SRI) on rice growth, yield and water productivity in addition to economic implications. Methodology This study was conducted in Mkindo Irrigation scheme in Mvomero, Morogoro, Tanzania during the dry and wet season (October 2020 to June 2021). The experiment was laid out in a split plot design with three levels of irrigation for main plots which were 100% of the irrigation water requirement (40mm) imitating the SRI alternate wetting and drying pattern and induced deficit irrigation applied at 80% and 50% of the irrigation water requirement as IR100, IR80 and IR50, respectively. Irrigation was carried out at the appearance of soil cracks in IR100. The sub-plot fertilizer treatments were five in number namely: (A) Diammonium Phosphate (DAP) and Urea (normal practice), (B) DAP, Urea and 100% of recommended foliar fertilizer (Lithovit Standard), (C) DAP and 50%(Lithovit and Urea), (D) Lithovit Standard only and (E) no fertilizer. The combined irrigation and fertilizer treatments tested were IR100A, IR100B, IR100C, IR100D, IR100E,IR80A, IR80B, IR80C, IR80D, IR80E, IR50A, IR50B, IR50C, IR50D, and IR50E. The data was analyzed using IBM SPSS version 20 at 5% probability level and mean separation done using Duncan’s multiple range test. Results and discussion The integration of deficit irrigation and carbonate foliar fertilizer application into SRI enhanced rice growth, yield and water productivity in addition to increasing benefit cost ratio (BCR). Treatment IR80 had the best overall performance followed by IR100 and IR50.However, there was no significant difference among the water applications IR100, IR80 andIR50 for all growth and yield attributes due to disruption of water regimes by heavy rainfall in both seasons. Fertilizer treatment B had the highest yield followed by A, C and D while E had the least. It was found that, IR100Battained the highest yield of 11.10 t/ha followed by IR80B (10.90t/ha) and (IR50B and IR100A)with 9.40 t/ha for the dry season.For the wet season, IR80B (6.93 t/ha) had the highest yield followed by IR50B (6.68 t/ha)and IR100B (6.6 t/ha). The least yield was attained by IR50E with 7.10 and 3.78 t/ha for the dry and wet seasons respectively. The foliar treatments (C and D) performed as good as the conventional fertilizer treatment A due to the impact of the calcium carbonate foliar fertilizers. Lithovit supplies higher concentrations of carbon dioxide than in the atmosphere especially during water stress periods thereby aiding photosynthesis hence increasing crop growth and yield. Treatment B had the highest water productivity (WP) followed by A, C, D and E. The highest and lowest WP was 0.851 kg/m3 and 0.562 kg/m3 attained by IR80B and IR80E respectively for the dry season. For the wet season, the highest and lowest WP was attained by IR50B (0.540 kg/m3) and IR50E (0.306 kg/m3). The high WP is attributed to the impact of alternate wetting and drying practice under SRI that heavily cuts down on unproductive water losses. In addition, Lithovit foliar fertilizer that acts as a long term reservoir for carbon dioxide especially during water stress periods played a key role on yield enhancement of foliar treatments. Across water regimes, the highest benefit-cost ratio (BCR) for the dry and wet seasons was 2.81 and 1.67 respectively attained by IR100.Among fertilizer treatments, the highest BCR was attained by D (3.45) and C (1.74) forthe dry and wet seasons respectively. Treatment A had the least BCR of 1.96 and 1.06 forthe dry and wet season respectively. Combination IR100D had the highest BCR of 3.82and 2.08 for the dry and wet season respectively. All BCR >1 except IR80A and IR50Aeach with a BCR of 0.97. For all growth, yield, water productivity and BCR, the dryseason performed better than the wet season. Conclusion The integration of deficit irrigation and carbonate foliar fertilizers into SRI enhancedgrowth, yield, water productivity and BCR. Among water regimes, IR80 had the bestoverall performance. Also, the combination of foliar and basal fertilizers had the bestoverall growth, yield and WP performance. Foliar treatments also performed as good asthe conventional basal practice due to the impact of calcium carbonate fertilizers whichenhanced production following the good yield attained. In terms of BCR, foliar treatmentshad the best performance. Generally, the dry season performed better than the wet seasonfor all growth, yield and water productivity attributes due to the low temperatures in thewet season that affected crop growth and development. Therefore, incorporating deficitirrigation and carbonate foliar fertilizers into SRI farming practices is capable ofenhancing growth, yield and water productivity.
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    Modelling groundwater-surface water interactions and recharge dynamics in the Usangu plains, Tanzania
    (Sokoine University of Agriculture, 2022) Sahinkuye, Thomas
    In Tanzania, irrigated and rainfed agriculture is a key sector of the national economy, and it accounts for more than 75% of the population’s livelihoods. In the Usangu Plains located in the Southern Highlands of Tanzania, little is known about the groundwater recharge dynamics and its interactions with surface water bodies, despite the fact that the area is rich in research initiatives. Consequently, the irrigation schemes and other water user sectors are using groundwater and surface water without a clear understanding of the contribution of each of the two water resources. This study modelled the groundwater-surface water interactions and recharge dynamics in the Usangu Plains. Specifically, the study evaluated the groundwater recharge dynamics in the Usangu Plains using the WetSpass model, analyzed water exchange processes between groundwater and surface water in the Usangu Plains and evaluated the future climate change influence on the groundwater recharge in the Usangu Plains. The GIS-based hydrological WetSpass model was used to evaluate the groundwater recharge dynamics and the future climate change influence on the groundwater recharge while the hydrograph separation techniques were used to analyze water exchange processes between groundwater and surface water. About 13.1% of the mean annual rainfall was found contributing to the groundwater storage. Approximately, due to the lack of groundwater withdrawal information during this study, 0% to 10% of the annual recharge were tentatively considered to be cautiously extracted for economic and domestic use. Except for Great Ruaha River at Msembe, other five rivers manifested a great dependence (more than 90%) on groundwater discharges. Nevertheless, the projected climate change and variations are expected to provoke the decrease of groundwater recharge quantity and distributions within the Usangu Plains. As a result, the surface water volumes will decline as they are used to be sustained by the baseflow. Therefore, in addition to rainwater saving initiatives, effective policies to cope with and mitigate the climate change effects towards groundwater recharge dynamics will guarantee the water availability to meet the future economic, domestic use and crop water requirements.
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    Responses of orange fleshed sweet potato (Ipomoea batatas L.Lam) Varieties to deficit irrigation in Tanzania
    (Sokoine University of Agriculture, 2022) Osore, Makama Arnold
    Climate change has put a strain on water resources in most parts of the world. Water, on the other hand, is a critical input for agricultural production and plays a critical role in food security. As a result, the risk of various forms of malnutrition has increased, potentially leading to under nutrition as well as overweight and obesity, which is likely to worsen further due to the health and socioeconomic effects of Covid-19. Thus, the importance of producing food to improve nutrition security is obvious, as it is a promising approach to combating malnutrition. However, improving food production is faced with the challenge of water scarcity, especially in sub-Saharan Africa. Methods that enhance efficiency in water use are promoted to improve food production. Deficit irrigation (DI) strategies in pressurized irrigation systems are beneficial in reducing applied irrigation water and nutrient loss through leaching, as well as crop vegetative vigour. This strategy is useful for dealing with water scarcity and improving water productivity. This study used field experimentation to assess the effects of deficit irrigation on orange-fleshed sweet potato storage root yield, water productivity, and nutritional water productivity, as well as the financial implications in Tanzania. Orange fleshed sweet potato (OFSP) varieties are documented to offer a balanced nutritional composition, mature early and can withstand marginal conditions where other crops fail. To achieve the intended goal, three irrigation rates were used for scheduling: 100 per cent (Full irrigation (FI)), 60 per cent (60 DI), and 30 per cent (30 DI) of total available water (TAW) in a factorial arrangement of treatments laid out in a randomized complete block design (RCBD), with Naspot-13 and Jewel of orange-fleshed sweet potato crop as test varieties. A 3 x 2 factorial design with three replications was used. When 20 per cent of the total available water (TAW) was depleted, the FI treatment was irrigated to 100 per cent field capacity, whereas the 60 DI and 30 DI treatments received 60 per cent and 30 per cent of the amount applied in the FI treatment, respectively. A drip irrigation system was used to apply irrigation water using a continued deficit irrigation strategy. The strategy was implemented eight days after the plants were planted. Analysis of Variance was performed on response variables data and treatment means separated using Tukey’s multiple range test at p<0.05. The first goal was to evaluate the yield, water productivity, harvest index, and dry matter content of OFSP varieties subjected to deficit irrigation. The fresh yields were harvested 120 days after planting then weighed and weight converted to tons per hectare. In this study, only marketable storage roots were considered. Marketable storage roots were defined as storage roots weighing 100 g or more and free of defects caused by diseases or mechanical damage. The dry matter content of the test varieties was determined by drying peeled and sliced OFSP in a solar drier for 48 hours at a temperature of 62.4 O C. The second goal was to evaluate the nutritional root quality parameters and nutritional water productivity of OFSP varieties in response to deficit irrigation. To obtain an analytical sample, four medium-sized orange-fleshed sweet potato varieties were homogenized in a food processor. The analytical sample was extracted for 1 minute with methanol: tetrahydrofuran (THF) (1:1) and then filtered into petroleum ether (PE), as described by Rodriguez-Amaya and Kimura (2004). An Atomic Absorption Spectrophotometer (ASS) was used to determine the iron and zinc micronutrient content of a portion of the analytical sample, as described by AOAC (2002). The third goal was to evaluate the production economics of drip-irrigated OFSP varieties subjected to deficit irrigation. The benefit-cost ratio (BCR) analysis is a financial measure of the value of a project. The economic return analyses of the production system of OFSP varieties under each irrigation regime were calculated using BCR in this study. However, BCR components including the capital cost of a drip irrigation system and the gross and net return of each irrigation regime were estimated assuming a field area of one hectare and flat land. According to the results of the first objective, the Naspot-13 variety demonstrated a high yielding ability to water stress, recording 17 t/ha, whereas the Jewel variety recorded 9 t/ha of storage root yield. The Jewel variety produced the most storage root yield, with the highest at 25 t/ha during the first season, while the Naspot-13 variety performed poorly. This could be attributed to the rain effect that occurred during the first season. Under deficit irrigation, the varieties' water productivity (WP) and harvest index (HI) increased. The varieties' WP ranged from 1.8 to 11.0 kg/m 3 , and their HI ranged from 52 to 58 per cent. Both varieties' dry matter content ranged from 23 to 31 per cent and was statistically similar. The fresh above-ground biomass decreased significantly as the amount of water applied decreased. According to the findings of the study, the Naspot-13 variety can be strategically used as a feasible crop for producing more food with less water. In the second objective, it was discovered that the beta-carotene content of the Jewel cultivar was 27 per cent higher than that of the Naspot-13 cultivar. Iron and zinc concentrations in both cultivars were found to be sufficient and minimal respectively. Otherwise, when deficit irrigation was compared to full irrigation, neither cultivar's root quality changed. All the same, a typical serving (125g) of test OFSP varieties provides more than 100% of the vitamin A, sufficient iron, and minimal zinc dietary requirements for 4-8-year-old children and 10-50-year-old pregnant women. In general, the nutritional water productivity of root quality parameters increased as water application decreased. Finally, a positive water-food-nutrition nexus was established under the Naspot-13 variety, which is capable of alleviating Vitamin A, and iron as well as minimising zinc deficiency health-related problems, particularly in children and pregnant women living in areas with limited water resources. The results of the third objective show that a net positive return using the benefit-cost ratio (BCR) was observed, with the highest net financial return (6516 US $ per ha) observed for the Naspot-13 variety at the 60 DI deficit strategy. As a result, for Naspot-13 cultivation using drip irrigation in sandy-clay soils, the 60 DI strategy is a more cost- effective option than full irrigation. However, in the case of water-limiting situations, the highest net financial return was observed under Jewel variety at 30DI treatment (8404 US $).In summary, the findings in this study indicated that the production of OFSP for deficit irrigation is economically feasible.