Browsing by Author "Kahimba, Frederick C."

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Agronomic management strategies for adaptation to the current climate variability: the case of North-Eastern Tanzania
(2014) Tumbo, Siza D.; Rwehumbiza, Filbert B.; Kahimba, Frederick C.; Enfors, Elin; Mahoo, Henry F.; Mbilinyi, Boniface P.; Mkoga, Zacharia; Churi, Ayubu
Rainfed agriculture in semi-arid areas of sub-Saharan Africa faces a great challenge due to increasingly high variability and unreliability of rainfall. Two of the effective adaptive responses to reduce the vulnerability to the changing climate are through use of soil and water conservation technologies and employment of improved agronomic practices. A study was conducted to quantify the risk and profitability of agronomic management strategies for maize using long-term climatic data and a crop simulation model. APSIM model was used to perform long-term simulations of different management strategies. Simulated maize grain yield for different cultivars and sets of management strategies were evaluated to establish the associated risks and benefits. Results indicate that planting Situka or SC401 during Masika season instead of Kito or other cultivars, gives a yield of more than 1 ton/ha under conventional methods. Maize yield increases to 2t/ha or even higher with the use of fertilizers and recommended management practices. The cost benefit analysis indicated that income greater than USD 700 per ha could be obtained when recommended practices are applied, with Situka and SC401 as the maize varieties planted. Based on the results of the study, it is recommended that farmers should employ improved agronomic management practices only when the seasonal forecast indicates above normal rainfall. The early availability of seasonal rainfall forecast is thus vital. Alternatively, farmers are much safer if they continue to employ their conventional approaches of farming because these have lower risks.
Comparison of silicon status in rice grown under the system of rice intensification and flooding regime in Mkindo Irrigation Scheme, Morogoro, Tanzania
(TAJAS, 2020) Gowele, G. E.; Mahoo, H. F.; Kahimba, Frederick C.
Silicon (Si) is the second most abundant element available in the earth's crust, and is considered as a benefcial element for crop growth especially rice. A study was conducted in Mkindo irrigation scheme, Mvomero District, Morogoro, Tanzania to assess the Silicon status in rice grown under the System of Rice Intensifcation and continuous ﬂooding at various growth stages. The experiment was laid out in a randomized complete block design (RCBD) with two treatments which were two water application regimes: T1 was alternate wetting and drying using SRI technology and T2 was continuous ﬂooding. The treatments were replicated three times and the rice variety used was SARO 5 (TXD 306). The experiment was conducted in two seasons from October 2019 to January 2020 and from March 2020 to June 2020. Si status in rice seeds and grains as well as rice plant leaves at various growth stages were evaluated according to elemental analysis based on Energy Dispersive X- Ray Fluorescence and results were analyzed using GENSTAT software. Si content in rice seeds observed prior to the experiment was 6.76%. Si content in rice grains was gradually increasing during reproductive stage and later drops during harvest. Si content in rice plant leaves increased signifcantly from vegetative to ripening stage whereby the highest Si content was recorded in T 1 (12.37%) while T2 recorded the lowest value (10.15%). It was concluded that, the alternate wetting and drying feld conditions enhances adequate uptake of Si compared to continuous ﬂooding practices.
Estimating conveyance efficiency and maize productivity of traditional irrigation systems in USA river catchment, Tanzania
(Hindawi, 2020-07) Haymale, Humuri K.; Njau, Karoli N.; Kahimba, Frederick C.
Estimating the conveyance efficiency of traditional irrigation schemes systems is very important. It is because of understanding the volume of water lost along with the transportation facility, enhancing water usage and productivity, hence making better decisions about the utilization of water resources. (e objective of the study was to determine water abstraction permit compliances and estimate conveyance efficiency and crop and water productivity of traditional irrigation systems in northern Tanzania. (e task involved measurement of irrigation water flows to determine the amount of water abstraction, inflow (head) and outflow (tail) between the canals to determine the conveyance efficiency of the main, secondary, and tertiary canals of the traditional irrigation systems. Moreover, water and yield obtained at the farm level were determined. Results indicate that approximately 72% of water transported reaches the destined farm which produced maize (Zea mays L) yields of 1054.5 kg/ha, 892.4 kg/ha, and 875.156 kg/ha at downstream, midstream, and upstream which equals 0.41 kg/m3, 0.15 kg/m3, and 0.09 kg/m3, respectively, while about 28% of water is lost along the canals through evaporation, seepage, and deep percolation and overtopping. Consequently, water measured at furrow intakes in total was 3, 500 L/s, equal to 23% more than the permitted amount of 2856.14 L/s at Usa River Catchment. Interventions to minimize water losses starting at the furrow’s intakes are urgently required in the current trend of the increasing demand for water resources for food production and schemes performance. Subsequently, more effective conveyance technologies and water management strategies other than canal lining are required.
Evaluation of the performance of CORDEX regional climate models in simulating present climate conditions of Tanzania
(ResearchGate, 2016-06) Luhunga, Philbert; Botai, Joel; Kahimba, Frederick C.
Regional climate models (RCMs) are widely used in regional assessment of climate change impacts. However, the reliability of individual models needs to be assessed before using their output for impact assessment. In this study, we evaluate the performance of RCMs from the Coordinated Regional Climate Downscaling Experiment program (CORDEX) to simulate minimum air temperature (TN), maximum air temperature (TX) and rainfall over Tanzania. Output from four RCMs driven by boundary conditions from three General Circulation Models (GCMs) and ERA-Interim data are evaluated against observed data from 22 weather stations. The evaluation is based on determining how well the RCMs reproduce climatological trends, interannual, and annual cycles of TN, TX and rainfall. Statistical measures of model performance that include the bias, root mean square error, correlation and trend analysis are used. It is found that RCMs capture the annual cycle of TN, TX and rainfall well, however underestimate and overestimate the amount of rainfall in March–April–May (MAM) and October–November–December (OND) seasons respectively. Most RCMs reproduce interannual variations of TN, TX and rainfall. The source of uncertainties can be analysed when the same RCM is driven by different GCMs and different RCMs driven by same GCM simulate TN, TX and rainfall differently. It is found that the biases and errors from the RCMs and driving GCMs contribute roughly equally. Overall, the evaluation finds reasonable (although variable) model skill in representing mean climate, interannual variability and temperature trends, suggesting the potential use of CORDEX RCMs in simulating TN, TX and rainfall over Tanzania.