| Summary: | 博士 === 國立屏東科技大學 === 熱帶農業暨國際合作系所 === 98 === The main climate features in Burkina Faso are characterized by a low rainfall and high temperature. For dealing with the climatic constraints, the country has put priority on irrigated agriculture as a supplementary production strategy. The climatic constraints added to the world global food crisis deteriorated the food situation and also weakened the fragile political stability in Burkina Faso. The development of effective management strategy based on water balance analysis is essential to mitigate the climatic constraint and then improve the crop productivity. Evapotranspiration is a major component of hydrological cycle and its determination is a key factor for computerizing accurate crop water balances. Penman–Monteith equation is the most accurate methods to evaluate reference evapotranspiration (ETo) at different time steps, its application is still limited due to the large number of data required. An accurate estimation of ETo, especially in semiarid regions such as Burkina Faso, has a great importance for irrigation water management. Besides, in low rainfall areas it is decisive to emphasize on crop yield modeling, on-farm reservoir system and irrigation scheduling determination for enhancing the efficiency of water use. Crop water yield function is crucial in water resources planning. For agriculture water management in Burkina Faso, on-farm reservoir (OFR) system is highly needed because it can store rainwater and reuse it for supplementary irrigation. The on-farm reservoir systems have been considered as an economically viable means to store and conserve rainwater to alleviate drought and intensify cropping in drought prone rainfed areas. Moreover, scheduling the irrigation in low rainfall area is a necessary step in the water resources efficient use. Therefore, this present study aims firstly to model the crop water yield relationship in Burkina Faso based on minimum climatic and required variables. Secondly; to determine the optimum cultivation size of the OFR used to develop supplementary irrigation strategy. Thirdly, the soil holding capacity which is central in irrigation scheduling is also evaluated with different dosage of organic matter by using soil data generated under computer simulation assistance. From the results of this study, it is found that ETo can be successfully computed in Burkina Faso with minimum climatic, but the wind speed needs to be considered as the most effective and required variable. Accordingly, the nonlinear complex process of crop water yield relationship can also be modeled in poor data situation in the semiarid zone of Burkina Faso. From the results, it was found that the difference between potential and expected yields was causally affected by the planting dates applied. By comparing the expected yields of the suitable planting dates to the average values, the yields were increased between 5 to 18% and 4 to 23% in Ouagadougou and Banfora, respectively. The difference is small when the planting dates are closer to the established suitable dates. The suitable cropping calendar determined using the model in this study should therefore be used to alleviate water shortage and yield deficit under rainfed condition. Furthermore, the total farm area to be optimally occupied by the OFR can vary between 11.10 and 28.39% regarding to the planting dates. As a result, an OFR facility is able to improve the water availability for reaching the potential yield. From the observed data conditions, the time of irrigation numerically computed were 5 times for both maize and bean and 12 for rice. Finally, it was found that when the content of the soil organic matter increases up to an optimum value of 4 tons, the soil holding capacity including permanent wilting point, field capacity, saturation, saturated hydraulic conductivity improve for all types of soil.
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