Ingénierie des systèmes d’irrigation et de drainage

The study was conducted based on the objective to evaluate the optimal soil moisture depletion level of stevia (Stevia rebaudiana Bertoni). Six levels of soil moisture depletion (20, 30, 40, 50, 60, and 100%) with four replications were used in a randomized complete block design. Different levels of total available water depletion significantly (p<0.05) affected all recorded yield and yield components. Significantly highest plant height, fresh and dry leaf weight, fresh and dry stem weight, aboveground fresh and dry biomass, and water productivity were obtained as stevia was irrigated below 40% TAW depletion level. However, water productivity was decreased both at higher and lower depletion levels and higher was at 30 and 40% depletion levels. The pooled mean revealed that irrigating stevia under different soil moisture depletion levels had a significant (p<0.05) effect on fresh leaf weight, fresh stem weight, dry stem weight, fresh biomass, and water productivity. Moreover, plant height, dry leaf weight, and dry biomass of stevia were also highly significantly (p<0.01) affected due to different soil moisture depletion levels. The maximum plant height (23.95 cm), fresh leaf weight (3300.3 kg/ha), fresh stem weight (1213.3 kg/ha), fresh biomass (4513.6 kg/ha) and water productivity (1.92 kg/m3) were recorded at 30% TAW. Moreover, the maximum dry leaf weight (1155.8 kg/ha), dry stem weight (869.0 kg/ha) and dry aboveground biomass (2024.7 kg/ha) were recorded at 40% TAW. On the other hand, the minimum growth, yield and yield component, and water productivity were recorded at 100% TAW. The current study revealed that irrigating stevia after 40% of the total available water in the soil depleted could be practiced in the study area and similar agroecology and soil type as the wider irrigation interval could be achieved without significantly affecting yield and water productivity.

The North East and South East side of the country have limited water resource that is the cause of reducing precipitation patterns would significantly affect livestock production and potentially food security. Recently drought risk has affected high land areas and trends suggest that the risk has been increasing in Ethiopia. The annual rainfall across the country has fluctuated significantly which indicates that high seasonal anomalies in rainfall- a major contribute of food intensity. GIS is an important tool that can be used for optimal allocation of water resources of an irrigation project. CROPWAT 8.0 and CLIMEWAT 2 Tool window support dissection technology has been done identify the analysis of evapotranspiration, crop water requirement, irrigation water need and irrigation schedule in Addis Zemen, Amhara region, Ethiopia. Several input data (temperature, humidity, and wind speed) were used to calculate the reference evapotranspiration by Penman-Monteith method was 3.89mm/day. Crop and irrigation water requirement analysis in CROPWAT plat form were 476.8 and 460.9mm/dec respectively. Crop water requirement was categorize under very low sensitive (early stage), low sensitive stage (late stage) high sensitive stage (develop stage) and very high sensitive (middle stage). The irrigation water need throughout all growing season was 456.4mm. Irrigation was scheduled from October 9, 2021 to February 27, 2021.

Water resources availability is a crucial limiting factor for crop production in arid and semi-arid area. Consuming these limited resources carefully and efficiently is unquestionable. The planning of irrigation permitting to the water stress tolerance and water use efficiency of crops remains the only way to guarantee the continuity of production in an arid area. Considering this an experiment has been conducted in Melkassa Agricultural Research Center where shortage of moisture is a problem. The experiment was laid out in RCBD with three replications having 15 experimental treatments. The treatments had four crop growing seasons or stages (Initial, Development, midseason and late season stages. Melkassa II maize variety was used for seed materials. Water stress had significant different effect on grain yield, above ground dry biomass, plant height and water productivity (P<0.05). Lower grain yield of maize cultivar was obtained from moisture stress treatment that irrigated only at initial stages (2.09 ton/ha) and higher grain yield was obtained from non-stressed treatment at all growth stages (6.19ton/ha). Maximum above ground dry biomass was gained from non-stressed treatment (9.67ton/ha) were as irrigating only at initial stage produces lower yield of biomass (3.06 ton/ha). Higher water productivity was obtained from treatment irrigated only at initial growth stage (2.15kg/m3).The lower water productivity of the study was obtained from treatment irrigated at all growth stages (0.82kg/m3). The result revealed that there was no significant (p>0.05) difference in grain yield among treatments stressed only at initial stage, late stage and non-stressed. However, stressing of maize at development and mid-season crop growth stage led to significant reduction of grain yield, above ground dry biomass and plant height. Therefore, stressing maize at combination of development stages and mid stages was more sensitive with significant yield penalty.

In the Holeta river watershed, inefficient irrigation practices contribute to a significant waste of the amount of water required to cultivate crops. It appears that managing water resources at the farmer's home level by adopting economically efficient irrigation systems is the key to achieving sustained irrigated agriculture production. The purpose of this study was to evaluate the irrigation types used in the Holeta river watershed and to recommend economically viable irrigation methods. According to these reviews, the gravity-fed drip irrigation system outperformed traditional surface irrigation systems in terms of cost. Therefore, adopting a small-scale gravity-fed drip irrigation system at the household level is an efficient and economically feasible system, in terms of getting a high yield and saving water.