Innovative irrigation water management: a strategy to increase yield and reduce salinity hazard of small scale irrigation in Ethiopia

To address the problem of water scarcity and to achieve food self-sufficiency, huge efforts and massive irrigation developments have been made in the last twenty-five years by the Ethiopian Government. However, the performance of many small-scale irrigation (SSI) schemes is still very poor. Deficient irrigation water management is one of the major factors challenging the success and the sustainability of the SSI. Farmers are constrained by inappropriate irrigation management strategies, which result in irrigation water scarcity, yield loss and undesirable environmental impacts in most SSI. The issue of sustainability is given hardly attention. This thesis tries to assess, understand and evaluate the current irrigation water management practices in relation to crop yield and soil salinization and then come-up with simple and innovative irrigation water management strategies that can influence the farmers’ decision and enable them to cope with the problem of water scarcity and soil salinity. In Chapter 2 farmers’ irrigation water management practices, challenges, perceptions and adaptation were studied. We evaluated farmers survey data, field observations and measurements and found that the farmers’ perception of the major causes for aggravating water scarcity, crop yield decline and soil salinization were in line with field observations. The overall plot level and scheme level adaptation strategies of the farmers were not good enough. The farmers are constrained by lack of technical knowledge, weak enforcement capability of the Water Users Association (WUA) and poor irrigation infrastructures to manage the irrigation water properly at plot as well as at scheme level. The government involvement on sustainability of irrigation schemes is poor. Also, the top-down approach by local government authorities has been constraining the farmers’ adaptation strategies. The study showed that allowing beneficiaries to make their own decision resulted in innovative drought adaptation strategies. For sustainable utilization of the irrigation scheme, priority should be given to interventions focused on improvement of water efficiency at farm as well as at scheme level. In Chapter 3 we developed a simple irrigation scheduling method based on an FAO procedure (Brouwer et al., 1989), the Hargreaves ET0 equation and the opinions of local farmers and extension agents. Then, under participation and close observation of farmers the method was compared to CropWat simulated and local (Traditional) scheduling practices, using maize as indicator crop. We found that the simple irrigation schedule method resulted in higher grain yield, substantial irrigation water saving and subsequently in significant improvement of water productivity as compared to the other approaches. Farmers’ and experts’ opinions were in favour of the Practical scheduling method. The practical irrigation scheduling method is thus recommended for maize in the Gumselassa area. The presented procedure can be adopted for preparation of irrigation calendars of other crops, and in other regions. In Chapter 4 we presented a sustainable utilization of the scarce irrigation water resources using cyclic (conjunctive) irrigation strategies for the production of onion. The effects of irrigation strategies using fresh water, moderately-saline water and cyclic combinations of both waters on onion yield and soil salinization were evaluated based on two years experimental data. The study was conducted under close observation and involvement of farmers and extension agents. The results indicated that the cyclic irrigation strategies are promising options for the production of onion without undue onion yield reduction and soil salinization as compared to irrigation using fresh water. In Chapter 5 the long-term (ten years) impact of cyclic irrigation strategies on relative onion yield and soil health were evaluated. Climatic data, and data collected from the irrigation scheme and the field experiment (Chapter 4) were used to calibrate and validate the Soil-Water-Atmosphere-Plant (SWAP) model. Two scenarios, i.e. 60 mm pre-plant irrigation (PPI) for the 1st case and 70 mm PPI plus 20 percent leaching fraction (LF) for the 2nd case, were used for long-term simulations. Results of the simulation revealed that salinity build-up is critically affected by irrigation water qualities and the application frequencies and the amount of annual rainfall. Irrigating using seepage water resulted in lower onion yield and higher salt accumulation in the root-zone, for both scenarios. Considering soil salinization, results of the long-term simulation indicated that, the cyclic irrigation strategies can be used safely through increasing the PPT to 70 mm and introducing 20% LF

Irrigation water management : Farmers’ practices, perceptions and adaptations at Gumselassa irrigation scheme, North Ethiopia

Poor irrigation water management associated with water scarcity is the major reason for underperformance of most small-scale irrigation schemes in Ethiopia. In order to devise appropriate measures for rehabilitation of the failing schemes and to enhance farmers’ adaptation capacity to water scarcity, it is important to assess site specific plot and scheme level water management practices, challenges, farmers’ perceptions and adaptation strategies. So far, there is no such study in the context of Tigray, Ethiopia. A survey was conducted on 109 farmers in three groups based on the source of irrigation water, which included canal, seepage and both canal and seepage water users. Focus group discussions with elders, water users association (WUA) committee and women headed households were also made. Furthermore, random field measurements on conveyance loss, groundwater depth and quality (EC) were also taken to verify the farmers’ perception. The respondents’ perception of severe water scarcity at scheme level and poor on-farm and scheme level water management practices are among the major causes for aggravating water scarcity, crops yield decline and soil salinization were in line with field observations. Despite several adaptation strategies of the farmers at plot and at scheme level, yield is still declining. The only adaptation strategy that has been enforced by the local government authority was reduction of the irrigated land. However, in the 2016 irrigation season the farmers were allowed to make their own decisions that resulted in innovative water scarcity adaptation strategies and that doubled the irrigated land as compared to the local authority plan. This showed the significance of allowing the beneficiaries to make their own decisions. To rehabilitate Gumselassa irrigation scheme as well as to enhance the adaptation capacity of the farmers to water scarcity capacity building and empowerment of the WUA and improvement on the existing water structure is required.</p

Effect of cyclic irrigation using moderately saline and non-saline water on onion (Allium cepa L.) yield and soil salinization in semi-arid areas of Northern Ethiopia

Due to the scarcity and/or unreliability of canal water supply, seepage water is haphazardly used for sole irrigation or in conjunction with canal water in most small-scale irrigation schemes in northern Ethiopia. This has been a major cause of low crop yield and has aggravated soil salinization. The problem is more exacerbated for onion, which is the major irrigated vegetable crop and is sensitive to salinity. Thus, it is essential to assess a sustainable way to use both water resources conjunctively for the production of onion. A new study in the Ethiopian context was conducted to evaluate the effect of cyclic irrigation using non-saline canal water (EC, 0.41–0.78 dS m−1) and moderately saline seepage water (EC, 0.82–2.19 dS m−1) on onion yield and soil salinization for two seasons (2014/2015 and 2015/2016) in the Gumselassa irrigation scheme, Ethiopia. Four irrigation water treatments were applied with three replications consisting of: C (canal), S (seepage), 2CS (two canal and seepage) and CS (canal and seepage). In both seasons, the onion bulb yield variations between the C, 2CS and CS treatments were not significant; however, the S treatment reduced the onion yield significantly compared to all but CS in 2015/2016. The S treatment resulted in significant salt accumulation in the upper soil profile (0–20 cm). The alternate (C : S) cyclic option is thus recommended for alleviation of the problem of freshwater scarcity, without undue onion yield reduction and soil salinization in Gumselassa and similar irrigation schemes.</p

A participatory and practical irrigation scheduling in semiarid areas: the case of Gumselassa irrigation scheme in Northern Ethiopia

Poor irrigation scheduling practices have been quoted as the major challenges for sustainability of small-scale irrigation schemes in Ethiopia due to complexity of scheduling techniques, cost and inaccessibility of soil-water monitoring tools, lack of various local climatic data and soil-water parameters. For local experts to easily schedule irrigation and to promote adoption by farmers, a cheap and simple computation procedure of irrigation scheduling is needed that considers local resources and opinions. So far, there is no such study in the context of Ethiopia. A simple irrigation scheduling method (Practical) was developed based on the FAO procedure (Brouwer et al., 1989), employing Hargreaves ET 0 equation and the opinions of local farmers and extension agents. Then, the method was validated on-farm through participatory and close observation of farmers by comparing with CropWat simulated (Sophisticated) and local (Traditional) scheduling practices for 2015and 2015/16 irrigation seasons considering maize as indicator crop. Data on irrigation depths, yield and yield components and soil salinity were collected and analysed. Furthermore, a farmers’ day was arranged to collect opinions on the crop stand and scheduling techniques. In both irrigation seasons, the practical irrigation schedule method resulted in higher grain yield while saving substantial amount of water and in significantly higher water productivity (WP) compared to the other methods. Maximum (0.68 kg m −3 in 2015) and minimum (0.47 kg m −3 in 2015/16) WP were found in the practical and sophisticated approaches, respectively. The average root zone salinities among the alterative irrigation scheduling methods were not significantly different, in both irrigation seasons. Farmers’ and experts’ opinions were in favour of the practical scheduling method. The practical irrigation scheduling method is thus recommended for maize, around Gumselassa area. Further, the presented procedure can be adopted for preparation of irrigation calendars of other cops and in other regions. </p

Transdisciplinary innovation in irrigated smallholder agriculture in Africa

SIInternational audienceBoosting the productivity of smallholder farming systems continues to be a major need in Africa. Challenges relating to how to improve irrigation are multi‐factor and multisectoral, and they involve a broad range of actors who must interact to reach decisions collectively. We provide a systematic reflection on findings from the research project EAU4Food, which adopted a transdisciplinary approach to irrigation for food security research in five case studies in Ethiopia, Mali, Mozambique, South Africa and Tunisia. The EAU4Food experiences emphasize that actual innovation at irrigated smallholder farm level remains limited without sufficient improvement of the enabling environment and taking note of the wider political economy environment. Most project partners felt at the end of the project that the transdisciplinary approach has indeed enriched the research process by providing different and multiple insights from actors outside the academic field. Local capacity to facilitate transdisciplinary research and engagement with practitioners was developed and could support the continuation and scaling up of the approach. Future projects may benefit from a longer time frame to allow for deeper exchange of lessons learned among different stakeholders and a dedicated effort to analyse possible improvements of the enabling environment from the beginning of the research process. © 2020 The Authors. Irrigation and Drainage published by John Wiley & Sons Ltd on behalf of International Commission for Irrigation and Drainag