Sustainable water use in potato production in Algeria: Introduction of a subsurface fertigation system in the desert

Along the Mediterranean coast of Algeria, agriculture depends on rainfall, whilst in the rest of the country, agriculture depends on scarce, or at least hard to reach, underground water. However, in the El Oued region of Algeria, an enormous sub-Saharan Aquifer comes close to the surface. Here, agriculture has developed on a sandy soil, of which the potato cultivation is the most important agricultural activity. Generally, farmers in El Oued continuously irrigate the potatoes, which are planted between the ridges in 1 ha circular fields. Irrigation is done with a locally developed pivot system with overhead sprinklers. The current practices are unsustainable and much can be gained by improving water use, fertilizer and pesticides use, varieties choice, quality of the starting material and prevention of post-harvest losses. In this project, more sustainable potato growing practices were piloted in a real life situation. In close cooperation with staff members and students from the Hamma Lakdar Univerity in El Oued, a 5 ha demonstration farm was set up and managed over an autumn and a spring growing season to test and illustrate the innovative technique of subsurface fertigation (combination of irrigation and liquid fertilization) and how it can contribute to more sustainable water use practices. The pipes used for the fertigation system were integrated in the potato ridges by a tractor drawn machine, which in one operation makes the ridge and plants the seed potatoes in the ridges under the fertigation drip. New (climate smart) varieties were tested. During the growing seasons, water consumption with subsurface irrigation system was measured and compared to water use per pivot circle. Apart from measuring the amounts of water being applied to the field, also soil and air temperature, the dynamics of the soil moisture and evapotranspiration, plant development and tuber production were measured during the growing seasons. The introduction of the subsurface irrigation method and different potato varieties resulted in a clear improvement of the potato production in terms of land use and labor efficiency, sustainable water use and yield: 1) Planting and installation of driplines could be done at the same time, 2) Water saving was about 50% and 3) Tuber yields slightly increased (mainly in Autumn), while the new potato varieties Arizona, Manitou and Rudolph yielded better than the traditionally used Spunta. During various field visits and workshops, the new technique and the comparison in water use and productivity between pivot and subsurface irrigation were shared with local farmers, representatives of the (local) government, business people, representatives from other organizations and the local and national TV press. From the start of the project, there had been great interest in the field activities. As a demonstration pilot, the project was successful. The data collected on water waste when using a pivot convinced everyone that improvement of the pivot methodology is urgently needed. However, the adoption rate of the new technique was low, probably due to a knowledge gap on technology and lack of skills to get it running. But given the great interest and enormous publicity the pilot received, it is expected that with financial incentives and political and societal support the adoption rate will increase. For the Netherlands, which is increasingly confronted with recurring periods of long-term precipitation shortfall, the project also yielded several intriguing insights for practical use, such as: 1. Mechanical planting of potatoes easily combines with the unwinding and installation of subsurface hoses. 2. With well-drained soils, multiple and short irrigation doses are more effective and yield greater water savings than prolonged irrigation at greater intervals. 3. The technology offers possibilities to guide the irrigation based on tuber setting and tuber size, thereby offering added value for seed potato companies. 4. Insight into crop propagation and the water, nutrient, pesticides and energy savings make it possible to calculate the economic feasibility of the technology for each company.