Transforming Irrigated Agriculture in Semi-Arid and Dry Subhumid Mediterranean Conditions: A Case of Protected Cucumber Cultivation

Pressure from population growth and climate change stress the limited water resources in the Mediterranean region and threaten food security and social stability. Enhancing food production requires the transformation of irrigation systems and enhancement of local capacity for sustainable water and soil management in irrigated agriculture. The aim of this work is the conversion of traditional irrigation practices, by introducing the practice of optimal irrigation scheduling based on local ET estimation and soil moisture monitoring, and the use of continuous feeding by fertigation to enhance both water and nutrient use efficiency. For this, two trials were established between August and November 2023 in two different pedoclimatic zones (Serein and Sultan Yacoub) of the inner Bekaa plain of Lebanon, characterized by semi-arid and dry subhumid conditions and different soil types. Protected cucumber was tested to compare the prevailing traditional farmer’s practice of empirical nutrient and water management using closed tanks with the advanced methods of water accounting and soil moisture monitoring using differential injector that allow more homogeneous application of nutritive solutions and simple tensiometers. Results showed a significantly higher amount of water applied by the farmers to the protected cucumber with a potential for average saving of 105 mm by improved practices. Water input was accompanied by higher amplitude of variation of soil moisture in the farmer’s practice before and after the irrigation cycle revealing potential stress to plant performance caused by higher water depletion followed by over irrigation. With more than 20% increase in cucumber yield by the transformed practices, a general trend in both locations was observed in the fertilization approach and amounts resulting in lower nutrient recovery in the farmer’s plots. The science-based practices of water and nutrient management showed higher application and agronomic water use efficiency of full fertigation, exceeding 60%, associated with double and triple higher nitrogen use efficiency, compared to those results obtained by the traditional water and fertilizer application methods. The monitored factors contribute to severe economic and environmental consequences from nutrient buildup in the soil-groundwater system in the Mediterranean region.