Irrigation strategies alternative to continuous flooding to decrease water use and increase water productivity in Mediterranean rice-based agroecosystems

In the Mediterranean basin, rice is cultivated over an area of 1,300,000 hectares. The most important rice-producing countries are Italy and Spain in Europe (72% of the EU production; 345,000 ha), and Egypt and Turkey among the extra-EU countries (almost totality of the production; 789,000 ha). Traditionally, in these areas, rice is cultivated under continuous flooding; thus, it requires much more irrigation than non-ponded crops. On the other hand, rice is strategic for food security in some countries and its consumption in the whole Mediterranean basin is steadily increasing. The MEDWATERICE project (https://www.medwaterice.org/) includes 7 case studies (CSs) representative of different rice agroecosystems in 5 Mediterranean countries (Italy, Spain, Portugal, Egypt and Turkey). Innovative irrigation strategies alternative to the traditional wet-seeding and continuous flooding (WFL) were tested and tailored to local conditions in each CS, including: alternate wetting and drying (AWD), dry-seeding and delayed flooding (DFL), subsurface drip irrigation (SDI), surface drip irrigation (DRIP), reduction of water input (RWI), hybrid irrigation (HYBRID) and multi-nozzle sprinkler irrigation (SPRINKLER). In each CS, strategies were compared to WFL and field trials were carried out at least for two years during the period 2019-2021. A minimum dataset including agroclimatic data, soil physico-chemical properties, groundwater depth and salinity, irrigation water inflow and outflow, irrigation water salinity, grain yield and quality was collected and analyzed in all case studies. Results suggest that AWD and DFL might be sound alternatives to WFL in Lomellina (IT), Baix Ter (SP), Lower Mondego and Lis Valleys (PT), and Bafra Valley (TR), leading to an increase in water productivity up to 30%. SPRINKLER and HYBRID irrigation tested in the Nile Delta (EG) resulted in an increase in water productivity of about 50% in both cases. Surface and subsurface drip irrigation systems have a great potential in reducing water use, while maintaining yield production as demonstrated in the Nile Delta (EG), Bafra Valley (TK), and Baix Ter (ES), where water productivity increased from 40 to 100% compared to WFL. Nevertheless, when adopting drip irrigation techniques, special attention must be paid to the irrigation system design and management, by considering the site-specific soil hydraulic properties and agroclimatic conditions. This communication describes the main aspects affecting rice production in each area participating in the MEDWATERICE project, and quantifies the water use and the quantity and quality of the rice production achieved with the traditional irrigation method (WFL) and the innovative irrigation solutions tested in each CS.