Assessing concerns about fertigation costs with desalinated seawater in south-eastern Spain

Desalinated sea water (DSW) provides a steady agricultural water supply that overcomes climatological and hydrological constraints, fostering food security and socio-economic stability in water-stressed regions. In the last decade, seawater desalination for irrigation has been massively implemented in south-eastern (SE) Spain amid rising pressure and competition for water resources. However, farmers seem reluctant to replace conventional water sources with DSW due to its higher price and the need for additional fertilization. This article assesses how fertigation cost increases can affect farming profitability when integrating DSW for irrigation. The increases in water and fertilizer costs of totally (100 %) and partially (50 %) replacing conventional water with DSW were calculated for the most representative crops of the Segura basin in SE Spain. The results show that the total replacement of conventional resources implies a fertigation cost increase equivalent to 3.2-35.5% of the crop production costs. However, replacing only 50 % of the conventional resources reduces these figures by more than half (1.5-15.7%). This supra-linear decrease comes from the fact that although water blending halves the water cost increase, the fertilizer cost increase is reduced by more than half. Looking at the fertigation cost increase relative to crop profit, remarkable profitability losses were observed for all crops in the total replacement scenario (21.6-129.1%), which only fell to more acceptable levels in the partial replacement scenario (10.3-57.1%). In the scenario with 100 % DSW, the estimated revenue increase required to compensate for the increase in the fertigation cost seems unrealistic for traditional crops (> 15 % for melon and > 25 % for lemon) whereas substantially more moderate increases are demanded from all crops (< 10 %) when only 50 % DSW is used. Overall, this study stresses the need to properly evaluate water blending options to maintain agricultural profitability.