Experimental Evaluation of the Water Productivity and Water Footprint of a Greenhouse Tomato Crop for Different Blends of Desalinated Seawater and Two Growing Media

An experimental evaluation of water productivity and footprint was carried out in a Mediterranean greenhouse tomato crop irrigated with different blends of desalinated seawater (DSW) for two different growing media: soil and soilless culture. Total and commercial water productivity values (expressed in terms of kg of fruit/m3 of water) and water footprint were calculated from empirical data on water consumption and crop yields. Regarding the growing media, the results of the experiment showed that the soilless culture had significantly lower water productivity and a higher water footprint, mainly due to the greater water consumption in these systems. These findings seem to indicate that fostering closed-loop soilless systems with water and nutrient recirculation is highly beneficial for improving the efficiency and sustainability of these soilless systems. The salinity of the irrigation water blends did not seem to have a significant influence on water productivity and water footprint. Nevertheless, treatments with higher DSW fractions and better quality showed slightly better productivity values and lower water footprints than those with higher salinity. These findings seem to support the fact that the conjunctive use of DSW and conventional water, within the range proposed in this study, is a favorable option from both economic and environmental perspectives.