Effects of irrigation with desalinated seawater and hydroponic system on tomato quality

Abstract

The use of desalinated seawater (DSW) as an alternative to conventional water resources is gradually gaining more interest due to the strong water deficit and increasing pressure on water resources in semi-arid regions. Furthermore, the combination of this alternative irrigation with the hydroponic cultivation system would allow continuous production almost through the whole year and hydroponic-related high crop yield. Nevertheless, the e_ects of DSW irrigation in hydroponic systems on the product quality need to be firstly studied to avoid product quality losses. In this study, we evaluated the e_ects on the quality of two tomato cvs. (Ramyle and Racymo) of three di_erent irrigation treatments (T1, DSW; T2, DSW/well water mix; and T3, well water) under hydroponic or traditional cultivation systems. The soluble solid content of samples (highly correlated to dry matter content) grown under hydroponic conditions and T3 irrigation showed the highest values (5.8 _Brix) although such di_erences (<0.6 _Brix) with T1 might not be sensorially appreciated. Similarly, although T3 samples showed higher acidity than T1 samples, such di_erences (0.06%) would be not appreciated by the consumer. Tomatoes grown in hydroponic conditions had 1.1–1.2-fold higher firmness than conventional soil conditions showing hydroponic T3 samples had the highest value (21–23 N). Tomato cv. Racymo displayed higher color index (chroma) than cv. Ramyle, registering hydroponic T1 samples the most intense red color correlated with the highest lycopene content of 41.1 mg/kg. T1 irrigation of tomatoes cv. Ramyle did not induce significant changes while di_erences lower than 10% were observed in the tomato cv. Racymo. The highest total antioxidant capacity, which was highly correlated to the total phenolic content (R2 = 0.80), was found for hydroponic T1 samples with 1637/1243 _mol/kg for the tomato cvs. Ramyle/Racymo. Conclusively, the use of DSW would not compromise the consumer acceptance of tomatoes due to the low (not appreciable) quality di_erences, with even the total antioxidant capacity of these samples being increased. Furthermore, the mix of DSW with conventional water resources (lower cost) would not compromise the tomato quality.