Effect of saline irrigation on yield and fruit quality of tomato and rockmelon grown on sandy soils under Mediterranean climatic conditions

Saline water is increasingly being considered for irrigation in arid and semi-arid regions amid growing pressure on freshwater supplies. This study aimed to evaluate the impact of saline irrigation on yield and fruit quality of tomato and rockmelon grown on coarse sandy soils under a Mediterranean climate in Western Australia. Two field experiments were conducted over consecutive seasons using drip irrigation and plastic mulch. Tomato and rockmelon were irrigated with water of five salinity levels (EC_i 0.4, 2.5, 5.0, 7.5, and 10 dS/m). Soil salinity (EC_e), plant ion content, yield, and fruit quality – including total soluble solids (TSS), acidity, firmness, and bioactive compounds – were measured. Irrigation water with EC_i ≤ 2.5 dS/m did not significantly affect marketable yield in either crop. Marketable yield declined by ~ 7–8% per unit EC_i above this threshold, mainly due to reduced fruit size. In tomato, saline irrigation enhanced TSS (up to 49% increase), acidity, and concentrations of phenolics, flavonoids, and antioxidants. Rockmelon fruit quality, including TSS (~ 12 °Brix), firmness, and nutritional content, was unaffected by salinity or postharvest storage. Moderate saline irrigation (EC_i ≤ 2.5 dS/m) can be used for tomato and rockmelon cultivation on coarse sandy soils without adverse effects on yield or quality. Higher salinity improved tomato fruit quality, which may compensate for yield losses.