Irrigation with brackish water under desert conditions VII. Effect of time of application of brackish water on production of processing tomatoes (Lycopersion esculentum Mill.)

Processing tomatoes, cv. VFM 82-1-8, were sown in the field and irrigated from the outset with water having electrical conductivities of 1.2 (control), 4.5 and 7.5 dS/m, or were irrigated from the outset with 1.2 dS/m water and then transferred at the four or eleven-leaf stage to irrigation with 4.5 or 7.5 dS/m water. The total yield of fruit in the control was 13.6 kg per 10 m² and the marketable yield 12.1 kg per 10 m². When tomatoes were irrigated from the outset with saline water with an electrical conductivity of 7.5 dS/m, the total yield was reduced by 60% relative to the control. However, when saline water irrigation started at the appearance of the fourth or the eleventh leaf, a water salinity of 7.5 dS/m reduced the yield by only about 30%. Salinity increased the acidity, electrical conductivity, and total dissolved solids of tomato fruit. Irrigation with saline water resulted in three- and 1.5-fold increases, respectively, in the sodium and chlorine concentrations in tomato leaves, while the leaf potassium content did not change. A water salinity of 7.5 dS/m did not markedly affect the osmotic potential (π) of tomato leaves up to 77 days after sowing, but decreased it towards the end of the season. Salinity decreased the water potential (ψ) of young tomato plants (27 days after sowing) but had no effect on ψ of 77-day-old plants.