Effects of application timing of saline irrigation water on broccoli production and quality

Irrigation with moderately saline water is a necessity in many semi-arid areas of the Mediterranean Basin, and requires adequate irrigation management strategies. Broccoli (Brassica oleracea var. italica), a crop moderately sensitive to salinity stress, was used to evaluate the effects of the application of saline (S) and non-saline (NS) irrigation water during two growth phases in terms of plant growth, water status, floret yield, glucosinolate profile, and quality. Use of S-water (4 dS m⁻¹) from transplanting to appearance of the inflorescence, alternated with NS-water (2 dS m⁻¹) from inflorescence appearance to harvest and vice versa were compared with continuous use of S- or NS-water. Irrigation with S-water during the first growth-phase decreased leaf water and osmotic potential, net CO₂ assimilation rate, and favoured Na⁺ and Cl⁻ accumulation at toxic levels causing ion imbalances and reducing broccoli plant growth. Application of S-water exclusively after inflorescence appearance caused a 22.2% decrease of the head dry biomass compared to NS-NS plants. Regardless of application timing, irrigation with S-water decreased broccoli yield and head mean fresh weight compared to NS-NS plants by 20% and 24%, respectively. Use of S-water in one or both growth stages improved broccoli dry matter and soluble solid content, while had no impact on total glucosinolate concentration. However, application of S-water during the first growth-phase resulted in an increase of indolic glucosinolates (glucobrassicin and neoglucobrassicin) and potential effects on broccoli nutritional properties and flavour.