Irrigation with brackish water under desert conditions X. Irrigation management of tomatoes (Lycopersicon esculentum Mills) on desert sand dunes

A series of trials were conducted over a period of three growing seasons in the Negev desert highlands of Israel to determine optimal conditions for irrigation of processing tomatoes (cultivar M82-1-8) planted on a sandy soil. Cultural conditions was the same for all trials. Tomatoes were drip irrigated with brackish (EC_i = 6.2 dS m^-1) and fresh (EC_i = 1.2 dS m^-1) water. In the first trial, the effect of irrigation frequency (twice a day, once a day, every second and every third day) was determined. Yields in the fresh and the brackish water treatments were similarly affected by one or by two irrigations per day. Irrigation every 2 and every 3 days significantly reduced yields in the two water quality treatments. On average, yields of brackish water irrigated plants were about 44% of yields from fresh water plants. The effect of three planting dates ( 15 3, 1 5, 15 6) on yields of fresh and brackish water irrigated tomatoes was investigated in the second season. Fresh water yields were similar for the first two planting dates but significantly reduced at the third planting date. Brackish water yields were reduced with each subsequent planting date. Relative yield of brackish water plants was 59%, 43% and 30% for the first second and third planting date, respectively. The detrimental effect of brackish water on tomato yield was completely overcome through the use of pulse-irrigation (five times per day). Pulse irrigation markedly reduced midday rhizospheric salt concentration (EC_r) as compared with that of plants which were irrigated only once a day. Brackish water irrigation resulted in lower leaf water potential, higher crop stress index but had little effect on leaf carbohydrate content. Salinity had no effect on chloride concentration in leaves but more than doubled the concentration of sodium. It had little effect on leaf calcium content but reduced the levels of potassium and phosphorus.