IRRIGATION WITH BRACKISH-WATER UNDER DESERT CONDITIONS .10. IRRIGATION MANAGEMENT OF TOMATOES (LYCOPERSICON-ESCULENTUM MILLS) ON DESERT SAND DUNES

A series of trials were conducted over a period of three growing seaso ns in the Negev desert highlands of Israel to determine optimal condit ions for irrigation of processing tomatoes (cultivar M82-1-8) planted on a sandy soil. Cultural conditions was the same for all trials, Toma toes were drip irrigated with brackish (EC(i) = 6.2 dS m(-1)) and fres h (EC(i) = 1.2 dS m(-1)) water. In the first trial, the effect of irri gation frequency (twice a day, once a day, every second and every thir d day) was determined. Yields in the fresh and the brackish water trea tments were similarly affected by one or by two irrigations per day. I rrigation every 2 and every 3 days significantly reduced yields in the two water quality treatments. On average, yields of brackish water ir rigated plants were about 44% of yields from fresh water plants. The e ffect of three planting dates (15/3, 1/5, 15/6) on yields of fresh and brackish water irrigated tomatoes was investigated in the second seas on. Fresh water yields were similar for the first two planting dates b ut significantly reduced at the third planting date. Brackish water yi elds were reduced with each subsequent planting date. Relative yield o f 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 mi dday 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 concent ration of sodium. It had little effect on leaf calcium content but red uced the levels of potassium and phosphorus.