The effects of three irrigation salinity levels (1.8, 3.3, and 4.8 dS/m) on ion accumulation and relative turgidity of Cabernet Sauvignon (Vitis vinifea) grapes on 'Rugerri' and 'Salt Creek' rootstocks were studied in order to introduce more saline water in the Negev Desert of Israel. Leaf samples were taken four times during the summer of 1997 and analyzed for total diffusible ions, which included sodium (Na), calcium (Ca), potassium (K), and magnesium (Mg), and for soluble ions, which included zinc (Zn) and manganese (Mn). Quality and quantity of yield were also measured. The lowest relative turgidity, 0.8, was measured at ECi (electrical conductivity of irrigation water) 4.8 dS/m, which decreased with time to 0.75 for all treatments. The Na/K ratio indicated relative sodium accumulation. It increased fast with time from about 0.1 to 1.4 under high salinity and more slowly, from 0.1 to 0.5, under the low-salinity treatment. Average yield of fresh berries under all treatments (except one) ranged between 8.0 and 8.5 kg/vine under the respective saline and fresh-water irrigation. This difference was not significant, but in view of the first-year experiment this result should be regarded as provisional. The juice quality criteria, as determined by the production of total soluble solids (TSS) pH(2), improved from 321 to 288, indicating low acidity under the saline treatment and higher acidity under the non-saline treatment. The ratio of TSS/acidity, which changed slightly from 34 to 32, also indicated a moderate reduction in acidity under saline conditions, especially under the 'Ruggeri' rootstock. Thus, it was concluded that (a) by the use of saline water the quality of the berries may be improved, (b) 'Ruggeri' rootstock was less affected than 'Salt Creek' by salinity in both quantity and quality of yield, and (c) relative sodium (Na) content in the lamina and the petiole increased with time during the growth period while relative turgidity declined, indicating a possible accumulation of toxic ions over time.

Brackish water (7dSm−1) is frequently utilized to drip-irrigate crops in the Negev desert of Israel, the practice being to use deep sandy soils (96% sand) to avoid soil salinization. When muskmelon (Cucumis melo L.), a moderately salt-sensitive crop species, was grown using brackish irrigation under these conditions, yields declined due to a significant reduction in fruit size, but fruit quality parameters improved markedly. In the present study, we tested the hypothesis that the use of fresh irrigation water during the early vegetative phase would increase canopy size and leaf area index (LAI) and hence the potential productivity of the melon plant. The application of brackish water during the reproductive phase, on the other hand, would improve fruit quality. Using multiple irrigations within a 24-h period, applied with drip irrigation, we examined the timing, the duration, and the concentration of brackish irrigation water as tools to optimize fruit yield and quality in late-summer melons. Indeed, the combination of fresh (1.2dSm−1) and brackish (7dSm−1) irrigation water increased the yield level to that of fresh water plants whereas it brought about the improvement of fruit quality typical to brackish water plants, thus providing an attractive approach to optimize late-summer melon production. Our results demonstrate the trade-off between fruit size and fruit quality as related to the timing and the duration of brackish irrigation water. The use of a milder (<4.5dSm−1) salinity level of irrigation water from plant emergence until harvest may be considered as well.

Production of spring potato (Solanum tuberosum L. cv. Désirée) on a deep sandy soil in the central highland of the Negev desert of Israel under drip irrigation with saline water (up to 6.2 dS m−1) was studied in the years 1992–1997. The objective of the study was to determine the effects of saline water irrigation on potato production in an arid environment with special focus on the interactions with weather conditions. Although yields were often high, salinity effects were evident in some years. Thus 1992 and 1996 yields were 6–7 kg m−2 and showed no significant effect of salinity, while a pronounced drop in yield with increasing salinity was observed in 1993 and 1994. Analysis of weather data for 1993–1994 suggests that the decline in yield was due to interactions between saline irrigation and prolonged heat wave events occurring during crop development. Further experimental work (1997) revealed that tuber yield was most sensitive to combined salt and heat stress when heat waves occurred at 40–60 days after emergence. The combined stress apparently leads to the collapse of mechanisms for avoiding salt accumulation in young expanding leaves, resulting in failure of vegetative growth recovery and a consequent reduction in the leaf area index and canopy functioning. The relationship between tuber sink demand and available photoassimilate supply at certain stages of plant development is discussed with reference to the ability of the potato plant to recover from the combined stress.

The effect of irrigation with saline water on several citrus genotypes was evaluated in a short-term field experiment. Salinity levels ranged from 2.0 to 6.4 dS.m(-1) Comparatively salt-tolerant Citrus species and Citrus x Poncirus hybrids were tested for their possible use as rootstocks for commercial citrus cultivars irrigated with brackish water. All the tested genotypes survived the highest salinities. At all salinity levels, the best chloride excluder was Cleopatra mandarin (Citrus reshni Hort, ex Tan.), and the worst was sour orange (C aurantium L,), Gou Tou Cheng (C. aurantium hybrid?) and Rangpur (C. limonia Osb.) x Troyer citrange (C. sinensis L. x Poncirus trifoliata L,) RT803 were found to be promising genotypes for further evaluation as rootstocks tolerant to high salinities. Rangpur was unsuitable because of foot rot.

Three commercial clones of jojoba (Simmondsia chinensis) (64, Q-106 and 879-154) were planted in June 1991 at the Ramat Negev Experimental Station (Israel) and fertigated with water at three salinity levels, 1.2, 3.4 or 6.2 dS m(-1). The effects of salinity over three and a half years on key metabolic activities, on plant growth and development, on flowering characteristics, and on yield were studied. Salinity barely inhibited the rate of net photosynthesis, although it did reduce stomatal conductivity by about 50%. Salinity also affected the water status of the plants by reducing water potential. Growth of the plants was not greatly affected by salinity. It was found that jojoba plants accumulate sodium and chloride ions in their leaves and use a strategy typical of many halophytes to cope with the salinity. The effect of salinity on flower development was also studied, since the vitality of flowers is a key factor in obtaining seeds. Salinity did not affect the timing of the breaking of flower bud dormancy in the 1992-93 season, although it did delay flower bud growth in clones Q-106 and 64. Salinity brought forward the flowering of clone 879-154 by about a fortnight in the 1993-94 season, but did not affect the flowering pattern of the other clones. Fruit set was not inhibited by salinity in the 1994 or 1995 season, and no significant effects were found on yield and wax content in 1994 season, but yield was reduced by salinity in the 1995 season.

Agrosoak®, a polyacrylamid (PAM) hydrophilic gel was tested as a soil conditioner for increasing the water absorbing capacity of sand dunes. This enabled the replacement of an expensive drip irrigation system with an inexpensive, more commonly used sprinkling method. Cabbage (Brassica oleraceae L.) was irrigated by sprinkling with double line-source technique to achieve different water amounts and salinity levels (1.9–7.8 dS·m−1), and with different concentrations of Agrosoak added to the soil (0.00, 0.15, 0.30, 0.45% by weight). Agrosoak increased water availability which indeed contributed to the increase in the yield of the crop irrigated with saline water. However, it was confirmed that this particular PAM enriched the soil solution with Na+ reducing the yield when irrigated with fresh water. The results indicated that Agrosoak may have increased the water use efficiency with plants grown on sandy soils when the crop is tolerant to Na+. The use of a modified type of PAM, that will not release sodium to the soil solution, is recommended.

The polyacrylamid (PAM) hydrophilic gel Agrosoak® was tested as a soil conditioner for improving water availability to crops grown on sand dunes. Corn (Zea mays L.) was grown in the field, in a factorial design array using four rates of Agrosoak (0.00, 0.15, 0.30, 0.45% by weight in the upper 25 cm of the soil), three water amounts (70, 85 and 100% of the recommended Class A evaporation pan ratio), and two water salinity levels (1.2 and 6.5 dS·m−1). Irrigation and fertilization were provided by trickling. The water storage capacity of the soil increased with the rate of Agrosoak but the applied water was accumulated and stored in the vicinity of the emitters leaving relatively dry sections between the drippers. This caused a reduction in the density of the plants. Even so, yield components, except shoot dry weight per meter (cob yield per plant and per meter, and shoot dry weight per plant) increased with the Agrosoak application rate. Concentrations of nitrogen and sodium in the leaves increased, but phosphate and potassium were unaffected by the Agrosoak application rate with the use of fresh water or brackish water. The use of Agrosoak did not avoid salinity damage to the plants. The results show that the use of trickle irrigation with PAM soil conditioner require a reevaluation of the method of irrigation.

Conventional sprinkler irrigation methods used in a Mediterranean desert climate include pre-irrigation to wet the rooting zone of the soil profile to field capacity, followed by light irrigation daily during the germination period, and thereafter by the irrigation schedule appropriate for the crop and season. When brackish water is used under the high-evaporation conditions of the desert summer, the light daily irrigations during the germination period result in rapid salinization of the seedbed and in very poor germination. However, in soils with high water infiltration rates, these problems can be averted by omitting pre-irrigation, and applying all the water thus saved for leaching of the seedbed during the germination period.