Sodicity, conventional drainage and bio-drainage in Israel

Abstract

Years of intensive irrigated farming in the inland valleys of northern Israel have caused secondary salinity in vast areas. Soil salinity/sodicity surveys, conducted after the problem was recognised, showed relatively high levels of sodium adsorption ratio (SAR) in the active soil layers. In a sample of 7 affected fields, 92.5% of the 1584 SAR measurements on cored soil samples had values >5, and 39% had values >15. Two ameliorative approaches were conceived to reverse the evident salinity/sodicity trends in the Yizre’el Valley: (a) a gravitational, newly engineered, subsurface drainage system; and (b) bio-drainage, using eucalypts as a means to control the high water tables. Both approaches were very successful according to the chosen criteria. The drainage system, comprising 3 drain components, effectively controlled excess water from 3 sources: direct infiltration, lateral subsurface flow, and a deep, presumably upward-seeping, artesian aquifer. The groundwater table response to the installation of the applied drainage system was immediate. In the next rainy season, there was an associated and appreciable deep leaching of Cl– and somewhat less of Na+. More than 3000 ha of land has been drained in this way in the past 10 years in the northern, salinity-prone, inland valleys. The bio-drainage approach, tested in 5 different waterlogged and salinity-affected sites in the Yizre’el Valley, also proved very successful. The rates of growth of Eucalyptus camaldulensis provenances was impressive from the first year. In the best plot, in the fifth year, biomass production reached 30 t/ha.year for the Broken-Hill ecotype (NSW) and peaked at 57 t/ha.year for the Hadera (Israel) ecotype. The annual transpiration of selected trees at Nahalal was 1360 mm, or 3 times the local average annual precipitation. The groundwater table dropped to below 3 m in the summer of the fifth year—sufficient to provide saltflushing conditions. In a related study at the Nahalal site, it was demonstrated that E. camaldulensis screens out the salts while consuming soil water. That, coupled with prolonged stresses of salinity and flooding, can be detrimental to eucalypts. In conclusion, despite sodic conditions, which are ‘formal’ by definition and which prevail in much of the area of our northern valleys, drainage, whether conventional or biological, if well-designed and implemented, is a viable means for controlling local hydrology and restraining salinitysodicity trends.

Hydrological and salinity impacts of a bio‐drainage strategy application in the Yizre'el Valley, Israel

“…A moderate reduction in SAR (to around 3 dS m 1 ) was noted in all layers below the 60-90 cm stratum. These relatively very low SAR values of the heavy, very clayey valley soil are an exception to the norm (Gafni et al, 1991a;Gafni and Salinger, 1992;Gafni and Zohar, 2001). At Nahalal, the lack of temporal changes in SAR below 60 cm indicates the permanence of the waterlogged conditions, as manifested in the persistently high water table (Figure 3).…”

“…This is expressed in the similarity of the water table hydrographs within and outside the plots ( Figure 3); during most of the year the water table was within 1 m of the soil surface, though it was somewhat deeper inside the plot, possibly because of the water uptake by the trees. The plantation enjoys practically unlimited inflows of relatively low-salinity water, which support the tree growth and are responsible for the record biomass yield of many of the trees (Gafni and Zohar, 2001).…”

“…Moderate to severe salinization in various locales in the irrigated Yizre'el Valley, northern Israel, detected since the mid 1980s, has triggered an extensive research effort to trace the causes of the waterlogging and salinization, and to devise strategies to reverse the phenomenon (Gev, 1989;Gafni and Salinger, 1992;Schein and Livne, 1998;Gafni and Zohar, 2001). A salinity survey in the Yizre'el Valley revealed 1500 ha of lands affected by salinity, of which 800 ha were already in advanced stages of salinization and sodicity (Gafni, 1992).…”

“…It was soon realized that a prerequisite for any preventive action was to stop and reverse the steady rise of the shallow groundwater. A threecomponent gravitational drainage system was conceived, tested and then widely applied throughout the cultivated valleys in Israel, and it proved highly successful (Gafni et al, 1991b;Schein and Livne, 1998;Gafni and Zohar, 2001). Nonetheless, the steady decline in returns from field cropping in Israel and the lack of a government subsidy have combined to render conventional drainage economically unjustified.…”

Review and Case Studies on Biodrainage: An Alternative Drainage System to Manage Waterlogging and Salinity

“…The rate of fall of groundwater tables doubled with the development of the trees (Rodríguez‐Suárez ). It has been demonstrated that under ideal conditions, the consumptive use of trees varies between 6500 and 28 000 m 3 ha ‐1 yr ‐1 and a tree canopy may lower water tables by 1–2 m over a period of 3–5 years (National Institute of Hydrology (NIH) ; Gafni and Zohar ; Kapoor ; Heuperman et al ). For biodrainage, of the different trees, Eucalyptus has been used the most for this purpose because of its luxurious water consumption (Dong et al ).…”