Biological drainage characteristics of alakalized desert soils in north-western China

Years of intensive irrigated farming in the Oasis area of Xinjiang in north-western China has caused secondary salinization of vast areas of land since the mid 1980s. Soil salinity/sodicity surveys in the area, conducted after the problem surfaced, showed relatively high levels of the sodium adsorption ratio (SAR) in the upper soil layers. In one. study, 92% of cored soil samples of the affected fields showed SAR values above 5, while 42% had values above 15. One ameliorative approach, bio-drainage using different desert vegetations, was used to control the high water-tables and reverse the observed salinity/sodicity trends in the border area of the Manas Alluvial Fan. The ground-water table dropped to below 2.28 m in the summer of the fifth year, which was sufficient to prevent secondary salinization. A related plot study showed that Lycium barbarum and Puccinellia Chinamponsis consumed large amounts of soil water while leaving most of the salts behind. The salt contents of leaves and young branches were different for different vegetation. Soil profile salt distributions for the deep-rooted and shallow-rooted systems were different in two of the three years after planting. Commercial forestry of L. barbarum and other timber products under current conditions, and without irrigation, appears a viable agricultural alternative that could bring higher returns than for wheat or cotton. Results of this study indicate that both conventional and biological drainage are attractive options for controlling the local hydrology and limiting or diminishing salinity-sodicity trends. (C) 2003 Elsevier Science Ltd. All rights reserved