Spatio-Temporal Dynamics of Soil Salt under Saline Irrigation in Taklimakan Desert Artificial Shelterbelt

Abstract

Irrigation with saline water is in risk of soil salinity, which is a major threat for plant growth since salinity stored within the root zone. To determine the effects of saline irrigation on soil salinity, an experiment was carried out at the artificial shelterbelt in Taklimakan Desert Highway to examine soil salinity under different salt concentration irrigation. The rationale for conducting this study was to understand the movement for salinity in soil profile under saline irrigation. The results showed that topsoil (0-5 cm) salinity was greatly correlated with the mineralization of irrigation water, at temporal scale. During an irrigation cycle, the topsoil salinity increased at first four days, the largest soil salinity presented at the 4th day (11.7 dS m-1), and then presented a decreasing trend at the last ten days, while at the under layers (5-210 cm), soil salts were great less than the topsoil, and presented a decreasing trend within an irrigation cycle. During a growing season, topsoil salts presented a unimodal distribution under higher salinity irrigation (28 g L-1), from Apr to Jul it presented a rising trend, and then presented a decreasing trend to Oct, and the larger salinity presented from Jun to Aug, this phenomenon because great higher evaporation during Jun to Aug which lead to upward flux exceeding downward flux, while soil salinity did not change much throughout the soil profile of 5 cm to 200 cm. Yearly dynamics for topsoil salinity presented an increasing trend with the irrigation years, and also changed little at the under layers (5 cm to 210 cm) from 2002 to 2008. The spatial or profile distribution for soil salt showed salt not only accumulated at the topsoil, but also leached to the under layers (130 to 280 cm) and ground water (410 cm), but no salinity at the root zone(5 to 130 cm). These results documented that even with saline irrigation in Taklimakan Desert Highway artificial shelterbelt; it will lead no sodality for plants, since the content of soil salt at root zone was small (about 0.4 dS m-1). Therefore, saline groundwater should be used for protecting the Taklimakan Desert Highway. However, the impact of long-term irrigation with such salinity groundwater for vegetation should not be ignored; low saline water and also limiting irrigation quantities and frequency should be considered in future.