How Does Saline Water Irrigation Affect Soil Development and Plant Growth in the Taklimakan Desert Highway Shelterbelt

Water scarcity is a world-wide problem, especially in desert ecosystems. To overcome this shortage, saline groundwater is increasingly being used, although it has risks of increasing soil salinity and causing plant salt toxicity. The Taklimakan Desert Highway distances 556 km and traverses through the Taklimakan Desert, the largest mobile sandy desert in the China. For reducing wind erosion and keeps the highway from being blocked by sand, the artificial shelterbelt was completed in 2005.

To investigate the effects of saline water irrigation on soil properties and plant growth along the Taklimakan Desert Highway shelterbelt, the researchers selected seven sampling sites with differences in groundwater salinity (3.6–26.2 g L^-1) and sampled five times at each site using an auger at eight soil depths of 0–5, 5–10, 10–20, 20–30, 30–40, 40–60, 60–80 and 80–100 cm. They also investigated the plant roots of three species, Haloxylon, Tamarix and Calligonum.

The results showed that soil salts (about 8 mS cm^-1) and nutrients significantly accumulated at the soil surface (crust and 0–10 cm soil layers) with saline irrigation, but the soil salinization did not increase (<1.0 mS cm^-1) within the 40–60 cm soil depth where abundant lateral roots also germinated and extended horizontally. While the deepest main root system was 200 cm for Tamarix, it extended to about 150 cm for other two species studied (Haloxylon and Calligonum). More than 87% of the biomass of the lateral roots was present in the 20–80 cm soil depths for the three species; although no active absorbing roots were found within the 0–10 cm soil depths where the salts had accumulated.

These findings indicated that saline water irrigation within artificial shelterbelts may be beneficial for soil nutrient accumulation and accentuates the potential uses of these sandy soils. After 7-yrs irrigation with nutrient accumulation, structured soil under shelterbelt has progressively formed, as indicated by increased soil aggregate size and stability. Saline water irrigation did not influence the normal growth of adaptive plants, which may be attributed to the plant adaptability to salt stress through root morphology adjustment.

The results suggests saline groundwater irrigation offers potential advantages and opportunities for plant growth on sandy soils evolution in a desert environment where saline groundwater is the sole water resource for plants. The study was published online in Soil and Tillage Research in May 2014.