Soil salt distribution under mulched drip irrigation in an arid area of northwestern China

•Soil salinity distribution under mulched drip irrigation has been explored.•Salt will accumulate above finer particle layer under mulched drip irrigation.•Soil particle size distribution has great impact on soil salt distribution.•Salt decreases beneath the drip pipe and accumulates in the inter-film zone.•Surface salinity distribution is dominated by mulched drip irrigation.

Mulched drip irrigation (MDI) has now become popular in arid and semi-arid areas, under which, however, salts are likely to build up in the surface soil due to deficient leaching water. To explore this new kind of secondary salinization issue, a 3-year experiment was conducted in an arid area in Xinjiang, northwestern China from 2008 to 2011. Over 15,000 soil samples were collected during the experimental years. The patterns of soil salinity distribution under MDI along the horizontal direction as well as vertical direction have been explored. Our results indicate that soil particle size distribution has great impact on soil salt migration and distribution. The salt will build up above the relatively impermeable layer along the soil profile. The zone below drip pipe obtains the lowest salinity level and the salt accumulates in the inter-film zone at the end of growth period. The salinity in the inter-film zone is 1.24–2.34 times the value in the zone below drip pipe within 50 cm soil depth, according to the soil texture. Furthermore, our analysis suggests that surface salinity distribution is dominated by MDI while the influence of MDI on salinity distribution is decreasing with the downward distance from ground surface.