Preliminary Study on the Effects of Saline Water Irrigation on Soil Salinization in Deep Groundwater Area:A case study of Minqin oasis

Massive exploitation of underground water in Minqing oasis in recent decades caused a sharp decline in groundwater level,and underground salt water is still being mined for agricultural irrigation.The present study investigates the effects of salt water irrigation on soil salinity in the deep groundwater zone by using the field experiment.The salt from irrigation water is the main source of salt accumulated in soil surface of areas where groundwater table is very deep and saline water is used for agricultural irrigation.During the process of saline water irrigation,soil salinity of the root zone increased rapidly after previous fresh water leaching process.High salt concentration of the irrigation water leads to a significant increase of soil salinity in the soil.The rate of salt accumulation were 22.67% and 35.30% under 2 g·L-1 and 5 g·L-1 saline water irrigation respectively.Referring to sweet melon planted with high ridge and film mulching,the soil salt is leached significantly under film-furrow irrigation.However,due to the field partially covered by film mulching,uncovered soil encounters a strong evaporation which results in salt accumulation.Saline water irrigation increases pH value and enhances soil Exchangeable Sodium Percentage(ESP),especially when the salinity of irrigation water is 5 g·L-1.The ESP value is 5.7 in plough layer and soil shows slight alkalization when 5 g·L-1 salt water is used.