Non-uniform Distribution of Soil Salinity Along a Transect of an Irrigation Field in an Arid Region

抄録

We assessed soil salinity at field scale and suggested appropriate water and salt management practices for an arid region. Specifically, we focused on non-uniform salinity distribution along a transect in a research field. We also examined factors affecting the distribution of salt, including irrigation, drainage and salt movement. The non-uniform salinity distribution across the field was probably formed by irrigation management and distance from main drainage channel, while the effect of soil physical properties and groundwater was limited. The main drainage channel functioned well during the past irrigation period when abundant Karez water was available for leaching irrigation, and this contributed to the present non-uniform salinity distribution. Currently, farmers use less irrigation water, which does not promote desalinization. Vertical movement of soluble salts near the soil surface was dominated by irrigation management. Border irrigation promotes desalinization but drip irrigation enhances salt accumulation, with salinity increasing after irrigation because of high evaporation rates in the hyperarid climate. Based on these results, we explained the following points to local farmers in non-technical language: 1) a drainage channel is important for desalinization but the current channel is no longer sufficient to discharge salt from the field; 2) drip irrigation is effective for deficit irrigation but it enhances salt accumulation; 3) border irrigation has a positive effect on salt leaching from surface layers but the leached salt returns to the surface after irrigation ceases; and 4) there are high salinity layers below 60 cm soil depth, distributed widely across the fields.