“…The natural factors influencing the spatial distribution of soil salinity include soil types (Fang et al, 2005;Yu et al, 2014), soil water content (Wu et al, 2014), geology (Sheng et al, 2010;Yu et al, 2014), climate (Nosetto et al, 2008), normalized difference vegetation index (NDVI) (Yahiaoui et al, 2015) and soil texture (Wang et al, 2012;Zhao et al, 2016). The anthropogenic factors include irrigation practices (Akramkhanov et al, 2011), drainage systems (Mirlas et al, 2012;Yu et al, 2015), groundwater table (Shah et al, 2011;Wu et al, 2014) and land use (Akramkhanov et al, 2011;Nosetto et al, 2013). It is widely established that using correlated influencing factors as auxiliary variables can improve the mapping accuracy of soil properties (Liu et al, 2006;Zhang et al, 2013).…”