Spatiotemporal changes in soil salinity in a drip-irrigated field

We explored the spatiotemporal variability in soil salinity using in situ data of soil electrical conductivity (EC) sampled on six dates in 2007 in a drip-irrigated cotton field. Descriptive statistics and geostatistics were used to analyze the data, and the kriging method was applied to map the spatial patterns of EC. The results showed that EC was negatively correlated with cotton yield (p < 0.01) and was the key limiting factor for cotton growth under the drip irrigation system. Mean EC increased during the pre-irrigation period and decreased in the drip-irrigation stages. The coefficient of variation (CVi) showed an increasing trend from 45.2 to 64.5%. In the cotton growth stages, the effective ranges of spatial correlation generally decreased from 138.84 to 102.76 m. The six smoothed contour maps displayed quite similar patterns, with high salinity in the eastern and southern sections and low salinity in the western and northern sections of the study area. The topography and climate highly influenced the spatiotemporal variability of soil salinity. The widespread practices of plastic film mulching, organic matter and drip irrigation also affect soil salinity. The use of saline groundwater for irrigation requires that surface soil salinity be controlled by leaching and draining excess water and salt. While cotton can be safely planted in this region, other crops with low thresholds of salinity tolerance cannot be planted in early spring until the surface salinity level decreases.