Sodic Soil Toposequence Related to Focused Water Flow

Abstract

AbstractPresent concepts of sodic soil formation do not adequately account for observed variability of sodic soil properties on many landscapes in North Dakota. A conceptual model was developed to explain sodic soil genesis related to water and salt movement on a coarse‐loamy till landscape in central North Dakota. The relationship between subsurface water flow and sodic soils was determined by monitoring soil water using neutron attenuation and water wells at three contiguous landform positions. Electrical conductivity, major ions, and water‐dispersible clay were determined on extracts from selected soil samples from each landform position. Typic Argiaquolls, characterized by low salinity (electrical conductivity [EC] < 2.0 dS/m), occurred at the wetland position and were areas of recharge to groundwater. Typic Natraquolls also occurred at the wetland position but were characterized by high salinity (EC > 5.0 dS/m) and were areas of groundwater discharge. Udic and Leptic Natriborolls were areas of groundwater discharge at the intermediate and upland positions. Udic Haploborolls were hydrologically inactive areas at the upland position. Variations in sodic soil development were attributed to the concentration of water flow (focused flow) into specific areas of groundwater discharge or recharge. The most important factors that affected the direction and intensity of focused flow were stratigraphy and landform position.