Hydrological Separation of Event and Pre-event Soil Water in a Cultivated Landscape

Soil water mixing is a complex process that is dependent on vegetation, soil physiochemical characteristics, and climate. In this research, we utilize natural tracers, delta O-1(8) and delta H-2, to determine if hydrological separation of recent precipitation event and pre-event water occurred within the soil profile of a maize field in central Ohio. Soil samples were collected at three sites and four depths, and the soil water was extracted via cryogenic distillation. Soil water isotopic composition showed mixing of precipitation event and pre-event water that reflected weighted average precipitation isotopic composition. The range in isotopic signatures also indicated that hydrological mixing within the soil profile was facilitated by soil physical characteristics and effective gravitational drainage of event water. These results support previous work that hydrological separation does not occur in soil water in temperate climates and contribute to ongoing research to conceptualize soil water cycling in monoculture systems.