A new experimental design reveals the impacts of land use and irrigation characteristics on bromide leaching

The impact of different land use systems and rainfall characteristics on water and solute transport has not been the subject of many studies. One challenge in solute leaching experi- ments is the high natural spatial variability of flow-controlling soil properties. To overcome this limitation and reveal the impacts and relative influences of land use (either grassland or cropland), irrigation amount and intensity, and application time delay on water infiltration and solute leaching, a field-scale leaching experiment was conducted where treatments were arranged in a repetitive patiern along a transect. This design approach permitied spatial vari- ation scale analysis and frequency domain analysis of variance components. The experiment was evaluated in terms of changes in the soil matric potential and in the infiltration depth of the applied tracer (KBr). The results gave evidence that water infiltration was mainly con- trolled by the amount of water and to a smaller extend by the land use with a larger increase in soil water content on the cropland. Contrarily, solute leaching was mainly controlled by the land use with a larger infiltration depth on the cropland. The relative influences of irriga- tion amount and intensity were smaller. Irrigation intensity and application time delay were negatively correlated with leaching depth, indicating a decreasing risk for deep leaching with increasing time between solute application and rainfall. The presented experimental design may be highly useful to overcome limitations resulting from the high spatial variability of physical soil properties when studying field-scale hydrological and transport phenomena.