engleski

Estimation of preferential flow in agricultural soil using dye tracer and numerical simulations

The appearance and distribution of soil pores have a significant influence on water flow and solute transport in the soil vadose zone and are easily affected by tillage, trafficking, crop rotation, and various management practices in arable areas. Pore geometry in the soil is highly variable, especially in agricultural soils due to various management. Such heterogeneity can have a considerable influence on water and solute transport within the soil vadose zone. The aim of this study was to assess preferential flow pathways in agricultural soil. To quantify structure, undisturbed soil columns were taken on which outflow experiments using water and Brilliant Blue tracer were applied. Soil hydraulic parameters (SHP) were estimated on undisturbed soil cores (250 cm3) using the simplified evaporation method and the HYPROP automatized system. HYDRUS-1D numerical modeling was performed using single and dual-permeability models. In the latter, the Richards equation is applied separately to two overlapping pore regions – the macropore and matrix domains. A dual-permeability model is used because the extensive macropore network was revealed and due to its ability to differentiate flows in soil macropore and matrix regions. The use of the dual-permeability model resulted in a faster response of outflow to irrigation and higher outflow rate peaks. Dye distribution was uneven because of enhanced dye penetration along biopores and in regions with a higher fraction of larger interaggregate pores formed in the root zone. Simplified single porosity model could not reproduce deeper staining patterns (e.g., below 15 cm depth). Modeling of the transport of Brilliant Blue dye revealed the necessity of using dual-region transport models to capture non-equilibrium flow patterns in agricultural soils with complex pore systems.

dye staining ; numerical modeling ; HYDRUS ; dual-permeability model ; preferential pathways ; vadose zone

nije evidentirano