Mathematical modeling of water fluxes in arable chernozems under different land use

Abstract

The hydrologic regimes of arable chernozems were simulated for two plots located within a watershed. For the last fifty years continuous corn monoculture was practiced in one plot, and permanent bare fallow was practiced in the other plot. Carbonates are detected from a depth of 140–160 cm under corn and from 70–80 cm under bare fallow. The objective of the simulation study was to test the validity of the hypothesis that the shallower depth to carbonates under bare fallow is related to carbonate rise due to changes in the hydrologic regime of bare soil compared to soil under vegetation. Mathematical modeling using the HYDRUS-1D software and the FAO56 method confirmed that the hydrologic regimes of arable chernozems within the two plots are different. The soil water content under bare fallow is generally higher than that under corn. The downward soil water fluxes for the two plots are comparable. The upward soil water fluxes under bare fallow significantly exceed those under corn and affect a thicker soil layer. The changes in the hydrologic regimes of chernozems under bare fallow favor the upward movement of carbonates through both the direct transfer by upward water fluxes and the diffusion of ions.