Changes in Water and Solute Fluxes in the Vadose Zone after Switching Crops.

Switching crop type and therefore changing irrigation and fertilization regimes lead to alternation in deep percolation and concentrations of solutes in pore water. Changes of fluxes of water, chloride and nitrate under a commercial greenhouse due to a change from tomato to green spices were observed. The site, located above the southern Mediterranean coastal aquifer of Israel, was monitored for the last four years. A vadose-zone monitoring system (VMS) was implemented under the greenhouse and provided continuous data on both the temporal variation in water content and the chemical composition of pore water at multiple depths in the deep vadose zone (~20 m). Chloride and nitrate profiles, before and after the crop type switching, indicate on a clear alternation in soil water solutes concentrations. A one dimensional unsaturated water flow and chloride transport model was calibrated to transient deep vadose zone data. A comparison between the simulation results under each of the surface boundary conditions of the vegetables and spices cultivation regime, clearly show a distinct alternation in the quantity and quality of groundwater recharge.