Simulations of water flow and nitrate transport in field lysimeters installed on gley soils

Nitrogen fertilizers, which cannot be completely absorbed by plants, are frequently used on agricultural soils in large amounts, and therefore leaching, usually closely linked with the soil water flow, is likely to occur. As computer models are becoming more important in the assessment of groundwater pollution, the objectives of this research were to assess water flow and nitrate transport in gley soils and to validate the HYDRUS-1D model based on the collected field data from lysimeters installed at the Biđ field (12 lysimeters at 6 locations). Extensive measurements of soil physical properties, lysimeter outflow and nitrate concentration were performed and coupled with the climatic data and collected information about the crop rotation and fertilizer application. The results confirmed good reliability of the model that fit the observed lysimeter water outflow and nitrate dynamics during 2014-2016 period. Increased nitrate concentrations were mostly observed during the period without crops, or during the winter/spring period with a large amount of rainfall. The results suggest that groundwater nitrate concentration may significantly increase due to agricultural practices, even in soils with heavier texture. The results also show that the tested model can be used as a tool for the prevention of groundwater pollution by indicating optimal application of different fertilizer (amount, timing, type).