Modeling water flow and nitrate-nitrogen transport on golf course under turfgrass

Golf courses are constructed from artificial layers on top of natural soil as the goal is to rapidly drain excess water through the soil profile using subsurface tile drainage system. Golf turf is one of the most intensively managed systems due to the high use of fertilizer and irrigation. Leaching and runoff of nitrogen (N) from turf can pollute surface- and groundwaters. Our objective was to understand the fate of water and nitrate-N in constructed golf course turf. We conducted a modeling study for system 1 with tile drainage and artificial soil layers and system 2 with a natural soil profile using HYDRUS 2D. Experimental data from a planned golf course in Istria, Croatia for natural soil were used. Artificial layers were constructed according to United States Golf Association (USGA) recommendations. Urea was used as the fertilizer N source at three application rates (50, 75, and 100 kg ha(-1)). Water flow modeling showed a large amount of tile drainage outflow in system 1, where tile drains aided in lowering the pressure head in the soil above the tile drains. In system 2, low permeability of the natural soil and lack of drainage resulted in lower pressure head in the topsoil with surface runoff during high rainfall. Results of solute simulations using HYDRUS 2D revealed that at 100 kg ha(-1) scenario, 66 % of ammonium-N, and 39 % of nitrate-N were leached through tile drains rather than infiltrate into the subsoil. The distribution of the nitrate-N was predominantly influenced by the highly permeable layers and tile drainage system. However, in the absence of drainage, modeling revealed that a large amount of nitrate-N can reach bottom of the soil profile and thus leach into groundwater. The modeling study revealed that using a USGA recommendation for golf course construction can reduce nitrate-N leaching into subsoil and consequently groundwater. The presence of tile drains provided a rapid conduit for transmission of water and nutrients (N species in this specific case), thus limiting infiltration of water and associated solutes into subsoil layers. Subsurface drainage systems are typically installed only on golf greens and not on the entire golf course area, while fertilizers are applied across entire golf course, which can lead to greater leaching of nitrate-N.