Numerical simulation of water and nitrogen transport in three turfgrass systems

Abstract

The relative contributions to N leaching in turfgrass systems from over irrigation, over fertilization, N form, and soil texture, require characterization. In this study, water transport parameters were calibrated using an inverse simulation with a Kentucky bluegrass landscape. Subsequently those parameters were applied to simulate water use by tall fescue and buffalograss turfgrasses using numerical modeling. Using the calibrated soil hydraulic parameters obtained from the water transport simulation, N transport and transformation was modeled with Hydrus-1D. A variable boundary condition was used to describe irrigation and fertilization schedules, including the composition of applied fertilizer and the estimated N content of returned turf clippings. Numerical simulations using multiple fertilization events at two rates (1X, 2X) of actual applied fertilizer (2010) and three irrigation levels (1X, 1.5X, and 2X) of optimized irrigation amounts (2010), and a quick-release fertilization with 1X irrigation for each turfgrass species were used to compare N leaching from the root zone. To demonstrate the influence of soil texture on N leaching, three different soil textures were also simulated. Simulation results showed that over irrigation was the main contributing factor to NO 3 -N leaching and that soil texture also affected NO 3 -N leaching rate significantly. However, N form or over fertilization alone, without over irrigation, did not affect NO 3 -N leaching in turf.