Adaptation of the STICS model to subsurface drained soils

The generic crop model STICS was modified to take into account shallow water-table fluctuations and subsurface drainage in the context of French waterlogged soils. This was accomplished by incorporating a subsurface drainage component into STICS code. The SIDRA (Simulation du Drainage) model was adapted to a daily time-step. For the dimensional aspect, the passage from two-dimensional drainage functioning to STICS one-dimensional conceptualization is done by taking an average water elevation between drain and mid-drain spacing. Simulation performances of the new STICS were evaluated by comparing its predictions with six years (1979-1983 and 1985-1986) of measured data from the field experiment of Arrou, located in northern France. Comparisons of STICS predictions with the measurements of drain-flow rates, total drained volumes and depths to water table for different crops and drain spacings were satisfactory. Nevertheless, the performances were better for drain spacings of less than 20 m and for winter crops or covers.