Evaluation of the DAISY model for predicting nitrogen leaching in coarse-textured soils cropped with maize in the Mediterranean zone of Chile

The DAISY model (version 5.18) was evaluated for cultivated coarse-textured soils in the Mediterranean zone of central Chile. The model was field-tested using climate and soil data collected between 2011 and 2013 from four experimental sites with differing nitrogen (N) management regime, irrigation system and crop rotation: i) maize with furrow irrigation, mineral N fertilisation and fallow (site PM); ii) maize with furrow irrigation, pig slurry and fallow (PS); iii) maize with centre pivot irrigation, pig slurry and cover crop (SS); and iv) native annual prairie under rainfed conditions (SN). The model was statistically evaluated by comparing simulated and measured soil water content at different depths (25, 50 and 100 cm) and simulated and measured mineral N content in the topsoil layer (0-25 cm). In situ net N mineralisation and C:N ratio measurements were also used to evaluate simulated N dynamics. Observed and predicted water content at different depths was in satisfactory agreement. For the simulation period, the coefficient efficiency (E) ranged between 0.60 and 0.66 in PM; 0.53 and 0.92 in PS; 0.54 and 0.58 in SS; and 0.70 and 0.88 in SN. However, for topsoil mineral N content a broad range of E values was found, ranging from −0.93 to 0.81 for nitrate-N and from 0.36 to 0.77 for ammonium-N in the experimental plots. Sensitivity analysis showed that dispersivity was the most sensitive parameter in nitrate-N simulations. These results show that DAISY is applicable for predicting water and N dynamics in cultivated coarse-textured soils under Mediterranean conditions in central Chile.