EFFECTS OF 4 CULTIVATION SYSTEMS FOR MAIZE ON NITROGEN LEACHING .2. MODEL SIMULATION

The GLEAMS simulation model (version 2.03) was used to analyse the exp erimental results presented in M. Borin et al., 1996 (M. Borin, C. Giu pponi and F. Moran, 1996. Effects of four cultivation systems for maiz e crop on nitrogen leaching in shallow water. 1. Field experiment. Eur . J. Agron., 5: 295-306) and to derive useful indications on the envir onmental impacts of the four maize cultivation systems. On the basis o f a first test it was found necessary to introduce in the model a subr outine to represent the phenomenon of crack flow (water movement throu gh soil cracks). The modified model (GLEAMS-CF), tested on the experim ental data, demonstrated better capability of simulating the held wate r balance and the nitrogen leaching and was therefore used to simulate the most probable long-term nitrogen leaching that would occur in the various cultivation systems. This was done using a 100-year record cr eated using a climate simulator. This exercise revealed a wide variati on in nitrogen leaching caused by the four different cultivation syste ms studied. Average simulated nitrogen leaching in the four systems we re: 85 (system A), 42 (system B), 20.4 (system C) and 19.8 kg ha(-1) y ear(-1) (system D). (C) 1997 Elsevier Science B.V.