Effects of four cultivation systems for maize on nitrogen leaching. 2. Model simulation.

摘要

The GLEAMS simulation model (version 2.03) was used to analyse the effects on N leaching of 4 cropping systems studied on the Venetian Plain, NE Italy. The four systems were: (a) a 3-year rotation (barley-soyabeans/silage maize/ryegrass [Lolium]-silage maize) with high inputs of pesticides, chemical N fertilizer and liquid manure; (b) a 3-year rotation (maize/maize/soyabeans) with high inputs of pesticides and chemical N fertilizer; (c) a 7-year rotation (maize/wheat/sugarbeet/rye-maize/lucerne [Medicago sativa]/lucerne/lucerne) with low inputs of chemical N fertilizer and manure and post-emergence herbicides and use of cover crops; and (d) a 7-year rotation (flint maize/sugarbeet/wheat/rye-tomatoes/lucerne/lucerne/lucerne) with low inputs of manure and no chemical fertilizers or pesticides. On the basis of a first test it was found necessary to introduce into the model a subroutine to represent the phenomenon of crack flow (water movement through soil cracks). The modified model (GLEAMS-CF), tested on the experimental data, demonstrated better capability of simulating the field water balance and N leaching and was therefore used to simulate the most probable long-term N leaching that would occur in the various cultivation systems. This was doneusing a 100-year record created using a climate simulator. This exercise revealed a wide variation in N leaching caused by the four different cultivation systems studied. Average simulated N leaching in the four systems was: (a) 85 kg ha-1 year-1; (b) 42 kg; (c) 20.4; and (d) 19.8.