Nitrogen distribution and potential nitrate leaching in a combined ...

content in the willow zones of the small and large paddocks (Fig 9a). The mean Nmin contents
in the 0-25 cm and 25-75 cm soil layers in November are respectively more than 3 and 4
times higher in the willow zones of the small paddocks compared to the willow zones of the
large paddocks and the reference willow zones (Fig 9b). However, the means are not
significantly different. In the 0-25 cm soil layer, the mean Nmin of the SP willow zones was
significantly different from the other zones at 6 % level of significance. A high degree of
variation was found in the soil Nmin in November compared to the other two measuring
periods. In April 2010 the mean Nmin content was significantly higher in the willow zones of
the small paddocks, in the 0-25cm and 25-75cm soil layers compared to the other willow
zones (Fig.9c). In the same soil layers there was no significant difference between the large
willow zones and the reference willow zones.
To sum up, the Nmin contents were in most cases not significantly different between the
willow reference zones and contents in the soil of the large paddocks. Nmin contents varied
considerably in the willow zones in November 2009.
3.3 Nitrogen balance
3.3.1 Water balance and potential nitrate leaching
Figure 10 illustrates the COUP simulation of the percolation in the soil of the willow
reference area.
Percolation
(mm/day)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1/1/2009 5/1/2009 9/1/2009 1/1/2010 5/1/2010 9/1/2010
Figure 10 Simulation of the soil water percolation (mm/day) from the willow reference area from January 2009
to late August 2010
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