poster - International Conference of Agricultural Engineering

4. Results and discussion
4.1. Spatial distribution of soil moisture content
Figure 5 shows the spatial distribution of soil moisture content measured by sampling soil 3
hours after the beginning of the wind flow at the points shown. The soil moisture content at
the upwind dry portion was lower than that found downwind. Soil water loss by soil surface
evaporation was prevented because of the interception of wind flow by the crop model body.
At the wet portion, the soil moisture content at the shallow layer was lower than that at the
deep layer.
Depth(m)
0.00
0.05
0.10
0.15
0.20
Fetch(m)
0.2 0.4 0.6 0.8
Volumetric water
content(%)
30
25
20
15
10
5
0
FIGURE 5: Spatial distribution of soil moisture content
4.2 Model accuracy
Figure 6 shows the comparison of the simulated and observed volumetric water content 3
hours after the beginning of the wind flow. At the upwind dry portion, the volumetric water
content was constant. The volumetric water content at the wet portion increased gradually as
the fetch increased and reached a peak. After peak, the volumetric water content decreased
gradually.
At the upwind edge of the wet portion, the volumetric water was low because the soil water
moved to the upwind dry portion. Soil water was lost due to increased soil surface
evaporation caused by the relatively dry airflow from the upwind dry portions. The gradual
decrease of the soil moisture content after peak in the wet portion occurred because dry air
from the dry portions mixed with the relatively humid air in the wet portions. Downwind of the
dry portion, the volumetric water content decreased abruptly and reached a constant value.
The simulated volumetric water content reproduced the variation of the soil moisture content.
25
Volumetric water content (%)
20
15
10
5
Simulation
Observation
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Fetch (m)
FIGURE 6: Comparison of the simulated and observed volumetric water content 3 hours
after the beginning of the wind flow