THE IMPACT OF VEGETATION AND ANTECEDENT SOIL WATER CONTENT ON INFILTRATION
Lichner, L.1, Niznanska, Z.1, Hallett, P.D.2, Sir, M.3, Tesar, M.3
1Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 931 02 Bratislava, Slovakia.
Email: lichner@uh.savba.sk, niznanska@uh.savba.sk
2Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, United Kingdom. Email:
Paul.Hallett@scri.ac.uk
3Institute of Hydrodynamics, Academy of Sciences of CR, Pod Patankou 5, 166 12 Praha, Czech
Republic. E-mail: milo_sir@yahoo.com, miroslav.tesar@iol.cz
Various studies have shown that soil water repellency is influenced by vegetation and varies spatially,
primarily due to shifts in soil water content and the deposition of organic compounds throughout the
season. The objective of this study was to assess an impact of vegetation and antecedent soil water
content on infiltration into soil. Two sites with similar soil properties but different surface vegetation at
the locality Mlaky II near Sekule (southwest Slovakia) were selected (Table 1). The soil type is a
Regosol (WRB, 1994) with a loamy-sand texture (Soil Survey Division Staff, 1993). The impact on
water transport was characterized by the hydraulic conductivity and sorptivity measured using a mini
disk infiltrometer (Decagon Devices, Inc.) at a suction rate of –2 cm.
Table 1: Physical and chemical properties of the soil samples taken two sites at Mlaky II near Sekule
(southwest Slovakia).
Vegetation
Sand (%)
Silt (%)
Clay (%)
CaCO3 (%)
C (%)
pH(H2O)
pH(KCl)
Grass
91.3
2.81
5.93
<0.050
0.640
5.55
4.20
Moss
94.1
0.84
5.02
<0.050
0.110
5.52
3.96
The persistence of water repellency was measured using the water drop penetration time (WDPT)
test. The index of water repellency R was calculated from (Hallett & Young, 1999):
R = 1.95 Se / Sw
(1)
where Se and Sw are 95% etanol and water sorptivity measured at a suction rate of –2 cm,
respectively.
There were much smaller values of both the unsaturated hydraulic conductivity k(–2 cm) and water
sorptivity Sw for soil under a grass meadow than moss. However, 95% ethanol sorptivity was not very
different (1.3 times smaller under grass compared to moss), suggesting that water repellency was
responsible for the differences measured. The water drop penetration time tp was 16.4 times greater,
and index of water repellency R was 2.9 times greater under grass compared to moss. These findings
suggest a strong influence of surface vegetation, which is likely a product of the level of carbon in the
soil, which is 6 times higher under grass compared to moss (Table 1). Further research will investigate
the concentration of amphiphilic compounds (from the root exudates, decomposition of thatch, and
dead roots) produced by the plants. The hydraulic conductivity k(–2 cm) rose with an increase in
antecedent soil water content, and declined with an increase in water drop penetration time at both
sites.
Keywords: water repellency, soil, plant cover, hydraulic conductivity, sorptivity
References:
Hallett, P.D., Young, I.M., 1999: Changes to water repellence of soil aggregates caused by substrateinduced microbial activity. Eur. J. Soil Sci., 50: 35–40.
Soil Survey Division Staff, 1993: Soil survey manual. Soil Conservation Service. U.S. Department of
Agriculture Handbook 18, 437 p.
WRB (1994): World Reference Base for Soil Resources. Wageningen/Rome, 161 p.