FACTORS INFLUENCING WATER STRESS SPATIAL VARIABILITY AT FIELD SCALE
Tomáš Orfánus1, Viliam Novák1, Josef Eitzinger2
of hydrology, Slovak Academy of Sciences, Račianska 75, 83102 Bratislava,
Slovakia, orfanus@uh.savba.sk
2 Institute of Meteorology, University of Natural Resources and Applied Life Sciences, Vienna,
Peter Jordan Straße 82, 1190 Vienna, Austria
1Institute
Abstract
There are many factors influencing availability of soil water to vegetation and are active at
various spatial and temporal scales. Disregarding direct human in- or outputs of water, the
most important factors, which determine the spatial variability of soil water content (SWC) in
agricultural ecosystems are meteorological conditions, plant canopy properties, soil
hydrophysical properties, groundwater dynamics, relief and different landscape constituents
such as roads, hedgerows or biocorridors.
The relative changes in soil water content for nearby locations can be expected similar but in
alluvial areas the soil physical properties can change dramatically over small distances
(Orfánus et al., 2008) and the presence of landscape structures, like hedgerows (Eitzinger et
al., 2009) also influence the spatial distribution of SWC significantly. The joint effect of soil
properties and atmospheric conditions on water stress occurrence can be defined by the critical
value of SWC of limited availability la, which characterizes an average SWC of the soil root
zone layer; below it transpiration rate and biomass production start to decrease.
Results of two field studies show the effect of soil texture spatial variability and potential
evapotranspiration temporal and spatial variability on water stress threshold values ( la) at field
scale.
The research was focused on trans-boundary region with semi-arid climate, which covers
Záhorská lowland in south-western Slovakia and Marchfeld in north-eastern Austria. Intensive
soil sampling and estimation of soil hydrophysical characteristics were performed in April 2002
on a 4,5 ha field near Moravský Sv. Ján village in S-E Slovakia to study the influence of
different soil types on areal distribution of SWC. Calculations of maize-evapotranspiration were
performed with the mathematical model with evapotranspiration submodel based on modified
Penman-Monteith equation for the following vegetation season to determine the possible range
of la values over the vegetation season in texturally heterogeneous field (Fig. 1). la was
calculated according to empirical equations 1 – 3 (Novák and Havrila, 2006).
 k1   la 
1

 k 2
(1)
k2 = 0,67. WP
(2)
 = - 2,27. Etp + 17,5
(3)
where k1 , k2 are the so called „critical“ SWCs indicating the beginning and the end of the
transpiration decrease rate range, WP is the SWC of the permanent wilting point. Coefficient 
depends on the potential evapotranspiration rate Etp.
The la values strongly depend on both, the transpiration rate and the textural heterogeneity of
soil (variability of SWC related to wilting point). Values of calculated la ranged between 19 and
34% in clay loam soil when the transpiration was the highest calculated (5,1 mm / day) and in
the range from 9 to 25% of vol. when the evapotranspiration was low (0,97 mm / day). In case
of loam-sandy soil the corresponding intervals of la for the same evapotranspiration rates were
16 – 25% and 6,6 –15% of vol., respectively (Fig. 1).
E t p = 5 m m .d a y -1
loamy sand
clay loam
E tp = 1 m m . d a y -1
clay loam
loamy sand
Fig. 1 Field-scale spatial variability of la as influenced by textural heterogeneity of soil and evapotranspiration rate.
Etp [mm.day -1]
Hence, the maximal differences Δla due to temporal variability of evaporative demand under
maize cover reached about 100 mm of water layer in one-meter thick soil layer during the
vegetation season 2002. The influence of soil texture was roughly the half of the la variability
due to different transpiration rates.
The influence of 8m-high hedgerow on spatial variability of la was studied in the field situated
near the Rutzendorf village in N-E Austria. The soil and microclimate research lasts here from
2004. Automatic atmometers were used to estimate the potential evapotranspiration.
The
hedgerow
influences
the
4 days with minimum Etp rates during 2004 vegetation season
evapotranspiration rate over the field by its
shadowing effect (Fig. 2). Consecutively,
1.2
this influence manifests itself also in the
calculated values of la. During days with
1
low Etp rates the effect is small (Δla is only
0,6% vol.) but during days with high
0.8
8 m from hedgerow
evaporative demand of the atmosphere it
0.6
20 m from hedgerow
reached even 19 % vol. during the
80 m from hedgerow
vegetation season 2004, which means 190
0.4
mm of water layer in one-meter thick soil
layer at the same agricultural field.
0.2
The evapotranspiration nearby hedgerow
and followingly SWC are influenced
0
184
177
197
211
significanly, therefore its impact should be
Julian day
involved in practicies in context of the
avised climatic change (IPCC, 2007).
Fig. 2 Evapotranspiration rates as influenced by the distance from hedgerow in the field near Rutzendorf.
Keywords: water stress, soil water content of limited availability, spatial variability,
evapotranspiration, agricultural ecosystems
References:
Eitzinger, J., Gerersdorfer, T., Schume, H., Mursch-Radlgruber, E. (2005): Influence of a hedge row on field evapotranspiration in the semi-arid region of northeast Austria.. In: Deutscher Wetterdienst (DWD): 17th International Congress of Biometeorology (ICB 2005), September 5-9 2005, GarmischPartenkirchen; Annalen der Meteorologie, 41, 50-53; DWD, Offenbach am Main; ISBN 3-88148-405-1; ISSN 4122
IPCC, (2007). Climate Change 2007 – The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the IPCC (ISBN 978
0521 88009-1 Hardback; 978 0521 70596-7 Paperback).
Novák V .- Havrila J.: 2006. Method to estimate the critical soil water content of limited availability for plants. Biologia, Bratislava, Suppl. 19, 223-224.
Orfánus, T. – Nagy, V. – Štekauerová, V. – Lichner, Ľ.: 2008. A geostatistical analysis of soil water content at the field scale. Cereal Research
Communications, vol. 36, no. 1, 1023-1026.