Universität Hohenheim Kasetsart University Project partners:
Dr. Thomas Hilger
Chalemchart Wongleecharoen Khalid Hussain
Ass.prof. Thanuchai Kongkaew Wattanai Omsunrarn
Channarong Khetdan
Sebastian Rudolph
To get a more detailed understanding of the competition for water, 2- or 3-D monitoring of the water fluxes in the soil-plant-atmosphere system is necessary. Previous studies stress the promising capabilities of Electrical Resistivity Tomography (ERT), but the difficulties to interpret the measured electrical resistivity remain, certainly under field conditions.
Sensitivity and resolution of ERT for soil moisture monitoring in contour hedgerow intercropping systems
Garré, S.
1; Günther, T.
2; Diels, J.
1; Vanderborght, J.
3[ AGU Fall Meeting 2011 | H51A-1180 ]
(1) KULeuven, Earth and Environmental Sciences, Soil and Water Mangement, Belgium (sarah.garre@ees.kuleuven.be) | (2) Leibniz Institute for Applied Geophysics,Germany | (3) Forschungszentrum Juelich GmbH, Agrosphere (IBG-3), Germany
Objectives
* Reproduce realistic soil moisture distributions and resulting resistivity as can be expected under a monocropping and intercropping systems ;
* Analyze the performance of different ERT surveys using measures looking at spatial variability and classical geophysical measures;
* Identify an optimal survey design to capture the generated patterns with ERT during the growing season.
Soil moisture monitoring in intercropping systems…
Agriculture on infertile, shallow or steep soils in the humid tropics often leads to a low efficiency due to a combination of high leaching rates in the growing season and shallow root development of annual food crops. Mixed cropping systems have been proposed as an alternative to traditional agricultural practice with a single crop.
However, sometimes a negative impact on crop response has been observed due to competition.
…with ERT?
General approach
monocropping
inter
croppin
g
Results
Hydrological model
Tested electrode arrays: * dipole-dipole * pole-dipole * Wenner * dipole-dipole + Wenner 2 variations: * only surface electrodes (OS) * electrodes at 0, -25 & -50 cm depth (All)1-D profiles Spatial variability
Semivariogram
* 1-D profiles generally well reproduced
!! Sharp contrasts problematic: due to smoothness constraint
* Slight underestimation of spatial variability. Spatial structure is
detected by ERT, but ‘softened’.
* Best performing array: combination of Wenner & dipole-dipole
* Additional use of deep electrodes generally improves the result,
most of the time, the effect is not very large
* ERT can be used to observe effects of cropping systems on soil
moisture distribution
Conclusions
0.75 m
0.75 m
6 m
Minimum electrode distance: 0.33 m
R rainfall D drainage
EB bare soil evaporation ETMmaize evapotranspiration ETL leucaena evapotranspiration
BERT (Rücker et al. 2006)
BERT (Rücker et al. 2006)
1%
Resolution radius
t = 60 days
All electrodes Only surface electrodes
W en W enne r P olD ip Di pD ip Di pD ip ² ) ( h ² ) ( h Average 1-D water
content profiles for the monocropping case at t= 0, 60 and 108 days for a profile of 2m width and 3 m depth in the middle of the simulated domain.
Standard deviation of
the modeled and
inverted water
content for mono- & intercropping case at t = 60 days. The colours represent the depth classes.
Distribution of the resolution radius (r) for all
arrays for the monocropping case. Semivariograms of the water content of the simulation and the inverted WC for the
