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On quantifying soil water deficit of a partially wetted root zone by the response of canopy or leaf conductance
Year:
2004
Source of publication :
Agricultural Water Management
Authors :
Cohen, Shabtai
;
.
Cohen, Yehezkel
;
.
Fuchs, Marcel
;
.
Volume :
65
Co-Authors:
Li, Y., Xinjiang Inst. of Ecol. and Geogr., CAS, 40-3 South Beijing Road, Urumqi, Xinjiang 830011, China
Cohen, Y., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
Wallach, R., Department of Soil and Water, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
Cohen, S., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
Fuchs, M., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
Facilitators :
From page:
21
To page:
38
(
Total pages:
18
)
Abstract:
Quantifying the soil water deficit (SWD) and its relation to canopy or leaf conductance is essential for application of the Penman-Monteith equation to water-stressed plants. As the water uptake of a single root depends on the water content of the soil in its immediate vicinity, the non-uniform distribution of water and roots in the soil profile does not allow simple quantification of SWD from soil-based measurements. Using measurements of stem sap flux (with a heat pulse technique), soil evaporation (with micro-lysimeters) and meteorological parameters the canopy conductance was obtained through inversion of the Penman-Monteith equation. SWD was evaluated by averaging the soil water content profile of the root zone (monitored by layers with the TDR sensors) weighted by root distribution of the layers. The average canopy conductance at midday (11:00-15:00, Israel Summer Time), denoted as G noon, was computed for each day of the experimental period. Stable summer weather, typical of the Mediterranean region, and the fully developed crop canopy, made water stress the only plausible cause of a Gnoon decline. However, the daily decline of Gnoon did not occur at the same weighted average soil water content during the successive drying cycles. For the cycle with less irrigation, the decline in Gnoon occurred at higher soil moisture levels. Alternatively, when SWD was determined from the water balance, i.e., by defining water deficit as irrigation minus accumulated evapotranspiration, the Gnoon decline occurred at the same value of water deficit for all irrigation cycles. We conclude that a climate-based soil water balance model is a better means of quantifying SWD than a solely soil-based measurement. © 2003 Elsevier B.V. All rights reserved.
Note:
Related Files :
Canopy conductance
climatology
evapotranspiration
irrigation
Soil testing
Stomatal conductance
transpiration
Wetting
Show More
Related Content
More details
DOI :
10.1016/j.agwat.2003.07.004
Article number:
Affiliations:
Database:
Scopus
Publication Type:
article
;
.
Language:
English
Editors' remarks:
ID:
30455
Last updated date:
02/03/2022 17:27
Creation date:
17/04/2018 00:54
Scientific Publication
On quantifying soil water deficit of a partially wetted root zone by the response of canopy or leaf conductance
65
Li, Y., Xinjiang Inst. of Ecol. and Geogr., CAS, 40-3 South Beijing Road, Urumqi, Xinjiang 830011, China
Cohen, Y., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
Wallach, R., Department of Soil and Water, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
Cohen, S., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
Fuchs, M., Dept. of Environ. Phys. and Irrigat., Volcani Center (ARO), Ministry of Agriculture, Bet Dagan 50250, Israel
On quantifying soil water deficit of a partially wetted root zone by the response of canopy or leaf conductance
Quantifying the soil water deficit (SWD) and its relation to canopy or leaf conductance is essential for application of the Penman-Monteith equation to water-stressed plants. As the water uptake of a single root depends on the water content of the soil in its immediate vicinity, the non-uniform distribution of water and roots in the soil profile does not allow simple quantification of SWD from soil-based measurements. Using measurements of stem sap flux (with a heat pulse technique), soil evaporation (with micro-lysimeters) and meteorological parameters the canopy conductance was obtained through inversion of the Penman-Monteith equation. SWD was evaluated by averaging the soil water content profile of the root zone (monitored by layers with the TDR sensors) weighted by root distribution of the layers. The average canopy conductance at midday (11:00-15:00, Israel Summer Time), denoted as G noon, was computed for each day of the experimental period. Stable summer weather, typical of the Mediterranean region, and the fully developed crop canopy, made water stress the only plausible cause of a Gnoon decline. However, the daily decline of Gnoon did not occur at the same weighted average soil water content during the successive drying cycles. For the cycle with less irrigation, the decline in Gnoon occurred at higher soil moisture levels. Alternatively, when SWD was determined from the water balance, i.e., by defining water deficit as irrigation minus accumulated evapotranspiration, the Gnoon decline occurred at the same value of water deficit for all irrigation cycles. We conclude that a climate-based soil water balance model is a better means of quantifying SWD than a solely soil-based measurement. © 2003 Elsevier B.V. All rights reserved.
Scientific Publication
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