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Analysis of soil-water uptake from a drying loess soil by an oat crop using a simulation model
Year:
1981
Source of publication :
Irrigation Science
Authors :
Steinhardt, Reuven
;
.
Volume :
2
Co-Authors:
Steinhardt, R., Agricultural Research Organization, Institute of Soils and Water, Bet Dagan, Israel
Ehlers, W., Institutes of Agronomy and Plant Breeding, Georg-August University Göttingen, Germany
van der Ploeg, R.R., Institute of Soil Science and Forest Nutrition, Georg-August University Göttingen, Germany
Facilitators :
From page:
237
To page:
258
(
Total pages:
22
)
Abstract:
A simulation model of water uptake by a crop was developed to facilitate synthesis of field and laboratory observations with existing knowledge, and to analyze and predict affects of management practices, such as tillage, on water uptake from a drying soil. Radial water flow resistance in soil R s was estimated by the single root flow model. Leaf stomata closure was represented by an observed minimal leaf water potential. Flow resistances, per unit root length R r and in the plant R p, were assumed to be constant and were evaluated together with an effective root length factor F rl, in the course of simulating a ten week period of observed soil water depletion by a crop of oats. R r, R p, and F rl were found to have similar values to those reported in the literature. Potential transpiration and evaporation and their ratio were estimated by the methods of Van Bavel (1966) and Denmead (1973). Evaporation reduction due to soil drying was estimated empirically. Cessation of soil water depletion (attainment of a permanent wilting soil water content) in the 0 - 20 cm soil layer, during the last ten-day period, was explained to be the net result of soil water extraction by the roots and backflow of water from the roots into the soil. Simulated onset of crop stress (closure of stomata) was found to be characterized by: (a) a steady decrease in average soil water potential, at a rate of about 500 cm-water per cm-soil water depletion; (b) a tenfold increase in the average soil resistance to radial flow, to about the same magnitude as average radial flow resistance in the roots; and (c) soil water diffusivities in the 0 - 50 cm layer being about 6 cm2/day. Sensitivity analyses showed that the ratio of actual to potential cumulative transpiration RCT depended primarily on potential evapotranspiration, rainfall, the unsaturated-to-saturated hydraulic conductivity exponent and plant cover. RCT was affected similarly by changes in R r and in R s. Under the conditions tested, zero tillage may increase RCT significantly only if it increases deep rooting beyond the 50 cm depth. © 1981 Springer-Verlag.
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DOI :
10.1007/BF00258377
Article number:
Affiliations:
Database:
Scopus
Publication Type:
article
;
.
Language:
English
Editors' remarks:
ID:
28930
Last updated date:
02/03/2022 17:27
Creation date:
17/04/2018 00:43
Scientific Publication
Analysis of soil-water uptake from a drying loess soil by an oat crop using a simulation model
2
Steinhardt, R., Agricultural Research Organization, Institute of Soils and Water, Bet Dagan, Israel
Ehlers, W., Institutes of Agronomy and Plant Breeding, Georg-August University Göttingen, Germany
van der Ploeg, R.R., Institute of Soil Science and Forest Nutrition, Georg-August University Göttingen, Germany
Analysis of soil-water uptake from a drying loess soil by an oat crop using a simulation model
A simulation model of water uptake by a crop was developed to facilitate synthesis of field and laboratory observations with existing knowledge, and to analyze and predict affects of management practices, such as tillage, on water uptake from a drying soil. Radial water flow resistance in soil R s was estimated by the single root flow model. Leaf stomata closure was represented by an observed minimal leaf water potential. Flow resistances, per unit root length R r and in the plant R p, were assumed to be constant and were evaluated together with an effective root length factor F rl, in the course of simulating a ten week period of observed soil water depletion by a crop of oats. R r, R p, and F rl were found to have similar values to those reported in the literature. Potential transpiration and evaporation and their ratio were estimated by the methods of Van Bavel (1966) and Denmead (1973). Evaporation reduction due to soil drying was estimated empirically. Cessation of soil water depletion (attainment of a permanent wilting soil water content) in the 0 - 20 cm soil layer, during the last ten-day period, was explained to be the net result of soil water extraction by the roots and backflow of water from the roots into the soil. Simulated onset of crop stress (closure of stomata) was found to be characterized by: (a) a steady decrease in average soil water potential, at a rate of about 500 cm-water per cm-soil water depletion; (b) a tenfold increase in the average soil resistance to radial flow, to about the same magnitude as average radial flow resistance in the roots; and (c) soil water diffusivities in the 0 - 50 cm layer being about 6 cm2/day. Sensitivity analyses showed that the ratio of actual to potential cumulative transpiration RCT depended primarily on potential evapotranspiration, rainfall, the unsaturated-to-saturated hydraulic conductivity exponent and plant cover. RCT was affected similarly by changes in R r and in R s. Under the conditions tested, zero tillage may increase RCT significantly only if it increases deep rooting beyond the 50 cm depth. © 1981 Springer-Verlag.
Scientific Publication
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