Steinhardt, R., Institute of Soils and Water, ARO, Bet Dagan, Israel

Van der Ploeg, R.R., Institute of Soil Science and Forest Nutrition, Georg-August University, Göttingen, Germany

Ehlers, W., Institute 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

Ehlers, W., Institute of Agronomy and Plant Breeding, Georg-August University, Göttingen, Germany

Different forms and solutions of the single root model (SRM) arise from: assumed functional relationships between the radius of the SRM soil cylinder and the rooting density (Lr); averaging modes of hydraulic conductivity (K); steady-state or steady-rate flow assumption; and methods of evaluating the root geometry factor (B). SRM forms and solutions, in particular B approximations, were evaluated by analytical comparison and by performance, when incorporated into a water uptake simulation model for oats. The approximation of B as a constant, or as an exponential function of rooting density (B′), had only a small temporary effect on soil water extraction rates and potentials at the soil-root interface. A combination of B′ with exponential rooting profile estimation is proposed as an optimal SRM form for water uptake analysis. It is shown (in appendices) that: (1) assuming SRM steady-state flow to originate on average from the volumetric middle of the SRM soil cylinder is nearly equivalent to the assumption of a steady-rate flow; and (2) utilizing a geometric mean K for the SRM soil cylinder may cause soil water extraction rates to be underestimated. © 1982.

Comparing forms and solutions of the single root soil water extraction model

2

Steinhardt, R., Institute of Soils and Water, ARO, Bet Dagan, Israel

Van der Ploeg, R.R., Institute of Soil Science and Forest Nutrition, Georg-August University, Göttingen, Germany

Ehlers, W., Institute 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

Ehlers, W., Institute of Agronomy and Plant Breeding, Georg-August University, Göttingen, Germany

Comparing forms and solutions of the single root soil water extraction model

Different forms and solutions of the single root model (SRM) arise from: assumed functional relationships between the radius of the SRM soil cylinder and the rooting density (Lr); averaging modes of hydraulic conductivity (K); steady-state or steady-rate flow assumption; and methods of evaluating the root geometry factor (B). SRM forms and solutions, in particular B approximations, were evaluated by analytical comparison and by performance, when incorporated into a water uptake simulation model for oats. The approximation of B as a constant, or as an exponential function of rooting density (B′), had only a small temporary effect on soil water extraction rates and potentials at the soil-root interface. A combination of B′ with exponential rooting profile estimation is proposed as an optimal SRM form for water uptake analysis. It is shown (in appendices) that: (1) assuming SRM steady-state flow to originate on average from the volumetric middle of the SRM soil cylinder is nearly equivalent to the assumption of a steady-rate flow; and (2) utilizing a geometric mean K for the SRM soil cylinder may cause soil water extraction rates to be underestimated. © 1982.

Scientific Publication

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