HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by de Jong van Lier, Q. Articles by Duijnisveld, W. H. M. PubMed Articles by de Jong van Lier, Q. Articles by Duijnisveld, W. H. M. GeoRef GeoRef Citation Agricola Articles by de Jong van Lier, Q. Articles by Duijnisveld, W. H. M. Related Collections Water Stress Root Growth/Water Uptake Models

SPECIAL SECTION: ROOTS AND ROOT FUNCTION

Macroscopic Root Water Uptake Distribution Using a Matric Flux Potential Approach

^a Exact Sciences Dep., Esalq-Univ. of São Paulo, 13418-900 Piracicaba (SP), Brazil
^b Dep. of Environmental Sciences, Wageningen Univ., Droevendaalsesteeg 4, 6708 PB Wageningen, The Netherlands
^c Eastern Cereal and Oilseed Research Center, AAFC, Ottawa, ON Canada
^d Federal Institute for Geosciences and Natural Resources, PO Box 510153, 30631 Hannover, Germany
^e current address, Dep. of Environmental Sciences, Wageningen Univ., Droevendaalsesteeg 4, 6708 PB, Wangeningen, The Netherlands
^f is funded by Fapesp, Brazil
^g is funded by the framework of the Dutch National Research Programme Climate changes Spatial Planning
^* Corresponding author (qdjvlier{at}esalq.usp.br).

Received 27 April 2007.

Hydrological models featuring root water uptake usually do not include compensation mechanisms such that reductions in uptake from dry layers are compensated by an increase in uptake from wetter layers. We developed a physically based root water uptake model with an implicit compensation mechanism. Based on an expression for the matric flux potential (M) as a function of the distance to the root, and assuming a depth-independent value of M at the root surface, uptake per layer is shown to be a function of layer bulk M, root surface M, and a weighting factor that depends on root length density and root radius. Actual transpiration can be calculated from the sum of layer uptake rates. The proposed reduction function (PRF) was built into the SWAP model, and predictions were compared to those made with the Feddes reduction function (FRF). Simulation results were tested against data from Canada (continuous spring wheat [(Triticum aestivum L.]) and Germany (spring wheat, winter barley [Hordeum vulgare L.], sugarbeet [Beta vulgaris L.], winter wheat rotation). For the Canadian data, the root mean square error of prediction (RMSEP) for water content in the upper soil layers was very similar for FRF and PRF; for the deeper layers, RMSEP was smaller for PRF. For the German data, RMSEP was lower for PRF in the upper layers and was similar for both models in the deeper layers. In conclusion, but dependent on the properties of the data sets available for testing, the incorporation of the new reduction function into SWAP was successful, providing new capabilities for simulating compensated root water uptake without increasing the number of input parameters or degrading model performance.

Abbreviations: DVS, development stage • FRF, Feddes reduction function • PRF, proposed reduction function • RMSEP, root mean square error of prediction

This article has been cited by other articles:

				T. H. Skaggs and P. J. Shouse Roots and Root Function: Introduction Vadose Zone J., August 1, 2008; 7(3): 1008 - 1009. [Full Text] [PDF]