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Root uptake Parameters

Posted: Thu Oct 24, 2019 9:07 am
by Tausifilyas
I have to model/simulate root water uptake using Hydrous-2D. In fedes model, there are lot of parameters related to transpiration are given. Do you guide me , how to determine them for my case? Any Methodology?

Re: Root uptake Parameters

Posted: Thu Oct 24, 2019 2:22 pm
by Jirka
A database of suggested values for different plants for the Feddes et al. [1978] model is provided in HYDRUS based on studies by Wesseling [1991] and Taylor and Ashcroft [1972]. For methodology, you can look into the original references:

Feddes, R. A., P. J. Kowalik, and H. Zaradny, Simulation of Field Water Use and Crop Yield, John Wiley & Sons, New York, NY, 1978.
Maas, E. V., Crop salt tolerance. In K. K. Tanji (ed.), Agricultural Salinity Assessment and Management, ASCE Manuals and Reports on Engineering practice, No. 71, NY, 1990.
Taylor, S. A. and G. M. Ashcroft, Physical Edaphology. Freeman and Co., San Francisco, California, p. 434-435, 1972.
Wesseling, J. G., J. A. Elbers, P. Kabat, and B. J. van den Broek, SWATRE: instructions for input, Internal Note, Winand Staring Centre, Wageningen, the Netherlands, 1991.

J.

Re: Root uptake Parameters

Posted: Sun Oct 27, 2019 10:29 am
by Tausifilyas
Thanks Jirka!
I have gone through these publications and find difficult to assess the input parameters regarding root water uptake.
I have potential ET data measured by weather station, could i use that value instead of above mentioned parameters to encounter root water uptake?

Re: Root uptake Parameters

Posted: Sun Oct 27, 2019 3:53 pm
by Jirka
You really need to first understand how the model works overall. Your questions suggest that you don’t'. The manual gives the main details. The full description is in:

Šimůnek, J., and J. W. Hopmans, Modeling compensated root water and nutrient uptake, Ecological Modeling, 220(4), 505-521, doi: 10.1016/j.ecolmodel.2008.11.004, 2009.

J.

Re: Root uptake Parameters

Posted: Tue Oct 29, 2019 5:35 am
by Tausifilyas
Thanks jirka!
I have gone through this document. I have learnt a lot about the mechanism of root water uptake.
There is an issue regarding determination of inputs required to put in HYDRUS simulation i.e. h values to see variations in stress function (alpha).
Can you guide me how do we determine these inputs?
Tausif

Re: Root uptake Parameters

Posted: Tue Oct 29, 2019 11:22 am
by Jirka
I do not have any other guidance beyond that provided in the above- mentioned paper and in the HYDRUS texts (manuals, help). J.

Re: Root uptake Parameters

Posted: Mon Apr 20, 2020 5:23 pm
by Malik
I need feddes parameter for cucumber crop which are not provided in the database. Moreover, could not find these parameters from literature. Need guidance plz.