I am going to model the root growth of barley with time to define the rooting depth at specific time t. I use the classical Verhulst-Pearl logistic growth function (see attached for detailed formulation) that is implemented in the HYDRUS model. However, this equation needs the growth rate of barley root as [T-1] as a priori known data. I do not have measured time series data of barley root growth to define the variable "r" (as highlighted in the attached file). I appreciate anyone who can assist me about any similar study or literature or measured value of r that is determined for barley. Many thanks!
Seyed
Thank you Dibakar Pal
Very Good paper and I could calculate the root growth rate of barley (rgr) based on the equation 12 in this paper "An integrated soil-crop system model for water and nitrogen". However, please note that there is a slight problem in this equation 12 as it results in negative rgr. If you see the equation 12 in the paper, the value in the parenthesis is less than 1 and as natural logarithm (ln) is applied to it, it yields negative rgr which is not physically correct. If you ignore the negative sign behind the rgr in Equation 13, it will correct the calculation. I found rgr=0.04 (d-1) (of course -0.04 based on Eq. 12) for barley that is in the range of the value for other crops such as canola and maize, 0.03 and 0.07, respectively. Please note that the unit of rgr is (d-1) while the paper says (cm d-1) that does not look correct based on the formulation of equation 12 and the manual of the HYDRUS model.
I attach the paper that you introduced for the benefit of those who are interested in it.
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