Page 1 of 1

Walker equation and nitrification

Posted: Mon Jan 07, 2019 2:46 pm
by David Radcliffe
I am working on a nitrogen chain model. I am using the Walker equation for water content dependence for denitrification (ramps up as water content approaches saturation). I would like to use the Walker equation for nitrification. Is there a way to manipulate the equation parameters so that it ramps down at high water contents? Thanks.

Re: Walker equation and nitrification

Posted: Sat Jan 12, 2019 8:08 pm
by Jirka
Walker's equation has been developed for the degradation of pesticides and can produce the following reduction functions.
Walker.png
Walker.png (22.97 KiB) Viewed 247 times
I think that it would be difficult to manipulate it to produce different shapes. J.

Re: Walker equation and nitrification

Posted: Sat Jan 12, 2019 8:14 pm
by Jirka
Hi David,

I have looked at that again. If you select negative values for B, you can likely achieve what you want.
Walker1.png
Walker1.png (30.38 KiB) Viewed 247 times
J.

Re: Walker equation and nitrification

Posted: Sun Jan 13, 2019 2:25 pm
by David Radcliffe
Perfect! Thanks so much.

Re: Walker equation and nitrification

Posted: Tue Jan 15, 2019 2:47 pm
by David Radcliffe
Oops, when I use a negative exponent I get an error:

"Floating Point Error! Calculation unstable.
Please check out input data..."

Re: Walker equation and nitrification

Posted: Wed Jan 16, 2019 1:21 am
by Jirka
The code was indeed working only for Walker equation with positive exponent (as designed). I copy below the computational module that can handle both cases (I do not think that PC-Progress will be updating version 2 of HYDRUS (2D/3D) when version 3 is already released).

J.
H2D_Calc.rar
(494.29 KiB) Downloaded 14 times

Re: Walker equation and nitrification

Posted: Thu Jan 17, 2019 2:06 pm
by David Radcliffe
Thanks again.