Walker equation and nitrification

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David Radcliffe
Posts: 25
Joined: Wed Oct 07, 2009 3:32 pm

Walker equation and nitrification

Post by David Radcliffe » Mon Jan 07, 2019 2:46 pm

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.

Jirka
Posts: 4760
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Walker equation and nitrification

Post by Jirka » Sat Jan 12, 2019 8:08 pm

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 689 times
I think that it would be difficult to manipulate it to produce different shapes. J.

Jirka
Posts: 4760
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Walker equation and nitrification

Post by Jirka » Sat Jan 12, 2019 8:14 pm

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 689 times
J.

David Radcliffe
Posts: 25
Joined: Wed Oct 07, 2009 3:32 pm

Re: Walker equation and nitrification

Post by David Radcliffe » Sun Jan 13, 2019 2:25 pm

Perfect! Thanks so much.

David Radcliffe
Posts: 25
Joined: Wed Oct 07, 2009 3:32 pm

Re: Walker equation and nitrification

Post by David Radcliffe » Tue Jan 15, 2019 2:47 pm

Oops, when I use a negative exponent I get an error:

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

Jirka
Posts: 4760
Joined: Sat Mar 16, 2002 3:47 pm
Location: USA
Location: Riverside, CA

Re: Walker equation and nitrification

Post by Jirka » Wed Jan 16, 2019 1:21 am

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 35 times

David Radcliffe
Posts: 25
Joined: Wed Oct 07, 2009 3:32 pm

Re: Walker equation and nitrification

Post by David Radcliffe » Thu Jan 17, 2019 2:06 pm

Thanks again.

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