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### 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 (22.97 KiB) Viewed 936 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 (30.38 KiB) Viewed 936 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.

### Re: Walker equation and nitrification

Posted: **Thu Jan 17, 2019 2:06 pm**

by **David Radcliffe**

Thanks again.