Dear Richard,

How are you? I am pleased to receive your recent 2 e-mails related to codes of CERES rice. In fact I have also lots of problem in understanding the code. I am still doing and fixing my other stuff related to experiments in Australia, bangladesh and India. As soon as I have time I will start looking at the codes and will get back to you.

It was nice to meet and talk with you in Griffin, Georgia in December.

Regards

Jagadish

-----Original Message-----
From: Richard Ogoshi [mailto:[log in to unmask]]
Sent: Wednesday, 21 May 2003 2:19 PM
To: [log in to unmask]
Subject: Re: NFLUX


Hello Reinder,
   This is how I interpret the source code you mention below with help from
the books "Understanding options for agricultural production" and
"CERES-Maize: a simulation model of maize growth and development" . If
anyone sees anything incorrect, please let me know.
   The code you sent describes the upward flow of nitrate from soil layer K
to layer K-1.
1. SKGN is the amount of nitrate in a soil layer (kg N/ha).
2. XMIN is a small amount of nitrate that is never in soil solution, so
cannot denitrify (kg N/ha that is equivalent to 0.25 ppm nitrate).
3. FLOW(K-1) is the amount of water leaving layer K to the layer above (K-1).
4. SW(K) is the volumetric water content in soil layer K.
5. DLAYR(K) is the depth of soil layer K.
6. FLOW(K) is the amount of water coming into layer K from the soil layer
below.
So,
(1) SKGN(K)-XMIN is the amount of nitrate in solution.
(2) FLOW(K-1)/(SW(K)*DLAYR(K)+FLOW(K)) is the proportion of water that
leaves soil layer K to the layer above.
(3) multiplying (1) by (2) gives the amount of nitrate that could leave
layer K to the layer above.
But, because soil water moves upward by vapor transfer and suction, the
nitrate does not move as readily with water as when it leaches. So, to
account for this reduced movement of nitrate, (3) is multiplied by 0.5.
Sincerely,
Richard

At 08:17 AM 05/20/2003 -0700, Reinder De Jong wrote:
> Dear colleagues,
>
>In the NFLUX subroutine, which determines nitrogen drainage and leaching,
I encounter the following line:
>
>               OUTN    =MAX((SKGN(K)-XMIN),0.0)*(FLOW(K-1)/
>     +                  (SW(K)*DLAYR(K)+FLOW(K)))*0.5
>
>My questions is, why is the latter part of this equation multplied by 0.5?
Could somebody explain this to me?
>
>Reinder De Jong
>Agriculture and Agri-Food Canada
>Ottawa, ON
>Canada
>