agmip.github.io

AgMIP open source software development and use.

View the Project on GitHub

ROOT_DIST - Root distribution function

Distributes roots (or other soil parameters) using an exponential decay curve from a maximum value in the top soil to a minimum value at depth.

Inputs:

Implicit Inputs (i.e., available in the data):

Outputs:

Procedure:

/* exponential decay rate */
 k = LN(0.02)/(RD - PP)

/* loop thru soil layers */ 

/* midpoints of soil layers */
 mid(1) = SLLB(1) / 2 
 mid(j) = [SLLB(j) + SLLB(j-1)] / 2

 
If mid(j) <= PP
  then F(j) = M
  else F(j) = M * EXP{k *(mid(j) - PP)}

Examples

Example 1 - Root growth factor:

FILL, SLRGF, ROOT_DIST(), 1.0, 20, 180

For M = 1.0, PP = 20 cm, RD = 180 cm, the rate constant, k is calculated to be -0.02445 and the array of factors, F, are computed as:

sllb mid F
5 2.5 1.000
15 10 1.000
30 22.5 0.941
60 45 0.543
90 75 0.261
120 105 0.125
150 135 0.060
180 165 0.029

image

More Samples: The following DOME spreadsheet uses this function: Machakos Overlay DOME

Dome functions page

Home