The APSIM slurp Model

Description

The APSIM slurp module provides a user-defined sink for soil water that can be used to fill the role of a crop within a simulated system.

Inputs for the slurp module consist of plant root (root length profile and extraction potential) and canopy (live LAI, dead LAI, extinction coefficients and canopy height) information. There is also a switch to state whether slurp is to calculate its own soil water uptake or receive this information from another APSIM module.

The slurp module can operate in two modes. The first and simplest mode is where the uptake_source is set to 'APSIM'. In this type of operation slurp is simply a provider of information to other modules in the APSIM system that perform extraction of water and solutes (eg APSwim). In the second mode of operation the uptake_source is set to 'calc' and the soil water demand is taken from the soil by SLURP (if adequate reserves exist) and root length is used to partition uptake between layers.

Parameter File Settings

The following describes a possible parameterisation of the slurp module

[sample.slurp.parameters]

crop_type = wheat     ! type of crop represented by slurp

lai = 6.0             ! leaf area index (m2/m2)

laid = 0              ! dead leaf area index (m2/m2)

kg = 0.5              ! green leaf extinction coefficient

kd = 0.5              ! dead leaf extinction coefficient

vpd = 0 10 50         ! vapour pressure deficit for interpolation (hPa)

fvpd= 1 1 1           !Interpolated VPD stress factor (0-1)

height = 800.         ! Canopy height (mm)

frgr = 1              ! Relative growth rate (0-1) - to capture effect

                      ! of growth limitation.

ll = 0.230 0.240 0.240 0.250 0.260 0.270 0.280 () !mm3 water/mm3 soil

kl = 0.07  0.07  0.07  0.07  0.05  0.05  0.04  () ! 1st order decay rate for PAWC

XF = 1.0   1.0   1.0   1.0   1.0   1.0   1.0   () ! root exploration factor (0-1)

RLV= 0.05  0.03  0.02  0.01  0.01  0.005 0.001 () ! mm/mm3 root length density

Solute module outputs