- `BM`
  Standing biomass in kg DM per ha.
- `BMG`
  Standing green biomass (kg DM / ha).
- `cBM`
  Cumulativeley grown biomass (kg DM / ha).
- `dBM`
  Daily grown biomass (kg DM / ha).
- `hvBM`
  Cumulative harvested biomass (kg DM / ha).
- `OMD`
  Organic matter digestibility (kg / kg).
- `OMDG`
  OMD of green matter (kg / kg).
- `ST`
  Temperature sum in degree Celsius days.
- `REP` Reproductive function. Gives the fraction of growth that is 
  assigned to reproductive growth. The remainder goes into vegetative growth. 
  Dimensionless.
- `PGRO`
  Potential growth in kg DM / ha.
- `GRO`
  Effective growth in kg DM / ha.
- `LAI`
  Leaf area index, accounting for the proportion of light intercepted by the 
  sward. Dimensionless.
- `LAIGV`
  LAI of green vegetative biomass. Dimensionless.
- `AET`
  Actual evapotranspiration in mm.
- `WR`
  Water reserves in mm.
- `ENV`
  Function representing environmental effects on growth. Acts as a 
  multiplicative factor. Dimensionless.
- `ENVfPAR`
  Part of ENV due to strength of incident radiation. Dimensionless.
- `ENVfT`
  Part of ENV due to temperature. Dimensionless.
- `ENVfW`
  Part of ENV due to water limitation. Dimensionless.

