## 3.17 Primary production

For primary producers the production is estimated as a function of the producers' biomass, Bi, from a simple saturating relationship

**Eq. 67**

where, *r*_{i} is the maximum production/biomass ratio that can be realized (for low *B*_{i} 's), and *r*_{i}/h_{i} is the maximum net primary production when the biomass is not limiting to production (high* B*_{i} 's). For parameterization it is only necessary to provide an estimate of *r*_{i} / (*P*_{i}/B_{i}), i.e., a factor expressing how much primary production can be increased compared to the base model state. If a Forcing function is applied to primary production (see Apply FF (primary producer)), it multiplies the r parameter in Eq. 67.