  Star formation rate density, $\Sigma_{\rm SFR}$, has shown a remarkable
correlation with both components of the baryonic mass at kpc scales (i.e., the
stellar mass density, and the molecular gas mass density; $\Sigma_{\ast}$, and
$\Sigma_{\rm mol}$, respectively) for galaxies in the nearby Universe. In this
study we propose an empirical relation between $\Sigma_{\rm SFR}$ and the
baryonic mass surface density ($\Sigma_{\rm b}$ =$\Sigma_{\rm mol,Av}$ +
$\Sigma_{\ast}$; where $\Sigma_{\rm mol,Av}$ is the molecular gas density
derived from the optical extinction, Av) at kpc scales using the
spatially-resolved properties of the MaNGA survey - the largest sample of
galaxies observed via Integral Field Spectroscopy (IFS, $\sim$ 8400 objects).
We find that $\Sigma_{\rm SFR}$ tightly correlates with $\Sigma_{\rm b}$.
Furthermore, we derive an empirical relation between the $\Sigma_{\rm SFR}$ and
a second degree polynomial of $\Sigma_{\rm b}$ yielding a one-to-one relation
between these two observables. Both, $\Sigma_{\rm b}$ and its polynomial form
show a stronger correlation and smaller scatter with respect to $\Sigma_{\rm
SFR}$ than the relations derived using the individual components of
$\Sigma_{\rm b}$. Our results suggest that indeed these three parameters are
physically correlated, suggesting a scenario in which the two components of the
baryonic mass regulate the star-formation activity at kpc scales.
