  We report on observations of SN 1006 with the X-ray Imaging Spectrometers
(XIS) on board Suzaku. We firmly detected K-shell emission from Fe, for the
first time, and find that the Fe ionization state is quite low. The broad band
spectrum extracted from the southeast of the remnant is well fitted with a
model consisting of three optically thin thermal non-equilibrium ionization
plasmas and a power-law component. Two of the thermal models are highly
overabundant in heavy elements and, hence, are likely due to ejecta. These
components have different ionization parameters: $n_et \sim 1.4\times 10^{10}$
cm$^{-3}$ s and $n_et \sim 7.7\times 10^8$ cm$^{-3}$ s and it is the later one
that produces the Fe-K emission. This suggests that Fe has been heated by the
reverse shock more recently than the other elements, consistent with a picture
where the ejecta are stratified by composition with Fe in the interior. On the
other hand, the third thermal component is assumed to be solar abundance, and
we associate it with emission from the interstellar medium (ISM). The electron
temperature and ionization parameter are $kT_e \sim $0.5 keV and $n_et \sim
5.8\times 10^9$ cm$^{-3}$ s. The electron temperature is lower than that
expected from the shock velocity which suggests a lack of collisionless
electron heating at the forward shock. The extremely low ionization parameter
and extreme non-equilibrium state are due to the low density of the ambient
medium.
