  We computed the evolution of the abundances of O, Mg, Si, Ca, K, Ti, Sc, Ni,
Mn, Co, Fe and Zn in the Milky Way. We made use of the most widely adopted
nucleosynthesis calculations and compared the model results with observational
data with the aim of imposing constraints upon stellar yields. In order to fit
at best the data in the solar neighborhood, when adopting the Woosley and
Weaver (1995) yields for massive stars and the Iwamoto et al. (1999) ones for
type Ia SNe, it is required that: i) the Mg yields should be increased in stars
with masses from 11 to 20 M_sun and decreased in masses larger than 20 M_sun.
The Mg yield should be also increased in SNe Ia. ii) The Si yields should be
slightly increased in stars above 40 M_sun, whereas those of Ti should be
increased between 11 and 20 M_sun and above 30 M_sun. iii) The Cr and Mn yields
should be increased in stars with masses in the range 11-20 M_sun, iv) the Co
yields in SNe Ia should be larger and smaller in stars in the range 11-20
M_sun, v) the Ni yield from type Ia SNe should be decreased, vi) the Zn yield
from type Ia SNe should be increased. vii) The yields of O (metallicity
dependent SN models), Ca, Fe,
  Ni, and Zn (the solar abundance case) in massive stars from Woosley and
Weaver (1995) are the best to fit the abundance patterns of these elements
since they do not need any change. We adopted also the yields by Nomoto et al.
(1997) and Limongi and Chieffi (2003) for massive stars and discussed the
corrections required in these yields in order to fit the observations. Finally,
the small spread in the [el/Fe] ratios in the metallicity range from
[Fe/H]=-4.0 up to -3.0 dex (Cayrel et al. 2003) is a clear sign that the halo
of the Milky Way was well mixed even in the earliest phases of its evolution.
