  We consider a general d=4 N=1 globally supersymmetric lagrangian involving
chiral and vector superfields, with arbitrary superpotential, Kahler potential
and gauge kinetic function. We compute perturbative quantum corrections by
employing a component field approach that respects supersymmetry and background
gauge invariance. In particular, we obtain the full one-loop correction to the
Kahler potential in supersymmetric Landau gauge. Two derivations of this result
are described. The non-renormalization of the superpotential and the quadratic
correction to the Fayet-Iliopoulos terms are further checks of our
computations.
