This article: http://www.umweltinstitut.org/themen/radioaktivitaet/tschern... claims, that the Bavarian soil used for agriculture tends to not transfer radioactive particles quickly into plants. It seems the soil was also deeply plowed to distribute the particles amongst a large volume of soil. The situation in forests is different, as the trees captured more particles than the open farmland, and the soil is not plowed, leading to still high particle concentrations in the top layer.

Bavaria had been contaminated the most, other parts of Germany have less residual radiation - the weather situation (wind, rain) created very inhomogeneous distribution back then. I found this map about the distribution: http://files.abovetopsecret.com/files/img/gz54e7a9f2.png