Plowing involved soil inversion to 25–30 cm depth. Superficialtillage involved mechanical disturbance to less than 8 cm depth,without soil inversion. Direct seeding involved mechanical distur-bance in the upper 3 cm of soil in the sowing furrows, without soilinversion. The number of replicated plots per tillage type in eachindividual trial was 6 for trial A, 2 for trial B, 3 for trial C, 2 or 3 fortrial D. Information on crop rotations, pesticide use and fertilizationis given in