What type of farm machinery is used to turn over the soil in preparation for planting seeds?

The correct answer is the plough, as it is specifically designed to turn over the soil in preparation for planting seeds. The primary function of a plough is to break up the soil, aerate it, and create furrows, which can benefit the growth of crops by enhancing soil structure, incorporating organic matter, and controlling weeds.

While a seeder is used to plant seeds into the already prepared soil, and a tiller is typically used for cultivating and mixing soil near the surface, it is the plough that plays the crucial initial role in soil preparation. A harvester, on the other hand, is utilized for collecting mature crops, thus playing a completely different role in the agricultural process.