Each year we must prep our land for planting. This process varies based on the crop we would like to grow, but generally we plow and disc most of our fields. Plowing buries any remaining crop residue from the previous year, along with any bugs or diseases living in or on that residue.
We then usually disc the field. A disc will remove most uneven spots left by the plow along with breaking up any tough clods. If we need a really smooth seed bed we may follow that with a drag harrow or a culti-mulcher/packer. This makes the soil surface very smooth.
For fields that may be going into grain crops like corn or soybeans, we would use vertical tillage implement called a field cultivator. This works the top several inches of soil and mixes the crop residue and soil along with exposing the roots of any newly germinated weed seeds.
Here are a pictures and videos from this spring: