A disc harrow is designed to tackle tough soil conditions by using its rotating discs to cut and turn the soil, breaking up clods and mixing in crop residue. This process helps in creating a fine, even seedbed, which is essential for successful planting. The discs are typically set at an angle, allowing them to slice through the soil more effectively and improve soil aeration. There are different types of disc harrows, including offset, tandem, and vertical, each with its specific design and purpose depending on the soil conditions and the desired outcome.