It eliminates many of the benefits of including forage in the rotation in the first place. Tillage brings dormant weed seeds to the soil surface, giving them a new lease on life. Cultivation also destroys soil aggregation. Tillage exposes the soil to the elements by burying surface mulch, allowing the soil to dry and creating the possibility of erosion. It also reduces the snow-catching benefits of trash.
Tillage increases the risk of nitrate leaching.
Nitrogen released from forage residue may leach below the root zone, making it unavailable for most annual crops. Tillage exposes the soil to erosion and allows moisture to escape. Quackgrass is often present when the time comes to remove alfalfa from the rotation. Tillage will eliminate the opportunity for effective treatment with Roundup. In fact, tillage may also encourage the spread of quackgrass.