The soil drainage class and some characteristic features associated with each class are depicted in the following figure (from Soil Survey). One characteristic feature in the figure is the depth of rooting that typically occurs in each drainage class, providing there are no other restrictions (i.e., compacted layer) to root penetration. Deeper rooting depths are associated with well drained soils, because the depth of the water table below the surface is not restricting root growth and oxygen exchange. Although not all plant species respond the same, for most common agricultural crops, a deeper and healthy root environment translates into higher biomass productivity. Studies in New York have shown 2 to 3 fold yield increases in corn and forage production on well drained soils as compared to those grown on somewhat poorly to poorly drained soils. Another major benefit of well drained soils that affects productivity is that the soil is more conducive to timely tillage operations without creating structural damage. This is particularly important in the Northeast, where the seasonal moisture distribution causes soils to be wet in the spring and fall, and the growing season is limited.

 image source: NRCCA Soil and Water Management Study Guide