The blade plow or sweep plow, a common tillage implement in the High Plains, cuts weeds at the roots and leaves most of the residue anchored at the surface with minimum disturbance of the soil surface. Blade plowing is typically a summer fallow operation after small grain harvest. It kills weeds and loosens the surface. In moist soils, particularly those with higher clay contents, a blade plow may cause soil smearing below the blade, thereby limiting its use as a spring tillage implement.
For maximum weed kill, the blade plow should be operated at a shallow depth and used on a hot day when the soil is dry. Small weeds are lifted and uprooted so they dry out. Larger weeds are cut off from their root system. Deep operation often leaves roots in the soil and weeds re-root. Attaching a rod-weeder or mulch-treader behind a blade plow to bring roots to the surface improves weed control. Using these attachments, especially the mulch treader, results in greater residue loss and soil pulverization.
Using either a blade plow or rod weeder at progressively shallower depths provides a firm seedbed while controlling subsequent weed growth. These implements work beneath the soil surface and are typically used in drier climates; 30% or more residue can usually be maintained. However, substituting either a disk or field cultivator for secondary tillage greatly decreases the probability of leaving adequate residue for erosion control.
Using herbicides for weed control and planting after one pass of the blade plow reduces or eliminates secondary tillage operations, leaving more residue on the soil surface for soil and water conservation. However, this may cause problems at planting time because the soil is loose and fluffy, making it difficult to cut the loosened residue and difficult to obtain good seed-to-soil contact. The secondary tillage operations firm the soil and deceases the amount of residue, improving residue flow through the planting equipment.
(Photos above from Drew Lyon, PHREC, Scottsbluff)