The furrowing shovel moves the crop residue and weed seed between the rows where any weeds that emerge can be controlled with cultivation. Incorporated herbicides do not need rainfall or irrigation to move them into the soil. It is a mistake to plant through large weeds like tansymustard, kochia, lambsquarters, prickly lettuce, horseweed, smartweed, and Russian thistle. If growing between the rows, these weeds will probably not be killed at planting time. Furthermore, they can quickly remove all the moisture in the seedbed.
Large weeds can keep the planter from operating at the proper depth.
Since these weeds may not have been killed at planting time, they become more difficult to control at cultivation. At first cultivation these large weeds may not be cut off with the disks or sweeps. They will compete with the crop and present a harvest problem. Weeds growing on the side of the ridge at planting time also present problems. The trouble arises along the cutting edge of the planter sweep or disk, where large broadleaf weeds may not be uprooted or covered.