Overview: Rotating subsurface rod action pulls and uproots weeds, depositing them on the surface fully exposed to sun and wind. Under heavy weed conditions, the net effect can be a weed residue mulch. The rod leaves a layer of loose soil as its main mulching effect that deters weed regrowth and lessens subsoil moisture evaporation. Another benefit is the rod's slightly compacting effect on soil at its lower edge. 'Setting the moisture line' stops capillary action and seals moisture in suitable soil types. This combination of benefits is ideal for minimizing weeding passes while maintaining residue.
Rigid or flex frame rod weeders work in listed (furrowed) row-crop fields in final seedbed preparation, and to weed after planting where germinating crop seeds are deep enough for the rod to pass over them. The pass firms seed into moisture and gives it a weed-free, mulched covering to jump ahead of later weeds. If the seedbed benefits aren't needed, stubble-mulch tools may be preferable to rod weeders. They can leave about as much residue but have no moving parts to maintain.
Design Features: The leading edge of the rod spins upward as it travels 1.5" to 2.5" below the surface. Rods can be round, square or hexagonal of 0.78" to 1.12" high-carbon steel stock. They are fastened by U-shaped ground arms to a toolbar. Rods are powered by a reversing chain drive on ground-driven systems, hydraulics, or PTO. Most rod weeder implements have field cultivator sweeps running ahead of the rod to loosen the soil profile. This helps to maintain consistent rod depth. Section lengths (7', 10' or 12') overlap. Springs or hydraulics return rod sections to the soil after they trip up (10" to 20") to clear obstructions. Some makers provide rod weeder attachments for field cultivators, chisel plows or residue-managing plows. The rods add weeding, leveling and mulching effects and set a moisture line.
Model for comparison: 36' ground driven, pull/drawn type, with sweeps
Rec. PTO HP: 100 to 150
Speed: 5 to 7 mph
List price: $20,600
Width range (all makers/all models): 28' to 64'
Sources: 17, 58, 68
Farmers: Cavin, Smith