Augers and Dibbles (continued)

Power Augers

Function

Power augers create planting holes quickly and consistently. The holes are suitable for either bareroot or container seedlings. The large, well-formed holes are made without compressing the soil (as happens with many other tools), contributing to seedling survival and growth. Power augers are valuable for planting in hard, shallow soils and on harsh sites.

Description

Power augers used for reforestation have small gasoline engines. A growing number of these devices have been adapted to use chain saw engines. Some models use a backpack-mounted engine for power. The larger power augers (including two-person models, vehicle-mounted models, and hydraulic and remotely powered models) are not used commonly in planting operations, so they are not considered here.

Chain saw-powered augers use equipment commonly found at reforestation sites. Some varieties allow the chain saw engine to be attached and detached from the auger quickly, so operators can use the same equipment for slash and brush clearing and for creating planting holes.

Backpack powered augers have the engine mounted to a backpack frame for carrying. The auger drive and bit can be hung from the frame, freeing the operator’s arms for other tasks. However, many operators are uncomfortable with having the engine noise and exhaust fumes right behind their head.

Auger bits come in a wide variety of shapes and sizes. The standard bit has a replaceable, round nose piece of hardened or carbide steel at the end of the main shaft. The soil-augering mechanism wraps around the central shaft, spiraling up from the bit in evenly spaced rings.

For small container stock, core sampling bits are sometimes used to create uniform planting holes quickly. These bits consist of a main shaft with two clamshell coring devices attached to the lower end. In moist, firm soil conditions, the bit loosens the soil in a narrow column and the material is cleanly removed when the bit is withdrawn. The bit is vulnerable to hidden obstacles.

The cone-shaped auger bit has a double taper to the auger rings. The auger widens gradually from the tip to its widest point and then narrows again. The spacing between the auger rings is not consistent. Although the cone-shaped bits are heavier than standard bits, they create cavities that are more like the root patterns on bareroot stock. They also penetrate the ground more quickly and glaze the soil less.

The Moottorimyra Tree Planter is a specialized auger designed to create a planting hole and scarify the site simultaneously. A chain saw engine is the power source. The bit digs with a simple twisted tip. A disk is attached horizontally on the shaft, just above the tip. Teeth mounted on the disk's underside scalp the site around the hole as the hole is being dug. Tips can be changed to produce different hole diameters. The scalping mechanism can be moved on the shaft to create holes with different depths. The Moottorimyra system is limited to relatively small holes and usually to container or small barefoot stock. The bit weighs 14 pounds (6 kg) and the scalper clears a 9 inch (23 cm) area. (top)

Operation

Planting with a typical power auger requires a three- to four-person crew. One person prepares scalps, one or two persons operate the auger, and one person plants the seedlings. Fatigue is reduced by rotating the assignments. The planting hole is created by drilling a vertical hole with the auger, which also heaps soil around the hole. After the auger bit is withdrawn, a seedling is placed in the hole. Operators pack that soil firmly around the roots. A planting crew using a power auger can plant about 750 seedlings per day. (top)

Advantages

Survival rates for seedlings planted with power augers are usually high. Power augers produce large, deep holes with little effort by the operator. The large holes can accept bareroot seedlings that have spreading root systems. Augers are versatile devices with bits available for drilling postholes, drilling wood, and boring ice. (top)

Disadvantages

Power augers are not well suited for sites with very large rocks or roots. In loose soil or deep forest litter, material tends to fall into the holes before the seedlings are planted. If the dirt is not carefully firmed around seedlings, fine soils may settle to the bottom of the refilled hole. Auger bits are expensive and tend to wear out quickly.