With several thousand acres of corn grown under dozens of center pivots, Brent Clark depends on larger tractors, combines and grain carts to make the extensive operation work efficiently. But the tracks from those massive tires can create complications from compaction on the Dumas, TX, operation.

Fortunately, that thick hardpan isn't there long enough to thwart root development and shorten yields. Clark depends on a proven, yet still unique deep plow system to loosen the soil 1 ft. underground. And he does it without disturbing the firmness of the surface.

A 10-leg Bigham Brothers VersaTill is his deep tillage tool of choice. The plow features legs angled 45° to the side to work 12 to 17 in. deep. The angled leg actually “lifts” the soil, which fractures along its natural planes of weakness and then settles back again. The plow is designed to leave virtually all residue undisturbed in a conservation tillage program.

Better growing conditions

Loosening by deep tillage systems improves water infiltration and absorption, encourages root development and allows for deeper fertilizer placement. “I like the VersaTill's gentle lifting action,” Clark says. “It will not mix topsoil with subsoil, bury residue or require additional tillage trips. The bent leg does not throw up clods like a normal ripper plow. Also, we don't have to come back with an inner-row ripper behind the planter.”

Clark, who manages the farm for a local company, prefers 30-in. rows. The subsoiler follows corn harvest in the fall. “We first run a scalloped disk to chop the stalks, then follow with the deep tillage,” he says, noting that the 10 subsoiler legs are spaced 28 in. apart. “We run about 5 mph behind a Caterpillar 95, 430-hp tractor.”

A disk is attached to the front of the machine, while a basket attachment is used to level out the surface. “We can deep plow about 120 acres in a 12-hr. workday,” Clark says.

When is subsoiling warranted?

Tony Vyn, Purdue University extension cropping systems specialist, says that only well-defined, compacted soil layers 4 in. or more deep are candidates for loosening, or subsoiling. He suggests that growers evaluate for compaction when the ground is uniformly wet to a depth of 2 ft. or more.

“A farmer should dig a 20- to 24-in.-deep hole, exposing a vertical soil profile,” Vyn says. “Then, using constant pressure, try pushing a pocketknife blade along the exposed profile from the soil surface down to the maximum depth of the hole. If the farmer has a harder time sliding the blade through a particular area a few inches wide, a compacted layer might be present.”

Make the evaluations at four or more random areas in fields of 50-plus acres. “If a significant number of roots have grown sideways before finding a crack in the soil and growing down again, it may be a sign of compaction,” Vyn says, adding that subsoiling should be done only when soils are dry. “That's because we tend to get more shattering of the soil between the shanks of a ripper or subsoiling tool. If rains cause very damp soil conditions, then it's possible to create a greater problem using a subsoiling tool through smearing as the tool is pulled through the soil.”

Vyn describes the ideal subsoiling tool as one that efficiently achieves the required loosening, but leaves the surface soil level enough to eliminate the need for any subsequent tillage before planting the crop and retains sufficient residue cover for adequate erosion control.

Limit compaction

Agronomists and veteran subsoilers note that compaction can be limited by holding down the amount of ground driven on to 30% or less, with 20% as a more ideal target. However, even with minimum tillage operations, compaction can occur during mid-season applications and with combine, tractor and grain cart traffic during harvest.

“New GPS-coordinated parallel tracing systems may permit more control of wheel traffic placement in the same track paths in successive years,” Vyn notes.

The VersaTill is available in 4, 6-, 8-, 10- or 12-leg models, each with the capacity to have legs spaced from 20 to 40 in. apart. George Mayo, Bigham Brothers representative, gives the following general prices for the subsoiler, disk and basket attachment: 4-leg unit, $22,500; 6-leg, $28,345; 8-leg, $33,595; and 10-leg, approximately $37,000. For more information, contact Bigham Brothers, Dept. FIN, Box 3338, Lubbock, TX 79452, 800/692-4449, visit www.bigham brothers.com or www.freeproductinfo.net/fin.

Other popular plows

Deep tillage plows in the DMI ecolo-tiger series from CNH, Goodfield, also are popular. The ecolo-tiger 730B unit features “minimum residue disturbance shanks.” They are spaced from 15 to 30 in. and can go 16 in. deep. The maximum operating width is 17 ft. 6 in. Prices start at about $23,000 for the 730B equipped with a disk attachment and $18,000 for a small 530B unit with a disk attachment. For more information, contact CNH, Dept. FIN, Box 65, Goodfield, IL 61742, 309/965-2233, visit www.dmifarm.com or www.freeproductinfo.net/fin.

The Sunflower 4510 Rigid Disc Chisel is available with 11 to 15 shanks on 15-in. centers and disc gangs both front and rear. Front gangs are individual, and both gangs feature independent adjustments. It provides uniform soil fracturing to a depth of about 12 in. and a soil profile of mixed residue. Unit prices start at about $30,000. Contact Sunflower Mfg., Dept. FIN, Box 566, Beloit, KS 67420, 800/748-8481, visit www.sunflowermfg.com or www.freeproductinfo.net/fin.