Got Rocks? Try Rolling

The next time you're silently (or loudly) cursing a rock that snaps a section on your soybean head's sickle bar, think about farmers like Keith Van Kleek.

Soon after planting, the Terril, Iowa, farmer exacts revenge against rocks and corn root-balls that hatch soybean harvest havoc. He rolls soybeans with a large roller that smooths fields by pushing these obstacles down into the soil. This creates a smooth field nearly free of rocks and root-balls that can damage guards, sickle sections, or internal combine parts at harvest.

"You get a little bit of satisfaction hearing it banging away, giving those rocks a good headache," Van Kleek jests.

Rolling rolls rocks

Farmers have rolled alfalfa and grass seed for decades as a way to boost germination and to manage rocks. It's fairly new to row crops, though, and is practiced mainly in rocky areas of the Dakotas, Minnesota, and Iowa.

"We have quite a few rocks up here in certain fields," says Van Kleek. He first rolled a field eight years ago with a roller he rented from a neighbor. This made rolling fans out of him, his brother, and his father at harvest after combining a rolled field nearly free of rocks.

"We thought this was wonderful," says Van Kleek. "Rolling made it a lot easier to combine. We used to be replacing sickle sections all the time. We used to be under pressure at harvest all the time, worrying about all the rocks."

No more.

Meanwhile, rolling has become so popular that the farmers Van Kleek used to do custom work for now have their own units. He has expanded custom work to other areas, like rolling corn-on-corn ground prior to planting. The leveling and smoothing effect from rolling can create better planting conditions, he says.

"Rolling isn't an absolute cure-all," he says. "There are some bigger rocks that still have to be picked up."

Rolling can enable you to lower your combine's soybean head and to harvest pods that otherwise would not be combined due to concerns about striking rocks or root-balls. In rocky or rootball-infested fields, rolling has boosted yields up to 2.5 bushels, says Van Kleek. However, yield increases may not occur on smoother fields, he adds.

Costs

Roller costs can run $17,000 for a 20-foot unit; $32,000 for a 45-foot unit; $65,000 for the 85-foot model. Custom land-rolling rates can range from $3 per acre to $10 per acre, with a $6.55 per-acre average. That's according to Iowa State University's 2010 Iowa Farm Custom Rate Survey.

In some cases, the cost can be erased by lower harvest costs on rocky soils, points out Jodi DeJong-Hughes, a University of Minnesota (U of M) Extension educator.

"Custom combiners will charge $5 more per acre if you don't roll," she says. "They'll also come to your field faster than for fields that are not rolled."

Rolling can also benefit soybean seed producers by nixing corn root-balls, says DeJong-Hughes. Root-balls picked up by the combine carry dirt that can attach to soybean seeds. This attached dirt can cause seed companies to dock or to reject seed soybeans. Rolling also cracks root-balls and opens them to microbial decomposition.

Drawbacks

Agronomically, though, the benefits aren't as clear-cut. A multiple-location 2008 to 2010 U of M trial showed no stand, yield, or seed-quality differences between rolled and unrolled soybeans up to V3 (third trifoliate). Rolling can also increase soil-surface compaction, destroy soil-surface aggregates, and increase erosion potential.

"Soil sealing can happen if you get a pounding rain, especially if plants have not emerged," says DeJong-Hughes. "The pounding rain can hurt emergence."

Meanwhile, the resulting washing can also lead to potential phosphorous and nitrogen loss.

Residue can flatten out and blow like a kite into neighboring fields. The resulting pile not only can inhibit growing plants and create harvesting problems in those but also cause long-term nutrient loss in the original field.

"That residue contains lots of carbon, which helps build organic matter," says DeJong-Hughes.

Prescription Basis

Use rolling selectively, advises Seth Naeve, U of M Extension agronomist.

"It's another practice that will work best when done on a prescriptive basis," he points out.

Below are recommendations on how rolling can best fit your situation.

Trade-offs

Remember that pushing rocks into the field is a short-term solution, particularly if you till and bring them up again. There are other ways to manage residue, such as strip-tilling and using residue cleaners on planters.

"Everything you do has a trade-off," says Van Kleek. "In our case, the good outweighs the bad."