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Rolling Stones | If you Have Rocks (and Root Balls), Should you Roll?


“Rattle! Clank! Whomp!”

There’s quite a racket coming from Gary Dierks’ newly planted soybean field. It’s the sound of rocks and corn root balls being pushed down into the soil by a 50-ft. Degelman land roller sweeping over the field.

Land rolling is catching on with Upper Midwest soybean growers. The practice began in Canada, gained steam in North Dakota and northwestern Minnesota, where it has become routine, and now is spreading like crazy in southern Minnesota and Iowa.

Land rolling prepares fields for harvesting by pushing down rocks, flattening residue and leveling the ground. Proponents say rolling also makes combining beans faster, easier and less tiring. There’s less chance of picking up rocks or big corn root clumps, which can damage guards, sickle sections or expensive internal combine parts. “Farmers really like it,” says John Holmes, Iowa State University (ISU) Extension field agronomist.

Despite the growing popularity of land rolling, though, few Extension experts are ready to give it an unqualified endorsement. “This concept is new and not yet well tested in the field,” says Mahdi Al-Kaisi, ISU Extension soil scientist. Among his concerns: greater potential for soil compaction, surface runoff and soil erosion, as well as questionable economic return.

Gary Dierks, Chokio, MN, farms highly productive silt loam soils studded with rocks left behind by glaciers. For the last five years, he's paid the local co-op $5.50/acre to roll his soybean fields immediately after planting.

Rolling is a useful harvest aid, he says. “Since I started rolling, I’ve never broken a sickle section,” a mishap that used to often slow him down. “You get a cleaner cut, too, because the cutter bar isn’t bouncing around so much. It glides across the field.” And there’s a lot less soil in the grain tank, he adds.

Although some people claim that rolling soybeans increases yields, “we haven’t seen that,” Dierks says. He did on-farm strip trials to test rolling, and “there was no yield difference.” Recent research in North Dakota, Minnesota and Iowa confirms Dierks’ observations, finding no yield gains from rolling. The biggest advantage, Dierks says, “is peace of mind.”

Gary Naeve, a farmer and president of Custom Made Products in Humboldt, IA, is one of the largest Midwest land-roller dealers. He rolled his own soybean fields for the first time in 2004 and was an instant believer. His neighbors were curious about what he was doing, and before long he was leasing and selling the big rollers. He's sold over 200 of them; and last season he had 40 machines out smoothing Iowa soybean fields.

“If you once roll beans, you won’t want to plant again without it,” Naeve says. Seed bean buyers “love the rollers,” too, he adds, because rolling “eliminates dirt in the seeds.” Ditto for custom combiners, who can harvest rolled fields faster. Insurance companies like them, he says, because claims for combine damage drop.

Does the practice put money on growers’ bottom lines?

“That’s not the real issue,” Naeve says. “The real payback is that you can combine with no interruption for maintenance, no dirt in the beans and less downtime for repairs.” If your beans are ready, you can get into a rolled field even if the ground is wet, he says. And there’s less operator stress and fatigue, he says – a benefit that’s hard to put a dollar value on.

Rolling's red flags

Amid the rush to roll, some Extension experts are raising a red flag about the practice.

“I’m very concerned about damage to soil quality,” says ISU’s Al-Kaisi. The big drums “crush soil aggregates” on the surface, he says, raising the risk of crusting, reducing water infiltration and increasing the potential for soil-surface compaction, surface runoff and wind and water erosion.

Despite the size of the big rollers, deep soil compaction isn't much of a concern, according to Mark Hanna, ISU Extension engineer. The drums exert a packing force of about 3 lbs./sq. in., he says, similar to the pressure exerted by the closing wheels of a planter.

“The jury is still out on this,” Hanna admits. “I understand that it’s frustrating if a rock goes up onto the grain platform or into the combine.” But, he adds, “I’m a little skeptical about whether it’s a good idea in the long run.”

Both Hanna and Al-Kaisi also question the payback for rolling.

“It’s hard to see how the cost is being recovered,” Hanna says. “I hear it reduces the amount of soybeans left in the field, but I’m skeptical of that. Earlier research shows that if the beans are standing well and the combine is well adjusted, stubble-cut loss is less than 1 bu./acre, and should be closer to half a bushel.”

Al-Kaisi points to “the additional time, fuel and machinery cost” of rolling. “Is this an economically sound practice,” he asks, “even allowing for downtime for machinery repair?”

He continues: “What is the problem being solved? There is a lot of good technology to adjust and calibrate the combine correctly” and manage residue. If you have rocks, he adds, “hire some kids to pick them up. It’s cheaper.”

Naeve counters: “You can’t find kids to pick rocks these days. And it’s the rocks the size of eggs, which we don’t pick up, that damage the sickles.”

Some fields are better suited for ground rolling, says Seth Naeve, a University of Minnesota Extension soybean agronomist (and a distant relative of Gary Naeve). Instead of “rubber stamping the practice for every soybean acre,” he recommends “a more prescriptive approach.”

For example, rolling is a good fit for higher-value seed beans or food beans, where dirty beans could be docked at the elevator, says Jodi DeJong-Hughes, an Extension tillage specialist who led ground-rolling trials at the University of Minnesota.

It also makes sense for flat, rocky fields, she says, although she points out that “eventually, you’re going to have to pick rocks. Rolling doesn’t push down anything bigger than a football-sized rock.”

When is the best time to roll?

When is the best time to roll soybeans?

That’s one of the main questions farmers are asking about this new practice, says John Holmes, Iowa State University (ISU) Extension field agronomist. Recent research in North Dakota, Minnesota and Iowa evaluated the timing and risks of rolling soybeans.

University of Minnesota field-scale trials in 2009 and 2010 looked at rolling immediately before and after planting, at cracking and at V-1 and V-3. The research found that rolling did not significantly affect stand counts or yields, says Jodi DeJong-Hughes, a University of Minnesota Extension tillage specialist.

“We did all of our rolling in the afternoon when the plants were a little limp to decrease injury,” she notes. Rolling at V-3 did cause more plant damage, she says, but that damage didn’t lower yields. “Wheel traffic caused more damage than the actual rolling.” Still, she adds, “You are definitely increasing your risks if you roll after the plants are up,” so it’s safest to roll just before or after planting.

The Minnesota research also found that “rolling raises the risk of sealing the soil and consequent ponding,” DeJong-Hughes says. Leaving more residue on the surface protects both the soil and the plants from the roller, she adds. However, blowing residue can be an issue after rolling. Wet soil or cool, cloudy conditions also raise the risk of plant damage from rolling, she says.

Rolling may intensify runoff, too, especially on sloping fields. Trials in northern Iowa in 2010 showed that rolling “cut water infiltration rates by about 150%,” says Mahdi Al-Kaisi, an Iowa State University Extension soil scientist. “It’s only one year of data, but it raises questions.”

The Minnesota and Iowa findings confirm earlier research by North Dakota State University (NDSU). Trials in 2003 and 2004 concluded that “there was no yield loss from rolling,” says Greg Endres, an Extension soil scientist at the Carrington Research Extension Center. “But injury levels go up if you delay rolling until the first trifoliate stage,” when plants are 3-4 in. tall. “If you roll after the crop emerges, we recommend doing it at the unifoliate stage because the plant can recover more easily.”

NDSU also found that rolling breaks down soil-surface aggregates, increasing the potential for crusting and erosion, especially in finer-textured soils, Endres says. “If we have strong winds after rolling, that thin layer of soil can blow, or if we have heavy rains, it can wash.”

Judd Moore is an agronomist for New Horizons Ag Services in Chokio, MN. The co-op has been custom rolling soybean ground in west-central Minnesota for seven years, and keeps three 50-ft. Degelman rollers busy every spring. “We have been able to roll up to V-3 as long as the stems are soft” and the ground and plants are dry, Moore says. “You can’t roll if there is dew, because the plants stick to the rollers.”


Big wheels rollin’

The big drums rolling across Midwest soybean fields at planting time range in size from 20 to 85 ft. wide, says Gary Naeve, a farmer and president of Custom Made Products, Humboldt, IA, a large Midwest implement dealer. The hollow steel cylinders – no ballast – are generally 42 in. in diameter. A 62-ft. roller can cover about 600 acres/day, he says.

Naeve prefers models with independently suspended sections. On his own farm, Naeve rolls right ahead of the planter, or when the beans are 2-3 in. tall. Rolling right after planting can cause residue to blow if it’s dry and you get a strong wind soon afterward, he says.

The big rollers range in price from $17,000 for a 20-footer to $65,000 for the 85-ft. model, he says. Custom land-rolling rates range from $3/acre to $10/acre, averaging $6.55/ acre, according to Iowa State University’s 2010 Iowa Farm Custom Rate Survey.


January 2011

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