Using a land roller is a common practice to help improve harvestability, smooth fields for in-season applications and bury rocks. The footprint of a roller as it runs across the soil is light, which reduces the risk of compaction. When the roller rises up on a rock, the weight of the roller transfers to the rock pushing it into the ground.
Since 2014, the Farm Journal Test Plots program has been using a land roller to test if stressing soybeans at critical growth stages results in a yield increase. In a multiyear effort, Farm Journal Field Agronomists Ken Ferrie and Missy Bauer closely evaluated the impact early season soybean stress has on plant architecture and overall yield.
In 2015, Bauer found an average yield gain of 3 bu. using a Mandako land roller at V1 and V2 growth stages. In 2016, she followed similar protocol and data collection to further test her findings. She focused on studying if early season stress triggers the branching effect and shortens internodes, which can lead to higher yields.
To do this, Bauer and her crew collected stand, pod and seed counts, percent of broken plants after rolling and photo observations as well as analyzed nodes, harvest loss and yield. Aerial imagery was beneficial in collecting data as well.
“Our goal was to pinpoint exactly where the yield gains originate,” Bauer says. “We want to ensure it is from stressing the soybeans during critical growth stages and not from adjusting header height at harvest due to the rocky terrain.”
Bauer’s three plot locations were in two counties in southern Michigan and all planted within five days of one another. The plots compared rolling in different tillage environments and at various timings, including post-plant (pre-emergence), V1 (first trifoliate) and V3 (third trifoliate). Each field trial included three replications comparing the following:
- Farm site #1, vertical tillage: post-plant, V1, V3 and control
- Farm site #2, conventional tillage: post-plant, V1, V3 and control
- Farm site #3, no-till: post-plant, V1, V3 and control
Before digging into yield gains, Bauer and crew first evaluated the percent of broken plants after rolling and whether plants broke above or below the cotyledons.
“If plants break, it’s essential they break above the cotyledons because the plant typically still branches and survives due to additional growing points,” Bauer says. “However, if plants break below the cotyledons, they will likely die because there are no growing points left.”
Across the three farm sites in 2016, 12.1% of plants were broken after rolling at V1 and 4.3% were broken below the cotyledon. After rolling at V3, 15.4% of the plants were broken, with 11% below the cotyledon. Across six farm sites in 2015 and 2016, Bauer collectively found only 2.8% of the plants broke below the cotyledons after rolling at V1 versus 15.8% at V3.
Your tillage system might play a vital role in pushing the limits on the timing of rolling. In the two-year study, Bauer observed more broken plants in conventional-tillage systems compared with no-till systems.
“This is likely due to taller plants or less cushion from residue,” Bauer says. “Whatever the case, it might be smart not to roll plants at late V2 in conventional tillage if they are tall.”
The yield results in 2016 were similar to the previous year, across all three plot locations, showing an average gain of 2.4 bu. per acre from rolling at V1. On average, this resulted in a return of $16 per acre. Across the three plot locations, rolling at V1 resulted in 13.8% more pods per plant and 13.9% more seeds per plant. The increase helps pinpoint exactly where the yield response originated.
“This yield response is due to an improvement in individual plant yield components and a reduction in harvest loss,” Bauer says. “Using a roller to mechanically stress the soybeans at V1 reduces the internode length and increases the number of nodes with pods per plant, which leads to more pods and seeds.”
Bauer and crew also found using a field roller decreases harvest loss. In 2015 and 2016, there was a 0.4 bu. per acre decrease in harvest loss after rolling post planting and V1 compared with the check. Rolling at V3 resulted in a 0.3 bu. per acre increase in harvest loss compared with the control.
“The V3 roller pass resulted in many plants leaning over and growing horizontally along the ground; therefore, the amount of pods missed by the cutter bar was higher,” Bauer says. “There is also a chance the increase in soybeans on the ground is due to the cutter bar splitting open low-lying pods.”
Rolling at V1, approximately 15% of the yield gain comes from a reduction in harvest loss.
In a two-year study in central Illinois, Ferrie also evaluated the effects of stressing soybeans at critical growth stages using a land roller from Summers Manufacturing. In this region, rolling is a unique practice due to the lack of rocks compared with southern Michigan.
Across 10 different replicated plots in 2015 and 2016, Ferrie found surprisingly similar yield results to Bauer considering the different growing environments. On average, rolling at VE to V1 resulted in a yield decrease of 1.2 bu. compared with a yield increase of 2.4 bu. at V1 to V3.
Ferrie found rolling at the V2 growth stage increased pod set by 33% per plant, with minimal impact on plant stand. At VE to VC, rolling increased pod set by 7% per plant but reduced the overall stand by 16%.
“Even though pod set increased by 7%, at VE we snapped the necks of the plants resulting in plant death. At VC, we knocked off cotyledons, which reduced the overall stand and made yield go backward,” Ferrie says.
Knocking off cotyledons doesn’t usually result in plant death, but it does slow growth. The nutrients that drive growth come from food reserves in the cotyledons, Ferrie explains. Therefore, knocking off cotyledons before V1 stunts the plant, often resulting in poor pod set and reduced yield.
To ensure you’re rolling during the optimum window, Bauer and Ferrie suggest checking behind the machine to evaluate performance and possible damage. Throw a hula hoop into random spots in the field, evaluate if there are broken plants and, if so, where the breaks occur. Repeat this process for every field and every variety. Time of day, temperature and variety all can make a difference in the brittleness of the plants.
“Your ultimate window of opportunity to use a roller to stress soybean plants for potential yield gains is between V1 to V3 growth stages,” Ferrie says. “At this stage, the plant is more pliable, you can roll it or push it over and it still has the ability to bounce back.
Thank You to Our Test Plot Partners
Case IH, Jay Barth and CJ Parker; New Holland, Daniel Valen and Ken Paul; Burnips Equipment and Carl VanderKolk; Mandako Agri and Stew Peterson; Summers Manufacturing and Brian Perkuhn; Central Illinois Ag and Kip Hoke; Kinze Manufacturing and Susanne Veatch; Trimble, Frank Fidanza and John Pointon; Unverferth Manufacturing and Jerry Ecklund; Wells Equipment; Versatile and Adam Reid; Ag Leader Technology and Luke James; Yetter Corporation and Scott Cale; Precision Planting; AirScout, Brian Sutton and Maykol Hernandez; GeoVantage; Valent USA and Jeff Schulz; LDK Farms and Leon Knirk; Jim Caldwell; Bob and Mary Kochendorfer; Bob Miner; Lawrence Olson; Michigan Soybean Promotion Committee and Mark Seamon; Crop-Tech Consulting, Isaac Ferrie, Matt Duesterhaus and Eli Sloneker; B&M Crop Consulting, Bill Bauer, Amanda Anderson, Chad Roach and Terry Finegan
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