Early season soybean stress matters

Growth on the front end of soybean production is essential; however, what appears as a growthier plant doesn't always guarantee more bushels. To take a closer look at this theory, Farm Journal Field Agronomists Ken Ferrie and Missy Bauer continued their efforts in Illinois and Michigan using land rollers to evaluate timing stress during critical growth stages and if starter fertilizer pays in yield. The roller plots will continue this spring, including chemical comparison.

Benefits of Early Stress Extend Beyond Yield

Using a land roller on rocky terrain, such as in southern Michigan, is beneficial to bury rocks and improve harvestability. In 2014, Farm Journal Field Agronomist Missy Bauer incorporated a Mandako land roller into a multiyear plots effort to study whether stressing the soybean plant early can lead to yield gains. In her first year, Bauer's field trials showed an average 2.4 bu. per acre boost from rolling during early V stages (V1 is one trifoliate and V2 is two trifoliates).

In 2015, Bauer followed similar protocols to evaluate if early season stress triggers the branching effect and shortens internodes, which can lead to higher yields. To take a closer look at where the yield gains originates, the test plots crew took the research a step further and evaluated the percent of broken plants after rolling, pod and seed counts, and harvest loss.

What Ken Ferrie and Missy Bauer Think You Need to Know

  • Plots show an average 3 bu. yield gain using a land roller during V1 and V2 growth stages.
  • Using a land roller helps improve harvestability, smooth fields for other in-season applications and bury rocks.
  • Aggressive soybean growth on the front end does not always guarantee higher yields.

"We wanted to pinpoint if the yield gains are from stressing the soybeans during critical growth stages or from adjusting header height at harvest due to the rocky terrain," Bauer says.

Each of the five plot locations compared rolling in different tillage environments and at various timings, including post-plant (pre-emergence), early V stage and late V stage. Each field trial included three repetitions comparing the following:

  • Farm Site #1: post-plant, V1, V3, control, conventional till
  • Farm Site #2: post-plant, V1, V3, control, vertical till
  • Farm Site #3: post-plant, V1, V3,

    control, no-till
  • Farm Site #4: post-plant, V1, V3,

    control, no-till
  • Farm Site #5: V1.5, V2, control, vertical till

"The goal isn't to break the plants, but to stress them by bending them, which shortens the internodes," Bauer says. "It's important plants break above the cotyledons because each cotyledon provides an additional growing point. If the plant breaks below the cotyle- dons, it might die."

If Broken, Location Above or Below Cotyledons Matters

Nutrients that drive growth come from food reserves in the cotyledons. If plants break after rolling, it's important they break above the cotyledons for an additional growing point. Breaking below can result in plant death.

This placement is essential because nutrients that drive growth come from food reserves in the cotyledons. The food supply will last approximately 10 days after the VE or until the V1 growth stage, according to Farm Journal Field Agronomist Ken Ferrie.

"Within this 10-day time frame, cotyledons lose 70% of their weight," Ferrie says. "A loss of both cotyledons at VE can reduce yield by 9%."

Across four of the five farm sites, at V1 after rolling, on average 9.5% of the plants were broken compared with 25.4% at the V3 growth stage

At the V1 rolling, only 1.1% of the 9.5% broke below the cotyledons compared with 20.5% of the 25.4% at V3.

"The data shows rolling at the V3 growth stage can snap the stem causing a decrease in yield," Bauer says.

In 2015, across all five plot locations, the yield results were similar to 2014 data, showing an average 3 bu. per acre gain from rolling during early V stages

The timing of the early season stress changes the overall structure of the plant, Bauer says. Based on an average of three locations, the post-plant timing increased yields by 1.9 bu.; at V1, 3.1 bu.; and at the V3, 0.5 bu.

"We found the early season stress from bending caused the plant to bush out, shorten the distance between the nodes and add more total nodes, which allows for more pods per plant," Bauer says.

Across three plot locations, which showed a yield response after rolling, the pods increased 14% to 17% per plant and the seeds per plant increased 11% to 20%. The increases help show where the yield response originated.

Bauer and crew also took a closer look at harvest loss counts. Soybeans rolled at the post-plant timing had an average 0.42 bu. per acre decrease in harvest loss, and rolling at V1 had a 0.34 bu. decrease compared with the check. At the V3 rolling, there was an increase of 0.26 bu. per acre due to the plants lying closer to the ground.

Ferrie found similar results in his first year in central Illinois using a land roller from Summers Manufacturing.

"Using the land roller in our region eliminated the rock factor and allowed us to solely focus on yield gains derived from stressing the soybean," Ferrie says. "We were able to run our combine heads on the ground across the entire field."

In 2015, 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%.

"We actually snapped the necks of the plant causing damage to the arch at VE and knocked cotyledons off at VC," Ferrie explains. "Even though pod set increased by 7%, reducing the overall stand made yield go backward. Similar to rotary hoeing, check behind the machine to evaluate performance and possible damage."

After one year, Ferrie found the optimum window to use a roller to stress soybean plants for potential yield gains is V1 to V2.

"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," Ferrie says.

Early Growth Might Not Equal More Yield

In 2015, Farm Journal Field Agronomist Ken Ferrie and the test plots crew continued to study the use of starter fertilizer in soybeans.

"Early aggressive vegetative growth on the front end of soybeans does not always guarantee higher yields, like it can in corn," Ferrie says.

Previous starter fertilizer data in central Illinois has shown little to no yield response using starter, so in 2015, Ferrie increased the starter fertilizer rates in hopes of a stronger response.

The study was conducted in a no-till, soybean-following-corn field planted in 30" rows. The crew used a Kinze 8-row planter outfitted with Schaffert Generation 2 fertilizer disks for 2x2 applications. The Schaffert attachment cuts a trench 2" away from the seed and uses an injection nozzle to apply fertilizer. The field trial evaluated three starter blends: 16-54-8, 26-0-92 and 47-0-46. All applications were applied 2x2 and replicated three times in the field. The blends used elevated rates of nitrogen, phosphorus and potash to try to trigger different responses. When using starter fertilizer in soybeans, these totals would be a part of your overall nutrient program, not additional amounts, Ferrie notes.

In 2015, all three applications yielded within 1 bu. of the check, which isn't enough to justify starter fertilizer in soybeans in central Illinois. Although, using starter fertilizer for early season growth in soybeans helped close the rows quicker in wide-row soybeans for weed control.

"In this area, starter fertilizer is not necessarily required for early soybean growth, especially compared with the strong effects in northern states with shorter growing seasons," Ferrie says. Although the responses might not pay in certain regions, Ferrie says it' s critical to evaluate why corn and soybeans differ in the physical symptoms of using starter fertilizer.

"Corn sets yield early in the growing season, so keeping plants happy from the start often results in a yield boost," Ferrie says. "Soybeans set their yield later, during the reproductive stages, therefore the early vegetative growth has less of an effect."

Thank You to Our Test Plot Partners

Case IH, Jay Barth, Bill Hoeg, and CJ Parker; New Holland, Daniel Valen, Ken Paul, Mike Kizis and Sheldon Gerspacher; Burnips Equipment and Carl VanderKolk; Mandako Agri and Stew Peterson; Summers Manu- facturing and Brian Perkuhn; Central Illinois Ag and Kip Hoke; Kinze Manufacturing and Susanne Veatch; Schaffert Manufacturing and Paul Schaffert; Trimble, Frank Fidanza and John Pointon; Unverferth Man- ufacturing and Jerry Ecklund; Wells Equipment; Versatile and Adam Reid; Marco N.P.K. and Brian Waddell; Ag Leader Technology and Luke James; Yetter Corporation and Scott Cale; Precision Planting; AirScout and Brian Sutton; Schertz Aerial Service Inc. and Scott Schertz; GeoVantage; Yamaha; McLaughlin-Dooley Farms; LDK Farms and Leon Knirk; Jim Caldwell; Bob and Mary Kochendorfer; Bob Miner; Lawrence Olson; Don Schlesinger and Dan Reynolds; Michigan Soy- bean Promotion Committee and Mark Seamon; Crop-Tech Consult- ing, Isaac Ferrie, Brandon Myers and Eric Douglas; B&M Crop Con- sulting, Bill Bauer, Amanda Anderson, Chad Roach, Terry Finegan