In southern Michigan, Farm Journal Associate Field Agronomist Missy Bauer planted row-spacing test plots that evaluated 30", 15" and twin rows. Across the two fields, the narrow rows yielded stronger.
The environment is a driving factor when building soybean yield components and managing pests. For multiple years, Farm Journal Associate Field Agronomist Missy Bauer has led a Farm Journal Test Plots effort to learn more about the impact of row spacing, how to control white mold and more about the possibilities with variable-rate application, all in an effort to increase yields. —Margy Eckelkamp
Row Spacing Guides Management Decisions
In addition to impacting yield potential, row spacing affects pest management strategies. For the past two years, Bauer and her test plots crew in Michigan have evaluated three different soybean row spacings.
Although planting equipment often drives row spacing, Bauer encourages farmers to consider how different row spacings affect management decisions throughout the season. Row spacing influences the timing of canopy closure, the plant’s ability to harvest the maximum amount of sunlight and the environment for disease.
"We had two very different years. It was very dry in 2012, and the narrower the row, the better the outcome," Bauer says. "That allowed the canopy to close quicker and conserve more water."
In 2013, the study was conducted in two fields: the first field compared twin, 30" and 15" rows; the second field included twin and 30" rows. A Great Plains Yield-Pro planter was used for the 30" and twin rows and the cooperating farmer’s Kinze planter was used for the 15" rows.
"In the first field, comparing three row spacings provided interesting insight," Bauer says. "Across the field, the narrow rows yielded stronger. Most of the management zones showed we gave up yield in the wide rows. Twin-row yields fell between the 15" and 30" yields."
The field was planted in replicated treatments at 160,000 plants per acre, which was the farmer’s standard rate.
"There was more branching in the 30" and twin-row soybeans compared with the 15" rows," Bauer adds. "However, the rows closed sooner in the 15" rows, which allowed for earlier sunlight capture."
In three of the four yield zones, the 15" yielded the strongest; however, in the fourth yield zone 15" rows had a yield reduction of more than 1 bu. compared with other row spacings. The white mold pressure was heavy in one management zone, which was reflected in yield by row spacing. The 30" rows and twin rows had lower white mold infection, which led to higher yields than the 15" rows.
Both twin rows and 15" rows are considered narrow row spacing, says Farm Journal Associate Field Agronomist Missy Bauer. Narrow-row success stems from pest management. Zone B had heavy white mold pressure, which negatively affected the narrow rows the most.
"A lack of air circulation creates a favorable environment for white mold infection," Bauer explains. "As a result, narrow rows can see a higher rate of white mold."
Canopy closure and pest pressures drive the yield advantages with narrow row spacings.
"In 2012, we didn’t have high white mold pressures because of dry conditions, and closing the rows was a big deal," Bauer says. "Without the pest pressure, the 30" seemed to drop more and the twins and 15" rows did better."
In the second field, the farmer’s standard rate of 150,000 plants per acre was used in replicated plots comparing twin and 30" rows.