Row Width Trends, Advantages, and Considerations for Soybean
 Row width has been consistently related to soybean yield potential.
 Demonstrated in over 20 years of research, narrow rows can have a significant yield potential advantage over
wide rows.
 Machinery and time management issues have driven a recent switch to 15-inch row spacing in soybeans.
 Benefits and challenges of narrow rows should be evaluated to determine the proper row width for a farming
operation.
Background
Most literature indicates higher soybean yield occurs when
rows are spaced less than or equal to 20 inches compared to
30-inch rows.1 A study conducted from 2009 to 2011 in six
soybean producing states, compared wide (30-inch) soybean
row spacings to narrow (less than 20 inches) rows with either
normal practices (no additional treatment) or high input
management. The results showed an average of 9.9 bu/acre
advantage for narrow rows with high input versus the wide row
under normal practices. With no additional treatment, soybeans
planted in narrow rows had an average yield advantage over
wide rows of 2.1 bu/acre. Research from the Midwest and
Canada further supports a yield advantage for narrow rows
versus wide rows and indicated yield increases of 2 to 9 bu/
acre.2
Current Trends
In 1992, it was more common to use a grain drill (< 10 inches
row width) or a 30-inch row width to plant soybeans. Soybeans
in 15-inch rows have become a popular row width in recent
years.
Percent of Samples
50
40
30
20
10
0
<=10 in. row width 10.1-18.5 in. row
width
18.6-28.5 in. row
width
Differences in production areas, rotation, efficiency, and
economics can influence the trend to use narrow rows. For
example, residual phosphorus banded in corn rows could be
used by soybeans the following year when planted over the
band.
A grower can improve the efficient use of equipment by using a
split-row planter with additional row units that can be raised
and lowered to allow flexibility for soybean and corn planting.
Iowa State University research found that investment in a splitrow planter was economical for farms larger than 711 acres
with more than 30% of land base in soybean production as
long as a yield increase of 1.8 bu/acre was achieved.3 Farms
larger than 355 acres with at least 50% of the land base in
soybean production could benefit from the conversion from
wide to narrow rows.4 Even though economics favor the
decision to switch to narrow rows, there are additional pest and
environmental considerations that may influence the decision.
Narrow Row Width Advantages
Narrow rows intercept more light earlier in the season and
reach canopy closure more quickly than wide rows. The
relatively equidistant plant arrangement
1992
2006
2012
leads to increased leaf development and
light interception early in the season which
can increase crop growth rate, dry matter
accumulation, and seed yield potential.2
Canopy closure should occur before the R3
growth stage (pod set). In Iowa, 15-inch
rows often reach canopy closure 15 days
before 30-inch rows.2 Soybeans in 30-inch
rows
often do not reach canopy closure by
28.6-34.5 in. row >34.6 in. row width
the
R3
stage of growth.2
width
Soybean Row Width Distribution
Figure 1. Soybean row width trend of seven major soybean producing states. Sources: Agricultural
Statistics Board. 2007.3 Soybean objective yield survey data, 1992-2006. USDA NASS. Ob Y12 (7-07).
Data from 2012: National Agricultural Statistics Service USDA. 2012. Crop production. ISSN: 1936-3737.
www.stewartseeds.com
Soil moisture is preserved and sunlight
penetration is reduced with rapid canopy
closure.
Consequently, weed emergence and weed seedling growth are
suppressed by the canopy shading of narrow row crops.
According to research, the critical time for weed removal in
soybeans occurred earlier in wide rows versus narrow rows.5
These results potentially mean more flexible post–applications
of herbicides in narrow row soybeans.
Narrow row widths can improve combine efficiency because
plant distribution is even, allowing better flow into the combine.
Harvest losses may be reduced because narrow-row soybeans
have the lowest pods set higher than in wide rows.6
Row Width Considerations
Planter equipment, seed delivery, and placement concerns
have limited the adoption of narrow row widths in soybean for
some growers. Split-row planter technology can be a solution
to the cost concerns of having a planter/drill for soybeans and a
second planter for corn.2 Precision drills have improved seed
placement which can help reduce the need for high seeding
rates. A study conducted in Iowa found that a uniform harvest
population of 100,000 plants/acre or more is adequate to attain
yield potential.2 Additionally, research has demonstrated plant
establishment was greater for narrow rows than for wider rows
(Figure 2).
Narrow row soybean can create environmental conditions that
are more favorable to disease development compared to wide
rows. Cool, wet conditions during flowering promotes white
mold (Sclerotinia sclerotiorium). Soybean product selection,
seeding rate, and row spacing are essential for white mold
management. A 15-inch row width, rather than drilling
soybeans, can be a benefit along with other white mold
management recommendations. A 30-inch row width may not
be beneficial because of the yield trade-off, unless white mold
incidence is frequent. Soybeans in narrow rows may be more
susceptible to brown stem rot and soybean cyst nematode
when the environmental conditions are correct.2
A study conducted by Virginia Polytechnic Institute and State
University and University of Delaware found that, wheel track
damage during soybean reproductive stages can be a concern
in narrow row soybean. Such damage was found to decrease
yield in 7.5- or 15-inch row spacings, but not 30-inch rows.7
Water stress inhibited the ability of soybeans to compensate for
damaged rows in this study. A related issue concerns pesticide
penetration of the soybean canopy. While row width affected
fungicide spray coverage, disease severity was not affected.8
Spray penetration into the canopy may be compromised more
in narrow rows than wide rows, which may affect the efficacy of
some pesticides.
Final Plant Population
(plants/acre)
Row Width Trends, Advantages, and Considerations for Soybean
200,000
180,000
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
0
15"
30"
75,000 125,000 175,000 225,000
Seeding Rate (seeds/acre)
Figure 2. Row spacing and population effects on final population.2
Summary
Research has shown a potential yield advantage in narrow row
widths compared with soybeans planted in 30-inch rows.
Factors such as equipment costs, time allocation, and pest
management can vary by region, and farm operational needs.
Such factors must be part of the decision to change row width.
An individual farm assessment of costs and benefits is needed
to determine the best management practices for soybean
production.
Sources:
1
Haegele, J.W. and F.E. Below. 2013. The six secrets of soybean success. Illinois Soybean
Association. http://www.ilsoy.org (verified 9/27/13).
2
Pederson, P. Row spacing in soybean. Iowa State University Extension. http://
extension.agron.iastate.edu (verified 9/27/13).
3
Agricultural Statistics Board. 2007. Soybean objective yield survey data, 1992-2006. USDA
NASS. Ob Y12 (7-07).
4
DeBruin, J.L. and P. Pederson. 2008. Effect of row spacing and seeding rate on soybean
yield. Agron. J. 100: 704-710. http://extension.agron.iastate.edu (verified 9/27/13).
5
Bradley, K.W. 2006. A review of the effects of row spacing on weed management in corn
and soybean. http://www.plantmanagementnetwork.org (verified 9/27/13).
6
Elmore, R. 2005. Low soybean pod heights have increase harvest losses. University of
Nebraska, Lincoln. CropWatch. http://cropwatch.unl.edu (verified 9/27/13).
7
Holshouser, D.L. and R.D. Taylor. 2008. Wheel traffic to narrow-row reproductive-stage
soybean lowers yield. http://www.plantmanagementnetwork.org (verified 9/27/13).
8
Kroger, T.H. et.al. 2005. Fungicide spray coverage as affected by spray volume and nozzle
type in wide- versus narrow-row soybean. http://www.plantmanagementnetwork.org
(verified 9/27/13).
United Soybean Board. 2013. The Kitchen Sink Project. http://usb-extremebeans.com
(verified 9/27/13).
For additional agronomic information, please contact your local seed representative.
Individual results may vary, and performance may vary from location to location and from
year to year. This result may not be an indicator of results you may obtain as local growing,
soil and weather conditions may vary. Growers should evaluate data from multiple locations
and years whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL
DIRECTIONS. Leaf Design® is a registered trademark of Monsanto Company. Stewart and
Design™ and Stewart™ are trademarks of American Seeds, LLC. All other trademarks are the
property of their respective owners. ©2014 Monsanto Company. 04162013SEK,
10102013PLB.