There are still many questions about row spacing for soybean production. Our research information has found that narrow rows (15-inch or 7.5-inch) result in equal or greater yields compared to 30-inch rows when the yield environment is greater than 50 bushels per acre (regardless of planting date, seeding rate, or maturity). Below this yield threshold level, narrow rows tend to result in yields about equal to or slightly below (depending on the growing conditions, water status) yields in 30-inch row spacing. Narrow rows have several benefits such as early canopy cover, better light capture, improved weed control, and reduced erosion. Poor stands, however, are more common with narrow than with wider row spacing.
For the 2015 season, on-farm studies conducted in collaboration with the United Soybean Board and Kansas Soybean Commission showed a slight yield improvement with narrow rows (Fig. 1) in varying yield environments. Yields in narrow rows (15-inch) were higher at the Riley Co. (+2.7 bu/acre) and Franklin Co. sites (+1 bu/acre). Yields in narrow rows were slightly less at the Jefferson Co. site (-0.6 bu/acre).
At the Riley Co. site the overall stand counts were about 6,000 plants/acre lower in 15-inch rows then 30-inch (final plant population of 122,000 vs. 128,000 plants per acre for 15-inch vs. 30-inch, respectively). The opposite trend was found at the Jefferson Co. site, where the stand count in 30-inch rows was 104,000 vs. 86,000 plants per acre in 15-inch rows. For the third site, Jefferson Co., the stand counts for 15-inch was lower by approximately 10,000 plants per acre as relative to the 30-inch row width (final plant population of 119,000 vs. 128,000 plants per acre for 15-inch vs. 30-inch, respectively).
Riley County
Franklin County
Jefferson County
Figure 1. Yield average by individual replication for row spacing trial (15-inch vs. 30-inch) for three locations across the state of Kansas (Riley Co., Franklin Co., and Jefferson Co.) during the 2015 growing season.
Overall, narrow rows provided a yield response ranging from -0.6 to +2.7 bu/acre. An additional benefit for narrow rows was enhanced early light interception and better weed control.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
ciampitti@ksu.edu
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