T. S. Sahota¹

 ¹ Thunder Bay Agricultural Research Station, 435 James St. S, Thunder Bay, Ontario, Canada P7E 6S7 (e-mail: tarloksahota@tbaytel.net)

 Sahota, T. S. 2011. Effects of row spacing and direction on soybean yield at Thunder Bay. Paper presented at the ASA-CSSA-SSSA Annual Meetings in conjunction with the Canadian Society of Soil Science, Oct 16-Nov 19, 2011, San Antonio, TX. With corn planters around farmers are tempted to plant soybean at a wider spacing. While this may work in warmer areas with relatively longer growing seasons, it may not work in the colder regions of North America with short growing seasons of 100-120 days. It was thought that bi directional seeding that has been reported to improve solar radiation utilization might help in increasing soybean yield as compared to its uni directional seeding.  Field experiments were conducted at Thunder Bay, Northwestern Ontario, during 2008 – 2011 to study the effects of row spacings and direction on soybean yield. Treatments included all combinations of two row directions (uni directional seeding in East West direction and bi directional seeding in East West and North South directions) and five row spacings (6, 12, 18, 24 and 30 inches) and were replicated four times in a completely randomized block design. In two out of three years, increasing row spacings from 6 inches significantly reduced the soybean grain yield. In 2009 and also on an average over three years grain yield with 12 inches row spacings (2.28 t ha^-1) was not significantly lower than that with 6 inches row spacings (2.35 t ha^-1). Even though seed rate was kept constant for all row spacings, final plant stand was highest at 6 inches row spacings. Increased plant to plant competition within the rows at wider row spacings might have killed some plants. However, pods per plant were not significantly affected by the row spacings in any of the years. Effect of row direction on plant stand, pods per plant or grain yield was not significant. Interaction between row spacings and row direction was not significant. It may therefore be advisable to seed soybean uni directionally at 6 inch row spacings in colder parts of North America such as Thunder Bay, Northwestern Ontario!