Soybean seeding windows

Crop Soybean
Start Date2017
End Date2018
Principal InvestigatorMacMillan, Kristen, University of Manitoba

Research Objectives

Determine the optimum seeding window for soybeans in various agro-eco regions of Manitoba.

Project Description

Traditional recommendations are to plant soybeans when soil temperature has warmed to at least 10°C, which is typically May 15-25 in Manitoba. However, farmers are planting soybeans earlier and recent work by Tkachuk (2017) supports this trend. Tkachuk investigated soybean seeding dates across a range of soil temperatures from 6 to 14°C at Carman, Morden and Melita. At three site-years, soybean yield was optimized with the earliest planting date. To further validate these findings across a wider range of environments, this study was initiated at Carman, Arborg and Melita in 2017. Instead of soil temperature, which did not limit yield in previous work, seeding date treatments were defined as four seeding windows. Within each date, an early and long soybean variety was seeded.

Preliminary analysis of 2017 yield data was done by site-year; at Melita17 (M17), soybean yield was optimized within the early and normal seeding window compared to late seeding. Soybeans seeded very early at Melita showed a statistically similar yield to the other dates despite experiencing frost on May 18 and 19 (emergence was recorded May 16). At Carman17 (C17), seeding at the normal or late date decreased yield compared to the early date, and while the very early date had a statistically similar yield, soybeans in this treatment were damaged by frost on May 18. There were no statistical differences in yield across seeding dates at Arborg (A17), despite a numerical trend for reduced yield as seeding was delayed. Frost occurred in Arborg on May 11, 12, 18 and 19 but no emergence was recorded in any treatments on May 24. This trial will be continued in 2018 at Carman, Melita, Arborg and Dauphin. Overall, seeding one week earlier than normal optimized yield while reducing risk of frost exposure in 2017; in comparison Tkachuk (2017) found that the very earliest dates tended to optimize yield regardless of soil temperature. The final year of study in 2018 is anticipated to provide further clarity on seeding date recommendations.