Agronomic Management of Soybean in Manitoba – Impact of Including Soybean in Rotations

Although soybean has become a key part of the rotation on many Manitoba farms, relatively little research has been done to date to determine how preceding crops influence soybean and, in turn, how soybean might influence the crops that follow it.  To better understand the short-term effects of preceding crops on crop yield, quality and disease under Manitoba conditions, small plot studies were conducted near Brandon (2013-15) and Morden (2011-13) to assess various combinations of soybean, canola and wheat over a three-year period.  Preceding crop sequence had little effect on wheat or canola yield or quality.  In the case of soybean, preceding crop had no effect on root rot.  At Brandon, however, soybean yield was lower for soybean following soybean-canola than soybean-wheat although the reason is not known.  Because differences among rotations often build up slowly over time as pests increase and/or soil productivity and quality changes, the limited effects of crop sequence observed in this study were not necessarily unexpected.  In order to better understand the longer-term effects of rotation on crop productivity, a more in-depth rotation study was initiated near Brandon in 2014 as part of this project, and is ongoing.  This study includes five rotations:  soybean-canola; soybean-wheat; soybean-wheat-canola; soybean-canola-wheat; soybean-soybean-wheat, with each phase of each rotation is present each year.