Predicting soybean phenology in Manitoba

Soybean requires short days (<14 hours) to stimulate flowering. Maturity group classifications (often not established in Manitoba) are usually based on time (days) or Crop Heat Units (CHUs) to maturity and do not always accurately predict critical crop growth stages (such as the beginning of flowering or maturity) in Manitoba. There are 13 soybean Maturity Groups or MG in North America. In Manitoba, MG 000 to MG I can be grown depending on the amount of CHUs received. Each MG classification is further sub-divided into decimal units.
Earlier work by Morrison et al. (unpublished) from 2008 to 2010 comparing soybean varieties varying in maturity classification from MG 000.9 to MG 1.3 grown in Morden and Ottawa revealed that the greater day length during spring and early summer in Manitoba dramatically lengthened the vegetative period (17 to 23 days) and reduced flowering for soybeans relative to Ottawa. These changes in soybean phenological development in Manitoba happened even for varieties found to be day length insensitive in Ottawa.