Brandt: Determining the Barriers to Higher Canola Yields in Saskatchewan – An Extensive Analysis and a Closer Look at Heat Stress
Date: December 2001
Term: 2 years
Status: Completed
Researcher(s): Stuart Brandt, Agriculture and Agri-Food Canada (AAFC), Scott Research Farm
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
In a previous study, researchers confirmed that canola declined between 1991 and 1999, however yields of other major crops continuously increased. Although some regional differences existed, no conclusive evidence for the yield decline was found. In this study, researchers tried to determine whether this was due to abiotic stress of heat and/or water deficit or due to insufficient fertilizer use.
In a previous study (CARP 9818) an analysis of yield trends in Saskatchewan for various major crops showed that canola yields declined between 1991 and 1999. Researchers looked at historical trends as well as agronomic factors across Saskatchewan, and although the evidence showed that a canola yield problem did exist, the study did not find conclusive evidence for the yield decline.
Figure 1.In this study, researchers put forward a two-fold hypothesis for the yield decline: the yield problem was either due to abiotic or weather-related stresses of heat and/or water deficit or due to an agronomic management issues such as insufficient fertilizer use. The abiotic or weather-related stress factors were tested by two methods including a replicated field trial and a crop modeling exercise.
The moisture-heat field study resulted in surprisingly minor effects of heat stress on yield components given the unusually hot and dry summer of 2001. Although most of the heat stress effects were not statistically significant, they would still represent fairly significant economic losses to growers. For example, the yield decrease of 13 % caused by heat stress treatments would represent about $30/acre in a 40 bushel/acre crop when canola was priced at $6/bushel.
In the crop modeling exercise, the research found that 64% of location years studied had yields that did not differ from predicted yields, implying that only heat stress and water deficit were responsible for yield loss. However, in some crop districts the yields were significantly lower than predicted, suggesting that some other unknown factor was causing yield decline in those areas.
Overall, the study showed that growing conditions resulting in heat and water stress may have contributed significantly to the yield decline experienced in the 90s. Although there is no direct evidence to explain additional yield losses, insect pest survey reports for 1994-95 suggest that Bertha armyworm and diamondback moths may have contributed to this yield loss. Also, considering the relatively low fertilizer rates in Saskatchewan confirmed in the previous analysis, it is probable that insufficient fertilizer application played a role in the lower overall yields in Saskatchewan during this time period.