Research has shown that the variability in crop yield response to seeding date can often be attributed to environmental conditions experienced by the crop at important developmental or physiological stages, which vary with year and location. Producers would benefit in better understanding the effect of seeding date on crop productivity in relation to specific environmental variables and other local and regional factors. Yet, these environmental factors are rarely included explicitly in the study design or analysis of typical agronomic field studies, because the level of replication required to encompass the full and intersecting range of many intercorrelated environmental variables is often beyond their potential. The necessary level of replication can be achieved by utilizing extensive third-party data sets such as producer-reported management and weather data, obtained through provincial crop insurance programs. The Saskatchewan Crop Insurance Corporation (SCIC) provided such data for the purpose of examining the interacting effects of seeding date and environmental conditions on the yield of various crops in Saskatchewan.

The data included 10 years (2009-2018) of crop production data reported by quarter section, from all crop productions regions of Saskatchewan, and complementing weather data from 131 weather stations located throughout Saskatchewan. The analysis was completed for all crops with adequate replication which included barley, canaryseed, canola, Canada Prairie Spring White (CPSW) wheat, Canada Western Amber Durum (CWAD) wheat, Canada Western Red Spring (CWRS) wheat, field peas, flax, lentils, oats, and soybeans. Multiple linear regression with mixed effects models was utilized to examine the interactive effect of seeding date with several geographic and environmental variables on crop yield. The geographical variables were soil zone, crop district, and grain risk zone, and the environmental variables were rain accumulation, GDD accumulation, last spring frost, first fall frost, frost-free period by season and averaged across seasons by weather station.

It was found that the yield response to seeding date could be differentiated by soil zone, rain accumulation, GDD accumulation, and/or frost dates in all crops. Soil zones provided the most practical differentiation of the seeding date and yield relationship, and weather variables were used to further interpret the differential responses among soil zones. Producers should be able to use the information provided in this report to understand how environmental conditions affect the seeding date response, and to plan and manage their seeding dates based on their location and the crops they grow. Even when an operation’s usual crop seeding sequence is well established, producers will also benefit from being able to compare relative yield penalties with non-optimal seeding dates across several crops, to more confidently determine whether the seeding sequence should be modified in non-typical seasons.