Year, Region, and Temperature Effects on the Quality of Minnesota's Soybean Crop

Bulk commodity soybean [Glycine max (L.) Merr.] can now be sourced with great specificity through rail and container purchases. The objective of this study was to determine whether analyses of farmer-grown soybean seed samples could detect significant regional differences in soybean quality traits. Through analysis of 2706 farmer volunteered soybean samples representing harvests from 2003-2005, we found significant year and region effects on seed quality. An independent variable, temperature during seed filling (T-sf) was created for each soybean sample by kriging local daily mean air temperatures from 135 weather stations. A region x year interaction was noted for protein and the sum of protein and oil concentrations, but using T-sf as a covariate eliminated this interaction. The variable T-sf correlated with average regional oil concentrations such that oil concentration increased at a rate of 6.6 g kg(-1)degrees C-1. Overall, farmer produced and volunteered soybean samples provide an excellent means of identifying within-state soybean seed quality variation. Additionally, local climate data (T-sf) can be used to predict this variation in regional soybean seed quality.