Planting smaller soybean seed saves money

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

        Research confirms that there is no relationship between soybean seed size and agronomic performance factors such as seedling vigor and yield.  Thus, one method to save on input costs is to seed lots with a high number of seeds per pound (i.e. the most seeds per 50 lb. bag).  There has been a movement by some seed companies to begin selling soybean seed by seed count rather than by the pound.  It makes a lot sense but inventory management concerns have made this transition slow.  Of course it isn’t prudent to select varieties on seed size alone and give-up yield potential.  However, if given the choice between genetically similar or the same varieties, buy the lot with the smallest seed size.  The following table gives the seed cost for planting 200,000 seeds per acre with different seed sizes based on the initial cost per bag.

         Seed size is documented for all soybean varieties entered into the University of Wisconsin Variety Performance Trials.  One consistent trend over the past five years is that Roundup Ready varieties have consistently had a smaller seed size than conventional varieties (see figure below).  On average, the difference has been about 2000 more seeds per pound.