Plant population and row spacing are important factors for improving yields of specialty soybean varieties, according to University of Nebraska researchers.

In a four-year study, they compared production practices for large- and small-seeded soybeans, most of which are grown under contract and exported to Japan for food uses. Four large-seeded and three small-seeded varieties were grown in 10" and 30" rows at 75,000,150,000 and 225,000 seeds/acre.

The large- and small-seeded varieties averaged 18.5% and 27.6% less yield, respectively, than conventional varieties used as checks. Soybeans grown in 10" rows outyielded 30"-row beans by an average 7.2 bu/acre.

Yield gains from higher seeding rates were less consistent. Increasing seeding rates from 75,000 to 150,000 seeds/acre raised yields in two of the four years, and 225,000 seeds/acre outyielded 150,000 seeds/acre only one out of the four years.

Increasing seeding rates from 75,000 to 150,000 seeds/acre increased the average seed weight all four years. But in no case did the weight change enough to disqualify seed from its size category.

(George Hoffmeister Jr. and Roger Elmore, University of Nebraska)