Soybean Seed Treatments Interact with Locations for Populations, Yield, and Partial Returns

Abstract

Soybean [Glycine max (L.) Merr.] prices and profitability have increased recently, so growers manage the crop more intensively, including using seed treatments. Field‐scale studies were conducted at four locations in New York in 2012 and 2013 to evaluate agronomic and economic responses to rhizobia (Bradyrhizobium japonicum), biological, fungicide, and insecticide seed treatments. Plant populations, yield, and partial returns had location × seed treatment interactions. Rhizobia, biological, and fungicide seed treatments vs. untreated seed increased plant populations by 22 and 8% but not yield at two locations. Rhizobia, biological, fungicide, and insecticide seed treatments vs. untreated seed increased plant populations (20 and 10%) and yield (7 and 4.5%) at two other locations, along with partial returns (US$155 ha−1) where yield increased by 7% but not where yield increased by 4.5%. Growers seeded at 383,000 to 492,000 seeds ha−1, which may have been too high to fully realize the benefit of seed treatments. Application of rhizobia at planting vs. untreated seed did not increase yield and partial returns, even at locations where soybean had been grown only twice in the previous 10 yr. Growers who are risk averse to poor plant establishment will probably apply biological, fungicide, and insecticide seed treatments, whereas growers who are risk averse to additional inputs without a high probability of increased profit will probably not apply seed treatments or rhizobia inoculant, especially if low market prices prevail. The results of this study are site specific, so growers should conduct strip tests to determine if soybean seed treatments or rhizobia inoculants are beneficial, given their production practices, soil resources, and risk tolerance.