Adam P. Gaspar, Agronomy, University of Wisconsin-Madison, Madison, WI, Shawn P. Conley, Department of Agronomy, University of Wisconsin-Madison, Madison, WI and Paul Mitchell, 427 Lorch St., University of Wisconsin-Madison, Madison, WI
Earlier soybean [Glycine max (L.) Merr.] planting coupled with increasing seed cost and higher commodity prices has led to a surge in the number of hectares planted with seed treatments (Esker and Conley, 2012). Furthermore, recent studies have suggested that growers should consider lowering seeding rates to increase their return on investment (De Bruin and Pedersen, 2008; Epler and Staggenborg, 2008). Ultimately, growers would like to know the value proposition of combining seed treatments with lowered seeding rates. Therefore, the objectives of this study were to quantify the effects of seed treatments and seeding rates on soybean seed yield and assess the economic risk and profitability of seed treatments and seeding rates, including the calculated economically optimal seeding rate (EOSR) for each seed treatment. Trials were conducted at nine locations in Wisconsin during 2012 to compare no seed treatment (UTC), ApronMaxx (mefenoxam + fludioxonil at 0.0094 mg ai seed-1), and CruiserMaxx (mefenoxam + fludioxonil + thiamethoxam at 0.0858 mg ai seed-1) at six seeding rates of 98800, 148200, 197600, 247000, 296400, and 345800 seeds ha-1. Preliminary 2012 results indicate differences in yield, profitability and economic risk due to seed treatment and seeding rate. ApronMaxx provided no improvements in yield or profitability at any seeding rate compared to the UTC. Lower seeding rates (<247,000 seeds ha-1) showed increased yields and profitability with CruiserMaxx. At higher seeding rates (> 247,000 seeds ha-1) yield and profitability was not significantly affected by seed treatment use. ApronMaxx and UTC required higher seeding rates (>247,000 seeds ha-1) to achieve break-even probabilities >0.50 and their EOSR showed the largest average profit ha-1 increase. CruiserMaxx showed break-even probabilities >0.50 for all seeding rates except at 98,800 seeds ha-1, but the lowest risk (0.71) and highest average profit ha-1 increase ($38 ha-1) was achieved at its EOSR, which was 50,000 seeds ha-1 less than ApronMaxx and UTC.