Northeast Research and Demonstration Farm
Soybean planting date studies of various types have been conducted at this site since 1976. Earlier tests included later planting dates (May through mid-June), differing maturity varieties, and soybeans planted with and without starter fertilizer and Ridomil fungicide soil treatments.
Iowa State University
Pecinovsky, Kenneth T. and Benson, Garren O., "Twenty-six Years of Soybean Planting Date Studies" (2002). Iowa State Research Farm Progress Reports. 1627.