Evaluation of Simulated Fall Freeze, Planting Date, and Cultivar Maturity in Soybean

Abstract

In the northern fringe of the U.S. soybean [Glycine max (L.) Merr.] growing area, early planting dates of late-maturing cultivars would effectively increase growing season length and may increase yield. However, growing late maturing cultivars increases the risk of fall freeze damage. Planting early also increases the risk of a spring freeze. Our objective was to evaluate the effects of varying both planting and fall freeze dates on yield, reproductive stage, and U.S. Grain Grades of four soybean cultivars. A factorial arrangement of four cultivars, three planting dates, and three fall freeze dates were evaluated in a total of five environments across 2 yr. Cultivars included two from Maturity Group 0, which were considered adapted to the geographical region, and one each from Maturity Group I and II, which were considered unadapted, due to their late maturity. The first and second fall freeze dates were simulated by applying paraquat herbicide with a specially designed sprayer. Temperatures were warmer than normal in 1991 and cooler than normal in 1992. Increasing the length of the growing season by early planting of late maturing cultivars did not result in increased yield. However, there was a yield advantage for early planting of adapted cultivars when an early fall freeze occurred. A fall freeze near the R6 stage generally did not degrade grain quality.