Improving Edamame Seedling Establishment by Determining the Optimal Temperature

Abstract

Demand in the United States for edamame has increased over the past two decades. Edamame has become the second largest soyfood consumed in the US (25,000-30,000 tons annually). While domestic edamame production is slowly increasing, at least 70% of edamame consumed in the US is imported. Poor crop establishment is a major problem limiting edamame production. Seedling emergence ranges from 50-85%, which is lower than that of grain-type soybean ( >85%). Seedling stand can be improved by growing under the optimal temperature. Up to now, edamame is planted still based on grain-type soybean recommendations. The objective of this study was to determine the minimum, optimum, and maximum emergence temperatures of edamame. It will provide a scientific basis for deciding the best planting time of edamame, ultimately improving its seedling stand in the field. In this study, two edamame cultivars (VT Sweet and UA Kirksey) were tested for their seedling emergence percentage and emergence rate (i.e., emergence speed) at 5, 7, 10, 13, 16, 19, 21, 23, 25, 27, 29, 32, 35, 38, 41, 45 °C (soil temperature) using the LabFieldTM Simulation Table. Two grain-type soybean cultivars (MFS-48P1 and USF5618v) were checks. The results showed that the optimal temperature range for edamame seedling emergence is 25-32 °C, which is lower than that of grain-type soybean (29-36 °C). Soybean did not emerge at around 4 °C, however, edamame seeds may have a higher tolerance to low temperature compared with grain-type soybean. The maximum temperature varied little among soybean types, with an average of 41.08 °C. In addition, edamame needs more thermal time to emerge. The results indicate that edamame has a different emergence response to temperature compared with grain-type soybean. Edamame should be planted earlier than grain-type soybean and later planting may reduce edamame seedling emergence.