Understandably most growers are still concerned about getting all of their corn planted and debating when they should switch their corn relative maturity (Corn Hybrid Relative Maturity Switch Dates for 2011). This coupled with cool soil temperatures has delayed the progress of our 2011 soybean plantings. Many resources suggest that soybean should not be planted until soil temperatures reach 50° F and to tell the truth we were nervous to start planting our soybean variety trials until those temperatures where achieved (Table 1). With that said I, like many, saw the calendar date and have recently experienced several week delays in May due to wet weather so decided to start planting soybean on May 4th (This is called the do as I say not as I do paradigm). Given the soil temperature and lack of accumulated gdu’s (28 based on soil temp and base 50° F) I was surprised to see how far the soybean development has progressed to date. This furthers my thought that the base temp for soybean germination is less than 50° F. That is a topic for another day.
For more detailed information regarding soybean emergence please see Predicting When Soybeans Will Emerge.
Table 1. Soil temperature monitored at 2 inch depth at the Arlington Agricultural Research Station in 2011.
Image 1. Developmental images of soybean planted on May 4th at Arlington, WI in the long term-rotation study.