Soybean growth habit is much different than corn.  Wisconsin research shows that full season varieties can be planted and produce harvestable grain when planted through the end of June.  HOWEVER, there is a point where the prudent grower will plant a shorter season variety to increase yield potential and allow for an earlier fall harvest.  In an effort to identify this time period, we can refer to some Wisconsin planting date research done from 1992 through 1995 (Table 1).  Note that shorter season soybean varieties yielded about the same as full season varieties when planted on June 10, but matured about a week earlier (Sept. 27 versus October 5).  Yields for both maturities were about 3/4 of yields obtained with full season varieties planted on May 1^st. 

         Another important observation from this study is that a soybean variety will mature much more quickly when planted late compared to the same variety planted early.  Soybeans do not typically mature based on growing degree units or days from planting.  Rather, the soybean plant flowers based on day length (or more correctly, night length).  This is something of a good news – bad news scenario.  The good news is that a shorter life cycle reduces the risk for kill by a fall frost. The bad news is that there is not as much time to “build the factory” and grain yields are reduced. 

        Finally, growers are encouraged to plant varieties with high disease resistance.  This is especially important for diseases like Phytophthora root rot.  With an abundance of late planted soybeans this year, scouting for aphids will be extremely important.  They typically do their greatest damage on late plantings.