Late-Season Soybean Growth Stages

Corn harvest is begining across the Delta and early-planted soybean harvest won’t be far behind.  Identifying late-season soybean growth stages is important for a number of considerations, such as irrigation termination and harvest aid/desiccation timing decisions.

Growth Stage R6- Full Seed

Seeds fill the entire pod cavity and “square off” on the ends as they press against each other

There has been some debate and discussion about the exact definition of R6.  However, the simple definition of the R6 growth stage is when a pod contains full size seed at one of the four uppermost nodes. As the seeds are filling they will often press up against each other resulting in ends that look flat or square. If you observe a pod located in one of the top four nodes where the seeds have “squared off”, then the R6 stage has been reached.

R6 is a critical period for seed size determination so monitor soil moisture levels carefully.

Growth Stage R6.5

Seeds pull away from each other and the pod wall

Growth stage R6.5 is at the very end of the seed filling process.  The R6.5 growth stage has been reached when seeds in the pods in the upper four nodes pull away from both each other and the protective membrane of the pod wall.  Once the seeds pull away from the pod wall they begin to lose moisture and the pod begins to turn from green to yellow and then its mature color.

Up to this point, adequate soil moisture is needed to ensure that seed have fully developed. Soybean irrigation can be terminated at this growth stage.

Growth State R7- Beginning maturity

Once one pod on the mainstem completely reaches its mature pod color then the soybean are considered to be at growth stage R7.