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The final growth stages in soybean are plant maturation (R7-R8). During these stages plants attain their brown maturity color and dry down in preparation for harvest.
Soybean vegetative growth stages are numbered according to how many fully-developed trifoliate leaves are present. Soybean reproductive stages begin at flowering (R1-R2) and include pod development (R3-R4), seed development (R5-R6), and plant maturation (R7-R8). Growth stages can overlap within the crop, and is determined when 50% or more of the plants are in or beyond a growth stage.1
Figure 1. Full maturity is reached when 95% of the pods have achieved mature color.
Beginning Maturity (R7). One pod on the main stem has achieved brown or tan mature color (Figure 1). Eventually the seed and pods appear yellow and all green color is lost, resulting in peak dry matter accumulation within individual seeds. When physical maturity is achieved, seeds contain roughly 60% moisture. Stress during the R7 and R8 stages does not affect yield potential unless one or more of the following occurs:
When soybean plants reach beginning maturity, or the R7 stage, they are considered safe from a killing frost.
Full Maturity (R8). The soybean crop is considered fully mature when 95% of the pods have achieved their mature color. Typically, 5 to 10 days of good drying weather after R8 is all that is needed for the soybeans to reach harvest moisture of less than 15%. This rate of moisture loss can vary based on environmental conditions. For long-term storage, soybeans should be stored at 13% moisture or less. Harvesting closer to the ground can reduce crop losses. Leaving a 3.5-inch stubble may reduce yield by 5%, while a 6.5-inch stubble may reduce yield by 12% or more.
1 Pederson, P. 2007. Soybean growth and development. Iowa State University Extension and Outreach. PM 1945. http://extension.agron.iastate.edu/ (verified 9/9/2014); 2 McWilliams, D.A., et al. 2004. Soybean growth management quick guide. North Dakota State University Extension. A1174. http://www.ag.ndsu.edu/ (verified 9/9/2014). 140917122434