Stages of Development

	Corn
	Silage Hybrids
	Alfalfa
	Forage
	Soybeans
	Discounts
	General Agronomic Info

<< BACK

Soybean development is divided into vegetative (V) and reproductive (R) stages, VE is emergence, VC is unfolding of the unifoliate leaves, then the following stages (VI, V2,...Vn) are marked and defined by the uppermost fully developed leaf node. A fully developed leaf node is one that has a leaf with unrolled or unfolded leaflets above it. V3 then, for example, would have four nodes with unfolded leaves, and so on. Each node is an auxiliary bud (auxiliary growing point), so even severe stem and leaf defoliation above the cotyledonary node produces new branches and leaves. One open flower at any node signals the beginning of the reproductive (R) stages.

There are 8 reproductive stages all referring ot development on the main stem. R1 (beginning bloom) is one open flower at any node. R2 (full bloom) is an open flower at one of two upper most nodes with a fully developed leaf. This stage marks the beginning of rapid dry matter and nutrient accumulation. R3 (beginning pod) is a pod developing at anyone of four upper most nodes. R4 (full pod) the pod is 3/4 of an inch long developing at anyone of four upper most nodes. R5 (beginning seed) 1/8-inch seed is developing at anyone of four upper most nodes.

Late pod formation (R4.5 to R5.5) is the most critical time for yield loss due to pod abortion. Flowering can no longer be initiated to compensate for losses. Therefore, stress at this time reduces yield, due to a reduction in pods per plant. If irrigation is available, this may be the time it is warranted. R6 (full seed) plants have a pod containing a seed that fills the pod cavity at any one of four upper most nodes. As soybeans develop past R6, any stresses are not as critical, but can reduce the seed size, seeds/pod, and pods per plant. R7 (beginning maturity) is when one normal pod has reached its mature pod color. Stress occurring at R7 or after has no effect on yield. R9 (fully maturity) 95% of the pods have reached their mature pod color. Five to ten days of good drying weather will move soybeans to less than 15% moisture and close to harvest.