Soybean vegetative and generative growth stages

Pawel Wiatrak

Identifying the soybean growth stages is essential for proper management of pests and environmental problems. Generally, the soybean development can be divided into vegetative (V) and reproductive (R) stages. The beginning of each stage starts when at least 50% plants are at that stage. Vegetative growth stages start with the soybean emergence and reproductive growth stages start with the first flower.

Note: The growth stages are adapted from the Fehr, W.R., C.E. Caviness, D.T. Burmood, and J.S. Pennington. 1971. Stage of development descriptions for soybeans, Glycine max (L.) Merr. Crop Science 11:929-931 and also from 2004 edition of PM 1945 Soybean Growth and Development published by Iowa State University Extension, Ames, Iowa 50011.

Vegetative (V) growth stages                                              

The vegetative stages begin with emergence (VE stage) (Table 1). Prior to germination, soybean seed absorbs water equal to approximately 50% of its weight. The elongation of hypocotyl brings the cotyledons out of the soil, which starts the soybean emergence.

After emergence, unifoliolate leaves on the first node unroll in addition to cotyledons and start the VC stage. The following vegetative stages are designed numerically from V1, V2, V3, through V(n), based on the number of nodes with trifoliolate fully developed leaves unrolled. For example, the V1 stage starts with one unrolled fully developed trifoliolate leaf on the second node. The (n) represents the number of the last fully developed trifoliolate leaf. A fully developed trifoliolate leaf is one that has unrolled or unfolded leaflets.

Table 1. Vegetative (V) soybean growth stages.

Stage

Description

VE

Plant emergence (depends on temperature and moisture).

VC

Unifoliolate leaves unrolled in addition to cotyledons. One node.

V1

One unrolled trifoliolate leaf. Two nodes.

V2
Two unrolled trifoliolate leaves. Three nodes.

Vn

(n) number of trifoliolate leaves unrolled; (n) + 1 number of nodes


 VE – Emergence 
VE – Emergence.

 VC – Unifoliolate leaves unrolled in addition to cotyledons   VC – Unifoliolate leaves unrolled in addition to cotyledons.

 V1 – One unrolled fully developed trifoliolate leaf
V1 – One unrolled fully developed trifoliolate leaf.
V2 – Two unrolled fully developed trifoliolate leaves
V2 – Two unrolled fully developed trifoliolate leaves.
                                          

 

Reproductive (R) growth stages

The reproductive stages in soybeans start when at least one flower is present on the plant (Table 2). These stages describe the development of flower (R1 and R2), pod (R3 and R4), seed (R5 and R6), and maturity (R7 and R8). Vegetative growth continues through some of the reproductive stages. The reproductive growth stages are described in the Table 2 and also shown on images below Table 2.

 Table 2. Reproductive (R) soybean growth stages.

Stage

Description

R1

Beginning bloom. At least one flower is present on the main stem.

R2

Full bloom. Flowers are found on any of the top two nodes.

R3

Beginning pod. Pods are 3/16 inch long on one of the top four nodes.

R4

Full pod. Pods are 3/4 inch long on one of the top four nodes.

R5

Beginning seed. Seeds are 1/8 inch long on one of the top four nodes.

R6

Full seed. Pods are completely filled by seeds on one of the top four nodes.

R7

Beginning maturity. One mature pod found on the plant.

R8

Full maturity. 95% pods have reached mature pod color.



R1 – Beginning bloom. At least one flower on the main stem
R1 – Beginning bloom. At least one flower
on the main stem.

R4 – Full pod. Pods are at 3/4 inch long on one of the top four nodes
R4 – Full pod. Pods are at 3/4 inch long on

one of the top four nodes.

 R2 – Full bloom. Flowers are found on any of the top two nodes
R2 – Full bloom. Flowers are found on any
of the top two nodes.

R5 – Beginning seed. Seeds are at 1/8 inch long on one of the top four nodes
R5 – Beginning seed. Seeds are at 1/8 inch
long on one of the top four nodes.

 R3 – Beginning pod. Pods are at 3/16 inch long on one of the top four nodes
R3 – Beginning pod. Pods are at 3/16 inch
long on one of the top four nodes.

 R6 – Full seed. Pods are completely filled by seeds on one of the top four nodes
R6 – Full seed. Pods are completely filled
by seeds on one of the top four nodes.