With the planting season coming up, we thought it would be a good time to share a simple guide on soybean growth stages! It is sure to come in handy this growing season.
Germination begins when a soybean seed absorbs 50% of its weight in water. This is known as imbibition. Next up is the vegetative (V) stages, followed by the reproductive (R) stages.
Cotyledons appear on the surface of the soil
VC Unrolled unifoliolate leaves
The first two leaves are unifoliolate and are produced on opposite sides of the stem. This is the first leaf node.
V1 First unrolled trifoliolate leaves
Nitrogen-fixing nodules begin to form on the root system. At this step, it’s important to assess the population to determine if re-seeding is required. Of course, you’ll need to evaluate your soybean stand visually, but you’ll also need concrete evidence for a good idea of where things are. Get your shovel out to search for the seedlings!
V2-V3 Second and third unrolled trifoliolate leaves
Nodules have probably started actively fixing nitrogen. If you cut a nodule in half and see a pinkish colour on the inside, you’ll know that it’s in good health and fixation is taking place. Dig up a few plants with a shovel to confirm active nodulation.
V4-V5 Fourth and fifth unrolled trifoliolate leaves
Floral buds start to develop from stages V4 to V6. Plants can recover from 100% defoliation from hail at this stage with a minimal risk of yield loss.
R1 Beginning flowering
At least one flower (purple or white) will have bloomed between the bottom third and sixth nodes of the main stem.
R2 Full flowering
There is an open flower at one of the two uppermost nodes on the main stem. Flowering will continue for 3 to 5 weeks. From 20% to 80% of flowers will abort.
R3 Beginning pod
Pods are around 6 mm long (1/4”) at one of the four uppermost nodes on the main stem. The rate of potassium uptake peaks shortly after R2.
R4 Full pod
Pods are around 20 mm long (3/4”) at one of the four uppermost nodes on the main stem. Seeds start to develop and flowering continues. Nitrogen uptake reaches its peak between R4 and R5.
R5 Beginning seed
Seeds are around 3 mm long (1/8”) in a pod at one of the four uppermost nodes on the main stem. Seed growth picks up speed and root growth gradually slows down.
R6 Full seed
Green seeds fill a pod on one of the four uppermost nodes on the main stem. There is still significant nitrogen uptake from the soil, which then travels to the seeds.
R7 Beginning maturity
Most pods are yellow and at least one pod on the main stem has reached its mature colour (reddish brown). Seeds at the R7 growth stage are at 60% moisture.
R8 Full maturity
95% of pods have reached their mature colour (reddish brown). 5 to 10 days of drying weather are generally required after R8 to obtain grain moisture below 15%.