Soybean plant growth stages: Understand to optimize yields

Introduction to soybean growth staging

Soybeans (Glycine max) develop through a series of well-defined stages that help farmers and agronomists manage inputs more effectively. Understanding soybean plant growth stages is essential for maximizing yield, optimizing input timing, and reducing risks from pests, diseases, or drought. Agronomists divide development into vegetative stages (VE to Vn) and reproductive stages (R1 to R8).

Why understanding growth stages is essential

Timing fertilizer and irrigation

Soybeans change in nutrient and water demand across growth phases. Knowing the stages ensures efficient input use, especially since soybeans rely heavily on nitrogen fixation.

Managing pests and diseases effectively

Pests like aphids, cutworms, and stink bugs, as well as diseases like sudden death syndrome, have stage-specific impacts. Correctly identifying growth stages allows precise intervention.

Optimizing harvest timing

Harvesting too early reduces yield, while waiting too long increases shattering risk. Knowing R7 (beginning maturity) versus R8 (full maturity) is critical.

Vegetative stages (VE to Vn)

VE – emergence

Cotyledons are pulled above the soil surface. The seed provides initial energy for establishment.

VC – unifoliate stage

The unifoliate leaves are fully unrolled. Photosynthesis begins to fuel growth.

V1 – first trifoliolate

The first trifoliolate leaf is fully unrolled. This marks the beginning of nodal expansion.

V2 – second trifoliolate

The second trifoliolate leaf is fully unrolled. Nodulation begins, but external reserves and soil nitrogen still contribute significantly.

V3 – third trifoliolate

The third trifoliolate leaf is fully unrolled.

• Nodules are actively fixing nitrogen, reducing dependence on soil or fertilizer.

• The canopy expands rapidly, increasing photosynthesis.

• The plant becomes sensitive to stress from pests, herbicides, or drought.

• Weed management and foliar sprays are often targeted around this stage.

V4 to V12 (advanced vegetative stages)

Each additional trifoliolate leaf marks a stage (V4, V5, etc.). By V5–V6, biomass accumulates rapidly, and yield potential begins to be set.

Reproductive stages (R1 to R8)

R1 – beginning bloom

At least one open flower is visible at any node (purple or white). Transition from vegetative to reproductive growth.

R2 – full bloom

An open flower is present at one of the top two nodes on the main stem.

R3 – beginning pod

Pods are about ¼ inch long at one of the four uppermost nodes.

R4 – full pod

Pods reach about ¾ inch long at one of the four uppermost nodes. Nutrient demand surges.

R5 – beginning seed

Seeds inside pods are ⅛ inch long at one of the top four nodes. This is a critical stage for yield determination.

R6 – full seed

Seeds fill the entire pod cavity. Nitrogen fixation peaks here, and the crop requires high water availability.

R7 – beginning maturity

One pod anywhere on the main stem has reached mature color (tan/brown).

R8 – full maturity

95% of pods have reached mature color. Seeds are at maximum dry weight and the crop is ready for harvest.

Photo credit and source: Manitoba Pulse Soybean Growers

Environmental and management factors affecting growth stages

Temperature and day length (photoperiod)

Soybeans are short-day plants; flowering is triggered when day length drops below a certain threshold.

Water availability

Drought stress during pod fill (R5–R6) can reduce yield by up to 50%.

Nutrient supply

Adequate phosphorus, potassium, and micronutrients are critical during reproductive stages for seed formation.

Pest and disease pressure

Diseases like sudden death syndrome or pests like soybean aphids can be more damaging during early pod fill.

Using growth stage knowledge for better yields

Precision agriculture tools

Drone imaging, growth stage models, and NDVI mapping can help farmers monitor crop development and respond quickly.

Integrated pest management scheduling

Combining biological control, targeted chemical applications, and monitoring ensures efficient pest management.

Drought sensitivity and nitrogen management in soybeans

Soybeans are especially sensitive to water stress during reproductive stages, particularly R5 (beginning seed) and R6 (full seed). Drought at these stages can reduce seed size, lower protein content, and cut yields by up to 50%. One key reason is that nitrogen fixation by root nodules declines sharply under drought stress, depriving the plant of the nitrogen needed for seed development.

How Arevo organic nitrogen based on arginine can help

Unlike traditional fertilizers, which can inhibit soybean nodulation by competing with the symbiotic rhizobia in the roots, Arevo organic nitrogen based on arginine offers a unique solution. Because it is non-living or non-microbial, it does not compete with the rhizobia in root nodules. Instead, it provides soybeans with a direct source of organic nitrogen that the plant can absorb without disrupting its microbial partnerships. This dual benefit — sustaining nodulation while supplying extra nitrogen — makes Arevo both a nutrient and a stimulant, supporting stronger root growth and better yield even under stress conditions. 

Arevo is an arginine-based organic nitrogen solution that delivers nitrogen in a form that soybeans can directly absorb — even under dry conditions. Because arginine uptake is less energy-dependent than nitrate or ammonium uptake, plants can continue absorbing it during drought stress when carbohydrate supply to roots is reduced.

• It does not compete with nodules, allowing soybeans to maintain symbiotic nitrogen fixation.

• Arginine provides a direct, energy-efficient nitrogen source that plants can absorb even under stress.

• Applied as a seed coating and then in-furrow at planting, it ensures roots remain close to an available nitrogen source, even under drought conditions.

This dual strategy makes Arevo® both a nutrient and a stimulant, strengthening roots and stabilizing yields in challenging climates.

The two-step application strategy can maximize this advantage:

1. Seed coating with Arevo before planting
   Coating seeds ensures each germinating plant has immediate access to nitrogen during early root development, improving seedling vigor and stand establishment.

2. In-furrow application at planting
   Placing Arevo in the seed row ensures roots are close to a nitrogen source as they grow, giving them access even when dry soils limit the mobility of nitrate or ammonium.

Benefits in challenging climates

• Resilient nitrogen supply — Organic nitrogen in arginine form stays available to roots and soil microbes, reducing the risk of leaching losses and volatilization.

• Improved root development — Consistent nitrogen availability encourages deeper root growth, improving water access during drought.

• Sustainable yield stability — Ensures nitrogen delivery during the critical pod fill stages, supporting yield even in variable rainfall patterns.

FAQs on soybean plant growth stages

1. How long does it take soybeans to reach maturity?
   Typically 100–150 days, depending on maturity group and environment.

2. Which stage is most sensitive to drought?
   R5–R6 (seed fill), when nitrogen and water demand peak.

3. Why shouldn’t soybeans be heavily fertilized with nitrogen?
   High fertilizer levels suppress nodulation and nitrogen fixation, making them inefficient.

4. How does Arevo® help during drought?
   It supplies organic nitrogen directly to roots without disrupting rhizobia, ensuring access even when nodulation slows.

5. When is canopy closure achieved?
   Usually around V5–V6, depending on planting density and variety.

6. When should harvest be planned?
   At R8 (full maturity), when 95% of pods have reached their final color.

Conclusion

Soybean growth follows a clear progression from VE (emergence) to R8 (full maturity). Each stage represents a window of opportunity — or risk — for yield. By understanding these stages and integrating innovations like Arevo® organic nitrogen, farmers can better manage inputs, support nodulation, and buffer their crops against drought stress, ensuring more resilient and sustainable production.

References and sources

• Manitoba Pulse & Soybean Growers. (2018). Soybean growth staging guide. https://www.manitobapulse.ca

• Fehr, W. R., & Caviness, C. E. (1977). Stages of soybean development. Iowa State University Special Report 80.

• Salvagiotti, F., et al. (2008). Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review. Field Crops Research, 108(1), 1–13. https://doi.org/10.1016/j.fcr.2008.02.001

• Pedersen, P. (2009). Soybean growth and development. Iowa State University Extension. https://crops.extension.iastate.edu/soybean

Disclaimer

This article is based on publicly available research, scientific publications, and reliable online sources. While every effort has been made to ensure accuracy, it should not be considered professional or expert advice. Readers are encouraged to consult with qualified agronomists, soil scientists, or agricultural extension services before making management decisions.