The soybean’s vegetative stages begin with emergence and end when the plants have multiple trifoliate leaves. The final number of leaves depends mainly on the variety, but also on environmental conditions.
In this blog article, we explore the vegetative stages of the soybean. We also discuss misconceptions and reality; and analyze the impacts of insects and diseases on the leaves.
Happy reading!
Effects on leaves in the vegetative stages
In the early vegetative stages, soybean leaves may sometimes be paler than normal. The reason is simply that they were exposed to cooler soil and air temperatures. With the return of fine weather, the leaves usually recover their natural color and there is no loss of yield. If this isn’t the case, the soybeans are probably suffering from nutrient deficiencies or disease.
Insects can also damage soybean leaves, especially the upper ones. To minimize losses, the lower leaves have the capacity to absorb more light through increased photosynthesis. This allows the plants to keep growing to maturity.
When to intervene? When defoliation of the leaves at the centre of the plant exceeds 30%.
Vegetative stages
VE: Emergence (5 to 15 days)
- Cotyledons above the soil surface; dependent on soil temperature, planting date and planting depth.
VC: Unifoliolate leaves unrolled (3 to 10 days)
- The first two leaves are unifoliate and occur opposite each other on the stem at what is considered the first node.
- The cotyledons under the leaves are the initial reserve of nutrients and energy until photosynthesis begins. The plants will not recover if the cotyledons are damaged.
V1: First trifoliate unrolled (3 to 10 days)
- The second leaf node, and all subsequent nodes, are singular and will alternate on the stem.
- Nitrogen-fixing root nodules begin to form on the roots.
- At this stage, assess your stand (conduct a stand count) to determine if replanting is necessary.
V2: Second trifoliate unrolled (3 to 10 days)
- Lateral roots are growing rapidly just centimeters below the soil surface.
V3: Third trifoliate unrolled (3 to 10 days)
- Three nodes with fully developed leaves on main stem, beginning with unifoliate nodes.
- Nitrogen fixing has begun.
V4 & V5: Fourth and fifth trifoliate unrolled (3 to 8 days)
- Nodes four and five on main stem have fully developed leaves, beginning with the unifoliate nodes.
- Flower buds start to develop between V4-V6.
- Plants can recover from 100% defoliation at this stage with minimal risk of yield loss.
Misconseptions & reality
Plants must have uniform emergence to maximize yield.
- False – Uneven emergence has no impact on yield.
Stress suffered by soybeans early in the season has a beneficial impact on yield.
- False – There is no yield improvement from soybean stress early in the season.
Nitrogen fertilization helps optimize yield in fields that have a high yield potential.
- False – In zones with high yield potential, adding nitrogen does not contribute to maximizing yield.
For more information on this subject, feel free to contact your Prograin representative!
Sources :
Réseau d’avertissements phytosanitaires : Bulletin d’information : grandes cultures. (2016). Défoliation du soya par divers ravageurs : Méloé cendré, criquets, scarabée japonais, altises, limaces, etc. https://www.agrireseau.net/documents/Document_92899.pdf
Manni Singh. (2022). Science for Success: Misconceptions on Vegetative Stages of Soybean Growth. YouTube. https://www.youtube.com/watch?v=_2aBnTLoZKQ
ministère de l’Agriculture, de l’Alimentation et des Affaires rurales. (2017). Guide agronomique des grandes cultures. https://www.ontario.ca/files/2022-10/omafra-agronomy-guide-for-field-crops-chapter-2-fr-2022-10-13.pdf
Seth L. Naeve. University of Minnesota. (2018). https://extension.umn.edu/growing-soybean/soybean-growth-stages
Shaun Castel & al. The soybean growth cycle: Important risks, management and misconceptions. (2022). https://soybeanresearchinfo.com/wp-content/uploads/2022/01/Science-for-Success-Soybean-Growth-Stages-V3.pdf
Cool Bean – University of Wisconsin-Madison. (2017). A visual Guide to Soybean Growth Stage. https://coolbean.info/library/documents/2017_Soybean_GrowthDev_Guide_FINAL.pdf