Soybeans belong to the legume family of plants. Historically, soybeans have been considered one of the five crops essential to human life (soybeans, rice, wheat, barley, and millet). They have been an important source of dietary protein and oil for centuries and have played a key role in our growing world—Civil War soldiers used soybeans to brew coffee, farmers have used it as a forage crop, and they have also been used as a green manure source. Today, more than two billion bushels of soybeans are produced in the United States every year.
Sometimes referred to as the ‘miracle bean’ for its many uses, soybeans are the only beans with complete protein. Their high protein content makes them a healthy choice for both humans and other animals. Soybeans are grown for a variety of food, feed, and industrial uses. Most soybeans are processed commercially and divided into components of meal and oil. They normally contain about 18 to 20 per cent soy oil and 38 to 40 per cent soy protein. These two components are used in hundreds of different foods eaten throughout the world.
Producing high-yielding, quality soybeans requires a strong understanding of their growth throughout production. A deep understanding of each stage of development will help you better manage the crop from planting to harvest. Certain fertility decisions are only effective at specific stages of development, and factors like the climate and soil conditions can impact the evolution of growth. Thus, it is important to better understand soybean’s growth stages and development cycle to better manage crop production while meeting your goals. Knowing what stage of growth your crops are in will also allow you to better manage their health, assess crop quality, and determine the best time to harvest.
The interactive diagram below demonstrates the various stages of soybean growth and important considerations for each stage. Read each of the MORE buttons below to learn more.
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VE – Emergence
Emergence occurs when the cotyledons appear above the ground. The primary and lateral root begins to develop. Root hairs form shortly after planting. Scouting for emergence is suggested. Planting depth is critical for this stage—too deep can delay emergence and too shallow can create a weak plant.
VC – Cotyledon
During the first leaf stage, unifoliolate leaves expand. For the following 7-10 days the cotyledons are the main nutrient reservoir for the young plants. Scout for proper emergence and look out for weeds.
V1 – First Trifolioate
The first trifoliolate leaf unrolls. Unifoliate leaves are fully developed. At this stage the plant is becoming self-sustaining as new leaves carry out photosynthesis. New nodes will appear every 3-5 days until the V5 stage.
V2 – Second Trifoliolate
Two trifoliolates unroll (fully developed trifoliate leaves at nodes above the unifoliate node). At this stage, nodules have been initiated on the roots. Nitrogen fixation continues until late reproductive stages. Effective nodulation produces higher yields and more seed protein than a non-nodulated soybean plant. Scouting is suggested at this stage for early-season weeds, insects and diseases. Application of herbicides if needed. If nodes have been established, then nitrogen fertilization is not recommended.
Stages V3 – V(n)
Vegetative stage designations V3 through V(n) represent the number of nodes on the main stem (n) above the unifoliate node with fully developed leaves.If there is damage to the plant, axillary buds permit the plants to compensate for yield or loss. The root system continues to expand. The number of root nodules and nitrogen fixation increase throughout the vegetative stages. Flowering follows about one week after V5. At V6, new vegetative stages are unfolding about every 2-3 days. The plant is readying to switch over to reproductive stages. Determinate soybean plants complete most of their vegetative growth when flowering begins. Indeterminate plants produce trifoliolates until the beginning of the seed formation stage.
R1 – Beginning Flowering
During this stage, flowering begins at any node on the main stem on the plant. Indeterminate plants start flowering at the low- or mid-canopy and flower upward. Determinate plants start flowering at one of the top four nodes, and then flowering proceeds up and down the stem. Scout for insects and diseases and if needed, you can spray foliar insecticide or fungicide.
R2 – Full Bloom
At this stage, the plant has one open flower on the highest up nodes on the main stem with a fully developed leaf. Continue scouting for insects or diseases at this stage.
R3 – Beginning Pod
Pods are beginning to form on the higher up nodes of the plant with fully developed leaves. During this stage, scouting for insects and diseases is suggested. Spray insecticide or fungicide if needed. Water stress can affect pod formation, and irrigation is effective at this stage.
R4 – Full Pod
Pods are ¾ of an inch long near the top of the plant along the main stem. Seasonal nitrogen uptake relative to the final amount attained at maturity is at this stage. R4 marks the beginning of the most critical period of plant development. Late season diseases can impact yields. Irrigation may be needed at this stage, if available.
R5 – Beginning Seed
At this stage, seeds are almost 1/8 of an inch long in four of the highest nodes on the main stem. Primary roots are growing until R5. The deeper roots are expanding till R6.5. Scout for late season diseases, they could damage yield.
R6 – Full Seed
At full seed, pods contain green seeds that fill up the cavity. Most nutrients have been taken up at this stage. Scouting is suggested for insects and diseases, and spray if needed.
R7 – Beginning Maturity
One pod on the main stem has reached maturity. Watch for green stem syndrome, which is when the stem remains green while seeds mature.
R8 – Full Maturity
This stage is about 5-10 days before harvest. Pods should have reached full maturity, and 95% of pods are mature colored. Scout for green stem syndrome, if present, harvest slow and make sure harvesting equipment is in good condition.
After soybean crops are harvested, they are processed for use. Soybeans are cleaned, cracked, dehulled, and rolled into flakes. This ruptures the oil cells for efficient extraction. After soybean oil has been extracted, the remaining flakes are processed into various soy protein products.
