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| Uneven soybean emergence caused by crusted soil, a form of compaction. |
Stopping to think about all that needs to happen, seemingly on ‘autopilot’ between when soybean seed is planted and when seedlings emerge is awe-inspiring.
Water and temperature.
The soybean growing season begins in earnest when seed is sown. Seeds passively imbibe or absorb approximately 50% of their dry weight in water from the soil. Like other organisms that cannot regulate their own temperatures, the enzymes that catalyze the chemical reactions that need to take place in order for seeds to germinate are driven by the temperature of the surrounding environment – soil. Although soybean’s ideal soil temperature is ~70 degrees, in order to reduce the chance of seed or seedlings succumbing to disease losses by sitting idlily, it is recommended that minimum soil temperatures shouldn’t fall below 50 degrees.
Radical radicles.
The first plant part to break through the seed coat is the radicle, or first root to emerge. Cells in the radicle are gravitropic, meaning that they ‘know’ which end is up and grow downward in the soil profile. This downward growth helps to anchor the seedling in the soil.
Shoot growth.
The soybean hypocotyl, or the short stem between the cotyledons and radicle, begins to elongate upward, pulling the cotyledons (seed leaves) along for the ride. The hypocotyl remains bent over until the cotyledons emerge from the soil, typically 1-2 weeks after planting. Eventually, the cotyledons and apical meristem (primary growing point) sit at the top of the seedling and cotyledons unfold to lie flat.
Between emergence and the V1 growth stage, when the first trifoliate leaf unfolds, the seedling relies on the nutrients contained in cotyledons to supply its needs. After this point, the plant’s cellular machinery is up and running and using the sun’s energy the plant can combine CO2 and water to form carbohydrate through the process called photosynthesis.
G x E x M.
Selecting a locally-adapted soybean variety’s genetics (G) with high yield potential is one of the most crucial decisions farmers can make. As no two growing seasons are the same, it is the interaction of this variety with in-season management (M) practices and season-long environmental (E) conditions that will translate into yield.
Check out the links below for more information about soybean growth and development.
Soybean growth stages, Univ. of MN Extension
Soybean growth and management quick guide, NDSU Extension
A visual guide to soybean growth stages, Univ. of WI Extension
Soybean growth and development, Univ. of WI Extension
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