One easy barrier to break when it comes to maximizing higher corn yields is better understanding the growth and development stages of the crop. From vegetative (V) to reproductive (R) phases, a farmer can become an in-season diagnostic detective by learning how corn grows at those different times. This helps them better understand the corn’s physiological impact on nutrient management. Becoming a crop diagnostic detective starts with unlocking the key to the V stage – the seed.
When a corn kernel is planted into warm, moist soil, water is absorbed through the seed coat and the kernel begins to swell. The critical soil moisture required for corn to germinate is 30%, and a corn seed will absorb 1.5 to 2 times its weight in water during the germination process.
The radicle root will emerge from the seed in favorable growing conditions within two to three days, or 65 to 80 growing degree days (GDDs). Corn typically requires between 100 and 120 GDDs (or five to seven days) after planting to emerge from the soil. This process could, however, take several weeks if soil temperatures are cool or dry. After germination, the mesocotyl elongates from the seed, pushing the coleoptile towards the soil surface. The mesocotyl is a white, tubular, stem-like tissue that is sometimes called the first internode.
The VE growth stage is corn emergence. The first encounter with sunlight will set the depth of the crown, which is usually about 3/4 inch below the soil surface. This is where the first nodal roots will emerge. It’s at this time that the radicle and seminal roots are developing to supply water and some nutrients to the crop. Once the coleoptile breaks the soil surface and reaches sunlight, it stops growing, opens at the tip and the first true leaf unfolds.
The V1 growth stage is achieved when the first leaf has fully emerged and the leaf collar is visible. This first leaf will have a rounded tip, while all other leaves will have a pointed tip. At this growth stage, the plant is mainly relying on nutrients from the seed as it continues rapid root growth.
The V2 growth stage is when the second leaf has fully emerged and the leaf collar is visible. The leaf collar is the junction between the leaf blade and the leaf sheath. This is typically seven to 10 days after emergence, or about 200 GDDs in favorable growing conditions.
The V3 growth stage is the point at which the plant transitions from the seed being the main food source to the beginning of the photosynthetic process for energy production. The plant begins to rely more on the nodal root system as it continues to expand and produce root hairs. By this time, primary ear initiation has started, and seminal root growth has ceased. The V3 growth stage is reached about 10 to 20 days (around 350 GDDs) after emergence.
When the fourth leaf is collared, V4, the number of kernel rows around the primary ear is set.
At the V5 growth stage, the leaf collar is visible on the fifth leaf. The growing point of the plant moves from underground to the soil surface, and the plant now relies on the nodal roots for nutrients and water. All the leaves the plant will ever have are initiated during the first four to five weeks of plant development. Kernel rows around have been determined, and this is the last internode to remain underground.
At the V6 growth stage, tassel development is initiated. All the plant’s leaves are formed and rapid stalk elongation begins. This normally takes place 25 to 30 days after emergence, or approximately 475 GDDs.
Gaining familiarity with the early-season growth stages of corn is just the first step in becoming a crop diagnostic detective. The key to the V stage is now unlocked. Stay tuned later this season for the second part of growth detective training – how to raise the bar with the R stage of corn growth.
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