Understanding Corn Growth Stages: From Germination to Maturity

By
Tanya Eadie
-
71

Early Growth & Dry Matter Accumulation

  • Corn plants increase in weight slowly early in the growing season.
  • As more leaves develop and receive sunlight, dry matter accumulation increases.
  • Leaves emerge first, followed by:
    • Leaf sheaths
    • Stalk
    • Husks
    • Ear shank
    • Silks
    • Cob
    • Grain
  • High yields depend on favorable environmental conditions at all stages.
  • Unfavorable conditions can:
    • Affect leaf and root development in early growth stages.
    • Reduce silk production, poor ovule pollination, and limit kernel development.
    • Cause premature growth cessation, affecting kernel size.

Identifying Development Stages

  • Leaf counting methods:
    • Leaf Tip Method: Counts all leaves, including leaf tips emerging from the whorl.
    • Leaf Over Method: Counts only fully emerged, arched leaves.
  • Iowa State University System:
    • Divides development into vegetative (V) and reproductive (R) stages.
    • Vegetative (V) stages: VE (emergence) → V1, V2, V3, etc.
    • Last vegetative stage: VT (tasseling).
    • Reproductive (R) stages:
      • R1: Silking
      • R2: Blister
      • R3: Milk
      • R4: Dough
      • R5: Dent
      • R6: Physiological maturity

Vegetative Development (VE-VT)

Germination & Seedling Development (VE)

  • Germination requires 30% seed moisture and 10°C soil temperature.
  • Key stages:
    • Radicle (first root) emerges.
    • Coleoptile (protective leaf) pushes through soil.
    • Leaves emerge when exposed to light.
  • Planting depth influences emergence time:
    • Deeper planting: Slower emergence due to cooler temperatures.
    • Too deep planting: Risk of underground coleoptile opening, reducing emergence.
  • Management tips:
    • Fertilizer placement should be precise to avoid salt injury.
    • Seed treatments prevent insect and disease damage.

Early Stage Development (V1-V4)

  • Growing point remains below soil surface for the first 3-4 weeks.
  • Root system:
    • Nodal roots begin forming, becoming the main nutrient source.
    • Fertilizer placed near roots can enhance growth.
  • Environmental risks:
    • Light frost or hail may damage leaves but rarely impacts final yield.

Mid Vegetative Development (V5-V8)

  • By V5-V6, all leaves are formed (number varies by hybrid & temperature).
  • Growth milestones:
    • V6: Growing point and tassel emerge above soil surface.
    • Ear shoots and tillers appear.
    • V8: Ear size potential is determined.
  • Root growth:
    • Roots reach across rows and extend 18 inches deep.
    • Over-cultivation can damage permanent roots.
  • Yield considerations:
    • Nutrient deficiencies at this stage can reduce ear size.
    • 10-20% yield loss may occur if leaves are destroyed by hail or frost.

Late Vegetative Development (V9-V12)

  • Key developments:
    • Ear shoots become more visible.
    • Tassel growth accelerates.
    • Brace roots emerge, enhancing nutrient absorption.
  • Yield risks:
    • Moisture/nutrient deficiencies affect ear growth.
    • Hail or leaf damage results in higher yield loss.
    • Stress conditions reduce seed set potential.

Tasseling Stage (VT)

  • Final vegetative stage before reproductive growth.
  • Tassel fully emerges before silking.
  • Pollen shed starts 2-3 days post-emergence.
  • Yield risk:
    • Complete leaf loss = 100% yield loss.
    • Hail damage can severely impact future kernel development.

Reproductive & Grain Filling Stages (R1-R6)

Silking Stage (R1)

  • Most critical stage for yield determination.
  • Silks appear & receive pollen within 4-10 days of tassel emergence.
  • Yield risks:
    • Heat/drought stress may prevent pollen tube growth.
    • Delayed silking due to moisture stress results in poor seed set.
    • Nutrient deficiencies and damage from insects, disease, or hail reduce yields.

Blister Stage (R2)

  • Kernels appear as white blisters.
  • Dry matter accumulation accelerates.
  • Nutrients begin transferring from vegetative to reproductive parts.

Milk Stage (R3)

  • Kernels turn yellow and fluid inside is milky.
  • Yield risks:
    • Stress reduces kernel number and size.
    • Kernel moisture ~80%.

Dough Stage (R4)

  • Inner fluid thickens into starch paste.
  • Kernels begin denting.
  • Moisture level: ~70%.

Dent Stage (R5)

  • Kernels fully dented.
  • Milk line forms, indicating starch accumulation.
  • Dry weight peak:
    • Maximum whole-plant dry weight achieved at ~45% grain moisture.
    • Ideal time for corn silage harvest.
  • Yield risks:
    • Stress reduces kernel weight.
    • Early frost severely impacts yield.

Physiological Maturity (R6)

  • Kernels reach maximum dry weight.
  • Black layer forms at kernel base (~31-35% moisture).
  • Final considerations:
    • Grain needs further drying before storage (~13-15% moisture).
    • Dry-down depends on hybrid & environmental factors.

Conclusion

  • Corn growth is highly dependent on environmental conditions at each stage.
  • Managing planting depth, nutrients, moisture, and stress factors is key to maximizing yields.
  • Identifying and monitoring growth stages ensures optimal decision-making for fertilizer, irrigation, and pest control applications.

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