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Corn: Development

Author: OMAFRA Staff
Creation Date: 01 March 2002
Last Reviewed: 01 March 2002
Agronomy Guide > Pub 811: Corn > Development
Excerpt from Agronomy Guide for Field Crops (Chapter 3)
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

  1. Introduction
  2. Updates on Corn: Development
  3. Related links...

Introduction

The vegetative and reproductive growth stages in corn are described in Table 3-14. Vegetative Growth Stages in Corn, and Table 3-15. Reproductive Growth Stages in Corn.

Table 3-14. Vegetative Growth Stages in Corn - Part 1 (Part 2)
  Stage
VE VI V4 V6
Illustration Stage VE Stage VI Stage V4 V6 Stage
Leaf Collars1 0 1 4 6
Leaf Tips 1 3 7 10
Leaf Over 0 2 6 8
CHUs Required2 180 330 630 780
Target Date3 May 16 May 25 June 11 June 18
Notes
  • Emergence.
  • Days to emerge most often ranges from 6-21 days.
  • Uniform emergence essential to high yields.
  • Look for poor germination caused by chafer, wireworms, seedcorn maggot, seedcorn beetle, slugs, black cutworm.
    		•
  • Start of critical weed-free period.
  • Growing point below ground.
  • Ensure herbicide selection is safe for crop stage.
  • Ear Inititation.
  • Growing point below ground.
  • Expansion of nodal root system will soon completely replace seminal root system.
  • Risk from cutworm and flea beetle damage has passed.
    		•
  • End of critical weed-free period.
  • Lower leaves (1-4) dry up, may not be visible.
  • Growing point at or above ground; more susceptible to frost injury.
  • Initiated ears and tassel now visible upon plant dissection.
    		•

    1Refer to the section on Corn Leaf Stages, for a description of the methodologies of corn leaf counting.
    2Approximate CHUs required to reach various stages of corn development.
    3 Estimated date to reach various stages of development based on long-term heat unit accumulations for an average 2,800-CHU region (see the data fro Brucefield, Ontario, in Table 3-7. Average Seasonal Accumulations of Crop Heat Units From Various Sites Across Ontario) and anticipating a May 5 planting date.

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    Table 3-14. Vegetative Growth Stages in Corn - Part 2 (Part 1)
      Stage
    V8 V12 VT
    Illustration V8 Stage Stage V12 Stage VT
    Leaf Collars1 8 12 (varies)
    Leaf Tips 11 15 --
    Leaf Over 10 14 --
    CHU's Required2 930 1,170 1,310
    Target Date3 June 26 June 31 July 18
    Notes
  • Side-dressing nitrogen and inter-row cultivation beyond this point pose threat of root pruning.
  • Beginning rapid stem dlogation.
  • Risk from slug damage has passed.
    		•
  • Crop becomes increasingly sensitive to yield reduction by heat or drought.
  • Size of ear and number of potential kernels being established.
    		•
  • Tassel emerges.
  • Pollen shed begins 2-3 days prior to silk emergence.
  • Pollen viability reduced by drought and high temperatures.
  • Scout for corn leaf aphids, corn rootworm adults and goosenecking caused by rootworm larva.
    		•

    1Refer to the section on Corn Leaf Stages, for a description of the methodologies of corn leaf counting.
    2Approximate CHUs required to reach various stages of corn development.
    3 Estimated date to reach various stages of development based on long-term heat unit accumulations for an average 2,800-CHU region (see the data fro Brucefield, Ontario, in Table 3-7, Average Seasonal Accumulations of Crop Heat Units From Various Sites Across Ontario) and anticipating a May 5 planting date.

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    Table 3-15. Reproductive Growth Stages in Corn - Part 1 (Part 2)
      R Stage
    R1- Silking R2 - Blister R3 - Milk
    Description Silks emerge from husks at tip of ear. Kernels are white, filled with clear fluid and distinct from surrounding cob material. Kernels begin to have yellow colour. Inner fluid is milky white.
    CHUs Required1 1,480 1,825 2,000
    Target Date2 July 20 Aug. 3 Aug. 11
    Kernal Moisture NA3 85% 80%
    Notes
  • Pollination requires 3-7 days.
  • Silks continue to elongate until fertilized.
  • Environmental stresses very detrimental to yield.
  • Begin scouting for ear insect pests (corn earworm, fall armyworm).
  • Kernels beginning dry matter accumulation.
  • Relocation of nutrients from the leaves and stem to the ear begins.
  • Firing of lower leaves may become evident.
    		•
  • Rapid grain filling period.
  • Good plant health, clear skies and active photosynthesis add to kernel size and test weight.
    		•

    1Approximate CHIUs required to reach various stages of corn development.
    2Estimated date to reach various stages of development based on long-term heat unit accumulations for an average 2,800-CHU region. (See the data on Brucefield, Ontario, in Table 3-7. Average Seasonal Accumulations of Crop Heat units From Various Sites Across Ontario) and anticipating a May 5 planting date.
    3NA - not available, kernels not formed until after pollination.

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    Table 3-15. Reproductive Growth Stages in Corn - Part 2 (Part 1)
      R Stage
    R4 - Dough R5 - Dent R6 - Maturity
    Description Milky inner fluid becomes thicker and pasty. Outer edges of kernels become firmer. Some dents appear Majority of kernels are dented. Hard white layer of starch evident at top of kernel (milk line). Hard starch layer evident from top to botom of kernel. Black layer forms at base of kernel.
    CHUs Required1 2,165 2,475 2,800
    Target Date2 Aug. 18 Sept. 1 Sept. 18
    Kernal Moisture 70% 55% 30%-35%
    Notes
  • Top of kernel begins to firm up.
  • Killing frost may cause yield losses of 25%-40%.
  • Begin to assess ear rot incidence.
    		•
  • Milk line advances towrad tip as crop matures.
  • Whole plant moistures suitable for silage harvest.
  • 90% of grain yield reached by one-half milk line.
  • Examine fields for lodgin, ear drop and stalk rots - if high, consider harvesting early.
    		•
  • Physiological maturity.
  • Kernels have achieved maximum dry weight. Moisture loss from kernels still required for sutiable threshing.
    		•

    1Approximate CHIUs required to reach various stages of corn development.
    2Estimated date to reach various stages of development based on long-term heat unit accumulations for an average 2,800-CHU region. (See the data on Brucefield, Ontario, in Table 3-7. Average Seasonal Accumulations of Crop Heat units From Various Sites Across Ontario) and anticipating a May 5 planting date.
    3NA - not available, kernels not formed until after pollination.

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    Updates on Corn: Development

    No updates available at this time.

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    Related links...

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