Corn Growth and Development

Name: Corn Growth and Development
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Description: Corn Growth and Development

Corn Growth and Development
Chad Lee Grain Crops Extension Specialist ● Lee and Herbek, Grain Crops Extension © 2006 This is an introduction into corn growth and development.

Growth and Development Key Management Issues Scouting Techniques
Goals for Today Growth and Development Key Management Issues Scouting Techniques Biotech Options Lee and Herbek, Grain Crops Extension © 2006

Corn Growth Stages Vegetative (V) Reproductive (R)
How a Corn Plant Develops, Special Report No. 48 Iowa State University Lee and Herbek, Grain Crops Extension © 2006 Corn growth and development is divided into two major sections: vegetative and reproductive. There are several methods for determining vegetative stages, but we are going to focus on the leaf collar method or fully-extend leaf method. This method uses a defined, visible part of the plant to identify stages. The leaf collar is defined as the part of the leaf that connects the leaf to the sheath of the plant. The leaf collar resembles a an shirt collar with one button open around someone’s neck.

R6 physiological maturity
Vegetative Stages Reproductive Stages VE emergence R1 silking V1 first leaf R2 blister V2 second leaf R3 milk V3 third leaf R4 dough V(n) nth leaf R5 dent VT tasseling R6 physiological maturity * When staging a field of corn, each specific V or R stage is defined only when 50 percent or more of the plants in the field are in or beyond that stage. Lee and Herbek, Grain Crops Extension © 2006

“Spiking” Corn Lee and Herbek, Grain Crops Extension © 2006 Emergence occurs when the plant shoot pokes through the soil surface. The radicle emerges from the seed and starts the seminal root system. The seminal root system will be the major root system of the corn plant until the plant reaches about V3. The coleoptyle emerges upward from the seed and contains five leaves of the plant. The mesocotyl extends from the coleoptyle until the shoot reaches the soil surface. Once the shoot reaches the soil surface the mesocotyl stops growing and the leaves begin to emerge. Cool temperatures and/or severe compaction can prevent the mesocotyl from growing straight up toward the soil surface.

Corn Growth Stages: Vegetative
3 Collars V6 6 collars V12 12 collars V15 15 collars VT tassel Lee and Herbek, Grain Crops Extension © 2006 The vegetative stages begin at emergence (VE) and end at tassling (VT). We are going to focus on a few of the vegetative stages. The numbers following the V stage represent the number of collars that are visible.

V3 V6 V12 Corn Growth Stages 3 Collars 6 collars 12 collars
Nodal roots active. Growing point below ground. V6 6 collars Growing point above ground. Tassel and ear development starting. V12 12 collars Ear size, kernel size and kernel number being determined. Limits on water and/or nutrients will reduce yields. Lee and Herbek, Grain Crops Extension © 2006 V3 occurs when 3 leaf collars are visible on the stalk of the plant. V3 means that 3 nodes have fully developed in the plant. At this stage, roots have formed from the first node and these roots will become more important than the seminal root system at collecting water and nutrients and providing structural support to the plant. Nodal roots will eventually form at about the first six or seven nodes. The growing point is still below ground at the V3 stage, making the plant fairly tolerant of freezes. If all of the above-ground growth is removed and no damage is done to the growing point below ground, the plant will regrow a shoot and have minimal yield losses . . .as long as growing conditions are favorable. By V6, or six collars, the growing point is above ground and removal of all the above-ground growth will likely kill the entire plant. Tassel and ear development have started. Many post-emergence herbicides have restrictions against corn that is at the V6 growth stage. Applications of some herbicides directly on the corn plant at or after this stage of growth will damage the developing ears. At or shortly after V6, the corn stalk will expand and start to tear off older leaves and collars. The stalk of the corn plant may need to be split in two to identify the number of fully developed nodes. V12 has 12 fully developed nodes or collars. Ear size, kernel size and kernel number are being determined. Any limits on water or nutrients at this stage will reduce yields. The level of yield reduction depends on the intensity and duration of the stress. For example, a mild limit to water will hurt yields very little, but a severe drought will hurt yields by 10 to 15%, if growing conditions following this stage are favorable.

V3 – Three visible collars
Lee and Herbek, Grain Crops Extension © 2006

V3 Growing point is below the soil surface.
Frosts on the surface will not kill the plants. Freezing soil temps will kill the plant. Flooding can kill plants. Root hairs begin to form on Nodal Roots. Seminal Root growth has basically stopped. Lee and Herbek, Grain Crops Extension © 2006

V6 Tassel development has started.
Ear shoot formation has also started. Lee and Herbek, Grain Crops Extension © 2006

V6 Leaves start to tear off the plant
To be certain about V-stages beyond V6: Split the entire stalk (from the tip to the roots) in half with a knife. The first five nodes will be clustered near the bottom of the stalk and the 6th node will be very close to the soil line. Count nodes above the 6th node to determine how many nodes are present. The total number of nodes equals the V-stage of the plant. For example 7 nodes = V7 corn. Lee and Herbek, Grain Crops Extension © 2006

V6 Ear shoot. Growing point is above the ground.
Nodal Root System is the primary root system for nutrients and water. Lee and Herbek, Grain Crops Extension © 2006

V12 Both kernel size and kernel number are being determined.
Any limits on water or nutrients at this phase will drastically impact yields. Earlier maturing hybrids will pass through this phase faster than later maturing hybrids. Lee and Herbek, Grain Crops Extension © 2006

V15 VT Corn Growth Stages 15 collars tassel
Rapid growth, about 10 to 12 days before silking. Most critical stage for yield determination. Most sensitive to stress. VT tassel Last tassel branch is visible but prior to silking. Complete leaf loss will cause nearly 100% yield loss. Lee and Herbek, Grain Crops Extension © 2006 When the plant reaches V15

V15 About 10-12 days from silking.
Entering the most critical stage for yield determination. The plant is most sensitive to water and/or nutrient stress at this stage. Irrigation- the 4 weeks around silking are the most critical. Lee and Herbek, Grain Crops Extension © 2006

V18 Lower part of plant Upper part of plant
Lee and Herbek, Grain Crops Extension © 2006

VT - Tassel Occurs when last branch of tassel is visible but before silks emerge. Most susceptible to hail damage at this stage. Complete leaf loss at VT will result in little to no yield. Lee and Herbek, Grain Crops Extension © 2006

Corn Growth Stages: Reproductive
Silking R2 Blister R4 Dough R5 Dent R6 Physiological Maturity Lee and Herbek, Grain Crops Extension © 2006

R1 R2 Silking Blister Corn Growth Stages N and P uptake are rapid.
About 50% of total N is taken up after R1. K uptake is nearly complete. Water needed for pollination. Pollination occurs. R2 Blister Ear size nearly complete. Silks begin to dry out. A miniature corn plant is being formed in each fertilized kernel. Lee and Herbek, Grain Crops Extension © 2006

R1 - Silking N uptake is rapid. P uptake is rapid.
Silks starting to emerge. N uptake is rapid. P uptake is rapid. K uptake is nearly complete. Watch for corn borer feeding. Moisture is needed for pollination. Lee and Herbek, Grain Crops Extension © 2006

R1 - Silking Cob material Premature kernel
Two to three days are required for all silks on an ear to be pollinated. Lee and Herbek, Grain Crops Extension © 2006

R2 - Blister Ear size is nearly complete.
Fertilized silks are starting to dry out. An miniature corn plant has started to develop within the premature kernel. Lee and Herbek, Grain Crops Extension © 2006

R3 - Milk Kernels are becoming yellow on the outside. Silks are dry.
Kernels are at 80% moisture. Stress becomes less of a factor as kernels start to dry down. Lee and Herbek, Grain Crops Extension © 2006

R4 R5 Dough Dent Kernels have accumulated ½ of total dry weight.
Corn Growth Stages R4 Dough Kernels have accumulated ½ of total dry weight. Five leaves have formed in the kernel. R5 Dent Most kernels have dented and are near 55% moisture at start. Starch layer has formed and progresses down the kernel. Lee and Herbek, Grain Crops Extension © 2006

R4 - Dough Fluid in the kernel is becoming a consistency similar to dough. (70% moisture) Almost ½ of the dry weight has been accumulated. Five embryonic leaves have formed in the kernel. These will be the first five leaves of a new plant as it emerges next year. Lee and Herbek, Grain Crops Extension © 2006

R5 - Dent Most of the kernels have dented on the top.
Most kernels are about 55% moisture at the start of R5. A starch layer has formed and begins to progress down the kernel. A frost will stop dry matter accumulation and reduce yields. Lee and Herbek, Grain Crops Extension © 2006

R6 Corn Growth Stages Blacklayer has formed at bottom of kernel.
Physiological Maturity Blacklayer has formed at bottom of kernel. Kernel is about 30 to 35% moisture. For safe storage, needs to dry to 13 to 15% moisture Lee and Herbek, Grain Crops Extension © 2006

R6 – Physiological Maturity
Kernel is about 30 – 35% moisture. Kernels need to be at 13 to 15 % moisture for safe storage. Lee and Herbek, Grain Crops Extension © 2006

R6 – Physiological Maturity
Blacklayer Lee and Herbek, Grain Crops Extension © 2006

Corn Planting Dates in Kentucky
Corn should be planted by: Far Western KY May 1 Western-Central KY May 10 Eastern KY May 15 Plant an earlier-maturing hybrid if corn planting is delayed after: June 5 A 1% yield loss per day can be expected in corn planted after: May 10-15 Lee and Herbek, Grain Crops Extension © 2006

Corn: Seeding Rates Seeding rate* (seeds/acre) Grain 22,000 - 30,000
Table 3. Recommended corn seeding rates for Kentucky. Seeding rate* (seeds/acre) Grain 22, ,000 Silage 24, ,000 Irrigated 26, ,000 * Range depends on potential yield of soil ranging from less than 100 bu/ac for the low range to more than 200 bu/ac for the high range. Lee and Herbek, Grain Crops Extension © 2006

Biotech Tools for Corn Insects
Bt Corn YieldGard Corn Borer (Cry1Ab) YieldGard Rootworm (Cry3Bb1) YieldGard Plus (Cry1Ab+Cry3Bb1) Herculex I (Cry1F) Herculex RW (Cry34Ab1/Cry35Ab1) Herculex Xtra (Cry1F+Cry34Ab1/Cry35Ab1) Agrisure CB (Cry1Ab) Agrisure RW ? (Cry3A) Agrisure CB/RW ? Lee and Herbek, Grain Crops Extension © 2006 What is the difference between blue, yellow and black coloring. What is the deal with AGrisure?

Biotech Tools for Corn Weeds
Roundup Ready genes GA21 – “Roundup Ready” Applications from VE to V8 or 30 inches, whichever occurs first, up to 1.0 lb ae glyphosate/acre, depending on herbicide label (2 pt/A of 3 lb ae/gal formulation – Roundup Original) NK603 – “Roundup Ready 2” Applications from VE to V8 or 30 inches, whichever comes first, up to 1.12 lb ae glyphosate/acre, depending on herbicide label (3 pt/A of 3 lb ae/gal formulation – Roundup Original) Drop nozzles from 30 to 48 are allowed Lee and Herbek, Grain Crops Extension © 2006

Biotech Tools for Corn Weeds
Liberty Link T25 - Corn (PAT, BAR) Combined with Herculex (Cry1F) Used as a marker gene for the Cry1F event Lee and Herbek, Grain Crops Extension © 2006

Estimating Corn Yields
Simplest (least accurate method) Count number of kernels Multiply that number by 0.300 Using assumes 1) 27,000 ears per acre 2) 90,000 kernels per bushel 1 Lee and Herbek, Grain Crops Extension © 2006

Estimating Corn Yields
Including ears/acre as a factor and kernel size as a factor. Ears/Acre Large Kernel Size (70,000 kernels/bushel) Multiplier Medium Kernel Size (90,000 kernels/bushel) Small Kernel Size (110,000 kernels/bushel) 22,000 0.314 0.244 0.200 23,000 0.329 0.256 0.209 24,000 0.342 0.267 0.218 25,000 0.357 0.278 0.227 26,000 0.371 0.289 0.236 27,000 0.386 0.300 0.245 28,000 0.400 0.311 0.255 29,000 0.414 0.322 0.264 30,000 0.429 0.333 0.273 34,000 0.486 0.378 0.309 AGR-187: Estimating Corn Yields Lee and Herbek, Grain Crops Extension © 2006

Feet of row needed to equal 1/1000th acre Multiplier to Equal One Acre
Estimating Corn Yield Measuring 1/1,000th Acre Row Width (inches) Feet of row needed to equal 1/1000th acre Multiplier to Equal One Acre 15 34 feet 10 inches 1,000 20 26 feet 2 inches 22 23 feet 9 inches 30 17 feet 5 inches 36 14 feet 6 inches 38 13 feet 9 inches AGR-187: Estimating Corn Yields Lee and Herbek, Grain Crops Extension © 2006

Estimating Corn Yield More accurate stand measurements.
Row Width (inches) Measured Row Length (feet) Total Measured Area (ft2) Number of Ears per Measured Area Number of Ears per Acre 30 50 125 40 13,939 60 20,909 65 22,651 70 24,394 75 26,136 80 27,878 85 29,621 90 31,363 100 34,848 AGR-187: Estimating Corn Yields Lee and Herbek, Grain Crops Extension © 2006

Estimating Early Season Stand Losses
Table 2. Grain yields for various planting dates and population rates, expressed as a percent of optimum planting date and population rate (uniformly spaced within row). Planting date Plants per acre at harvest 12,000 14,000 16,000 18,000 20,000 22,500 25,000 (% of optimum yield) April 15 70 76 81 85 88 91 93 April 20 72 78 83 87 90 95 April 25 75 86 96 98 May 1 77 92 100 May 6 May 11 99 May 16 May 21 73 94 May 26 69 80 84 May 31 64 79 82 June 5 59 June 10 52 58 63 67 Data from National Corn Handbook Lee and Herbek, Grain Crops Extension © 2006

Keys to High Yields Good genetics Maximize days suitable for growing
90 to 95% light interception at silking (R1) Adequate nutrients and water to complete plant growth and seed fill Lee and Herbek, Grain Crops Extension © 2006

Keys to High Yields Good genetics Good yield potential
Good stress tolerance Good defense genetics Lee and Herbek, Grain Crops Extension © 2006

Keys to High Yields Maximize days Maturity group Stress tolerance
Planting date Lee and Herbek, Grain Crops Extension © 2006

Keys to High Yields 90 to 95% light interception at silking (R1)
Row spacing and population Planting date Hybrid Maturity Lee and Herbek, Grain Crops Extension © 2006

Keys to High Yields Adequate nutrients and water to complete growth and seed fill Soil pH Adequate N, P, K, Zn Precipitation Water infiltration Water availability Lee and Herbek, Grain Crops Extension © 2006

Slats on a Barrel Soil Fertility Hybrid Genetics
TOTAL YIELD Soil Fertility Hybrid Genetics Planting Date, Seeding Rate Pest Management Timely Harvest Soil Structure Economics Weather TOTAL YIELD Soil Fertility Hybrid Genetics Planting Date, Seeding Rate Pest Management Timely Harvest Soil Structure Economics Weather Lee and Herbek, Grain Crops Extension © 2006

Corn Growing Degree Days
Each day has a slightly different average temperature. Temperature affects corn growth rate. Attempt to relate temperature to corn growth rate. Corn Growing Degree Day Base 50° F Max 86° F Min 50° F Lee and Herbek, Grain Crops Extension © 2006

Corn Maturity (Days) GDD 85 to 100 2100 – 2400 101 to 130 2400 – 2800 131 to 145 2900 – 3200 GDD Requirements of a 2700 GDD Hybrid Growth Stage GDD V2 200 V6 475 V12 870 VT 1135 R1 1400 R6 2700 From NCH-40 Growing Season Characteristics and Requirements in the Corn Belt. National Corn Handbook. Lee and Herbek, Grain Crops Extension © 2006

Planting Date and GDD April 20 1155 --- May 3 1029 126 May 18 825 330
Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer Planting Date GDD As of 06/26/05 Difference From First Planting April 20 1155 --- May 3 1029 126 May 18 825 330 May 31 596 559 June 15 281 874 From University of Kentucky Ag Weather Center: Growing Degree Day calculator: Lee and Herbek, Grain Crops Extension © 2006

Planting Date and GDD April 20 1503 --- May 3 1377 126 May 18 1173 330
Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer Planting Date GDD As of 07/11/05 Difference from First Planting April 20 1503 --- May 3 1377 126 May 18 1173 330 May 31 944 559 June 15 629 874 From University of Kentucky Ag Weather Center: Growing Degree Day calculator: Lee and Herbek, Grain Crops Extension © 2006

Date of Planting – Corn and Grain Silage 1976 - Lexington
Date planted Relative Yield Ratio Maturity Bu/A 35% Ear:Forage April 20 Full 180 27.2 56:44 May 6 177 25.8 59:41 May 21 166 23.4 60:40 May 31 144 19.9 June 10 112 16.4 57:43 Early 128 18.1 June 29 64 11.2 48:52 May 20 S 77 18.2 42:58 Lee and Herbek, Grain Crops Extension © 2006

Effect of Tillage and Planting Date on Corn Yield 4-avg. (1979-1982)
Conventional No-Till Avg. Corn Yield (bu/A) Early May1 121 Mid-May 102 124 113 Early June 86 94 103 116 1 Three-year avg. only data missing for Early May. Lee and Herbek, Grain Crops Extension © 2006

Corn Planting Depth and Planting Date
April 13 May 2 (inches) % Stand Days to Emerge 1 85 10 93 9 2 77 15 98 11 3 76 18 92 12 4 73 21 89 13 Lee and Herbek, Grain Crops Extension © 2006

Germination Temperature for Corn
50 OF at a 2-inch depth for three or four days is excellent. Soil temperature at 50 OF at 7:00 am or 55 OF at 1:00 should ensure that temperatures are suitable for germination and growth. Lee and Herbek, Grain Crops Extension © 2006

Population Effect on Corn Yields (Hardin County, Kentucky, 1972-76)
Corn Yield (Bu/A) Plants/A No-Till Conventional 14-18,000 133 114 20-23,000 148 119 26-28,000 158 128 Average 146 120 Lee and Herbek, Grain Crops Extension © 2006

Effect of Row Width and Plant Population on Corn Yields (8 location average)
Yield (bu/A) Row Width 20 inch 170 ab* 30 inch 175 a 36 inch 169 b Plant Population 20,000 164 a 26,000 171 b 30,000 178 c *0.10 level for row width, 0.05 level for population. Lee and Herbek, Grain Crops Extension © 2006

Row Width Effect on Corn Yields (Hardin County, Kentucky)
Corn Yield (Bu/A) (inches) No-Till Conventional 19 161 137 38 162 133 30 109 116 Lee and Herbek, Grain Crops Extension © 2006

Corn Hybrid and Population Effect on Grain Yield
Plants/A Yield (bu/A) Irrigated Rainfed Pioneer 3160 B73 x PA91 20,000 155 139 163 152 28,000 192 132 169 134 36,000 176 130 189 133 DeKalb XL32AA A 136 121 119 167 131 129 172 Population resulting in highest yield varied across hybrids and water regimes. Lee and Herbek, Grain Crops Extension © 2006

What determines crop row width?
Duvick D.N., and K.G. Cassman Crop Science 39: Fig. 2 The relationship between hybrid yield at different plant densities and year of release. Data were obtained from field experiments conducted at three locations in central Iowa in 1994. Lee and Herbek, Grain Crops Extension © 2006

Row Width Effect on Corn Grain Yield (Non-Irrigated)
Yield (bu/A) 30 inch 36 inch Difference 1979 154 142 + 12 1980 122 120 2 1981 152 155 - 3 1982 116 130 14 Average 136 137 1 Lee and Herbek, Grain Crops Extension © 2006

Row Width Effect on Corn Grain Yield (Irrigated)
Yield (bu/A) 30 inch 36 inch Difference 1979 199 176 + 23 1980 143 141 2 1981 163 156 7 1982 175 177 - Average 170 162 8 Lee and Herbek, Grain Crops Extension © 2006

Corn Hybrid, Row Width and Plant Population Summary Across Years
Yield (bu/A) Row Width Pioneer 33Y18 155.4 a 20 inch 148.4 a So. States SS828 143.9 b 30 inch 150.9 a Plant Population 24,000 148.7 a 28,000 151.5 a 32,000 Lee and Herbek, Grain Crops Extension © 2006

Recommended Corn Seeding Rates (Greatest Limiting Factor to Corn Yield)
Plants / Acre Rainfed Grain Corn (No-Till and Conventional) 22,000 – 30,000 Irrigated Grain 26,000 – 32,000 Silage 24, ,000 From ID-139: A Comprehensive Guide to Corn Management in Kentucky. Lee and Herbek, Grain Crops Extension © 2006

Uneven Corn Stands Cost Money
Good stands = 2 inch deviation Example 26,000 seeds on 30 inch row Equals 1 plant every 8 inches Good stand is 6 to 10 inches apart 2.5 bushel lost for every 1 inch increase in deviation 3 inch deviation = 2.5 bushel loss 5 inch deviation = 7.5 bushel loss Lee and Herbek, Grain Crops Extension © 2006

Effect of Emergence Delays on Corn Yield
Uneven emergence of: 10 days = 6 – 9 % loss 21 days = 10 – 22% loss 7 days = 5.5% loss 14 days = 13.2% loss Primary Causes: 1. Soil Moisture 2. Poor soil-to-seed contact (Wisconsin and Illinois research) (Minnesota research) Lee and Herbek, Grain Crops Extension © 2006

The major factor influencing vegetative development in grain crops is:
TEMPERATURE Ideal Growing Temperatures for: Corn = 77 to 88 °F Soybean 65 to 84 °F Wheat 62 to 73 °F Lee and Herbek, Grain Crops Extension © 2006

Second Year Corn vs. Rotated Corn (Soybeans)
Corn Yield (Bu/A) (2002 – 2005) (4 yr. Avg.) Rotated Yield Advantage Corn Hybrid Second Year Corn Corn After Soybeans Bu/A (%) Non-Bt 177 196 +19 (11%) Bt 179 198 Avg. 178 197 Yearly Range +13-28 (7-15%) Lee and Herbek, Grain Crops Extension © 2006

Corn Growth and Development

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