lee and herbek, grain crops extension © 20061 corn growth and development chad lee grain crops...
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Lee and Herbek, Grain Crops Extension © 2006 1
Corn Growth and Development
Chad LeeGrain Crops Extension Specialist859-257-3203 ● [email protected]
www.uky.edu/Ag/GrainCrops/
Lee and Herbek, Grain Crops Extension © 20062
Goals for Today
• Growth and Development
• Key Management Issues
• Scouting Techniques
• Biotech Options
Lee and Herbek, Grain Crops Extension © 20063
Corn Growth Stages
• Vegetative (V)
• Reproductive (R)
How a Corn Plant Develops, Special Report No. 48Iowa State Universityhttp://maize.agron.iastate.edu/corngrows.html
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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 tasselingR6 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.
http://maize.agron.iastate.edu/corngrows.html
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“Spiking” Corn
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VE - Emergence
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http://maize.agron.iastate.edu/corngrows.html#stages
V1 – One Visible Collar
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Corn Growth Stages: Vegetative
V33 Collars
V66 collars
V1212 collars
V1515 collars
VTtassel
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Corn Growth Stages
V33 Collars
Nodal roots active.
Growing point below ground.
V66 collars
Growing point above ground.
Tassel and ear development starting.
V1212 collars
Ear size, kernel size and kernel number being determined.
Limits on water and/or nutrients will reduce yields.
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V3 – Three visible collars
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V3
Root hairs begin to form on Nodal Roots.
Seminal Root growth has basically stopped.
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.
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V6
Tassel development has started.
Ear shoot formation has also started.
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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.
V6 Leaves start to tear off the plant
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V6
Nodal Root System is the primary root system for nutrients and water.
Growing point is above the ground.
Ear shoot.
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V6
Premature Tassel
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V9
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V9Growth rate rapidly increases. Greater demand for nutrients and water.
Ear shoot.
Ear shoot.
Ear shoot.
Growing point.
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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.
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Corn Growth Stages
V1515 collars
Rapid growth, about 10 to 12 days before silking.
Most critical stage for yield determination.
Most sensitive to stress.
VTtassel
Last tassel branch is visible but prior to silking.
Complete leaf loss will cause nearly 100% yield loss.
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V15About 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.
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V15Ear shoots near the top of the plant are starting to out-grow ear shoots lower on the plant.
Lower part of plant Upper part of plant
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V18
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V18
Lower part of plant Upper part of plant
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V18
Lower part of plant Upper part of plant
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VT
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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.
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Pollen shed
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Corn Growth Stages: Reproductive
R1Silking
R2Blister
R4Dough
R5Dent
R6Physiological Maturity
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Corn Growth Stages
R1Silking
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.
R2Blister
Ear size nearly complete.
Silks begin to dry out.
A miniature corn plant is being formed in each fertilized kernel.
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R1- Silking
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R1 - Silking
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.
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R1 - Silking
Cob materialPremature kernel
Two to three days are required for all silks on an ear to be pollinated.
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R2 - Blister
An miniature corn plant has started to develop within the premature kernel.
Ear size is nearly complete.Fertilized silks are starting to dry out.
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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.
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Corn Growth Stages
R4Dough
Kernels have accumulated ½ of total dry weight.
Five leaves have formed in the kernel.
R5Dent
Most kernels have dented and are near 55% moisture at start.
Starch layer has formed and progresses down the kernel.
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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.
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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.
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Corn Growth Stages
R6Physiologica
l 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
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R6 – Physiological Maturity
Kernel is about 30 – 35% moisture.
Kernels need to be at 13 to 15 % moisture for safe storage.
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R6 – Physiological Maturity
Blacklayer
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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 © 200642
Corn: Seeding Rates
Table 3. Recommended corn seeding rates for Kentucky.
Seeding rate* (seeds/acre)
Grain 22,000 - 30,000
Silage 24,000 - 30,000
Irrigated 26,000 - 32,000* 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.
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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 © 200644
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 © 200645
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 © 200646
Corn, Narrow vs. Wide Row Widths
Location
1-TX 2-SC 3-KY 4-IL 5-MO 6-PA 7-IA 8-IA 9-MI 10-MI 11-MI 12-MI 13-WI 14-WI 15-MN 16-MN 17-MN 18-MN 19-MN 20-MN
Yie
ld D
iffe
ren
ce (
%)
-15
-10
-5
0
5
10
15
Narrow Row Corn
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Estimating Corn Yield
(kernels per ear) x (ears per acre) / (kernels per bushel) = (bushels/acre)
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Estimating Corn Yields
• Simplest (least accurate method)– Count number of kernels– Multiply that number by 0.300
Using 0.300 assumes 1) 27,000 ears per acre 2) 90,000 kernels per bushel
1
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Estimating Corn Yields
Ears/Acre Large Kernel Size(70,000
kernels/bushel)Multiplier
Medium Kernel Size(90,000
kernels/bushel)Multiplier
Small Kernel Size (110,000
kernels/bushel)Multiplier
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
Including ears/acre as a factor and kernel size as a factor.
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Estimating Corn Yield
Row Width (inches)Feet of row needed to equal
1/1000th acreMultiplier to Equal One
Acre
15 34 feet 10 inches 1,000
20 26 feet 2 inches 1,000
22 23 feet 9 inches 1,000
30 17 feet 5 inches 1,000
36 14 feet 6 inches 1,000
38 13 feet 9 inches 1,000
Measuring 1/1,000th Acre
AGR-187: Estimating Corn Yields
Lee and Herbek, Grain Crops Extension © 200651
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 © 200652
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 93 95
April 25 75 81 86 90 93 96 98
May 1 77 83 88 92 95 98 100
May 6 78 83 88 92 95 98 100
May 11 77 83 88 92 95 98 99
May 16 75 81 86 90 93 96 98
May 21 73 78 83 87 91 94 95
May 26 69 75 80 84 87 90 92
May 31 64 70 75 79 82 85 87
June 5 59 64 69 73 77 80 81
June 10 52 58 63 67 70 73 75
Data from National Corn Handbook
Lee and Herbek, Grain Crops Extension © 200653
Keys to High Yields
1. Good genetics
2. Maximize days suitable for growing
3. 90 to 95% light interception at silking (R1)
4. Adequate nutrients and water to complete plant growth and seed fill
Lee and Herbek, Grain Crops Extension © 200654
Keys to High Yields
• Good genetics– Good yield potential– Good stress tolerance– Good defense genetics
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Keys to High Yields
• Maximize days– Maturity group– Stress tolerance– Planting date
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Keys to High Yields
• 90 to 95% light interception at silking (R1)– Row spacing and population– Planting date– Hybrid Maturity
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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
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Slats on a Barrel
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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 © 200661
Corn Growing Degree Days
• Corn Growing Degree Day• Base 50° F• Max 86° F• Min 50° F
• Example 1: – 74° F average daily temperature– 74 – 50 = 24 GDD
• Example 2:– 90° F average daily temperature– 86 – 50 = 36 GDD
Lee and Herbek, Grain Crops Extension © 200662
Corn Growing Degree Days
Corn Maturity (Days) GDD85 to 100 2100 – 2400
101 to 130 2400 – 2800131 to 145 2900 – 3200
Growth Stage GDDV2 200V6 475
V12 870VT 1135R1 1400R6 2700
GDD Requirements of a 2700 GDD Hybrid
From NCH-40 Growing Season Characteristics and Requirements in the Corn Belt. National Corn Handbook.
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Planting Date and GDD
Planting DateGDDAs of 06/26/05
Difference From First Planting
April 20 1155 ---May 3 1029 126May 18 825 330May 31 596 559June 15 281 874
Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer
From University of Kentucky Ag Weather Center: http://wwwagwx.ca.uky.edu/Growing Degree Day calculator: http://wwwagwx.ca.uky.edu/cgi-bin/cropdd_www.pl
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Planting Date and GDD
Planting DateGDDAs of 07/11/05
Difference from First Planting
April 20 1503 ---May 3 1377 126May 18 1173 330May 31 944 559June 15 629 874
Hybrid: DKC67-91: 119 CRM, 3000 GDD to Black Layer
From University of Kentucky Ag Weather Center: http://wwwagwx.ca.uky.edu/Growing Degree Day calculator: http://wwwagwx.ca.uky.edu/cgi-bin/cropdd_www.pl
Lee and Herbek, Grain Crops Extension © 200665
Date of Planting – Corn and Grain Silage
1976 - LexingtonDate planted Relative Yield Ratio
Maturity Bu/A T/A @ 35% Ear:Forage
April 20 Full 180 27.2 56:44
May 6 Full 177 25.8 59:41
May 21 Full 166 23.4 60:40
May 31 Full 144 19.9 60:40
June 10 Full 112 16.4 57:43
June 10 Early 128 18.1 60:40
June 29 Early 64 11.2 48:52
May 20 S 77 18.2 42:58
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Effect of Tillage and Planting Date on Corn Yield
4-avg. (1979-1982)
Planting Date
Conventional No-Till Avg.
Corn Yield (bu/A)
Early May1 121 121 121
Mid-May 102 124 113
Early June 86 102 94
Avg. 103 116
1 Three-year avg. only. 1979 data missing for Early May.
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Corn Planting Depth and Planting DatePlanting Depth
Planting Date
April 13 May 2
(inches) % StandDays to Emerge
% StandDays to Emerge
1 85 10 93 9
2 77 15 98 11
3 76 18 92 12
4 73 21 89 13
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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.
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Population Effect on Corn Yields
(Hardin County, Kentucky, 1972-76)
Population 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
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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 © 200671
Row Width Effect on Corn Yields
(Hardin County, Kentucky)
Row Width Corn Yield (Bu/A)
(inches) No-Till Conventional
1972-1974
19 161 137
38 162 133
1975-76
30 109
38 116
Lee and Herbek, Grain Crops Extension © 200672
Corn Hybrid and Population Effect on Grain Yield
Plants/A Yield (bu/A) Yield (bu/A)
Irrigated Rainfed 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 A635 ---
20,000 136 121 119 119
28,000 167 136 131 129
36,000 172 130 133 130
Population resulting in highest yield varied across hybrids and water regimes.
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What determines crop row width?
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.
Duvick D.N., and K.G. Cassman. 1999. Crop Science 39:1622-1630
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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
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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 - 2
Average 170 162 + 8
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Corn Hybrid, Row Width and Plant Population
Summary Across Years
HybridYield (bu/A)
Row WidthYield (bu/A)
Pioneer 33Y18 155.4 a 20 inch 148.4 a
So. States SS828 143.9 b 30 inch 150.9 a
Plant PopulationYield (bu/A)
24,000 148.7 a
28,000 151.5 a
32,000 148.7 a
Lee and Herbek, Grain Crops Extension © 200677
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
(No-Till and Conventional)26,000 – 32,000
Silage 24,000 - 30,000
From ID-139: A Comprehensive Guide to Corn Management in Kentucky.
Lee and Herbek, Grain Crops Extension © 200678
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 © 200679
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 © 200680
The major factor influencing vegetative development in grain
crops is:
TEMPERATURETEMPERATURE
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 © 200681
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 +19 (11%)
Avg. 178 197 +19 (11%)
Yearly Range 161-193 177-219 +13-28 (7-15%)
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Corn Ears: Good and Bad
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Corn Ears: Good and Bad
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Corn Ears: Good and Bad
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