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Kinds of Corn 

Hybrids and varieties differ primarily in kernel starch.

Specialty Corns

1. Marketing niche hybrids
2. Management tool hybrids - IMI (IT/IR), Bt, RR, SR

DENT

1. 2/3 of starch is hard and 1/3 is soft
2. Dent caused by shrinkage of soft starch in crown as kernel dries. Surrounding hard starch shrinks less
3. 95%+ of US corn is dent corn

SWEET CORN

1. Endosperm contains water soluble reducing sugar instead of starch
2. Plants are leafy and tend to tiller
3. Leading states are WI, MN, and IL

FLINT

1. Very hard kernels, entire crown is hard starch
2. Grown where season is too short for dents
3. Kernels resist insect damage, but may be difficult for animals to digest

FLOUR

1. Starch is soft and easily ground into meal
2. Surrounded by thin layer of hard starch
3. Widely grown by American Indians

POP

1. Closely related to flint, but higher % of hard starch in pop corn
2. Moisture in each starch grain expands with heating
3. Good popper expands to 24X or more of its original volume
4. Popcorn Institute; 401 N. Michigan; Chicago, IL  60611-4267 (312) 644-6610

POD

1. Each kernel surrounded by husks
2. No economic importance

HIGH-OIL 

1. Larger germ than normal corn
2. 2x more oil content

WAXY

1. Special kind of starch with a waxy (shiny) appearance
2. Normal corn starch: 72% amylopectin (branched chain), 28% amylose (straight chain)
3. Waxy starch: 100% amylopectin
4. Introduced from China more than 90 yrs ago by an observant Presbyterian minister in Shanghai who noted its unusual endosperm
5. Endosperm stains light red (Normal endosperm = dark blue)
6. Slight improvement over dents in feeding value for fattening cattle 
7. Increased in popularity in US after SCLB epidemic in 1970
8. No difference between dent and waxy corn in yield
9. Used in food products (pie thickener and tapioca pudding) and industrially (glue for stamps and envelopes)

Selection Criteria

Important traits and characteristics that a variety or hybrid must have before it can be grown on-farm. 

Example: For corn use a Performance Index = PI

1. Yield potential: PI = 50 %
2. Maturity (moisture): PI = 35 %
3. Standability: PI = 15 %
4. Quality
5. Other factors

Yield potential and performance consistency

PI = 50 %

1. Information sources
2. Top performances - What is your yield potential?
3. Importance of using multi-location averages and PI

Maturity (moisture) 

PI = 35 %

Full season hybrid or variety: A hybrid or variety that uses (or requires) the entire available growing season to reach physiological maturity before killing frost or cool temperatures end the growing season.

Often has better yield potential than a shorter-season hybrid.

Full-season maturity depends upon:

1. Growing season temperature GDD
2. Soil type / texture / topography
3. Tillage system
4. Previous crop
5. Planting date

Percentage of farm in various maturities depends upon:

1. When you start planting
2. How fast you plant
3. Acres to plant
4. Days available / needed for spring fieldwork before planting
5. Drying costs
6. How fast you harvest, haul and dry
7. Days available / needed for fall fieldwork after harvest
8. Corn silage / high moisture grain acres
9. Your desire to take risks. Example: Suggested maturity ratios - conservative vs. risky
   • 50 % full-season (plant first)
   • 30 % mid-season
   • 20 % short-season

Relative maturity switch dates

1. Plant Full-season hybrids until May 10
2. Plant Mid-season hybrids from May 10 to May 25
3. Plant Short-season hybrids after May 25 to June 10
4. Switch to another crop after June 10

Standability 

PI = 15 %

High amounts of lodging will slow harvest and decrease yields. 

Caused by:

1. Disease
2. Insects
3. High winds

Hybrid's ability to develop a root system

Pest resistance

No hybrid or variety is resistant to all pests

Check with seed dealer about: stalk rot, rust, northern leaf spot, smut, Gibberella ear rot

Ear and Kernel Qualities

Quality factors

Test weight, protein, etc.

Other factors

1. Type of cross: greater yield potential with single crosses
2. Seed size and quality
3. Hybrid response to management - i.e. soil type, plant population, conservation tillage, soil fertility, herbicides, crop rotation, and irrigation
4. Specialty uses
5. "Yield lag" v. "yield drag"

Selecting the Top Performers

What data should you use?

1. Information sources

   • Seed company

   • Unbiased (university) performance trials

   • Local on-farm trials using field-scale equipment

2. Top performances - What is your yield potential?

3. Strategies for selecting hybrids in the UW trials

4. Importance of using multi-location averages and PI

Conclusion: Use multi-location, average data (wide range of locations and climates) for selecting the top performers

Steps in the hybrid selection process:

1. Begin with trials in zones nearest your farm

2. Compare hybrids with similar maturities within a trial

3. Evaluate consistency of performance across zones & years

4. Compare performance in other unbiased trials

5. Consider hybrid performance for other traits, i.e. standability, dry-down rate, grain quality, etc.

6. You are taking a tremendous gamble if basing your decision on one or two local test plots.

Summary

• Multi-Location information should be used to evaluate:

1. Grain yield

2. Moisture and maturity

3. Standability

• Single-Location information should be used to evaluate:

1. Consistency of performance

2. Test weight

3. Dry-down rate

4. Grain quality

5. Ease of combine-shelling or picking

The Wisconsin Corn Evaluation Program

2005 | 2004 | 2003 | 2002 | 2001 | 2000 | 1999 | 1998 | 1997 | 1996

The University of Wisconsin Corn Hybrid Trials -- Selecting the Top Performers

The Wisconsin Grain Relative Maturity (GRM) System for Corn

Corn Silage

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Background

• Importance of Corn Silage to Wisconsin
  • Largest acreage and production among U.S. States
  • Used extensively in forage base for state dairy herds
• Changing Wisconsin dairy production ‘climate’
• Wisconsin Corn Silage Consortium (Coors et al.)
  • Range for NDF and digestibility among commercial hybrids sold in Wisconsin is narrow.
  • Yield and quality differences among corn hybrids are repeatable.
  • Corn silage quality can be predicted using NIR

Corn Silage Compared to Other Forages

Advantages

• Palatable forage
• High dry matter yield and energy content
• Consistent quality
• Less labor and machinery (one harvest). Lower cost per ton of dry matter
• Manure management
• Flexibility, dual purpose

Disadvantages

• Few established markets
• Relatively low in protein
• High transportation costs
• Must be fed on or near farm
• Expensive storage facilities
• Limited production on erodible soils due to conservation requirements

What makes a good forage? (Carter et al., 1991)

• High yield

• High energy (high digestibility)

• High intake potential (low fiber)

• High protein

• Proper moisture at harvest for storage

• Ultimate test is animal performance

  • Milk2000 is our best predictor for performance (Schwab - Shaver equation)

Hybrid Selection

Criteria for Selecting Silage Hybrids

• Grain yield: allows flexibility (dual purpose)
• Whole plant silage yield
• Relative maturity: 5-10 days later than grain hybrids
• Standability: allows flexibility
• Pest resistance
• Silage quality

“Variation for silage yield and quality exists among commercial hybrids in Wisconsin.”

"Dual Purpose" Hybrids versus Silage Specific

Other silage Hybrids

• High sugar
• Waxy
• High-oil
• Leafy Corn
• Bmr Corn
• Tropical
• Sweet corn

Silage Quality

Bt versus Conventional hybrids