Corn for Grain Variety Trials

Joe E. Askew, Jr.
Manager, Variety Evaluations
Mississippi State University

Frank E. Boykin
Operations Manager
Black Belt Branch Experiment Station

David Ingram
Associate Agronomist
Brown Loam Branch Experiment Station

Billy Johnson
Research Assistant II
Coastal Plain Branch Experiment Station

Don Respess
County Extenstion Agent
Bolivar County

David Roberts
County Extenstion Agent
Monroe County

Art Smith
County Extension Agent
Desoto County

Clarence Watson
Experiment Station Statistician
Mississippi State University

Recognition is given to Jessie Selvie and Jerry Nail, research technicians for the Variety Testing Program, for their assistance in packaging, planting, harvesting, and recording plot data. Statistical analyses and computing assistance was given by Eric Hudson, computer programmer, Information Services and User Support and Chip Brooks, student worker, Department of Experimental Statistics. This publication was prepared by Jimmie Cooper, administrative secretary for MAFES Research Support Units. It was published by the Office of Agricultural Communications; Division of Agriculture, Forestry, and Veterinary Medicine; Mississippi State University. This information bulletin was edited and designed by Robert Hearn, publications editor, and coded and electronically published by Patsy Sykes, electronic publishing assistant.

Notice to User

This Mississippi Agricultural and Forestry Experiment Station information bulletin is a summary of research conducted under project number MIS 1414 and is intended for the use of colleagues, cooperators, and sponsors. The interpretation of data presented herein may change after additional experimentation. Information included is not to be construed as a recommendation for use or as an endorsement of a specific product by Mississippi State University or the Mississippi Agricultural and Forestry Experiment Station.

This report contains data generated as part of the Mississippi Agricultural and Forestry Experiment Station research program. The organizations listed in Table 2 provided seed and are sincerely appreciated.

Trade names of commercial products used in this report are included only for clarity and understanding. All available names (i.e. trade names, chemical names, etc.) of products used in this research project are listed in Table 2.

Contents

• Introduction
  • Procedure
  • Variables Measured in Corn Hybrid Tests
  • Use of Data Tables and Summary Statistics
  • Table 1. Location, number of entries, dates of planting, and dates of harvest for 1997 corn hybrid trials.
  • Table 2. Characteristics provided by sponsoring companies for corn hybrids entered in the variety Mississippi trials.
• Location 1 -- Hawks Farming, Inc., Hernando
• Location 2 -- Chris Ausborn Farm, Aberdeen
• Location 3 -- MAFES Black Belt Branch, Brooksville
• Location 4 -- MAFES Brown Loam Branch, Raymond
• Location 5 -- MAFES Coastal Plain Branch, Newton
• Location 6 -- Duke Morgan Farm, Shaw
• Location 7 -- Mississippi State University, Starkville
• Summary
  • Table 17. Average grain production, by areas, for early maturing corn hybrids grown in Mississippi.
  • Table 18. Average grain production, by areas, for late-maturing corn hybrids grown in Mississippi.
• Technical Advisory Committee

Procedure

Seed of all entries were supplied by participating companies (Table 2). All seed were packaged for planting at rates suggested by the participating company and planted with a cone planter. Phosphorus, potassium, and lime were applied according to soil test recommendations. Nitrogen was applied in Areas I and II at 140-200 pounds per acre. Plots in Area III received 200-300 pounds of N per acre. Plots in Areas I and II were grown in dry land conditions, while plots in Area III were irrigated, if necessary.

Variables Measured in Corn Hybrid Tests

• Yield: An Almaco SPC 20 plot combine was used to harvest the total area of each plot. Harvested grain was weighed, moisture was determined, and yields were converted to bushels per acre at 15.5 percent moisture.
• Root Lodging: Root lodging is the percentage of plants, based on actual counts of all plants in each plot, that were leaning more than 30 degrees from vertical at harvest.
• Stalk Lodging: Stalk lodging is the percentage of plants, based on actual counts of all plants in each plot, that were broken below the upper ear-bearing node at harvest.
• Ear Height: Ear height is measured as the distance from the soil to the highest ear-bearing node.
• Harvest Population: Harvest population is a measure of the number of plants per acre, based on actual stand counts at time of harvest.

Use of Data Tables and Summary Statistics

The yield potential of a given variety cannot be measured with complete accuracy. Consequently, replicate plots of all varieties are evaluated for yield, and the yield of a given variety is estimated as the mean of all replicate plots of that variety. Yields vary somewhat from one replicate plot to another, which introduces a certain degree of error to the estimation of yield potential. As a result, although the mean yields of some varieties are numerically different, the two varieties may not be significantly different from each other within the range of natural variation. That is, an ability to measure yield is not precise enough to determine what the small differences are, other than what might be observed purely by chance.

The least significant difference (LSD) is an estimate of the smallest difference between two varieties that can be declared to be the result of something other than random variation in a particular trial. Consider the following example for a given trial:

Variety	Yield (bu/a)
A	90
B	85
C	81
LSD	7

The difference between variety A and variety B is 5 bu/a (i.e. 90 - 85 = 5). This difference is smaller than the LSD (7 bu/a). Consequently we would conclude that variety A and variety B have the same yield potential, since we are not able to say that the observed difference did not occur purely due to chance. However, the difference between variety A and variety C is 9 bu/a (i.e. 90 - 81 = 9), which is larger than the LSD (7 bu/a). We would therefore conclude that the yield potential of variety A is superior to that of variety C.

The coefficient of variation (CV) is a measure of the relative precision of a given trial and is used to compare the relative precision of different trials. The CV is generally considered to be an estimate of the amount of unexplained variation in a given trial. This unexplained variation can be the result of variation between plots with respect to soil type, fertility, insects, diseases, moisture stress, etc. In general, the higher the CV the less precise a given trial is.

The coefficient of determination (R²) is another measure of the level of precision in a trial and is also used to compare the relative precision of different trials. The R² is a measure of the amount of variation that is explained, or accounted for, in a given trial. For example, an R² value of 90 percent indicates that 90 percent of the observed variation in the trial has been accounted for in the trial, with the remaining 10 percent being unaccounted. The higher the R² value, the more precise the trial. The R² is generally considered to be a better measure of precision than the CV for comparison of different trials.

Table 1. Location, number of entries, dates of planting, and dates of harvest for 1997 corn hybrid trials.
Location	Maturity¹	No. of entries	Planting date	Harvest date
Area I
Hawks Farming, Inc. (Hernando)	Early Late	17 20	April 1	September 11
Chris Ausborn Farm (Aberdeen)	Early Late	17 20	March 27	August 26
Black Belt Branch (Brooksville)	Early Late	17 20	April 2	September 3
Area II
Brown Loam Branch (Raymond)	Early Late	15 16	April 3	September 2
Coastal Plain Branch (Newton)	Early Late	15 16	March 25	August 25
Area III
Mississippi State University (Starkville)	Early Late	19 25	March 24	September 4
Duke Morgan Farm (Shaw)	Early Late	19 25	March 31	September 8

¹Early maturity = 115 days or less; late maturity = 116 days or more.

Table 2. Characteristics provided by sponsoring companies for corn hybrids entered in the Mississippi variety trials.
Company