Mississippi State University

Soybeans
1996 Variety Trials

NOTICE TO USER

This Mississippi Agricultural and Forestry Experiment Station information bulletin is a summary of research conducted under project number MIS 2348 at the following locations:

It is intended for the use of colleagues, cooperators, and sponsors. The interpretation of data presented herein is not to be construed as a recommendation by Mississippi State University or the Mississippi Agricultural and Forestry Experiment Station for use or as an endorsement of a specific variety or product.

This report contains data generated as part of the Mississippi Agricultural and Forestry Experiment Station research program. Joint sponsorship by the organizations listed here is gratefully acknowledged.

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

Recognition is given to Jessie L. Selvie and Jerry W. Nail, research technicians for the Variety Testing Program, for their assistance in packaging, planting, harvesting, and recording plot data. Statistical analyses and computing assistance were given by Eric Hudson, computer programmer, Information Services and User Support and Stuart Shull, student worker, Department of Experimental Statistics.

This publication was prepared and tables designed by Jimmie Cooper, administrative secretary for MAFES Research Support Units. Published by the Print Media Section, Office of Agricultural Communications, Division of Agriculture, Forestry, and Veterinary Medicine, Mississippi State University, Keith Remy, Senior Publications Editor. HTML coded by student assistant Jeffery S. Massey and proofed by Nancy Williams.

Contents

Mississippi Soybean Variety Trials, 1996

Trials were conducted at seven locations in 1996. Commercial seed companies were given the opportunity to enter one or more varieties for testing. Public varieties were selected by the Technical Advisory Committee for evaluation at each location.

There has been a proliferation of soybean varieties in recent years, and many good varieties are available to Mississippi soybean producers. No single variety is superior to all others, but in some situations, there are varieties that are more specifically adapted than others. Selecting a variety for planting requires knowledge of disease, nematode, and herbicide reactions, as well as the yield performance of each variety on a particular soil type. In many cases, planting the proper varieties will make substantial differences in yield and profitability on a farm. Proper management, including adequate lime, fertilizer, and weed control, is required to produce high yields of any variety. But yields may be limited, even under good management, unless the proper varieties are planted.

Research and Extension Faculty

Joe E. Askew, Jr., manager, Variety Evaluations
Alan Blaine, soybean specialist, MCES
Frankie Boykin, operations manager, Black Belt Branch
Robert Dobbs, research assistant, Northeast MS Branch
Floyd Hancock, former soybean production agronomist, Delta Branch, currently soybean breeder, Hartz Seed Company
David Ingram, assistant agronomist, Brown Loam Branch
Robert Martin, county agent, Issaquena County
Dennis Reginelli, county agent, Noxubee County
Art Smith, county agent, DeSoto County
Thomas R. Vaughan, manager, Foundation Seed Stocks
Mack Young, county agent, Quitman County

How To Select Varieties

Problem or Difficult Fields...

  1. Identify fields that have had problems in the past. Problems to consider may include diseases, nematodes, or fields that make planting or harvest difficult because of extremely dry or wet conditions. The Mississippi Cooperative Extension Service offers a disease diagnostic service and nematode analysis free of charge.

  2. Use Tables 9A-9D to select varieties for the fields that need nematode or other pest resistance.

  3. Select varieties from the multi-year average column at each location. Identify those varieties that have the desired pest resistance along with high yield potential. Use the data from a test site or sites with a soil type similar to that where the soybeans will be grown. Consider planting dates and maturity dates that may allow you to avoid historical field problems.

Non Problem Fields...

  1. Identify the farm's highest yielding fields that have no specific disease problems.

  2. Select varieties with the best yield potential from the multi-year average column at each location. Use the data from a test site or sites with a soil type similar to that where the soybeans will be grown.

  3. Try new varieties on a limited number of acres if the yields are good at several locations. Don't abandon older varieties that are yielding well unless research and experience show an advantage for newer varieties.

Planting Date and Maturity Date...

  1. Varieties in Maturity Groups IV, V, and VI are recommended. Earlier maturing varieties should be considered for planting where fall seedbed preparation was accomplished the previous year and in fields that are subject to drought stress during the growing season and/or wet soils during the usual harvest period. Later maturing varieties should be considered for planting in fields that are not as prone to drought stress or where irrigation will be used to alleviate drought stress. However, early planting of all acreage should be considered to reduce risk from drought that normally occurs in the state.

  2. Early season production is a practice that has been quite successful and consistent for several years. Cool, wet soils at planting may justify the use of a seed treatment that has activity against Pythium, since no varieties have resistance to infection and resulting damage from this organism. The Maturity Group IV soybeans that have been performing well in early season production have a narrow growth habit and narrow rows will be advantageous. Mid-April to mid-May plantings are recommended for early-season production of Group IV varieties. Irrigation will allow later plantings of these early soybeans; however, the full yield potential may not be realized. Timely harvest is crucial with the early-maturing varieties because dry weather at maturity may promote shattering. There is a large range in maturities in the Group IV soybeans. Determine if an early Group IV or a late Group IV or some acreage of both would fit into your planned harvest schedule.

  3. Timely planting is crucial for optimum production of all maturity groups of soybeans. An attempt should be made to complete soybean planting as early as possible. Plantings of MG V and VI can be made in April. Delays in planting can result in reduced yield potential for almost all varieties in all maturity groups.

Procedures

The experimental design at each location was a randomized complete block of each maturity group, with three replications of each entry. Plots were 4 rows 30 inches wide and 20 feet long. Ends of plots were trimmed to a uniform length three to four weeks after emergence. Cultural and pest control practices for optimum yields were followed. Plots were limed and fertilized on the basis of an annual soil test. All seeds were treated with Vitavax 200 fungicide prior to planting. Only herbicides currently registered for use on soybeans were used in these studies, with strict adherence to all label instructions.

Planting Rate...Seed of all private entries were supplied by the participating companies. All seeds were packaged for planting at the rate of nine seeds per foot of row. Plots were planted with a cone planter.

Yield...An Almaco SPC-20 plot combine was used to harvest two rows of each plot. Bags of harvested seed were allowed to dry at ambient temperature to a uniform moisture content before weighing. Weights were converted to yield in bu/acre (60 lb/bu).

Maturity Date...Maturity is considered to be the date when the pods are dry and most of the leaves have dropped. Under most conditions, the stems are also dry.

Plant Height...Plants were measured from the soil to the top extremity, at maturity, and plant height was recorded as the average of the height of plants measured.

Lodging...Lodging was rated and recorded on a scale of 1 = almost all plants erect, 2 = all plants leaning slightly or only a few plants down, 3 = all plants leaning moderately or 25 to 50% of plants down, 4 = all plants leaning considerably or 50 to 80% of plants down and 5 = all plants down.

Disease and Nematode Reactions

Recognizing disease and nematode problems is important for every producer in Mississippi. When a disease or nematode problem is correctly identified, the information in Tables 9A-9D may be used to select varieties that have genetically inherited resistance to the problem. Stem canker ratings shown in this report were determined by Drs. Bob Keeling, (retired plant pathologist); Joe Fox, MCES; and Gabe Sciumbato, MAFES.

General Characteristics of Varieties

Soybean varieties differ in significant characteristics that may not affect their performances. Tables 8A-8E give the general characteristics of most varieties grown in Mississippi.

Flowering...Varieties of Group IV maturity generally display an indeterminate growth habit. This means that a large portion of their vegetative growth occurs after flowering begins. In contrast, varieties of Groups V, VI, and VII display a determinate growth habit, where most of the vegetative growth occurs before flowering. The date of first flower will be related to the maturity category of a variety; i.e., a mid-MG IV variety may bloom three weeks earlier than a MG V variety, whereas a late MG IV variety may bloom only one week earlier than a MG V variety.

Soybean flower petals are purple or white. The flower color is controlled strictly by genetics, and only one flower color occurs in a pure variety.

Pubescence and Hilum Color...Brown (tawny) and gray are the basic pubescence (hair) colors found among varieties. Varying pod-wall colors result in different intensities of mature pod colors. The "eye" of the seed is called a hilum, or point of attachment to the pod, and it differs in color by variety.

Seed Size...There is no relationship between inherited seed size and seed yield. A small-seeded variety may yield as much as or more than a large-seeded variety. The average seed per pound for different varieties is shown in Tables 8A-8E, but this is subject to seasonal variation. Knowing the number of seed per pound is important in determining the amount of seed needed for planting. Fewer pounds are required for small-seeded varieties than for large-seeded varieties. Your county Extension office has a publication (Information Sheet 1194) that deals with seeding rates and plant populations.

Note to the Reader on the Use of Data Tables and Summary Statistics

Prepared by Dr. Clarence E. Watson, Jr., MAFES Statistician

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 that such 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)
Abe 40
Bill 35
Charlie 31
LSD 7

The difference between variety Abe and variety Bill is 5 bu/a (i.e., 40 - 35 = 5). This difference is smaller than the LSD (7 bu/a). Consequently it is concluded that variety Abe and variety Bill have the same yield potential, since the observed difference did not occur purely due to chance.

The difference between variety Abe and variety Charlie is 9 bu/a (i.e., 40 - 31 = 9), which is larger than the LSD (7 bu/a). Therefore, it is concluded that the yield potential of variety Abe is superior to that of variety Charlie, since the difference is larger than would be expected purely by chance.

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, drought 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% indicates that 90% of the observed variation in the trial has been accounted for in the trial, with the remaining 10% 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 is the CV, for comparison of different trials.

Within the Group IV trials, the wide variation in maturity dates is attributed to lack of rigid standards for classifying varieties within a group. It was decided to subdivide Group IV and Group V into two maturity groups. All maturity groups were assigned an early- and late-maturity check. They were as follows:

Maturity Group Early Maturing Late Maturing
Group IV Early --- TN4-86
Group IV Late TN4-86 R 499
Group V Early R 499 Hutcheson
Group V Late Hutcheson P 9592
Group VI P 9592 P 9692

To the results

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Information Bulletin 315

MAFES/MSU
Mississippi Agricultural and Forestry Experiment Station
Vance H. Watson, Director -- Mississippi State, MS 39762
Donald W. Zacharias, President, Mississippi State University
R. Rodney Foil, Vice President

This document is public information and may be reproduced in part or in total. It should not be used to imply endorsement of any specific brand or product.

Information Bulletin 315 / Last Update: 01-13-97