University of Illinois at Urbana-Champaign Variety Testing
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1998 General Information, Seed Sources, Weather Tables, and Map

The University of Illinois commercial soybean testing program was started in 1969 as a result of requests by seedsmen that their private varieties be tested. There were 489 varieties and 328 Roundup ReadyŽ varieties from 67 seed companies tested in 1998.

The purpose of this commercial soybean testing program is to provide unbiased, objective, and accurate testing of all varieties entered. The tests are conducted on as uniform a soil as is available in the testing area. Small plots are used to reduce the chance of soil and climatic variations occurring between one variety plot and another.

The results of these tests should help you judge the merits of varieties in comparison with other private and public varieties. Because your soils and management may differ from those of the test location, you may wish to plant variety strips of the higher-performing varieties on your farm. The results printed in this circular should help you decide which varieties to try.

 

TEST PROGRAM

Selection of entries: Soybean producers in Illinois and surrounding states were invited to enter varieties, brands, or blends in the 1998 Illinois soybean performance trials. Entrants were required to enter all nonirrigated, 30-inch-row-width trials on a regional basis (entry in a minimum of two locations required). Roundup ReadyŽ trials were offered on a locational basis only. To help finance the testing program, a fee of $65 ($80 for Roundup ReadyŽ) per location was charged for each entry entered by the seed producer. Most of these varieties, brands, or blends are commercially available, but some experimental varieties were also entered. A total of 2,051 entries were tested in 1998.

Number and location of tests: In 1998, tests were conducted at 9 locations in the state (see map). These sites represent the major soils and maturity zones of the state.

Nonirrigated, 30-inch-row-width trials were conducted on a regional basis. The regions are as follows:

Also nonirrigated 30-inch-row-width Roundup ReadyŽ trials were conducted at five locations: DeKalb, Urbana, Perry, Belleville, Carbondale.

Seven-inch-row-width trials were conducted at Urbana.

Field plot design: Entries of each test were replicated three times in a randomized complete block or alpha lattice design. The 30-inch-row trial plots consisted of four rows, each 21 feet long. The center two rows of each plot were harvested to measure yield. The 7-inch-row trial plots consisted of eight rows, each 21 feet long. The center six rows were harvested to measure yield.

Fertility and weed control: All test locations were at a high level of fertility. Herbicides were used at all test locations for weed control. Weed control for the Roundup ReadyŽ trials consisted of post-emergence applications of Roundup as needed, no pre-emergence herbicide was used. All plots were also weeded by hand.

Method of planting and harvesting: The 30-inch-row variety trials were planted with a modified bean planter. A custom-built, cone type, narrow-row drill was used to plant the 7-inch trials. Harvesting was done with a small-plot combine. No allowances were made for beans that may have been lost as a result of combining or shattering.

Soybean Cyst Nematode: Soil samples were taken from variety plots at each location at planting and harvest and evaluated for cyst populations by Illinois SCN Coalition. Threshold numbers of cysts per 100cc of soil are as follows:

Low 1-5
Medium 6-25
High >25

PERFORMANCE DATA

Yield: Soybean yield was measured in bushels (60 pounds) per acre at a moisture content of 13 percent. An electronic moisture monitor was used on the combine for all moisture readings.

Maturity: Maturity was stated as the date when approximately 95 percent of the pods were ripe.

Lodging: The amount of lodging was rated at harvest time. The following scale was used:

  1. Almost all plants erect
  2. All plants leaning slightly or a few plants down
  3. All plants leaning moderately (45°), or 25 to 50 percent of the plants down
  4. All plants leaning considerably, or 50 to 80 percent of the plants down
  5. Almost all plants down

Height: Height was measured shortly before harvest as the average length of plants from the ground to the tip of the main stem.

Shattering: The percentage of open pods was estimated at harvest time. The following scale was used:

  1. No shattering
  2. 1 to 10% of pods open
  3. 10 to 25% of pods open
  4. 25 to 50% of pods open
  5. Over 50% of pods open

SUGGESTIONS FOR COMPARING ENTRIES

It is impossible to obtain an exact measure of performance when conducting any test of plant material. Harvesting efficiency may vary, soils may not be uniform, and many other conditions may produce variability. Results of repeated tests are more reliable than those of a single year or a single-strip test. When one variety consistently out yields another at several test locations and over several years of testing, the chances are good that this difference is real and should be considered in selecting a variety. However, yield is not the only indicator. You should also consider maturity, lodging, plant height and shattering.

As an aid in comparing soybean varieties, brands, and blends within a single trial, certain statistical tests have been devised. One of these tests, the least significant difference (L.S.D.), when used in the manner suggested by Carmer and Swanson1 is quite simple to apply and is more appropriate than most other tests. When two entries are compared and the difference between them is greater than the tabulated L.S.D. value, the entries are judged to be "significantly different."

The L.S.D. is a number expressed in bushels per acre and presented following the average yield for each maturity group within each location. L.S.D.'s of 10% and 30% are shown, if the 10% L.S.D. is used, decisions made are true 9 out of 10 years, the 30% L.S.D. will be true 7 out of 10 years. The 30% L.S.D. is a smaller number and will include fewer varieties in the 'top group'. Decide the L.S.D. level that is best for your farm and find the highest yielding soybean variety within the maturity group and location, subtract the chosen L.S.D. level from the highest yielding variety, every variety with a greater yield than the resulting number is 'statistically the same' as the highest yielding variety. Consider the merits of the varieties in this group when making varietal selections.

In a study of the frequencies of occurrence of three types of statistical errors and their relative seriousness, Carmer2 found strong arguments for an optimal significance level in the range = 0.20 to 0.40, where is the Type I statistical error rate for comparisons between means that are really equal. Herein, values of = 0.10 and 0.30 are used in computing the L.S.D. 10- and 30-percent levels shown in the tables.

To make the best use of the information presented in this circular and to avoid any misunderstanding or misrepresentation of it, the reader should consider an additional caution about comparing entries. Readers who compare entries in different trials or row spacings should be extremely careful, because no statistical tests are presented for that purpose. Readers should note that the difference between a single entry's performance at one location or row spacing and its performance at another is caused primarily by environmental effects and random variability. Furthermore, the difference between the performance of entry A in one trial or row spacing and the performance of entry B in another trial or row spacing is the result not only of environmental effects and random variability, but of genetic effects as well.

1Carmer, S.G. and M.R. Swanson. "An Evaluation of Ten Pairwise Multiple Comparison Procedures by Monte Carlo Methods." Journal of American Statistical Association 68:66-74. 1973.

2Carmer, S.G. "Optimal Significance Levels for Application of the Least Significant Difference in Crop Performance Trials." Crop Science 16:95-99, 1976.

1999 TEST FIELDS

DeKalb

Dwight

Monmouth

Urbana

Perry

Brownstown

Belleville

Carbondale

Dixon Springs

1998 GROWING SEASON RAINFALL

Locations May June July August September
DeKalb 2.92 4.27 4.31 4.36 2.72
Dwight 4.89 10.55 2.29 1.60 0.69
Monmouth 4.91 6.16 0.70 3.90 4.36
Urbana 7.81 8.71 4.02 2.22 1.53
Perry 4.94 9.26 4.04 2.06 4.00
Brownstown 5.85 7.76 5.48 1.88 3.54
Belleville 3.87 7.45 4.18 3.10 0.85
Carbondale 3.84 8.26 4.19 2.84 1.05
Dixon Springs 2.58 7.66 4.07 4.71 0.97

SOURCES OF SEED
  Department of Crop Sciences
College of Agricultural, Consumer, and Environmental Sciences
University of Illinois at Urbana-Champaign
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