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1998 General Information, Seed Sources, Weather Tables

Test Program

Selection of entries. Each year, producers of hybrid seed corn and sorghum varieties in Illinois and surrounding states are invited to enter hybrids in the Illinois performance trials. This testing program is financed by a fee of $65 or $75 for each corn or sorghum hybrid entered, respectively, at a location. Most of these hybrids are commercially available, although a few experimental hybrids are also entered.

Number and location of tests. In 1998, 10 major tests were conducted at 9 locations in the state (see map). These sites represent the major soil and climatic areas of the state.

Hybrids. There were 482 corn hybrids from 64 companies and 28 sorghum hybrids from 7 companies tested in 1998.

Field plot design. Three replications of an alpha lattice design were used to give each entry an equal chance to show its merits.

Planting Methods. All trials were planted by a modern four row planter modified for small plot work. A soil insecticide (Force) was applied in furrow at planting for all trials. Corn plots were over planted by 30 percent and later thinned to desired stands. Sorghum plots were planted at a rate to achieve 4-6 plants per foot of row at harvest. Each plot was four rows wide and either 23 or 25 feet long. The center two rows of each plot were harvested to determine yields.

Fertilization. All test fields were at a high level of fertility. Additional fertilizer was plowed down or side dressed as needed to ensure top yields.

Method of harvest. All corn plots were harvested with a custom-built, self-propelled, corn plot combine. Sorghum plots were harvested with a soybean plot combine. Grain collected from each plot was weighed, and tested for moisture content. An electronic moisture monitor was used in the combine for all moisture readings. No allowance was made for grain that might have been lost in harvest.

Performance Data

Grain Yield. Grain weight and moisture was converted to bushels per acre of No. 2 shelled corn (15.5 percent moisture) while sorghum was reported using 56 pounds per bushel at 14 percent moisture.

Moisture content.Occasionally, hybrids too late in maturity for a given area are entered in these tests. These hybrids are often high in yield, but their moisture content may make them poor choices for farm use unless proper drying or storage facilities are available.

Erect plants. The number of erect plants in each plot of a hybrid was determined at harvest time. Any plant leaning at an angle of more than 45 degrees or broken below the ear was considered lodged. Plants broken above the ear were considered erect.

Population. Corn plots were over planted and thinned to the desired population. Stand differences may be caused by failure to germinate or by damage from diseases, insects, cultivation, or rodents.

Head Exertion. Sorghum hybrids were measured in late August for length of seed head exertion from the flag leaf to the base of the seed head (expressed in inches).

Plant Height. Sorghum hybrids were measured in late August from the ground to the top of the seed head (expressed in inches).

Head Compactness. Sorghum hybrids were rated in late August for seed head compactness. A rating of 1 was given for tightly compacted seed heads, 2 for moderate compactness, 3 for loose compactness.

Suggestions for Comparing Entries

It is impossible to measure performance exactly in 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, like those reported here, are more reliable than those of a single-year or a single-strip test. When one hybrid 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 a consideration in choosing a hybrid. When comparing yields, however, grain moisture content, percentage of erect plants, and plant population must also be considered.

A number of statistical tests are available for comparing hybrids within a single trial. 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 hybrids are compared and the difference between them is greater than the tabulated L.S.D. value, the hybrids are judged "significantly different."

The L.S.D. is a number expressed in bushels per acre and presented following the average yield for 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 hybrids in the 'top group'. Decide the L.S.D. level that is best for your farm and find the highest yielding hybrid at the location, subtract the chosen L.S.D. level from the highest yielding hybrid, every hybrid with a greater yield than the resulting number is 'statistically the same' as the highest yielding hybrid. Consider the merits of the hybrids in this group when making hybrid 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 a = 0.20 to 0.40, where a is the Type I statistical error rate for comparisons between means that are really equal. Herein, values of a = 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 hybrids. Readers who compare hybrids in different trials should be extremely careful, because no statistical tests are presented for that purpose. Readers should note that the difference between a single hybrid's performance at one location and its performance at another is caused primarily by environmental effects and random variability. Furthermore, the difference between the performance of hybrid A in one trial and that of hybrid B in another 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.

1998 Test Fields









Dixon Springs

1998 Growing Season Rainfall

Woodstock 5.77 6.50 1.15 3.50 2.30
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
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
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University of Illinois at Urbana-Champaign
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