Cotton variety trials are carried out as part of the Cotton Project of the University of Missouri Agricultural Experiment Station located at the U.M.C. Delta Center. These tests are conducted to provide a reliable, unbiased, up-to-date source of information for comparing varieties. The Roundup Ready trial had an application of Roundup applied over the top before five leaves appeared and one directed spray application later in the growing season.

Four locations were selected to represent the range of conditions found in the cotton growing area of southeastern Missouri. All locations were planted on 38" row spacing. Johnny Hux's farm near Sikeston (Bosket fine sandy loam soil), Charles Provance's farm near Clarkton (Bosket fine sandy loam soil), Charles Parker's farm near Senath (Dubbs silt loam soil). The trials at the Portageville location were planted at the UMC Delta Center's Lee Farm. Portageville irrigated trials were planted on Tiptonville sandy loam soil, while the Portageville clay trial was planted on Portageville Clay.

Field Plot Design: The trials were arranged in a randomized complete block design with four replications. The plots were four rows wide and 37 feet long, with the center two rows being used for yield and other data. Plots were end trimmed to 31 feet in length prior to harvest, to eliminate end plant effect.

Entries: All producers of cottonseed were eligible to enter varieties in the 2000 evaluation trials. Participation was voluntary and no control was exercised by the program over which or how many varieties were entered. However, to help finance the evaluation programs, a fee of $350 was charged for each variety entered by the seed producers. A total of 40 cotton varieties were compared in 2000, as outlined in the following table.

Plot Management: The trials were planted with commercial equipment modified for small plot work. The fields were managed during the growing season by the producer/cooperator. Once-over harvest was completed using a Case 1822 picker. The seed cotton was ginned on a 20-saw Continental micro-gin equipped with an incline cleaner along with a single stage lint cleaner.

Data Recorded: Lint yields are reported in pounds of lint per acre. H.V.I. quality characteristics of the lint were analyzed at the International Textile Center in Lubbock, Texas and the results are presented with the yield and other agronomic data.

Fiber Quality: Fiber quality characteristics were determined for each variety utilizing lint samples from all replications at each test location. These characteristics and their importance are described below.

A: Micronaire (Mic): The micronaire test provides a combined measure of maturity and fineness of cotton fibers. Fiber maturity is a relative measure of cell-wall thickening. Immature fibers result in the production of yarns and fabrics with low quality. In the test, air is passed through a compressed sample of cotton fiber. The rate of flow through the sample follows a relationship between diameter or thickness of the textile fibers and the air resistance they provide. Finer fibers result in greater resistance and therefore, a lesser air flow. Micronaire values that are very low or very high are undesirable. A low micronaire implies the fiber is either fine or immature. A high micronaire is indicative of a very coarse fiber. Value recorded can be interpreted as follows:

• Below 3.6 = fine and often immature
• 3.7 - 4.9 = premium range
• Above 4.9 = coarse fibers

B: Uniformity: Fiber uniformity is a measure of the degree of uniformity of fiber length in a sample. Uniformity is calculated as a ratio of the average length of all fibers to the average length of the longest half of the fibers in the sample. The ratio is then multiplied by 100. High uniformity values are desirable and indicate uniform fiber lengths.

• Below 77.0 = Very high
• 77.1 - 79.0 = Low
• 79.1 - 82.0 = Average
• 82.1 - 85.0 = High
• Above 85.1 = Very High

C: Strength: Fiber strength is reported in grams per tex. A tex unit is equal to the weight in grams of 1000 m of fiber. The strength values are reported in grams of force required to break one tex unit if fibers with the holding jaws separated 1/8 in. The 1/8 in. jaw spread breaks the fibers at the weak point. High fiber strength enables the yarn to be spun at a faster rate and produces a stronger yarn. The following chart categorizes strength readings and aids in the interpretation of strength values for an 1/8 in. gauge.

• Below 23.9 = Very Low
• 24.0 - 26.9 = Low
• 27.9 - 29.9 = Average
• Above 30.0 = High

D: Length: Fiber length is reported in hundredths of an inch as measured by a fiber-graph instrument and is the average of the longest half of the fibers in the sample, upper half mean (UHM). Long fibers are desirable because they produce greater yarn strength, aid in spinning finer yarns.

• Below 0.97 = Short
• 0.97 - 1.10 = Medium
• 1.11 - 1.28 = Long
• Above 1.28 = Extra Long

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