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EXPERIMENTAL
PROCEDURES
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. Our cooperator's farms are
Johnny Hux's farm near Sikeston (Bosket fine sandy loam soil) and
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
silt loam soil, while the Portageville clay trial was planted on
Portageville Clay. The Clarkton Flex variety trial was at the Rhodes
farm on Bosket fine sandy loam soil.
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 2006 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 51 cotton varieties were
compared in the Portageville, Sikeston, and Senath trials in 2006.
The Clarkton Flex trial had 32 entries and the Roundup trial had 31.
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 IH 2022 picker. A grab
sample was then ginned and the gin turnout calculated. The resulting
cotton lint was then analyzed for the fiber quality properties:
micronaire, length, strength, uniformity, color grade and trash
percentage.
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 Low
- 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 when fibers are held with the 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
and aid in spinning finer yarns.
- Below 0.97 = Short
- 0.97 - 1.10 = Medium
- 1.11 - 1.28 = Long
- Above 1.28 = Extra Long
E: Elongation: Elongation is the percent of fiber
length that a fiber will stretch or elongate before it breaks. A high
elongation is desirable and indicates that a fiber is not brittle.
F: Leaf: Leaf is the percent of the sample surface
area that is covered by trash particles such as leaf fragments, bark
and grass. High leaf content indicates that the sample will have a
high waste content when spun.
G: Rd: Rd is the amount of light reflected by a
sample. A high reflectance, which is desirable, indicates a bright
sample of lint that is unweathered and undamaged as far as color is
concerned.
H: +b: The amount of yellowness in a sample is
measured as +b. Weathering and damaged lint such as caused by insect
damaged locks will cause a high yellowness reading, which is
undesirable. Lint that has a high level of yellowness will require
more bleaching than lint that has a low level. Spots in samples will
increase the +b reading.
I: Base price was adjusted for color, leaf, staple,
micronaire, strength, and uniformity. Calculated by the 2006 Cotton
Loan Valuation Program, based on the national CCC loan schedule for
2006.
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