Agriculture Reference
In-Depth Information
capacitance of the cotton, which changes as the cotton moisture content changes.
Compared with spectroscopic devices, electrical instruments are generally less
expensive and more portable, but they also tend to be less accurate. Byler et al.
(2009) evaluated several electrical cotton bale moisture content meters and found
measured moisture content values to be significantly different from oven-based
moisture content. Most of the meters were found to have a significant offset from the
oven-based values.
6.4.3 C
OTTON
F
IBER
Q
UALITY
M
EASUREMENT
Several properties are measured to assess the quality of cotton fiber including length,
color, and cleanness of the fibers. Cotton produced in the United States is classed
in the U.S. Department of Agriculture (USDA) classing offices before entering the
market. Historically, cotton fiber quality was examined by human cotton classers
who had difficulty in consistently adhering to established grade levels. Modern
classing instruments are able to grade the cotton with higher repeatability and in
less time. The principal instrumentation system used by the USDA for cotton fiber
quality measurement is the High Volume Instrument (HVI) system. Another com-
monly used system that provides other measures of fiber quality is the Advanced
Fiber Information System (AFIS). Both systems are made by Uster Technologies
(Knoxville, TN). The parameters measured by these systems are given in Table 6.1
(Peters and Meier, 2010). HVI uses a series of sensors to rapidly measure the bulk
fiber color, representative fiber length, micronaire, strength, and foreign matter con-
tent of samples from millions of bales each year.
6.4.4 G
INNING
P
ROCESS
C
ONTROL
FOR
Q
UALITY
P
RESERVATION
Cotton must go through a series of mechanical processes between harvesting and
being pressed into a bale. In each step of the process, cotton fiber quality is affected
by interactions between fiber and mechanical actions (Mangialardi, 1985). Compared
to hand-picking, machine-harvesting decreases cotton fiber quality, particularly by
increasing nep content and short fiber content (Calhoun et al., 1996; Hughs et al.,
2000; Baker and Brashears, 2000; Willcutt et al., 2002; Baker et al., 2010; Faulkner
et al., 2008).
Seed cotton harvested by spindle-type harvesters contains about 8% trash,
whereas that by stripper harvesters contains about 35% trash (Mayfield et al., 2011).
It is desirable for as much foreign matter as possible to be removed from cotton fiber
with minimal damage to the fiber. Removal of foreign matter at the gin involves
cylinder cleaners and stick machines before fiber-seed separation to remove large
particles from seed cotton, and lint cleaners after fiber-seed separation to remove
smaller particles that remain in the lint. Two general types of lint cleaners are cur-
rently on the market: the air type and the saw type. The saw-type lint cleaners are
most common because of their higher cleaning efficiency. Seed cotton cleaning and
lint cleaning are necessary steps in the ginning process. However, it is also widely
realized that they, particularly saw-type lint cleaning, create fiber damage (Sui et al.,
2010).
