Causes of High Micronaire in Cotton
 An increased incidence of high micronaire cotton in both the 2012 and 2013 crops has concerned
growers.
 When cotton plants produce more carbohydrates than are necessary to support plant development,
the excess carbohydrates allow cotton fiber cell walls to thicken, resulting in high micronaire fibers.
 High micronaire is generally associated with anomalies such as drought stress, water stress, or
extremely high yields.
What is Micronaire?
Micronaire (mic) is a measurement of the thickness of the cell
walls of a cotton fiber. When cotton begins to bloom, cells that
will eventually form fibers elongate into the boll. Final fiber length
is reached about 16 to 20 days after formation. Once fibers are
fully elongated, the fibers begin to thicken from the inside out.
Carbohydrates produced through photosynthesis allow
cellulose to be added to the cotton fiber walls, thus increasing
both thickness and strength.1
“With fewer bolls on the plant, fibers in the bottom bolls used
the available carbohydrates to develop more high mic fibers,”
Collins says.
Management Considerations
One key to avoiding high mic grades is to be timely with
defoliation and harvest. The less mature fibers in the upper
bolls, blended with the more mature fibers in the lower bolls will
reduce the average mic for the crop.
Cotton buyers and textile manufacturers prefer a micronaire
range of 3.8 to 4.5, and a fiber length of 1 1/8 inch. Thicker or
thinner fibers cause problems in both spinning and uniform
dying of yarn. Buyers discount the value of both high and low
micronaire cotton.
“The main goal should be to capture as much yield as
possible,” Collins says. “With the advent of more round bale
harvesters, growers may be able to defoliate and harvest in a
more timely manner, as peanut and cotton harvest can now be
conducted simultaneously..
High Mic in 2012
Planning for 2014
“We had some reports of high mic cotton in 2012, and we’re
hearing a few reports of high mic cotton this year,” says
University of Georgia Extension cotton agronomist Guy Collins.
“The physiology behind high mic cotton is fairly simple. When
the plants produce more carbohydrates than are necessary to
support plant development, the excess carbohydrates are
available for fiber cell walls to thicken. Several things can lead to
the availability of excess carbohydrates.”
“Last year we had some exceptionally high-yield cotton,” Collins
says. “In some areas, essentially every boll on the plant reached
full maturity, and growers harvested 3 to 3.5 bales per acre.
Good growing conditions allowed the plants to continue to
produce carbohydrates to fully develop many of the upper bolls,
resulting in more high mic fibers.”
“We generally associate high mic cotton with drought-stressed
crops, where dry weather causes only the bottom crop to be
retained,” Collins continues. “With fewer bolls being set on the
middle and upper nodes, the majority of the harvested crop
consists of the more fully mature lower bolls, which may be high
mic.”
High Mic in 2013
Excess rainfall instead of drought set up the potential for high
mic cotton in some situations in2013. Excessive rainfall actually
had a similar effect that we normally see in some drought
conditions, where only the lower, higher mic bolls are retained.
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“Growers should not necessarily base their 2014 management
decisions solely on what they have experienced this season,”
Collins says. “Some growers are seeing some high mic cotton
and others are seeing mic within the normal range. The weather
we have experienced this season is like none other that I’ve
seen.”
“Growers need to look at multi-year data, and look for trends in
yields and fiber quality across a number of different locations as
they select cotton varieties. I would not let the unusual growing
conditions necessarily influence my variety selection,” Collins
says.
Sources:
1
Dodds, D., Cotton micronaire-potential problems exist this year, plan accordingly.
http://www.eytest.com/tech. (verified 10/25/2013).
Personal interview with Guy Collins, University of Georgia Extension cotton agronomist.
For additional agronomic information, please contact your Asgrow®, DEKALB® and Deltapine®
Brands Seed Representative
Individual results may vary, and performance may vary from location to location and from year
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weather conditions may vary. Growers should evaluate data from multiple locations and years
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