Planting and Protection
Fig. 2. fiber flax seedlings in a
flat, firm, and uniform field in South Carolina. |
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The southeastern U.S. has a long growing
season and mild winters which allow growers to potentially
produce a winter crop of flax (4). The CFF production system
involves precise seedbed preparation for planting. Flax
seedlings have difficulty emerging from crusted soils and
are sensitive to hot and dry conditions during growth. A
good seedbed includes weed control, conservation of soil
moisture and a flat (few large clods), uniform, and firm
seedbed for germination (Fig. 2). In addition, since the
plants will be mowed using a drum mower, a flat and even
field provides the greatest harvest efficiency (resulting in
less stubble) as plants are uniformly cut at the soil's
surface.
The seedbed can be prepared using a disc
harrow and field cultivator or any other combination
producing a flat and uniform field. Seeds should be
broadcast or drill planted with a row spacing of roughly 7
inches and approximately 0.4 inches deep with the depth
never to exceed 1 inch. fiber flax varieties are planted
closer together than seed flax varieties so that only the
main stem develops and the plants grow tall with fewer
branches and seeds, thus producing long, fine, and strong
fibers. Parks et al. (16) reported that 110 lb seeds per
acre is the desired seeding rate for fiber flax. Flax
tolerates a wide range of soil types but does best on
fertile, well-drained, medium to heavy textured soils (10).
Well-drained loamy or silty soils are desirable for planting
with subsoil clay or B-horizon within 12 inches of the
surface more desirable (16).
Before planting, the soil pH should be
between 5.8 and 6.5. In the absence of direct
recommendations for flax, the fertilizer rates suggested for
production of small grains can be followed. According to
Frederick (2000, unpublished data), a general target
for nitrogen, phosphorous, and potassium in the soil would
be 70, 60, and 150 lb/acre. Loadholt (11) evaluated the
influence of nitrogen, phosphorus, potassium, and
micronutrients on poor and well-drained coastal plain soils.
Management of nitrogen is critical with a total of 70 to 80
lb of nitrogen per acre for residual and added nitrogen
necessary (1,12,16,23). Nitrogen should not be placed next
to the seed (1), and excessive nitrogen should be avoided as
it encourages weed growth and lodging without enhancing
fiber production. Flax plants are sensitive to zinc
deficiency (16,23); however, micronutrient fertilization is
seldom recommended (1).
The growing practices for fiber and seed
flax are comparable (13), which allows use of flaxseed
herbicide (3,9,12), pesticide (1,3,9,12), fertilizer
(1,3,9,12,17,24), and insecticide recommendations
(1,3,9,12). Flax seedlings do not compete well with other
plants, and yield and quality are improved with weed
control. Herbicides on seed flax are superior to post-plant
tillage techniques in controlling weeds in flax (5). The
herbicides Treflan or Treflan EC are used prior to
planting with post-emergence herbicides such as Buctril,
MCPA , or Poast applied when the flax plant is between 2
and 8 inches (16). Management strategies, crop rotation,
different varieties, environmental conditions, soil types,
and controls may be required to avoid disease and plant
problems (1,9,15,17). To guard against diseases, a four-year
crop rotation of disease-resistant varieties is recommended
along with a seed treatment such as Thiram (16).
Depending upon the location within the
southeastern U.S., seeds planted between October and
December benefit from the cool and moist weather. Flax
benefits from this cool and wet weather since the plant
requires adequate soil moisture from planting until
flowering. Flax grows well with frequent, low volume
irrigation (10). To benefit from weather conditions planting
should be done as early as possible; crops grown in portions
of Arizona, California, and Mexico are planted from November
through December (7). Temperatures below 28F can kill flax
in the seedling stage so flax is planted along the coast in
South Carolina, Georgia, and Louisiana between October 15
and November 10. In some instances, temperatures below 15F
have killed fiber flax plants, with these deaths typically
related to the time that plants are exposed to these
temperatures. Flax grown in Texas is sown from late November
through early December. For locations further north such as
Virginia and Tennessee, flax is planted in March (20).
Harvesting and Retting
Flax roots do not contain fiber so it is not
necessary to harvest the entire plant. The time of harvest
is influenced by climatic conditions and the crop's final
use (Fig. 3). Harvesting of flax at different maturities
according to the CFF process provides a diversity of
products: (i) early crop for fiber only, with attached
immature seeds for greater fiber quality, or (ii) mature
crop for both seed and fiber production (19). The finest
fibers are obtained by harvesting the crop following a full
bloom with the stem and leaves green or at medium fiber
fineness when half to a third of the seed bolls are yellow
and brown with fully-developed seeds (19). According to the
CFF process, flax is cut with a drum mower (Fig. 4). When
harvesting with a drum mower, changes such as mower blade
angle and tractor speed relative to the greenness of plants,
as well as operator skill, field preparation, planting, and
harvesting techniques affect the height of the flax left in
the field as stubble.
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Fig. 3. fiber flax crop near
maturity in South Carolina. |
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Fig. 4. Drum mower to harvest
flax fiber as an early crop for fiber only or as a
mature crop for both seed and fiber production in
South Carolina. |
Flax that has been naturally dried or sprayed with a
desiccant produces a dry, usable seed. To harvest flax for
seed requires relatively dry stalk material; otherwise
stalks clog the stripper header of the combine. Harvesting
flax at maturity according to the CFF process requires that
the seeds be first removed from stalks with a stripper
header attached to a grain combine (Fig. 5). In combining,
seeds are easily damaged so the condition of the seed
determines the harvesting speed. Flaxseed can be safely
stored at moisture levels of 10.5% or lower (3). The
deseeded stalks are then drum-cut, field-dried, and raked
(Fig. 6) for even dew-retting and drying. Flax straw should
be raked into windrows and baled using standard hay baling
protocol such as straw dryness, baler setting, bale density,
speed, and packaging.
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Fig. 5. Grain combine with
stripper header for detaching fully-developed
flaxseeds prior to fiber production in South
Carolina. |
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Fig. 6. Mowed fiber flax straw
raked for consistent dew-retting in South Carolina. |
The fine bast fibers are released from the stem by a
process termed dew-retting. Mowed flax is dew-retted
according to weather conditions and completed in a week
(when weather is warm and moist) to months (when weather is
cold and dry) (18). In this process, indigenous fungi and
bacteria partially decompose the plant stems of flax. These
organisms produce enzymes capable of degrading the
non-fibrous tissues in flax stems with an influence on the
quality of the fiber. Through enzymes, the selective
biodegradation of the pectinaceous and matrix substances
facilitates the removal of cellulose fibers from the woody
portion of a flax plant (21). Due to weather conditions,
dew-retting is uncertain and so it is important to form a
uniform layer of mowed flax stalks and, if possible, rake
the crop for consistent retting.
Flax stalks can be over-retted, which
produces fibers of substandard strength due to the
decomposition of the cellulose fibers. Many variables,
including temperature, moisture, organisms, mowed straw
layers, and raking, influence retting and so the stems must
be inspected periodically for harvest optimization. Higher
temperatures and moisture increase the activity of
microorganisms that degrade the pectin while non-uniform
straw layers created during raking can create varying zones
of retting. Dew-retting is subjectively judged and
considered complete once the fibers appear silver and
separate easily from the stem. Following dew-retting, the
fibers are then dried for baling and further processing
(Fig. 7). According to the CFF process, flax can be baled
using a round or square hay baler (Fig. 8) for fiber
processing.
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Fig. 7. Round hay baler to
harvest dew-retted flax fiber in South Carolina. |
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Fig. 8. Round bales of flax
produced on a flat, firm, and uniform field in South
Carolina. |
Summary
As with any crop, intelligent farming is
required to produce high quality and profitable flax. Flax
production costs parallel other small grain production crops
in the southeastern U.S., indicating it may be a
supplementary crop for idle lands. No costly, specialized
harvesting equipment is required using the CFF system.
Research shows that high-quality, short-staple fibers are
found in early-harvested flax and from mature flax harvested
for seed and fiber. The CFF system in conjunction with new
processing methods allow the production of a domestic,
commercial source of flax fiber for textile, composite, and
paper industries. Flax as a winter crop for fiber,
especially in double-cropping with high value summer crops,
has the potential to enhance the income of local industries
in the southeastern U.S.
Acknowledgements
Mention of specific products is for
information purposes only and is not to the exclusion of
others that may be suitable. The contributions of James
Frederick to this work are gratefully acknowledged and
appreciated.
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