Indigo
B. Name: Indigofera
tinctoria
C. Name: Neel
Family : Leguminosae
History of Indigo:-
Indigo was used in India, which was also the earliest major center for
its production and processing. The Indigofera tinctoria variety of Indigo was
domesticated in India. Indigo, used as a dye, made its way to the Greeks and
the Romans, where it was valued as a luxury product. Indigo is among the oldest
dyes to be used for textile dyeing and printing. Many Asian countries, such as
India, China, Japan and South East Asian nations have used indigo as a dye
(particularly silk dye) for centuries. The dye was also known to ancient
civilizations in Mesopotamia, Egypt, Greece, Rome, Britain, Mesoamerica, Peru,
Iran, and Africa. Because of its high value as a trading commodity, indigo was
often referred to as Blue Gold.
Indigo does well if kept in an area that gets bright light, but is also
warm. Unless you live in a climate similar to India’s, don’t keep this plant
outdoors; it will not withstand cold temperatures. Indigo prefers moist, well
drained soils, so be sure to water regularly throughout its growing season,
April through September, but a little less in the cooler months. Feeding with a
high potassium fertilizer will encourage blooms. The best time to prune depends
on what your goals are. To encourage flowering, prune in May or June. If you
are using the leaves to make dye, you can prune anytime in summer.
Importance of Indigo:- The primary use for indigo is as a
dye for cotton yarn, which is mainly for the production of denim cloth for blue
jeans. On average, a pair of blue jean trousers requires 3–12 g of indigo.
Small amounts are used for dyeing wool and silk. Indigo carmine, or indigotine,
is an indigo derivative which is also used as a colorant. Approximately 20M
kilograms are produced annually, again mainly for blue jeans.
The precursor to indigo is indican, a
colorless, water-soluble derivative of the amino acid tryptophan. Natural
indigo was obtained from those in the genus Indigofera,
which are native to the tropics.
The primary commercial indigo species in Asia was true indigo (Indigofera
tinctoria, also known as Indigofera sumatrana). A
common alternative used in the relatively colder subtropical locations such as
Japan's Ryukyu Islands and Taiwan is Strobilanthes cusia. In Central and
South America the two species Indigofera
suffruticosa and Dyer's
Knotweed (Polygonum tinctorum), although the
Indigofera species yield more dye.
Plant characteristics:-
The root of the
indigo plant has the straight shape, and after the shoot appears from the seed,
the growth of the root is activated, and during the period when the leaves are
formed, subsequent to the growth of 6 to 8 leaves, the length of the root part
exceeds the length of upper of the plant
by three times.
Propagation:-
If you can’t find indigo plants in stores,
like other members of the legume family, it is relatively easy to grow from
seed. May is a good time to do this. Place seed in a starter pot filled with
good quality potting soil, and then sprinkle a fine layer of soil over the top.
Water well, and then cover with a sheet of glass or plastic dome to retain
warmth and moisture, and keep in a warm area. As the plant grows, carefully
re-pot in larger containers.
Fertilizer:-
During the
period of the growth and appearance of 4-5 leaves on average the sowings are
fertilized with the mineral fertilizers for the first time applying the ratio
of 100-110 kg of nitrogen (ammonia saltpeter) per hectare of soil.
Irrigation:-
It is necessary
to pay a special attention on the methods of irrigation of indigo plant. In
particular, during the early stages of the plant’s development, the beds should
be constantly irrigated with small amount of water. The water should not reach
the level of plant’s height, i.e. up to the very top of the bed. During the
active development, and when the side branches start to appear, the sowing are
irrigated 2-3 times. After appearance of seed beans and during the period of
plant’s maturity, the plant already requires a lot of water. The cultivation of
soil between the beds after each session of irrigation let the humidity remain
in the soil, which ensures the condition for exchange of air .
Harvesting:-
It is of a high
importance to harvest the biomass of indigo plant seeded in spring as the main
crop on timely basis, i.e. to identify correctly the time frame for harvesting
the leaf mass only in which case the high yield of crop can be guaranteed. The
incorrect identification of harvesting time may lead to the loose of the crop.
As it was mentioned above, the process for the development of biomass of indigo
plant’s leaves is continuing till the time of bean’s maturing. After this the
process intercepts, and the appeared leaves start to fall. The period of mowing
the mass of the leaves falls on the third decade of the August. However, it is
important to mention, that before the harvesting the biomass, the sowings must
be completely cleaned off weeds, as weeds affect very negatively on the quality
of the extracted plant.
Processing
of Indigo:-
Typically seeds were sown in March. By June the plants were three to
four feet high, setting flower buds, and ready to harvest. Branches were cut at
the base and hauled away for processing. New growth would emerge from the
roots, providing a second and sometimes third harvest if the weather was ideal.
The first step after harvest was to submerge the branches in a vat full
of water known as the steeper. In eighteen to twenty-four hours the plants
would ferment. At this point the liquid was drawn off into a second vat known
as the beater, where liquid was "beaten" by stirring or paddling in
order to introduce oxygen into the mix. After a couple of hours the liquid
would turn green and then blue. At this stage some planters added lime water to
the mix to speed up the process, but many planters thought doing so resulted in
inferior indigo.
With continued agitation, a chemical in the liquid known as indican
would precipitate and settle to the bottom of the vat. When enough sediment had
accumulated, the liquid was drawn off into a third vat to settle further. The
sediment in the beater vat, known as "indigo mud," had a pudding-like
consistency; it was scooped out and hung in cloth bags to drain. The next day
the mud was removed and pressed into brick-sized molds. Once dry, the indigo
was removed from the molds and cut into one-and-a-half-inch squares and packed
for export.
The noxious stench associated with processing indigo is well documented.
The fermenting liquid smelled so foul that processing facilities were always
located well away from dwellings. Long-term exposure to the vapors given off by
fermentation, oxygenation, and precipitation, as well as the presence of
disease-carrying insects, may explain why the life span for slaves
involved with indigo processing has been reported to have been a mere five to
seven years.
Further Study:
http://www.georgiaencyclopedia.org/articles/history-archaeology/indigo
http://www.indiaenvironmentportal.org.in/content/2237/the-revival-of-indigo/
Author:
Sohaib Hassan
University of Agriculture, Faisalabad.