The genus Indigofera, the third largest in the family Leguminosae, consists of almost 800 species. These species usually can grow on land between sea level at 1,650 m. Over 600 types can be found in Africa, nearly 200 in Asia, more than 80 in America, and another 50-60 in Australia. However, the most widely used types for natural dye indigo are found mainly in tropical and subtropical zones. Indigofera tinctoria L. (= I. sumatrana Gaertn) is one of these varieties.
“Indigo plant tinctoria L.” relates to the leguminous family. It is an annual shrub plant with the height of 1-1,5 meters. The plant does not have any wild forms, thus it is grown only in cultivated form. The leaves have the extended shape, and are complex odd pinnate. Its flowers are of red color, and they are located in the shape of cyst on the bud protruded from the source.
The bearings, i.e beans have the length from 2 up to 3 centimeters and are of red-yellow color. Each bean contains on average from 3 to 4 mellow seeds inside. The mellow bean has the brown tincture. The seeds are small in size andare of brown color. The side branches mainly arise in the bottom part of the stalk during the growing period and reach up to the height of the mainbody. Every single bush has up to 10-15 side branches depending on the planting density.
The other biological feature of the plant, which should be given with thespecial attention, is that up to period of beans’ and seed’s maturity, the growingupwards and formation of leaves takes place in an active form. After the beginning of the maturity period of beans, the formation of leaves sharply decreases. After the maturity of the beans, the leaves turn into yellow and shed. The given feature of the plant is very important depending on the aims for its cultivation (for the purpose of receiving the seeds or biomass of the leaves).
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 part of the plant by three times. During the period of plant’s development the growth of the root slows down, it becomes wider and side roots start to appear. Until the end of the period for plant’s growth, the length of the root equals to 15-20 centimeters.
The external appearance of the plant reminds of Glycyrrhí́za glabra (Uzb. shirin miya,buyon) that grows naturally in the steppes, or next to thecanals and ditches in the Central Asian region.
The plant is tropical and therefore its seeds start to shoot only at high soil temperature (18-20 оС). In the southern regions of the country, this period falls on the first decade, in the central zones - on the second decade, and in northern zones - on the end of April and the first decade of May. The full period of the plant’s growth (the full maturity of the seeds) is 100-110 days.
Growth and development
The plant starts to actively develop from the second half of July up to first half of August. That is when the hot temperature starts increasing. Simultaneously, the side branches start appearing. During this period, the flowers of the plant are being pollinated, and the development of beans accelerates. After this, the development of the plant decelerates, which continues until the end of the period of its development. At the end of development the plant reaches from 14 to 150 cm. As Indigo plant is classified as bunch-shaped plant, the side branches of the plant mostly develop in the bottom part of its footstalk. These branches appear when the height of the plant reaches 20-30 cm and grow top-wards together with the footstalk. In the beginning, these branches continue to grow until reaching the height of the footstalk. This period falls on the beginning of July. On average every plant has up to 10-15 side branches. Side branches first appear in the lower part of the bush, afterwards -on the top. This process continues until the end of August. The first branches reach the height of the footstalk, and in some cases they become higher than footstalk. The leaves of the side branches are of the same size as the leaves of the main footstalk. The leaves of later side branches usually are of a smaller size, while the seed beans do not mature completely.
The plant height and number of side branches depend mainly on density of seeding. At dense seeding the number of side branches does not exceed 3-4, they develop not completely, and the main footstalk grows higher. And contrariwise, awhen sparsely planted, the bushes do not become high and the number of side branches increases. On average, 20-25 bushes within one running meter should be growing in beds with a distance of 90 cm between the beds. The average stand density will be 220 000-250 000 bushes per ha. In experiments of 2007, the first yield seeded in April was harvested in the end of August, after which the irrigation works, cultivation and fertilizing continued until the middle of October, and footstalks were mowed at the height of 12 cm, they developed the side branches again and the leaf mass appeared. Such branches can reach the height up to 20-40 cm.
Brief history of cultivation and use
Indigo is the plant of the tropical zones, the source of the world known dye named “Indigo”. The sky-blue color is titled as the “king” of all dyes. The word ‘indigo’ comes from the Latin word indicum and the Greek indikos, both meaning ‘indian’. India is considered to be home for indigo.The dye is first mentioned in a written source for Western Europe in the histories of Herodotus (writing around 450 B.C.), who described its use in the Mediterranean area. In the excavation of Thebes an indigo garment dating from c. 2500 B.C. was found.
The color indigo, often associated with political power or religious ritual, has held a significant place in many world civilizations for thousands of years. People deified the colors and turned them into the symbols of their idols. Probably this served a reason for Pharaohs, sultans, emperors and the members of their families only to have the right to wear the blue-colored clothes. The ancient Egyptians believed their main deity was of sky-blue color. The Hindu god Krishna is most often depicted in blue, human sacrifices were often painted blue in ancient Mayan culture, and the Virgin Mary is regularly imagined draped in blue clothes in Christian art.
In the 16th century Portuguese, Dutch, and English traders brought it to Europe from India.Throughout the nineteenth century British India was the pre-eminent producer and supplier to the West of indigo for its thriving textile industry. Indigo, derived from plant sources in the nineteenth century, was an extremely important dye for the textile industries in the West.
Even today, in the countries like India, China and Japan, Indigo dye remains to be peculiar secret art of the famous craftsman, which is passed only from fathers to sons.
Up to this moment no one considered indigo for cultivation in the Aral sea basin. In Uzbekistan, the “Indigo” paint is mostly imported from abroad. Indigo plant was never cultivated before in soil-climate conditions of Uzbekistan. According to geo-botanic investigations Indigofera tinctoria were not previously grown and/or could not be cultivated in saline soil-climate zones of the Aral Sea region, without using of specific genetic approach as proposed in Ergashev et al., 1983.
Presently, the textile industry of Uzbekistan mostly uses the artificial paints. The extracting of such paints from the economical point of view does not cost a lot and the colours are beautiful, but it is a notorious fact that artificial substances are harmful for humans. Nowadays the need for qualitative and non-perishable natural paints is increasing. The natural paints are considered to be ecologically clean product and fabrics, which are being painted, using them, do not fade under the sun and do not lose their qualities even after many years. For example, the clothing of Pharaoh Tutanhamon, painted in indigo, almost did not lose its color after 3,5 thousand years.
Restoring the fertility of degraded (saline, low productive) land: Similar to other leguminious crops, Indigofera fixes atmospehere nitrogen and absorbs it in the soil; this leads to soil enrichment and improvement. The new crop is well adapted to growth and development on degraded soils in Uzbekistan and has the ability to synthesize valuable natural dye in its leaves.
Cultivating Indigo and extracting the pigment or dye can be attractive for local farmers.
The average green biomass yields of 30-35 t/ha gives 100-130 kg pigment. The cost of 1 kg pigment at home market is 100 000-130 000 UZS. If the farmer sells the pigment at the home market, he can get 10 mln UZS from 1 ha land. The price of 1 kg natural indigo at the European market ranges 80 -240 EUR (depending on quality).
In 2005-2007 by the initiative of the UNESCO representative office in Tashkent, Uzbekistan, the project named “Uzindigo” was organized in Uzbekistan. Within the frame of this project, the experiments were carried out in Karakalpakstan, Khorezm, Syrdarya and Tashkent regions on planting and cultivation of Indigo. In recent years few private and joint companies have been established, dealing with cotton, wool and silk processing and production for home market and export. Such companies as “Nurtob”, “Khiva carpet”, “Gultekis”, “Bogot tekstil” mainly use the artificial paints, which fade in the course of time. Besides, foreign tourists are mostly interested in local handicrafts painted using with natural dyes.
Since 2005, a team of scientists headed by professor A. Ergashev and with the assistance of the UNESCO/ZEF Bonn/UrSU project have started the study on cultivation of Indigo, the method for extracting of the paint base out of it and the issues related to seed farming and marketing. For these purposes, number of experiments on a preliminary basis was conducted in 2006 for its cultivation in a form of the major culture on the soils which were not used for 3-4 years, on the saline and low yield soils of the educational-experimental farm of UrSU, and in a form of secondary culture after harvesting winter wheat. During 2006-2007 some experiments were conducted within the territory of UrSU and Academy after Mamun on the possibility of cultivation of Indigo plant and yielding the harvest of biomass from two mows. In addition to this, some simple methods for extracting paint base from the green and dry biomass of the plant were developed. In 2008 some experiments were carried out on the fields of farmers association named after «М.Kuvakov» located in Bagat district on the possibility of applying fertilizers for the purpose of identifying its effects on the harvest of biomass. Some consequent recommendations were developed based on the results of these experiments.
“Feruz-1” new variety
In 2008, project team leaded by prof. Ergashev has created a new variety of Indigofera – “Feruz-1” based on the individual selection of unique genotypes. A new salt-resistant variety is well adapted to local conditions. Because of developed symbiosis with indigenous nitrogen fixing tubercular bacteria, this variety can grow in highly saline lands of the Aral Sea region. The variety is recommended for the cultivation in all regions of the country.
For interested farmers, scientists and others special seed farming of new “Feruz-1” variety is organized in Kibray District of Tashkent Region of Uzbekistan.
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