Developments in dyeing technology: 

 Indigo is a challenging dye to use because it is not soluble in water; to be dissolved, it must undergo a chemical change. When a submerged fabric is removed from the dye bath, the indigo quickly combines with oxygen in the air and reverts to its insoluble form. When it first became widely available in Europe in the sixteenth century, European dyers and printers struggled with indigo because of this distinctive property. It was also a toxic substance that, by requiring many chemical processes, had many opportunities to injure many workers.

A pre-industrial process for dyeing with indigo, used in Europe, was to dissolve the indigo in stale urine. Urine reduces the water-insoluble indigo to a soluble substance known as indigo white, which produces a yellow-green solution. Fabric dyed in the solution turns blue after the indigo white oxidizes and returns to indigo. Synthetic urea to replace urine became available in the 1800s.

Two different methods for the direct application of indigo were developed in England in the eighteenth century and remained in use well into the nineteenth century. The first method, known as pencil blue because it was most often applied by pencil or brush, could be used to achieve dark hues. Arsenic trisulfide and a thickener were added to the indigo vat. The arsenic compound delayed the oxidation of the indigo long enough to paint the dye onto fabrics.

The second method was known as china blue due to its resemblance to Chinese blue-and-white porcelain. Instead of using an indigo solution directly, the process involved printing the insoluble form of indigo onto the fabric. The indigo was then oxidized in a sequence of baths of Iron(II) sulfate. The china blue process could make sharp designs, but it could not produce the dark hues possible with the pencil blue method.

Around 1880 the glucose process was developed. It finally enabled the direct printing of indigo onto fabric and could produce inexpensive dark indigo print unattainable with the china blue method.

BY-PRODUCTS:

                           Indigo production produces a variety of waste products which must be handled carefully. In addition to the reactants described above, there are other reaction side products that are produced along with the indigo. Some of these materials are considered to be hazardous and must be disposed of in accordance with local and federal chemical waste disposal guidelines. These waste chemicals can enter the environment in at least three different ways. The first is during the actual manufacture of the molecule. The second is when the dye is applied to the yarn, and the third is when the dye is eluted into the wash water during the initial stonewashing or wet processing of the fabric. This last route typically occurs during the production of denim fabric.

Uses of indigo:

• Used to produce the dye indigo
• The chemical aniline, from which many important dyes are derived, was first synthesized from I. suffruticosa. 
• Several species of this group are used to alleviate pain. The herbs are generally regarded as an analgesic with anti-inflammatory activity, rather than an anodyne.
• Indigofera articulata Guan (Arabic Khedaish) was used for toothache,
• Indigofera oblongifolia Forsskal (Arabic "Hasr") was used as an anti-inflammatory for insect stings, snakebites, and swellings.
• Indigofera suffruticosa and Indigofera aspalthoides have also been used as anti-inflammatories.
• A patent was granted for use of Indigofera arrecta extract to relieve ulcer pain.
• Green manuring involves the incorporation into the soil of any field crop while green (fresh and relatively young) for the purpose of soil improvement. Among the good green manure crops is indigo (Indigofera tinctoria L.) It produces large amounts of biomass ranging from 2.19 to 2.57 t/ha in 210 days, which contributes 38-71 kg N/ha.

Use of Indigo as green manure:

Indigo (Indigoferatinctoria L.), locally known as “tayum,” is a shrubby legume that was initially introduced in the Philippines as a source of dye but was adopted by farmers as green manure (GM).

Benefits by adopting technology:

Ø Enhances fertility of soil.        

Ø Better growth and yield perforDDmance of rice with Indigo.

Ø Increases profits and reduces DDproduction cost per kilogram rice grains.

Ø Reduces use of chemical fertilDDizers.

Ø Sustains yield of companion DiDDrect Seeded crop.

Ø Catches residual soil nitrate, DDwhich otherwise would move at deeper soil layer and ultimately contaminate the groundwater.

How to Incorporate Indigo as Green Manure:

Ø Wait until the field has accumulated sufficient water

Ø For wetland preparation.

Ø Cut the indigo at ground surface or topple the plants using spike tooth harrow.

Ø Plow the field thoroughly using an animal-drawn plow or a tractor to incorporate the indigo.

Ø Transplant rice immediately or 3-5 days after GM.

Ø Incorporation.    

Ø The indigo biomass is incorporated as GM for the succeeding wet season in July-August depending on the availability of rainfall.

Ø It is incorporated in the soil while the land is prepared for transplanting.

ROLE OF INDIGO IN RICE FARMING:

Ø The Indigo can be planted as a monocrop after rice harvest. When planted as a sole crop, a seed rate of 6-8 kg/ha is needed.

Ø  It can also be planted in between the standing crop after the last interrow cultivation at 30-50 days after planting (DAP). The seed is dibbled in the furrows created during the hilling-up operation. (This is the most common method used by farmers in the local region. It is not suited as a short-duration pre-rice green manure due to its slow initial growth. It needs 45 months to accumulate high amounts of biomass and N.

Ø It can be grown after rice (Oct-Nov) as a companion crop to upland crops, such as corn, mung bean and tobacco. As an intercrop, it has not been observed to exert a yield-depressing competitive effect on its companion crop. It can be grown in combination with any of a number of food crops like mung bean, cowpea, peanut, corn, etc., because its slow, initial growth does not allow it to compete for sun or water.Indigo is plowed under at the start of the wet season to serve as a big-fertilizer for the rice crop. Under saturated conditions, the Indigo seeds plowed under were not observed to emerge. Therefore, the plant does not appear to be a significant weed problem in rice. It can withstand a long dry season (6 months or more), thereby providing soil cover during dry months.

IMPORTANCE AS FERTILIZER:

At 45 DAP, total N accumulated by Indigo was estimated to be equivalent to 45 kg N/ha.When planted as an intercrop prior to wet season rice, it can produce a biomass of 4-19 T/ha, equivalent to 84-267 kg N. Average amount of N required by rice can be reduced by one-half to two thirds when preceded by Indigo. Only a single application of fertilizer at 45-53 days after transplanting need be applied to rice when Indigo is incorporated.

 

 

HOW TO USE INDIGO AS FERTILIZER:

Ø Indigo may broadcast after fields are drained. The field is then harrowed to cover seeds. Furrowing to accommodate the intercrop can subsequently take place. In llocos, an average of 6-8 kg/ha of Indigo seeds are broadcast. Pre-soaked and dibbled between rows of a standing post-rice crop after interrow cultivation (3050 DAP).

Ø Planted after harvesting the post-rice crop in the same furrows in which these crops were planted.

Ø The Indigo is incorporated once the field accumulates enough water for land preparation for the rice crop. A peg tooth harrow drawn in one direction is usually used to flatten the stand. Then the Indigo is plowed under in the same direction as it was flattened. Harrowing and transplanting follow very soon after in order to avoid loss of nitrogen from the decomposing biomass.

Indigo bush (Amorpha fruticosa)

Ø Other common names: False indigo, ibush, lead plant

Ø Weed Class: B

Ø Year Listed: 1988

Ø Native to: Eastern and Central United States

Ø Toxic: humans, livestock

Why it is noxious weed?

           Although native to the Eastern United States, in some Western states it is considered invasive and has naturalized. It escapes planted areas and grows along streams and rivers and prairie draws forming dense thickets and outcompetes native species.

Identification Criteria ….

General Description: Indigo bush is a thorn less, deciduous, multiple stem shrub that can grow to over 12 feet tall and can form thickets.

Flower Description: Flowers are in dense, upright clusters, in the upper branches. They are blue-violet to dark purple and have 10 stamens.

Leaf Description: Leaves are made up of 13 - 25 leaflets which are one to two inches long. They are gland dotted and hairy with smooth margins.

Stem Description: Older stems are woody and younger stems are green and hairy.

Fruit/Seed Description: Seed pods are small, curved, dark brown, about 1/4 inch in size and are dotted with glands. Each pod contains 1 or 2 seeds.

 Reproduction mode:

              Indigo bush reproduces by seed.

Growing scale:

             Indigo bush grows in prairies, hillsides, sandy roadsides, along streams and rivers. Please to see a county level distribution map of indigo bush in Washington.

Mechanical Control:

Cutting plants may result in re-sprouting stems. Repeated cutting may be used to control seed production each year.