Chymistry applied to Agriculture.
By John Antony Chaptal, court of Chanteloup, Peer of France, Member of the Institute, &c.
Translated from the Second French Edition.
Boston: Hilliard, Gray, and co.
1836
For two centuries Woad (Isatis tinctoria) has been cultivated in Europe. This plant is biennial, and its hairy and branching stalk rises to the height of three feet. As it is not killed by frost, it affords excellent food for cattle during the winter. It has however been less cultivated for fodder than for yielding the only permanent blue color which was known before the seventeenth century.
The discovery of indigo has greatly checked the cultivation of this plant, and it is now limited to a few localities, where it is used for forming that coloring preparation known under the name of coques de pastel. I am, however, much inclined to think that the cultivation of woad may be restored to its former state, and that it will form, sooner or later, one of the most important branches of French agriculture; and this opinion has determined me to devote a chapter of this work particularly to the subject, and I shall treat of it under three heads.
1st. The cultivation of Woad.
2d. The manufacture of the cakes from the leaves of the plant.
3d. The extraction of Indigo from it.
Article I.
On the Cultivation of Woad.
It appears that the isatis tinctoria may be made to flourish everywhere excepting in moist lands; corn fields and ground which is prepared for cultivation are adapted to its growth; a good crop may be procured upon alluvial soils, but strong soils are preferable, provided they are not too clayey.
The ground in which the seed of the isatis is to be sown must be ploughed three times, not only that the ground may be thorough softened and divided, but that all the weeds which would injure the growth of the plant, and increase the expense of weeding, may be destroyed. The different ploughings should be performed at intervals of a month or three weeks from each other. In strong lands and those which are disposed to retain too much water, deeper furrows may be traced at certain spaces, so as to form small drains, by which the water that would injure the plant in drawn off. The nature of the manure which is employed in the culture of woad, exerts a powerful influence, not only upon the vegetation of the plant, but upon the quantity and quality of its coloring principle.
The manures which consist of well decomposed animal or vegetable substances are the best, and for this reason night soil, the dung of sheep and doves, the decayed fragments of wool and silk, and the chrysalises of the silk-worm, are preferred to any other manures.
Those substrances that act as stimulants to vegetation, such as lime, plaster, marine salt, poudrette, mortar-rubbish, ashes, &c. favor the growth of the plant without affecting the coloring principle.
When land has been dressed with barnyard manure, it may be made to yield a crop of grain or maize, and afterwards be sown with woad.
The season for sowing the isatis varies much in different parts of Europe. In Italy, Corsica, Tuscany, &c. it is sown in the course of the month of November. As it does not receive injury from the cold, it grows during the winter, and in March is sufficiently strong to overcome the weeds which usually make their appearance at that season. From the circumstance of its growing through the winter, it may be rendered a very important article of nourishment for horned cattle.
In the south of France, woad is sown in March, and in England in February. In certain other countries it is sown after the corn harvests; but in this case, a season favorable to vegetation is required, and the practice of sowing at that time can only be followed advantageously in those climates where rains are certain, so that the cultivator may be able to gather two or three harvests of leaves before winter. His fields of woad will afford him pastures for his cattle during the frosts, and he is secure at the return of summer of an abundant harvest of leaves.
The seed of the isatis should be soaked in water previously to sowing, as germination will be hastened by it. The seed is sown broadcast, in the same quantity as wheat, and harrowed in. The blade shows itself at the end of ten or twelve days. As soon as the plants have thrown out five or six leaves, they must be carefully weeded, and this must be repeated several times before gathering the leaves. The design of the weeding is to remove all strange plants that may spring up in the same soil, especially the roots of bastard woad, (bourdaigne), the mixture of which injures the coloring matter of the pure isatis; and to thin the rows of stalks, that those remaining may have more room to grow.
The isatis, like other plants, has its diseases and its enemies. The leaves are frequently seen covered with yellow spots, which turn brown: and acquire the appear, []nce of rust: this seems to be occasioned by the sudden changes which sometimes occur in the atmosphere; the rays of a hot sun darting immediately upon plants after a mist or rain, often produces a rustiness of the leaves and stalks.
It often happens, that, in consequence of a great degree of heat accompanied by drought, the plants are not fully developed; the leaves aicquire not more than one third of their usual size, yet exhibit all the other characteristics of perfect maturity; the harvest however is lost, for if the leaves be cut in that imperfect state, the plants either perish or languish without yielding any product.
The isatis is not exempt from the ravages of insects. There is one called the flea, which often destroys the first and second harvests of leaves; another, known by the name of the louse, attacks the last leaves, but does less injury than the other, because the first harvests are the most important. The snail and the cabbage-worm likewise commit some depredations upon woad.
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