In Caravaya and Bolivia the soil in which the Coca grows is composed of a blackish clay, formed from the decomposition of the schists, which form the principal geological features of the mountains. On level ground the plants are placed in furrows called _nachos_, separated by little walls of earth, _umachas_, at the foot of each of which a row of plants is placed; but this is a modern innovation, the terrace cultivation being the most ancient. At the end of eighteen months the plants yield their first harvest, and continue to yield for upwards of forty years. The first harvest is called _quita calzon_, and the leaves are then picked very carefully, one by one, to avoid disturbing the roots of the young tender plants. The following harvests are called _mitta_ (“time” or “season”), and take place three and even four times in the year. The most abundant harvest takes place in March, immediately after the rains; the worst, at the end of June, called the _Mitta de San Juan_. The third, called _Mitta de Santos_, is in October or November. With plenty of watering, forty days suffice to cover the plants with leaves afresh. It is necessary to weed the ground very carefully, especially while the plants are young, and the harvest is gathered by women and children. The green leaves, called _matu_, are deposited in a piece of cloth which each picker carries, and are then spread out in the drying yard, called _matu-caucha_, and carefully dried in the sun. The dried leaf is called _Coca_. The drying yard is formed of slate flags, called _pizarra_; and when the leaves are thoroughly dry, they are sewn up in _cestos_, or sacks, made of banana leaves, of 20 lbs. each, strengthened by an exterior covering of _bayeta_, or cloth.[139] They are also packed in _tambores_ of 50 lbs. each, pressed tightly down. Dr. Poeppig (writing in 1827-32) reckoned the profits of a Coca farm to be forty-five per cent. The harvest is greatest in a hot moist situation; but the leaf generally considered the best flavoured by consumers, grows in drier parts, on the sides of hills. The greatest care is required in the drying; for too much sun causes the leaves to dry up and lose their flavour, while, if packed up moist, they become fetid. They are generally exposed to the sun in thin layers.