Coffee Bean Cultivation
The coffee tree requires a stable environment. It cannot tolerate frost, nor can it survive prolonged periods of extremely high temperature. It requires at least 40 and preferably 70 or more inches (100 to 180 or more cm) of rain per year and it cannot survive drought. It is desirable to have heavy rainfall when the beans are developing, but light when they are ripening.
Arabica grows best at altitudes between 2,000 feet above sea level and the frost line, which is about 6,000 to 6,500 feet (600-2,000 meters). Robusta and liberica thrive between sea level and 2,000 feet (600 meters).
Coffee trees grow best in soils that are rich in potash and have good drainage. Some of the most productive trees are found on the slopes of extinct volcanoes. Organic debris, such as coffee pulp and manure, is preferred to commercial fertilizers.
Although trees may be propagated from cuttings or shoots, most are started from seeds. Cuttings are made from the upright branches and planted directly in the field or in nursery beds. Seeds are planted directly in the field or in seedbeds.
When sown directly, the seeds are planted in hills about 15 to 20 feet apart. The young plants are thinned to 8 or fewer plants per hill. If sown in seedbeds, the seedlings are transplanted after a few months to larger nursery beds. After a year or two, they are placed singly in the field. In some regions shade trees are used to shield the shorter coffee trees from direct sunlight. However, the need for shade trees has not been definitely established.
Coffee trees are usually pruned to 6 feet or slightly taller to expedite harvesting. The plantations must be weeded from 2 to 5 or more times per year. This is usually done by hand because of the hilly terrain, although mechanical weeders can be used where the ground is level. Insecticides and fungicides are sprayed on the trees to prevent damage by insects and diseases. Sometimes diseases can be controlled only by stripping the trees of their fruit and blossoms in the affected zones. The debris is then burned and the ground thoroughly raked.
The ripening season varies throughout the world, depending on local conditions of climate and altitude. In Sao Paulo, Brazil, harvesting continues from about May through September. In Java three crops are produced each year, requiring almost continuous harvesting. In Ethiopia the harvest extends through two periods, October through March and May through June. Harvesting is often a festive affair, involving whole families. Each member, with a basket slung over his shoulder, handpicks the ripened berries. Since only thoroughly ripened berries should be picked, harvesting is a selective process. It is difficult, therefore, to use mechanical harvesters.
Coffee Bean Processing
After the berries are harvested, the leaves, sticks, and other debris are removed. The berries are then prepared for market by either the wet or the dry method. Where water is scarce, the dry method is used. It consists of spreading the berries out in thin layers on flats to dry in the sun. The berries are raked and turned several times each day so that evaporation will be uniform. After about three weeks, the hulls are removed. On smaller plantations this is done by hand threshing and pounding; on larger estates, hulling machines are used.
In the wet method, the berries are soaked overnight in large tanks to soften the outer skins. Pulping machines remove the skins and pulp surrounding the beans. A fermentation process rids the beans of the gummy coating that clings to them. Then the beans are washed and dried.
The thin parchment-like covering and the silvery skin must be removed from the beans after hulling. This is done by polishing the beans in revolving cylinders, after which dust is removed by air blasting. The beans are then separated according to size by means of automatic sorters and inspected by hand. Broken or discolored beans are discarded.
The green coffee then is graded on the basis of quality, packed in bags, and transported to ports where coffee merchants blend varieties to meet market requirements.