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3 Production PLANTING Amaranths are usually seeded directly into the field. On rare occasion, vegetable amaranths are transplanted to the field as seedlings when they reach the stage of bearing four true leaves. Seeding density depends on the method of harvest anticipated. Preliminary density trials indicate that, for many Amaranthus hypochondriacus and Ama- ranthus cruentus cultivars, 320,000 plants per hectare is an acceptable density for yield as well as for stand management. Vegetable amaranths are often grown with densities up to 100 plants per m2. Seedbeds should be of good tilth, well drained, and fairly level to help prevent rain from washing away the tiny seeds or seedlings. Seeds must be planted no more than 1 cm deep, and the seedbeds must have fine soil without large clods. Rain falling on this type of seedbed can cause the soil to form a crust that inhibits germination. CULTIVATION Once the stand is established, maintenance is relatively easy. The broad leaves and erect habit quickly create a closed canopy, making understory weeds only a minor problem under most conditions. Grain amaranths can be mechanically weeded until the canopy closes. Most types of grain amaranth mature in 4-5 months. They mature more quickly in monsoonal areas. However, in some highland regions maturing may take as long as 10 months. HARVESTING A few varieties selected in Pennsylvania are now sufficiently uniform to be machine harvested, but most are not. The main difficulty in mechanical harvesting is that the central flower head matures and dries out while the numerous inflorescences on lower side branches are still moist. High-density planting modifies plant structure to a point where 18
PRODUCTION 19 Field of maturing amaranth, Emmaus, Pa. (Rodale Press, Inc.) a single seedhead is formed, and this makes mechanical harvest more efficient. Selection and breeding of new varieties that are adapted to mechanical harvest is now in progress. To avoid the problem of nonuniform maturity, the grain amaranth now produced in Latin America and South Asia is hand harvested. It is then dried in the sun and threshed and winnowed by hand. The small seed size makes cleaning awkward. However, winnowing is not too difficult, since the seed is heavier than the chaff.
1 Amaranth farmers, traditional and modern. 1. Northern India (M. Pal); 2. Bhutan (R.P. Croston, 1BPGR); 3. the high Andes of Peru (C.S. Kauffman); 4. Kansas, USA (Rodale Press, Inc.); and 5. Mexico (L. Feine).
22 AMARANTH PESTS Insect problems are not well documented. In Pennsylvania the lygus bug (Lygus lineolaris) has severely damaged grain amaranth yields by piercing the developing seed and sucking out the juices. Amaranthus cruentus (white-seeded types) seem more susceptible to damage than Amaranthus hypochondriacus. Leaf-miners have also been found on both grain and vegetable amaranth. In Lucknow, India, serious damage to both grain and vegetable types has often been caused by spider mites. In India the stem weevil (Lixus truncatulus) is a major pest of amaranth; its grubs damage foliage and roots and cause the plants to wilt. Leaf rotters (Hymenia recurvalis) also cause considerable damage during rainy seasons. Seedbeds should be guarded against ants and termites, which often carry away all the seeds. DISEASES More study is needed of diseases on both vegetable- and grain-type amaranths. The soil fungus Alternaria alternantherae causes much leaf damage and drastically reduces plant vigor. However, only Amaranthus caudatus has so far proved susceptible to this disease in Pennsylvania. A similar blight disease of leaves and flowers, caused by Alternaria amaranthi (Peck.), has been reported on Amaranthus hypochondriacus in India. White rust, caused by Albiyo bliti, in which white pustules on the underside of the leaves reduce the market appeal of vegetable amaranth, is also common in South India. There is evidence that a foliar disease (or perhaps air pollution) affects Amaranthus cruentus in the United States. Leaf and stem diseases caused by mycoplasms have been identified in Peru, and great differences in susceptibility between lines have been noted. Opposite Amaranth is a strikingly colored crop. Clockwise from top, Amaranthus caudatus, Amaranthus cruentus, Amaranthus hypochondriacus (all Rodale Press, Inc.), and an ornamental variety developed in India at the Lucknow Botanical Gardens for the brilliance of its leaves (T.N. Khoshoo). Overleaf Amaranth farmer and his crop in the uplands of western Nepal. (Â© Tony Hagen, courtesy National Geographic Society) Page 26 Amaranth seed is extremely small. It varies in color from black (vegetable type) to golden (grain type), and heating causes it to pop to form a light, white product (shown at the bottom). (Rodale Press, Inc.) The major promise of amaranth grain is its blends with cereals such as wheat. Incorporated into breads and other baked goods, amaranth flour improves their nutritional quality, particularly because it supplements the amino acids they lack. (Rodale Press, Inc.)
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