Introduction
Vegetable amaranth (Amaranthus spp.) known as chaulai in Hindi, is a very nutritive and highly suitable crop both for kitchen gardening and commercial cultivation. It is the most common leafy vegetable grown during the summer and rainy seasons in India. It fits well in a crop rotation because of its adaptability to a wide range of climate and soil conditions, rapid growth, quick rejuvenation after each harvest, and high yield of edible matter/area in a limited time. It is often described as a poor man’s leafy vegetable because of its low price and high nutritive value. The leaves and tender stems of amaranth are rich in protein, minerals like calcium, iron, zinc, copper, manganese, potassium, and vitamins such as vitamin A (carotene), vitamin C, folic acid, thiamine, niacin, and riboflavin. Leaves and succulent stems are good sources of iron (38.5 mg/100g), calcium (350-400 mg/100g), vitamin A and vitamin C. High oxalate content (1-2%) and nitrate (1.8-8.8 g/kg dry matter) levels are reported from leaves of various species. The crude protein content in the leaves ranges from 20-32% on a dry weight basis. It is reported that in children the incidence of blindness due to poor nutrition can be reduced with daily consumption of 50-100 g of amaranth leaves.
The genus Amaranthus has species that are used for grain, vegetable, and ornamental purposes. Amaranth is widely grown as a leafy vegetable in Southeast Asian countries especially Malaysia, Indonesia, southern China, and the hot and humid regions of Africa.
Table of Contents (toc)
Climate and soil
Vegetable amaranth grows well within a temperature range of 22-33°C. A minimum temperature of 15-17°C is required for seed germination. Amaranth is a C-4 plant that can make efficient use of CO₂ and suppresses its photorespiratory loss. The plant also grows better under adverse environmental conditions. It can photosynthesize at high rates even under high temperatures. Hence, it is grown successfully in the hot summer and humid conditions of Kharif. It can tolerate periods of drought after the plant has become established. Amaranth can be grown on a wide variety of soils. However, sandy loam soil with good water-holding capacity is best suited for its successful cultivation. Soil should be prepared well by 2-3 repeated ploughing. Amaranth can tolerate a soil pH from 4.5-8 with 6.5-7.0 being optimum. Amaranthus tricolor is relatively salt tolerant.
Varieties
Vegetable amaranth varieties come in various leaf colors such as white (light green), dark green, red, purple, and variegated. The choice of variety is influenced by an individual preference for leaf color, quality, and taste. Amaranth genotypes are available which bolt only under short-day conditions and can be grown as multi-cut types if planted very early, taking into consideration the day length of the locality at a specific month. Important varieties developed through mass selection, polyploidy breeding, and hybridization are discussed here.
Arka Arunima: Developed at IIHR, Bengaluru. It is a multi-cut variety and about 3 cuttings can be taken without the stem being fibrous. broad, succulent, and purple leaves with white rust resistance under field conditions. It yields 13-15 tonnes/ha by pulling and 26-28 tonnes/ha in 3 cuttings. It has low oxalate and nitrate contents, which are the antinutrient factors in leafy vegetables.
Arka Samraksha: Developed at IIHR, Bengaluru. It is a pulling type of amaranth variety with green leaves and stems. It yields 10.9 tonnes/ha in 30-35 days duration. The variety has an antioxidant activity of 500 mg (AEAC units) and minimum nitrate content of 27.3 mg and 1.3 g of oxalates per 100 g fresh weight of leaves.
Arka Suguna: Developed at IIHR, Bengaluru. It is a pure line selection from an exotic collection procured from Taiwan (IIHR 13560). It is a multi-cut variety and 8 cuttings can be taken without the stem being fibrous. It has broad light green foliage and a succulent stem. It comes to first cutting in 25-30 days after sowing and 5-6 cuts can be taken in 90-100 days. It yields 25-30 tonnes/ha.
Arka Varna: Developed at IIHR, Bengaluru. It is a pulling type amaranth variety with green leaves and pink stem, yields 10.6 tonnes/ha in 30-35 days duration. This variety has a high antioxidant activity of 417 mg (AEAC units), nitrate content of 37.6 mg, and 1.4 g of oxalates per 100 g fresh weight of leaves.
Arun: A mass selection from Palapoor local, its leaves are of deep red color. High-yielding variety. Average yield 20 tonnes/ha.
Badi Chaulai: Developed at IARI, New Delhi, it is quick-growing with green leaves and is suitable for growing both in summer and Kharif in plains. The leaves and stems are green and big in size.
Chhoti Chaulai (A. blitum):Developed at IARI, New Delhi, plants are erect, thin, and dwarf. It is suitable for its leafy shoots. Leaves are small-sized and green. It is low-yielding and suitable for kitchen and container gardening. Flowers are born in clusters in leaf axils. It is best suited for early summer and can be grown in Kharif also.
CO 1 (A. dubius): Developed at TNAU, Coimbatore, it is grown mainly for tender greens as well as immature stems which are thick and fleshy. Leaves are dark green, thick, broad with the ridged surface, the stem is round, glossy green, and succulent. It yields 8 tonnes/ha in 25-30 days after sowing. It takes 50-60 days for immature stem harvest. It flowers in 50-60 days and matures in 90-95 days.
CO 2 (A. tricolor): Developed at TNAU, Coimbatore, its leaves are long, green, and lanceolate. The plants are erect with moderate branching. The stem is green, suited for tender greens. Its green becomes ready for picking 20-25 days after sowing, the yield being 13 tonnes/ha. Immature stems are harvested 35-50 days after sowing. The inflorescence is green, terminal, and unbranched with small flower clusters in the leaf axil. It flowers in 40-45 days and matures in 85-90 days.
CO 3 (A. tristis): Developed at TNAU, Coimbatore, it is suitable for periodical cutting and can be retained for more than 3 months. It becomes ready for picking 20 days after sowing and thereafter at weekly intervals. It yields as high as 30 tonnes/ha of greens. The leaf to stem ratio is high (2.0). Unclipped plants flower in 35 40 days and mature 85-90 days after sowing. Leaves are highly palatable. The plants are erect with green nutritious leaves.
CO 5 (A. tricolor): Developed at TNAU, Coimbatore, the plants are medium in height with high biomass and nutritive value. Leaves are of double color i.e. green and pink and free from the fiber. The leaves are large obovate. It gives a rosette growth in the early stages and the first harvest is possible in 25 days. Leaf yield is 40 tonnes/ha in 55 days.
Krishnasree: A red amaranth evolved through selection, it is high yielding (14.8 tonnes/ha) with high nutritive value and low anti-nutritional factors.
Mohini: A high-yielding variety. Leaves are green.
Pusa Kiran (A. tricolor):Developed at IARI, New Delhi, its leaves are glossy green with broad ovate lamina. The lamina is 7-9 cm long and 6-7 cm wide. The petiole is 5.5-6.5 cm long. The stem is glossy green. It is suitable for Kharif. It becomes ready for first picking 21-25 days after sowing. The duration of harvest is 70 to 75 days. It takes 95-100 days to flower and the yield is 35 tonnes/ha.
Pusa Kirti (A. tricolor): Developed at IARI, New Delhi, it is recommended for commercial cultivation in summer. The leaves of Pusa Kirti are green with broad ovate lamina 6-8 cm long and 4-5 cm wide. The petiole is 3-4 cm long. It is ready for first picking 30-35 days after sowing. Its subsequent cutting may be taken at 10-12 days intervals, the yield being 50-55 tonnes/ha.
Pusa Lal Chaulai (A. tricolor):Developed at Indian Agricultural Research Institute, New Delhi, it is suitable for kitchen gardening as well as for commercial cultivation in northern plains. It is suitable for growing in both the summer and rainy seasons. On average, it yields, 45-50 tonnes/ha. Since the color of stem and leaves is bright red (magenta), it is suitable for ornamental purposes also. The red dye extracted from its plants could be used as a natural food additive. The dye can also be used in the textile and woolen industries.
Renusree: A green amaranth evolved through selection, it is high yielding variety (15.5 tonnes/ha) having green leaves and purple stem with low anti-nutritional factors.
RNA 1 (A. tricolor): Developed at Acharya N.G. Ranga Agricultural University, Hyderabad, it is a pulling type with thick stem and broad green leaves.
Utkal Cheka Leutia (A. tricolor):Developed at Odisha University of Agriculture and Technology, Bhubaneshwar, plants are dwarf and spreading type. The average height is 18.4 cm, the first harvest is 37 days after sowing. The leaf is green and small. It is suitable for both summer and Kharif. The average weight of 10 plants is 65 g.
Utkal Mayuri (A. tricolor):Developed at Odisha University of Agriculture and Technology, Bhubaneshwar, its plants are medium in stature and highly branched. Leaves are multicolor with a green and pink border. It is suitable for both summer and Kharif. Each plant weighs up to 570-925 g.
Cultivation
Sowing
Amaranth requires thorough land preparation and well-prepared soil for good growth. Amaranth should be sown during mid-March for the summer crop and mid-July for the Kharif crop. It is planted either by direct seeding or transplanting depending on the availability of seed, labor, and growing season. About 1.5-2.0 kg seed is enough for 1 ha.
Since seeds are very small, these should be mixed well with sand (1 g seed in 100 g sand) and sown in rows at 1 cm depth at a spacing of 30 cm. In some areas, seeds are also uniformly broadcast at a rate of 0.5-1.0 g/ m² of bed. Cover seeds lightly with a layer of compost immediately after broadcasting or line sowing. After sowing, light irrigation is essential for ensuring good germination. Seedlings 2-3 cm long are thinned out to a spacing of 3-4 cm.
For transplanting, seedlings can be raised in plug trays, lifted with intact rootballs and planted in well-prepared beds. Alternately, seedlings are grown in a raised nursery seedbed on which seeds are either lightly broadcast or sown in line and covered with soil. Cover the seedbeds with an insect-proof net to protect seedlings from insect pests. Three-week-old seedlings are pulled and planted in the afternoon or on a cloudy day to minimize transplanting shock. Make 10 cm deep holes on the bed, place each seedling, cover the roots with soil and lightly press the soil at the root zone for ensuring proper establishment. Irrigate immediately after transplanting to establish good root-to-soil contact.
Manures and fertilizers
A dose of well-rotted farmyard manure @10-25 tonnes/ha should be incorporated at the time of field preparation. Application of 150 kg single super phosphate and 80 100 kg potassium sulphate/ha is also recommended at the time of land preparation. A dose of 75-90 kg/ha of urea should be top-dressed in three split doses. The first dose should be applied 15-20 days after sowing, whereas the second and third after first and second cuttings.
Seed inoculation with Azotobacter, combined application of vermicompost and chemical fertilizers reported higher yield in vegetable amaranth. Under the pulling out method, 20 kg N should be top-dressed twice during subsequent pulling out of seedlings. Foliar spray of 1% urea or diluted cow urine at every harvest is good for promoting further growth and for high yield.
Irrigation
Since amaranth is grown as a short-duration crop, it requires plenty of water for growth and high yield. Though it is relatively drought-tolerant, insufficient water will reduce yield. Irrigate just after sowing or transplanting to ensure a good stand. In summer, frequent irrigation is required at 4-6 days intervals. Similarly, in Kharif, irrigation is scheduled as per the moisture content of the soil. Drip irrigation is recommended in areas with a limited water supply and has high water-use efficiency.
Weeds compete for light, water, and nutrients and reduce the yield of amaranth. One or two weedings or hoeings are sufficient for controlling weeds. Hoeing between the rows not only checks eds but also reduces the number of irrigation. In transplanted or line seeded crops, mulching is recommended as it conserves soil moisture, and reduces weed competition, soil compaction, and erosion. Mulching is done after the seedlings reach a height of 10 to 15 cm.
Seed production
The agro techniques for seed production are normally similar to those for leaf production. For seed crops, the plants should be maintained generally at 30 cm x 30 cm spacing. For tetraploid varieties, plant spacing should be kept at 45 cm x 30 cm. The fertilizer schedule of 50 kg each of N and P and 30 kg K/ha is recommended for better yield. In addition, spraying of micro-nutrients at the rate of 400 g/ha once in 10 days from first flowering increases the yield and quality of seed. The high alkalinity of the soil affects the seed quality.
Since vegetable amaranth is cross-pollinated by wind, an isolation distance of about 400 m is required between two cultivars and wild Amaranth species for foundation seed and 200 m for certified seed production. Generally, the crop that is used for leaf production is not used for seed production. Roguing off-types is highly essential at different stages of crop growth.
Harvesting of seeds starts when the plants turn yellow or deep brown in color and when the glumes turn brown in color and seeds turn black. Drying of the inflorescence is practiced in the sun while the sample seeds contain less than 15% moisture. Seeds are threshed with pliable bamboo sticks, cleaned by winnowing, and strained through a 2 mm sieve. Dried seeds with 6% moisture content are stored after treating with Bavistin @2 g/kg seeds. Seed yield ranges from 400 kg to 1,000 kg/ha depending on the variety. The viability of the seeds can be maintained up to 10 months in ordinary containers and over 18 months in moisture-proof 700 gauge polythene bags or polythene laminated aluminum foil bags.
Disease and pests
Alternaria leaf spot (Alternaria tenuissima): Dark brown to black, circular to oval, necrotic lesions of <1 mm to 7 mm diameter appear on the leaves.
Cercospora leaf spot (Cercospora sp.): Numerous small brown circular spots appear on the leaves which in the beginning are small, roundish with concentric rings but later increase in size and coalesce.
Leaf spot (Colletotrichum capsici): Small chlorotic spots of 2 to 5 mm appear on leaves that later turn brown, surrounded by a yellow halo. As the disease advances, the spot enlarges and becomes papery white with a distinct brown margin.
White rust (Albugo bliti): White, blister-like circular or irregular pustules appear on the lower surface of the leaf. A yellow patch develops opposite each pustule on the upper surface of the leaf. This disease is serious, especially during Kharif.
The important pests that attack the plant are described here.
Aphids (Aphis spp.): Aphids suck the plant sap, causing leaves to curl and become unattractive. Heavily infested plants have wrinkled leaves, stunted growth, and deformed seeds. Young plants may dry out and die.
Bugs (Lygus spp.): The lygus bug sucks juice from flowers and seeds, thus preventing flowers from producing seeds and reduces seed weight in the seed crop of vegetable amaranth.
Cutworms (Spodoptera frugiperda):Caterpillar of cutworms cut through the stem of young plants just above ground level and cause plants to wilt and die.
Leafminer (Liriomyza spp.):Maggots of leafminers make long, slender, white mines (tunnels) in leaves that may turn yellow and drop. Heavily attacked seedlings are stunted and may die.
Spider mites (Tetranychus spp., Mononychellus spp., and Oligonychus spp.): Spider mites feed on plants and cause a reduction in plant growth, flowering, and number of seeds. Damage is most severe, particularly during the dry season.
Weevils (Hypolixus haerens):Adult weevils feed on leaves and the larvae (grubs) bore into roots and stems, causing rotting and potentially lodging and predisposition to diseases. The larvae bore through stems to the root collar hollowing the stems, making the stems more susceptible to wind breakage. The larvae pupate in the stem.
Harvesting and post-harvest management
The young amaranth seedlings grown for commercial purposes are often uprooted when they are 8-10 cm tall (3-4 weeks after sowing). Whole plants are pulled from the soil with roots, washed, and tied in bundles. In the case of multiple harvests, the first cutting can be made 3 weeks after sowing. Subsequent 4-5 cuttings are made at 10-15 days intervals depending upon the vegetative growth. If inorganic pesticides are used, the minimum waiting period for harvesting the crop should be 10 days. Application of paclobutrazol at 80 ppm and at 100-120 ppm is reported to increase the number of branches, leaf stem ratio, leaf and seed yield, and ascorbic acid content; and resulted in early harvesting. Amaranth grown for seed is not usually harvested for greens. Seed plants are cut when mature and seed can be rubbed from the inflorescence and then removed by drying and threshing. These seeds may be separated from the chaff with fine screens and if necessary, by winnowing. The yield of gross products (total biomass) varies from 10-50 tonnes/ha depending on varieties.
The leaves lose water rapidly during storage, particularly at higher temperatures resulting in rapid wilting, a decrease in chlorophyll, ascorbic acid, and soluble protein content, and an increase in amino acid content. Hence, harvest during the cooler time of days, such as early morning or late afternoon. It can be stored for 6 days at 24-28°C temperature. Packaging of amaranth leaves in low-density polyethylene bags improves its shelf-life and nutritive value.
Value-addition
Amaranth leaf powder supplemented products are a very good source of protein, fiber, calcium, and iron and may contribute to improving the nutritional status of the poor. Black and green teas prepared with leaves of amaranth are reported to have prophylactic and therapeutic use. The red and yellow color extracted from colored varieties could be used as a natural food additive. The red and yellow dye can be used in the textile and woolen industry for dyeing purposes as the amaranth color does not fade easily.
