General Information and Agronomic Aspects
While originating from tropical America amaranth is now very widely distributed throughout the tropics.
Amaranth is an herbaceous annual belonging to the family Amaranthaceae with green or red leaves and branched flower stalks (heads) bearing small seeds, variable in colour from cream to gold and pink to shiny black. There are about 60 species of Amaranthus, however, only a limited number are of the cultivated types, while most are considered weedy species and hence rarely preserved. Many amaranth species are collected from the wild for subsistence, while only few are cultivated or occur as protected weeds in backyards and home gardens (Stallknecht and Schulz-Schaeffer, 1993; Ouma ; Biovision TTU, ICIPE: Keller, 2004).
Amaranth can be used as a high-protein grain or as a leafy vegetable. The seeds are eaten as a cereal grain. They are ground into flour, popped like popcorn or cooked into porridge. The seeds can be germinated into nutritious sprouts (GFU for Underutilized Species). The leaves are cooked alone or combined with other local vegetables such as spider plant and pumpkins. The leaves are rich in calcium, iron and vitamins A, B and C, but fairly low in carbohydrates (Ouma, Biovision TTU, ICIPE.). There is no distinct separation between the vegetable and grain type since the leaves of young grain type plants can be eaten as greens (Stallknecht and Schulz-Schaeffer, 1993).
Of all the indigenous tropical leafy vegetables, amaranth has the largest number of species and varieties. The choice of variety varies widely among regions and is dictated largely by the species available. Regardless of species, the choice of variety is influenced by individual preference for leaf colour and taste. Some of the most common commercial amaranths are selections of A. tricolor which come in various leaf colours such as white (light green), dark green, red, purple and variegated. To identify which varieties are best adapted to your location, compare during different growing seasons the yield potential of currently grown varieties with that of other available varieties (AVRDC 2003).
Nutritive Value per 100 g of edible Portion
|Raw or Cooked Grain||Food Energy(Calories / % Daily Value*)||Carbohydrates(g / %DV)||Fat(g / %DV)||Protein(g / %DV)||Calcium(g / %DV)||Phosphorus(mg / %DV)||Iron(mg / %DV)||Potassium(mg / %DV)|
|Amaranth grain cooked||102 / 5%||18.7 / 6%||1.6 / 2%||3.8 / 8%||47.0 / 5%||148 / 15%||2.1 / 12%||135 / 4%|
|Raw or Cooked Grain||Vitamin A(mg / %DV)||Vitamin C(mg / %DV)||Vitamin B6(mg / %DV)||Vitamin B12(mg / %DV)||Thiamine(mg / %DV)||Riboflavin(mg / %DV)||Ash(g / %DV)|
|Amaranth grain cooked||-||-||0.1 / 6%||-||0.0 / 1%||0.0 / 1%||0.8|
Amaranth grows from sea level to 2400 m altitude. The different species may suit different altitudes. Normally the hotter it is the better it grows and it generally thrives within a temperature range of 22 - 30°C. A minimum temperature of 15 -17°C is needed for seed germination. Amaranth is grown during both wet and dry seasons, though irrigation is normally required for dry season crops since the rate of transpiration by the leaves is fairly high. Frequent applications of water are required, related to the stage of growth of the crop and the moisture-retaining capacity of the soil. It can however tolerate periods of drought after the plant has become established. It is adapted to low to medium humidity (Bruce French, EcoPort).
Amaranth grows best in loam or silty-loam soils with good water-holding capacity, but it can grow on a wide range of soil types and soil moisture levels. Amaranth can tolerate a soil pH from 4.5 to 8. (AVRDC 2003).
Amaranth requires thorough land preparation and a well-prepared bed for good growth. Prepare 20 cm high beds during the dry season and 30 cm during the wet season using a plough. The distance between centres of adjacent furrows should be about 150 cm with a 90 cm bed top. Amaranth is planted either by direct seeding or transplanting. The choice of planting method depends on availability of seed and labour and may also vary with the growing season. Direct seeding is appropriate when plenty of seed is available, labour is limited, and during the dry season when frequency of flooding is less. Transplanting is preferred when there is limited amount of seed, plenty of labour, and during the wet season when heavy rains and flooding are most likely to wash out seeds. Raising seedlings in a nursery and transplanting them to the field shorten the crop duration in the field, and secure a better and more uniform stand especially during the wet season.
Direct seeding When direct seeding is used, seeds are either broadcasted or sown in rows. Broadcast seeds uniformly at the rate of 0.5 to 1.0 g/m2 of bed. Since amaranth seeds are very small, mixing seeds with sand at a ratio of 1 g seed to 100 g sand makes it easier to sow the seed and to obtain a uniform stand. Cover seed lightly with a layer of compost or rice hulls immediately after broadcasting. When plants are to be grown in rows make furrows 0.5 to1.0 cm deep and space rows 10 cm apart on the bed. Sow seeds 5 cm apart within the row and cover with a layer of compost or rice hulls. (AVRDC 2003)
There are two steps to transplanting:
1. Seedling production. Seedlings are grown in a seedbed, pulled and bare-root transplanted. They can also be grown in divided trays, lifted with the root ball intact and transplanted. If seedlings are started in a raised soil bed, the soil should be partially sterilised by burning a 3-5 cm thick layer of rice straw or other dry organic matter on the bed. This also adds minor amounts of phosphorus (P) and potassium (K) to the soil, which helps in the establishment of the seedlings. Broadcast the seeds lightly in a seedbed and cover them with soil. The seeds should be one 1cm deep. Cover the seedbeds with an insect-proof net to protect seedlings from pests.
2. Setting plants into the field. Transplant in the late afternoon or on a cloudy day to minimise transplant shock. Dig holes 10 cm deep on the bed using recommended spacing for the chosen variety. Place each transplant in its hole and cover the roots with soil and lightly firm. Irrigate immediately after transplanting to establish good root-to-soil contact.
Amaranth is a low management crop and can grow in poor soils, but it will benefit from application of organic fertiliser resulting in higher yield. Although amaranth is relatively drought tolerant, yet insufficient water will reduce yield. Water should be applied especially just after sowing or transplanting to ensure a good stand. As a rule, the plants should be irrigated if wilting occurs at noon. Another way to estimate soil moisture content is to take a handful of soil from the bottom of a 15 cm hole. Squeeze the soil. If it holds together when you release your grip, there is sufficient soil moisture; if the soil crumbles, it is time to irrigate. Irrigate thoroughly to maintain vigorous plant growth. Avoid over-irrigation, which may enhance disease development and nutrient leaching. Drip irrigation or micro-sprinkler irrigation is recommended in areas with limited water supply (AVRDC 2003)
First harvest is at a plant height of 30 cm, about 6 weeks after transplanting. Plants may be harvested at once or leaves and tender shoots maybe harvested several times. One single harvesting is adapted for short maturing and quick growing varieties such as A. tricolor. Whole plants are pulled from soil with roots, washed and tied in bundles. With multiple harvests, young leaves and tender shoots are picked at 2 to 3 week intervals. Eventually, the plants begin to flower and develop fewer leaves. Frequent harvesting of leaves and shoots delays the onset of flowering and thus prolongs the harvest period.
Amaranth and other leafy vegetables have a large surface and loose water rapidly. To reduce water loss, harvest during the cooler time of day, such as early morning or late afternoon.
Fresh Quality Specifications for the Market in Kenya
|© S. Kahumbu, Kenya|