The following information is about “Growing YAM”.
The most important food crop grown in the tropical climates is Yam. The Yam is the chief source of calories for the population in tropical and sub-tropical regions. There many nutrients, proteins and micronutrients in it. The Yams have multiple species, around 600 species approximately. These Yams are grown in Africa, Asia, South American region, the Caribbean and also in the islands of the South Pacific. The Yam is scientifically named as Dioscorea spp. The Yam belongs to Dioscoreaceae family. Yams are often confused with the sweet potato and Ipomoea batatas. The plants of Yam are referred to herbaceous annual and perennial crops that are often climbers or vines. The vines are mostly smooth or prickly; the vine reaches up to 10 m of height and also depends on the variety. The tubers are in purple, brown, gray, black, and pink, white, and orange.
They first originated in South Africa. Artifacts have dated that the first origin of the Yams was during the late 50,000 BC, in West Africa. Each and every species has its own taste and colour. So taste sweet and some tastes bitter. Mostly the Yam is fried, roasted or baked before consumption.
Characteristics of Yam:
- The genus of Yam is a perennial climber having tuberous roots.
- The plant stem grows in a spiral way.
- The tuber and bulblets are produced from the plant; these arise from the leaf axils. In these tubers rich carbohydrates are present, which gives the plant strength to survive in all types of climate. Each tuber weighs 5-10 kg.
- They contain white flesh, yellow flesh or purple flesh, and it completely depends on the variety.
- The leaves are large typically; they are heart shaped and bright green in colour. Due to the anthocyanins content the leaves may be sometimes purple.
- The plant has both male and female flowers. The blooming of the flowers takes place at irregular times. This makes the process of pollination difficult and also causes low yield.
Properties of Yam:
- The energy present in Yam is 494 kcal
- Yam has carbohydrates of 27.9 g
- Fat content in Yam is 0.17 g
- The protein content in it is 1.5 g
- The vitamins present in Yam are Vitamin B6, Folate B9, Vitamin C, Vitamin E and Vitamin K.
- The Yam contains these minerals; Magnesium, Iron, Calcium, Manganese, Phosphorous, Potassium and Zinc.
Cultivars/varieties of Growing Yam:
- Black bryony
- White Yam
- Purple Yam
- Wild Yam
- Air potato
- Chinese Yam
- Yellow Yam
- Bitter Yam
Soil and climate requirements for Growing Yam:
The soil preferred for Growing Yams is rich red loamy soil with well drained conditions. The soil should be sandy, but too clayey soils do not suit Yam cultivation. It is a tropical as well as subtropical plant. It needs a pH range of 5.5-7.0.
During the vegetative phase it needs distributive rainfall, humid and warm weather, during the corm development period the crop needs cool and dry weather. The Yam needs sunlight for growth. The temperature, which is required for Growing Yams is 18˚C – 34˚C. These tropical plants cannot tolerate frost. The annual rainfall, which is required for Growing Yams is 1200 mm – 1300 mm. They are also found to grow well at altitudes of 800 m above sea level.
Land preparation and planting for Growing Yam:
The soil should be brought to fine tilth and preparation of good and convenient size beds for sowing the seeds is needed. The dormancy period lasts for 45-60 days. The seed starts sprouting with the help of pre-monsoon rain, the transplantation of the seedlings should be done in the months of April – May.
Propagation method for Growing Yam:
The propagation of Yam is done by the transplantation of rhizomes. From the prior plantation, small Yams weighing less than 2 kg are selected. Until the planting time, they should be stored in a dry ventilated place. The rhizomes are planted directly by cutting them into small pieces of 100-150 g. Before planting, the rhizomes are treated with disinfectant solution so as to protect them from diseases and rots. Before the plantation of the tuber the soil should be ploughed to aerate it. Preferably, the planting should be done before the rainy season in the months of April, May and June. The harvesting of this crop takes place during November, December and January.
Manure and fertilization method in Growing Yam:
Before planting, the land should be supplied with farmyard manure @ 25 tonnes per hectare during the last ploughing. The fertilizer should also be supplied to the land in the form of N: P: K mixture in the ratio of 40:60:50 kg per hectare. It should be applied after 45 days of planting during the weeding and intercultural methods. After some time, the N: K should be re-applied in the ratio of 40:50.
Irrigation methods in Growing Yam:
Throughout the growing season, Yam plants need water regularly. The indirect form of irrigation is also needed for the Yam plants. The mounds of the soil should be kept moist most of the time. The foliage of the Yam should not be watered while irrigating the plants. As the climate gets warmer they should be watered more than once a day. The plant leaves are the best indicators of good and bad irrigation. If there is a good water supply the leaves look green and healthy. In case of less watering the leaves look wilted and dull.
Intercultural methods in Growing Yam:
Weed control: The only method of weed control is mulching the soil with wheat straw at the base of the plant. Mulching prevents loss of water, crust formation, controls weeds, improves humus content and also allows water penetration into the soil.
Intercropping: Intercropping cowpea with Yam is suitable and is most recommended. The Yams are profitably intercropped with other crops like bananas, coconuts, rubber, Areca nut and robusta coffee plants at the spacing of 90 x 90 cm between each plant. Farmyard manure of 12.5 tonnes per hectare should be applied and 1/3 of the N: P: K i.e. 27:20:33 is more than sufficient to the intercrop plants.
Control of Plant Development: The excessive plant growth should also be controlled by cutting the tips and some branches. This encourages the growth of tubers.
Thinning: The plant shouldn’t produce at only one place it should produce through the entire tree, so this thinning is performed by removing the elements which grow together in close circuits and block the development of the plant.
Pest and diseases control measures in Growing Yam:
The pests infesting the Yam plants are Dry rot, Root knot nematode, Mealy bugs, and white scale disease.
Control for the pest:
- The tubers should be treated with hot water for a 40°C min before sowing and also after harvesting. This helps reduce the pests and disease occurrence in the field and at the storage area.
- Practicing crop rotation with groundnut and maize the pests can be controlled.
- The pests can be controlled by the natural methods or by chemical pesticides.
The diseases occurring in the Yams are Anthracnose, Yam mosaic diseases.
Control of diseases:
- The intensity of the anthrocnose is controlled by applying TDA 291 or TDA 297.
- By selecting large tubers for planting it may help in controlling the Yam mosaic diseases.
Harvesting techniques in Growing Yam:
After 7-12 months of planting, the wilting of the aerial parts of the plant indicates maturity. The stems of the plants are slightly turgid and the leaves turn brownish in colour. The distal parts of the tuber also turn into brown colour. It is a symbol for harvesting the crop.
Post harvesting techniques in Growing Yam:
The Yam is graded according to the uniformity like size, shape, colour and also on the appearance of the Yam. When Yams are over matured, they get injured. The entire Yam, which are mostly preferred in the markets look small and medium in size.
Storage: The storage of the Yam should be at low temperatures as it reduces the respiration rate of Yams. The temperature should never be less than the 12˚C as it causes a breakdown in the internal tissues, water loss increases and eventually the Yams start decaying. The best temperature for the Yams is between 14˚C-16˚C.
Marketing: Yam market value is determined by their size, shape, weight and maturity. There should be lack of blemishes and decay. In supermarkets the Yam is sold as sections or as a whole fruit. Some varieties are marketed only when they are completely ripe.
Yield in Growing Yam:
The average yield of the Yam is about 30-35 tonnes per hectare in a year.
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