Yams are a tuber vegetable and member of the Dioscorea genus that originated in Africa and Asia. Yams are an essential crop in many tropical and subtropical regions. They serve as an important carbohydrate source and play a major role in food security for millions of people.
The origins of yam cultivation are linked to West Africa and Southeast Asia, where they have been farmed for over 60,000 years. Yams were later introduced to the Caribbean and South America through the transatlantic slave trade.
Today, over 95% of worldwide yam production comes from Africa. Nigeria is the largest producer, accounting for over 70% of the global yield, followed by Ghana, Ivory Coast, Togo, and Benin. Other top-producing regions include parts of Asia such as India and China.
Yam Varieties
There are over 600 varieties of yams, but some of the major types include:
1) White Yam: This variety has a cylindrical shape with white flesh. It has a drier texture than other yams. White yam grows well in tropical climates with sandy soil.
2) Yellow Yam: As the name suggests, this variety has yellow flesh. It is more moist and sweeter than white yam. Yellow yam thrives in loamy, well-drained soil.
3) Water Yam: The flesh of water yam is white and crispy. This variety prefers swampy areas and moist soil. Water yam tubers can weigh over 10 kg.
4) Chinese Yam: Chinese yam has a crunchy texture and is drier than other varieties. It is native to China and grows in colder climates. Chinese yam can tolerate partial shade.
5) Purple Yam: The flesh of purple yam is vibrant and sweet. It has excellent nutritional properties. Purple yam grows best in hot, humid environments.
6) Wild Yam: This variety is mainly found in forests and swamps. Wild yams are typically smaller than cultivated types. It contains a compound used to synthesize steroid hormones.
7) Greater Yam: Greater Yam can reach over 1 meter in length. It has brown, hairy skin and white flesh. This large variety requires plenty of space to grow.
The major differences between yam varieties come down to size, skin and flesh color, texture, taste, and ideal growing conditions. Selecting the right variety can help ensure a bountiful yam harvest.
Growing Yam Commercially
Yam can be a profitable crop for commercial farmers. Here are some key considerations for growing yam on a large scale:
1) Planting Yam
Yams are typically planted in the spring once the danger of frost has passed. The best time to plant is when soil temperatures reach 65-70°F.
2) Land Preparation
Yam requires loose, well-drained soil. The land should be thoroughly plowed and harrowed before planting. Prepare your soil well by mixing in several inches of compost or other organic matter. Yams prefer loose, well-draining, fertile soil.
3) Planting
Use high-quality, disease-free seed yams. Plant seed yams 6 -12 inches deep, with a spacing of 12 – 18 inches between plants. Staking the vines helps maximize growth and tuber production.
There are a few methods for planting yam tubers:
– Mound Method: Create mounds of soil 12-18 inches high and 2 feet apart. Place a few tuber pieces in each mound, 8-12 inches apart.
– Ridge Method: Till soil into ridges or raised rows 12-18 inches high and 3-4 feet apart. Plant tuber pieces every 12-18 inches along the ridge.
– Flat Method: Dig trenches 6 inches deep and 2-3 feet apart. Place tuber pieces in a trench 8-12 inches apart and cover with 2 inches of soil. As vines grow, continue mounding soil over vines.
Yam tubers are planted 2-6 inches deep depending on variety. Miniset tubers are planted shallower, while full-size tubers can be planted deeper. Plant each tuber piece flat with the cut side down. Space yams 8-12 inches apart.
Caring for Yam Plants
Yams require regular care and maintenance to grow successfully. Here are some key aspects of caring for yam plants:
#1. Watering Needs
Yam plants need consistent moisture, so water them regularly. Provide about 1-2 inches of water per week, adjusting for rainfall. Water at the base of the plants and avoid wetting the leaves. Yam thrives in moist, well-drained soil. Drought stress can result in poor growth and low yields. Ensure the soil stays moist but not waterlogged.
#2. Fertilizer Needs
Fertilize yams about 4-6 weeks after planting. Use a balanced fertilizer high in nitrogen and potassium. Work the fertilizer into the top few inches of soil around each plant. Reapply every 3-4 weeks during the growing season. Good fertilization helps yam plants grow vigorously and produce higher yields.
#3. Weeding
Weed control is important for yam plants. Weeds compete for water, nutrients, and sunlight. Stay on top of weeding, removing weeds by hand, or hoeing around yam plants. Create a weed-free area of at least 12 inches around each yam mound. Mulching after weeding helps suppress future weed growth.
#4. Pest Control
Scout regularly for pests like mites, nematodes, or yam beetles which can damage plants and tubers. Remove pests by hand or use organic sprays made from neem oil or insecticidal soap. Crop rotation with non-related crops helps prevent pest buildup in the soil over time.
Properly caring for yams by meeting their water, fertilizer, weeding, and pest control needs will support optimal growth and maximum yields.
Related: Use The Principles Of Crop Rotation To Control Crop Pests And Diseases
Harvesting Yam
Yams are ready for harvest 6-10 months after planting, depending on the variety. Harvesting generally takes place during the dry season.
There are a few ways to identify when your yam tubers are mature and ready for harvest:
– The vines start to turn yellow and die back. This is a sign that the yam tubers have reached full maturity.
– Try digging around the base of a few plants and gently feeling for tubers. Mature tubers will feel firm and full. Immature tubers will still feel small and soft.
– Check the size of the vines. Once they are large and fully developed, the tubers underground should be ready to harvest.
When you’re sure the yams are ready, use a spading fork, shovel, or hoe to carefully dig around each plant. Try not to damage the tubers as you dig them up. Gently lift the tubers from the soil and brush off any excess dirt.
Handle the tubers carefully to avoid cuts and bruises, which can lead to decay in storage. Damaged or bruised yams should be used right away. Healthy, undamaged tubers can be stored long-term or replanted for the next growing season.
Storing Harvested Yams
After harvesting yams, it’s important to cure them properly for storage. Curing involves leaving the yams in a warm, well-ventilated area for 2-3 weeks. This allows the skin to harden and any wounds to heal.
Proper storage conditions are crucial to preserve yams for several months. Ideal conditions are a temperature of around 60°F with high humidity of around 85%. The storage area should also have good ventilation. Avoid storing yams in the refrigerator, as temperatures below 55°F can damage them.
When stored properly, cured yams will typically last 4-6 months. Check on them periodically in storage and remove any that show signs of rotting. With the right curing and storage methods, you can enjoy homegrown yams for months after harvest.
Yam Pests and Diseases Control
Yam plants can be affected by various pests and diseases, which can reduce yields and quality. The main pests include:
– Nematodes: These tiny worm-like creatures attack the roots and tubers, causing galling, lesions, and rotting. Root-knot nematodes are the most problematic. Rotate crops, and resistant varieties, and apply nematode control products.
– White Grubs: The larvae of beetles feed on roots and tubers underground. Practice crop rotation and treat soil with appropriate insecticides before planting.
– Wireworms: The larval stage of click beetles that bore into roots and stems. Solarize soil before planting and apply appropriate insecticides.
– Yam Beetles: Adults and larvae of these beetles bore into tubers causing holes and tunnels. Remove crop debris, rotate crops, and apply insecticides.
– Rodents: Rats, mice, and squirrels dig up and feed on tubers. Use baits, traps, and barriers to control populations.
Major Yam diseases include:
– Anthracnose: A fungal disease causing leaf and stem lesions and rotting tubers. Improve drainage and avoid overhead irrigation. Apply appropriate fungicides.
– Yam mosaic virus: Causes mottling, stunting, and poor yields. Control aphids that transmit the virus. Uproot and destroy infected plants.
– Scab: A bacterial disease leading to corky lesions on tubers. Rotate crops and treat seed material.
– Soft rot: Bacterial infection causing wet rotting of tubers. Improve drainage and harvest tubers carefully.
Good prevention involves practicing crop rotation, removing debris, improving drainage, and using clean seed material. Protect healthy plants by applying insecticides and fungicides appropriately. Remove and destroy any infected plants.
Conclusion,
I hope you find this guide helpful in your journey of yam cultivation. Perhaps, if you need more clarification, you can drop your question in the comment box below.