The cause of the growth of yam deformity and its prevention
July 26 10:02:43, 2025
In the process of yam cultivation, various factors such as environmental conditions, farming practices, and management techniques can lead to structural changes in the tubers, resulting in deformed or irregular yams. These abnormalities not only affect the appearance but also the quality and marketability of the crop.
**1. Germplasm Factors**
(a) Influencing Factors: Most yam cultivation relies on yam sets (yam mouth) and cuttings. These planting materials are often grown in the soil for at least one year, making them prone to carrying pathogens like root-knot nematodes and diseases such as anthracnose and brown rot. During the hot and rainy season (June to July), these diseases can spread rapidly, leading to deformities in the yam tubers. Additionally, older yam sets (4–5 years old) are sometimes used due to their lower cost, even though they tend to age and mutate more easily, resulting in bifurcated or bent tubers.
(b) Preventive Measures: Soak yam sets or cuttings in mancozeb (500–800 times dilution) or carbendazim solution for 3–5 minutes before planting to reduce disease risk. It is advisable to use high-quality, young yam sets (1–2 years old) for better growth. Using thick yam sets (20–25 cm) helps promote strong vine growth and enhances disease resistance.
**2. Soil Factors**
(a) Influencing Factors: The quality of the soil plays a crucial role in yam development. Yams grown in black clay tend to have snake-like or tuber-shaped tubers with thick hairy roots, while those in sandy soils are often thin and underdeveloped. A shallow groundwater level can cause root rot, and continuous cropping leads to an accumulation of pests and root exudates, darkening the tuber skin and reducing quality.
(b) Preventive Measures: Rotate planting areas every three years to avoid soil depletion. Choose well-drained, deep loamy or sandy loam soils that are consistent in texture. Avoid planting in previously cultivated plots without proper soil management.
**3. Planting Factors**
(a) Influencing Factors: Shallow trenches can cause lateral growth of the tuber base, leading to foot-shaped or snake-like forms. Uneven soil in the trench may cause the tuber to bend or deform when encountering stones or hard soil. Improper placement of yam sets can result in multiple shoots, leading to multiple tubers and reduced quality.
(b) Preventive Measures: Dig trenches deep enough (1.3 meters or more) depending on the variety. Mix organic fertilizer into the top 20–30 cm of soil using a rotary plow three times for even distribution. Place yam cuttings and sets at a 45-degree angle to encourage strong apical growth and prevent unnecessary branching.
**4. Management Factors**
(a) Influencing Factors: Excessive rainfall or improper irrigation can create waterlogged conditions, causing tubers to bend or develop deformities. Insects like cockroaches and pests can damage the tubers or meristems, leading to blemishes or splits. Diseases such as root-knot nematodes and stalk rot further harm the plant and reduce yield quality.
(b) Preventive Measures: Ensure timely watering and drainage during rainy seasons to prevent trench collapse. Use fully decomposed organic fertilizer mixed with a small amount of trichlorfon to control pests and pathogens. Soak yam sets in carbendazim (500–800 times) before planting, and sprinkle a mixture of sand and trichlorfon in the planting trench. Apply thiophanate-methyl and mancozeb (500 times) every 15 days starting from June to prevent disease outbreaks.