Guangzhou Fuerle Health Technology Co., Ltd , https://www.fuerlegroup.com
Treating Rice Seedlings with Prescriptions
Rice seedlings, also known as "stuck seedlings," refer to a condition where the roots of transplanted rice plants become obstructed, leading to slow emergence of new leaves and tillers, stunted growth, clustered plant development, and dark green or red-brown spotted foliage. This phenomenon can occur due to various factors, including nutrient deficiencies, soil toxicity, cold damage, herbicide misuse, and pest infestations. A proper diagnosis is essential to determine the root cause and apply effective preventive or corrective measures.
1. **Zinc-deficient Seedlings**
These typically appear 2-4 weeks after transplanting, with peak symptoms around day 20. Affected plants show yellowish-white discoloration at the base of new leaves, while older leaves develop brown spots along the veins. The lower leaves may have dry tips, and the newly emerged leaves are short, narrow, and stunted. Farmers call this condition "shrinking seedlings." To address it, zinc sulfate (1–2 kg per acre) can be mixed into the soil, or a 0.2% solution (50–70 kg per acre) can be sprayed every 7–10 days, preferably in the morning or late afternoon.
2. **Potassium-deficient Seedlings**
Symptoms usually appear after the rice has turned green, peaking 20–30 days post-transplanting. Plants grow slowly, with dark green leaves and few tillers. Lower leaves develop yellow-brown or reddish streaks from tip to base, and severe cases may result in leaf margins drying and dying. To correct this, apply potassium chloride or potassium sulfate (10–20 kg per acre), or use 200 kg of wood ash. This helps restore plant vigor and promote root development.
3. **Phosphorus-deficient Seedlings**
New leaves appear dark green, while older leaves turn purplish-red. Leaves are small, erect, and the leaf sheaths are longer than the leaves themselves. Root systems are weak, with few white roots. Prevention involves using calcium phosphate or calcium magnesium phosphate fertilizer, applied directly to the root zone. For severely deficient fields, apply 30–50 kg of superphosphate or 7–10 kg of diammonium phosphate, or spray a 2% superphosphate solution every 7 days for two applications.
4. **Toxicity and Freezing Seedlings**
After transplanting, if the rice fails to green up quickly, the plants become stunted, with yellowing leaves and slow tillering. Roots may appear dark brown, with many deformed or blackened roots. This often occurs in waterlogged or poorly aerated soils. To treat this, perform deep irrigation to flush out toxins, then drain the field and allow the soil to dry and aerate. Apply phosphorus and potassium fertilizers to improve root health, and later use quick-acting nitrogen to boost growth.
5. **Soil Sogging**
This condition is common in areas with long-term flooding, soft plow layers, or cold water immersion. The soil becomes too wet, causing the roots to sit in floating mud, which prevents proper root development. To prevent this, ensure proper drainage, increase soil aeration, and raise soil temperature to encourage better root establishment.
6. **Cold Damage**
Cold weather after transplanting can lead to slow growth, yellow-brown roots, and thin, weak new roots. Leaves may show brown spots or dry tips, and severe cases may result in "knotty white" or "knotty yellow" symptoms. Preventive measures include draining excess water, adjusting irrigation water temperature, and using mulch or night-time irrigation to maintain warmth.
7. **Herbicide Injury**
Overuse of certain herbicides like sulfonylureas or chloriduron can lead to abnormal root development, such as "chicken claw roots," and stunted growth. Leaves may turn yellow with little tillering. Prevention involves avoiding overuse of these chemicals, and if injury occurs, drain the field and wash it with clean water to reduce residual herbicides.
8. **Pests and Diseases**
Uncontrolled pests like rice blast or thrips can cause poor growth, delayed tillering, and even plant death. Treatments include applying fungicides like tricyclazole or triazophos, or insecticides like omethoate or double insecticide, depending on the specific issue.
In addition, for severe cases of stuck seedlings, growth regulators such as gibberellins or other plant hormones can be used to stimulate recovery and promote healthy growth. Regular monitoring and timely intervention are key to preventing and managing these issues effectively.