After transplanting rice seedlings, some of them fail to regain their green color, while others turn green but do not tiller properly. Some grow slowly and gradually wither away. This condition, known as "stiff seedling" or "sitting worm," is characterized by poor growth and is often caused by environmental or soil-related stress. Affected plants typically produce fewer tillers, fewer panicles, and fewer grains, resulting in a yield reduction of 20–30%, and sometimes even over 50%. Preventing such issues is therefore a crucial step in ensuring high rice yields.
**I. Poisonous Virus**
1. **Symptoms**: The seedlings take longer to turn green. Leaves become stiff and stand upright, while the roots turn dark brown. Older leaves may die off, and the overall plant appears weak.
2. **Prevention and Control Measures**:
(1) Dig drainage ditches to lower the water table and remove cold or polluted water. This improves soil aeration, increases oxygen levels, and reduces toxic substances that harm root development.
(2) Use fully decomposed organic manure, such as pig manure, and avoid excessive application. Green manure should not exceed 2000 kg per mu, and it should be plowed into the soil at least 15 days before transplanting. Apply 50 kg of quicklime per acre to accelerate decomposition.
(3) If seedlings are already poisoned, apply 50–100 kg of quicklime along with a small amount of barley per acre to improve soil conditions and promote recovery.
**II. Phosphorus Deficiency Type**
1. **Symptoms**: After turning green, the seedlings grow very slowly and do not tiller. The plants are short, and the leaves appear pale green or dark green. In severe cases, the leaf tips turn purple. The roots are stunted and mostly yellow.
2. **Prevention and Control Measures**:
(1) Construct proper drainage systems, including ring ditches and field channels, to ensure good water flow and prevent waterlogging. This helps increase soil temperature and oxygen levels, promoting healthy root development.
(2) Combine this with the application of superphosphate at a rate of 20–25 kg per mu during cultivation.
**III. Potassium Deficiency (Rape Blight)**
1. **Symptoms**: Growth stops, the plants remain short, and there are few tillers. Leaves develop reddish-brown spots or patches that spread into streaks, eventually turning the entire leaf or plant red. The roots become tan, start to rot, emit a foul smell, and may even completely decay.
2. **Prevention and Control Measures**:
Timely drainage is essential. Combine this with the application of 50–100 kg of a mix of wood ash and lime (3:1 ratio) per acre. Also, apply a moderate amount of nitrogen fertilizer to help the rice absorb potassium more effectively.
**IV. Cold Damage Type**
1. **Symptoms**: Leaf emergence is delayed, root development is poor, and the leaves turn yellow with dry tips. The overall growth of the plant becomes stagnant.
2. **Prevention and Control Measures**:
(1) Practice crop rotation between dry and flooded fields. Use shallow irrigation and deep plowing to warm the soil and improve aeration.
(2) Drain the fields and spread about 500 kg of wood ash per acre to improve the microclimate and support healthier plant growth.
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