After transplanting rice, some seedlings fail to regain their green color, while others do not tiller even after turning green. Some grow slowly and gradually wither away. This condition, known as "stiff seedling" or "sitting worm," is a sign of poor growth. Affected plants typically have fewer effective tillers, smaller panicles, and fewer grains, leading to a yield reduction of 20-30%, and in severe cases, over 50%. Preventing such issues is crucial for achieving high rice yields.
**I. Poisonous Virus**
1. **Symptoms**: The seedlings take a long time to turn green. Leaves are curled, and the plant stands upright. The roots appear dark brown, and the older leaves may die off.
2. **Prevention and Control Measures**:
(1) Dig drainage ditches to lower the water table, drain cold and polluted water, improve soil permeability, increase oxygen levels and temperature, and reduce toxic substances in the soil. This helps promote root development.
(2) Fully compost pig manure and other organic fertilizers before use. Avoid excessive application. Green manure should generally not exceed 2000 kg per mu and should be incorporated into the soil at least 15 days before transplanting. Apply 50 kg of quicklime per acre to accelerate decomposition.
(3) After symptoms appear, apply 50–100 kg of quicklime and a small amount of barley per acre to help detoxify the soil.
**II. Phosphorus Deficiency Type**
1. **Symptoms**: Seedlings grow slowly after turning green and do not tiller. Plants are short, with sparse leaves that are grayish-green or dark green. In severe cases, leaf tips turn purple. The roots are stunted and mostly yellow.
2. **Prevention and Control Measures**:
(1) Dig ring ditches, central drains, and field side ditches to ensure proper drainage, filter out dark water, and prevent cold water from accumulating. This helps raise soil temperature and improve oxygen levels, promoting healthy root development.
(2) Combine this with plowing and top-dress with 20–25 kg of superphosphate per mu.
**III. Potassium Deficiency (Rape Blight)**
1. **Symptoms**: Growth stops, plants are 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. Roots become tan, show signs of aging, rot, emit a foul smell, and may even rot completely.
2. **Prevention and Control Measures**:
Timely drainage of the field, combined with plowing, and top-dressing with 50–100 kg of a mix of black and white ash (3 parts ash, 1 part lime) per acre. Also, apply a moderate amount of nitrogen fertilizer to help rice absorb potassium more effectively.
**IV. Cold Damage Type**
1. **Symptoms**: Leaf emergence is delayed, growth is slow, roots develop poorly, leaves turn yellow, tips dry out, and overall growth stagnates.
2. **Prevention and Control Measures**:
(1) Practice crop rotation between dry and flooded fields. Use shallow irrigation, deep plowing, and intensive farming to warm the soil and increase oxygen levels.
(2) Drain the field, spread about 500 kg of plant ash per acre, and improve the field's microclimate to support better plant health.
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