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Rice seedlings using paclobutrazol five notes
Paclobutrazol has proven to be highly effective in rice seedling cultivation, offering benefits such as stunted growth, stronger plants, earlier maturity, enhanced resistance to diseases and weeds, and increased yield and profitability. However, improper application can lead to negative outcomes like excessive dwarfing, growth stagnation, or even plant death, as well as late maturity and overgrowth. To prevent these issues, based on years of experimental and practical experience, the following five key points should be carefully considered when applying paclobutrazol to rice seedlings:
1. **Appropriate Dosage Based on Variety and Season**
The concentration of paclobutrazol should vary depending on the rice variety and the season. Overuse can cause severe dwarfing, while underuse may not achieve the desired effect. For example, for early rice, a typical dosage is 120 grams of 15% wettable powder per 667 square meters (about 1 acre), mixed with 60 kg of water. For late rice, it's 200 grams in 100 kg of water. Mid-season varieties require 150 grams in 75 kg of water for early maturing types, and 180 grams in 90 kg of water for late maturing ones. It’s important to spray evenly. If over-application causes stunting, a diluted solution of "920" (gibberellic acid) at a 10:2 ratio can help restore normal growth.
2. **Timing Varies by Rice Type and Season**
The timing of paclobutrazol application depends on the type of rice and the growing season. In early rice, where temperatures are lower and growth is slower, the goal is to strengthen seedlings and improve their resilience. The best time is during the three-leaf stage. For late rice, the focus is on controlling elongation and promoting tillering. The ideal period is at the end of one leaf and one heart stage, no later than two leaves and one heart. For mid-season rice, early-maturing varieties are treated at the 2–3 leaf stage, while late-maturing ones are sprayed at the one-leaf and one-heart stage.
3. **Effective Field Management After Spraying**
After spraying paclobutrazol, field management should be timely and proactive. Seedlings tend to recover quickly and grow vigorously after transplanting, so it's important to implement the “three early†approach—early management, early watering, and early control of seedlings. The drying period (baking the field) can be shortened by 2–3 days. Avoid delaying this process, as it may lead to excessive growth, increasing the risk of pests, diseases, empty grains, reduced grain weight, and lodging.
4. **Preventing Late Maturity in Late Rice**
Late rice often experiences delayed growth due to paclobutrazol use. To manage this, ensure proper scheduling of sowing times. The key is to sow 2–3 days earlier than usual to avoid delays in the growth cycle and potential problems caused by late maturity.
5. **Be Aware of Residual Effects**
Paclobutrazol is slow to break down in the soil, and repeated use in the same field can lead to residual accumulation. This can negatively affect subsequent crops, especially if they are planted without plowing. To minimize this risk, it’s essential to monitor dosages and avoid continuous use in the same area. Rotating crops and reducing frequency of application can help maintain soil health and protect future planting.