Maize seedling management is crucial for producing strong, healthy seedlings that are suitable for mechanical transplanting, which directly impacts the success of rice mechanized planting. "Good seedlings lead to good harvests," and the quality of the seedlings plays a vital role in determining the number of panicles, grains, and grain weight during the later stages of rice growth. For mechanized transplanting, the seedlings must be well-balanced and robust, with uniform height and thickness—essentially, "no tall or short, no thick or thin."
High temperature and humidity are beneficial for seedling development. After rice seeds germinate and are sown, a period of high temperature and humidity promotes healthy growth. To ensure even emergence, it's important to use proper temperature and moisture control methods, such as raising the seedbed and managing the water level carefully. Water should not be too deep to avoid flooding, which can cause root rot.
Covering seedlings with grass or plastic film is common, especially in warmer conditions. This includes double-membrane techniques, floppy disk sowing, and direct machine seeding. During this stage, two key points should be considered: first, maintaining an even and appropriate thickness of the cover to prevent heat damage during sunny afternoons; second, removing excess water from the film after rain to avoid water pooling, which could cause the straw to become heavy and press down on the seedlings, leading to weak growth.
Arch sheds are used in areas with lower temperatures, particularly in early spring or late spring when cold weather persists. Once seedlings are established, the temperature inside the shed should be kept below 35°C during midday to avoid burning the young plants.
During the seedling stage, the bed is usually covered with a film to maintain warmth and moisture. Ventilation is necessary only when the internal temperature exceeds 35°C at noon. If the seedlings show signs of drying out or leaf rolling, it’s time to apply "Happy Valley Water" to keep them hydrated.
Timely hardening off is essential for preparing seedlings for transplanting. The timing of film removal depends on local temperature conditions. Generally, the film should be removed when the seedlings have emerged about 2 cm and the first leaves have started to unfurl (3–5 days after transplanting). If left too long, the seedlings may be damaged by intense sunlight. The principle for removing the film is: expose on sunny evenings, cloudy mornings, before light rain, and after heavy rain. In case of cold weather, it's better to delay removal and cover the seedlings at night if needed.
Once the seedlings turn green, the arch shed should be removed when the minimum temperature stabilizes above 15°C. Otherwise, manage by exposing the seedlings during the day and keeping the soil moist at night.
Water management is critical for healthy seedling growth. A wet-dry irrigation method is recommended, where the seedbed is kept moist but not flooded. This helps regulate temperature, protect the seedlings, and promote strong root development. When the film is removed, drain the water, let it dry naturally, then refill. During hot afternoons, if the leaves start to curl, spray a light layer of water to cool them down. In cases of sudden cold snaps, block the water to protect the roots from damage. Once the temperature stabilizes, gradually change the watering schedule to improve root vitality.
Three to five days before transplanting, control the water to prepare the seedlings for field conditions.
Water management also involves filling the beds with enough water once the film is removed, allowing it to drain through the soil or using a sprayer. Keep the drainage channels clear to prevent waterlogging and ensure proper irrigation. If the leaves curl in the afternoon, spray water in the evening or early morning to keep the soil moist. Avoid overwatering unless necessary, as dirty water can harm the seedlings.
Applying "weaning fertilizer" is an important step in seedling care. It should be done based on soil fertility, seedling age, and temperature, typically around the time of one-leaf-one-heart stage (7–8 days after sowing). For each mu of land, you can apply 500 kg of diluted manure or 1000 kg of urea, or 5 kg of urea (about 2 grams per tray) mixed into 500 kg of water. Apply it in the evening. If the soil is already fertile, reduce the amount to avoid excessive growth, especially in wheat fields.
In response to cold stress, protecting the seedlings with deep water can help regulate temperature. Avoid immediately draining the water after a cold spell, as sudden temperature changes can cause physiological dehydration. If the weather warms up quickly, the deep water layer can help stabilize the environment.
Before a cold snap or after a cold wave, spray 100–150 grams of fungicide per 1000 liters of water to prevent rot and death. After prolonged rainy or cloudy weather, spray Zhuang Bao to prevent blight.
If the weather remains cold for an extended period, consider building an arch shelter to provide additional insulation and protection.
Avoid applying fertilizer too soon after a cold spell, as the seedlings may be weakened. Fertilizing too early can further stress the plants and increase the risk of death. Wait 3–4 days after the cold has passed before applying any top dressing.
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