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Nutritional characteristics of banana
Bananas have a unique root system, lacking a central taproot. Instead, they develop adventitious roots from the underground bulb, also known as the "pig's head." These roots grow horizontally and vertically, with the majority of the root system concentrated in the topsoil between 10 to 25 cm deep. The bulb serves not only as a root structure but also as the origin for leaves and suckers. Suckers emerge from axillary buds on the bulb and can be classified into flag leaf buds and large leaf buds. Among these, flag leaf buds are typically selected as parent plants for propagation. This dual function makes the bulb both a vegetative and reproductive organ, directly influencing the plant’s growth and productivity.
Bud germination usually begins in February each year. During this time, careful selection of buds is essential to prevent excessive nutrient consumption by unwanted shoots, which could hinder the mother plant’s development and fruiting. The optimal time for selecting and retaining new shoots is when the mother plant has developed 20 to 22 leaves and the young panicles start forming. At this stage, the most vigorous suckers are chosen to replace the mother plant, while other sprouts should be removed promptly to ensure efficient resource allocation.
The growth cycle of banana plants can be divided into four distinct stages:
1. **Seedling Stage (2–3 months):** From emergence until the plant develops large leaves, this phase focuses on increasing leaf area and establishing the bulb and root system. Nutrients are initially supplied by the mother plant before transitioning to soil absorption. Growth during this period is relatively slow.
2. **Vegetative Growth Period (5–6 months):** This stage begins with the appearance of large leaves and continues until flower bud differentiation. It involves rapid leaf production and nutrient accumulation, laying the foundation for flowering. About 10–16% of the total biomass is accumulated during this time.
3. **Budding Period (3–4 months):** Characterized by thickened petioles, dense leaf spacing, and pseudostem enlargement ("pregnant" stage), this period sees the completion of female flower differentiation and the initiation of male flowers. Fruits and leaves develop simultaneously, and the final leaf count varies depending on the variety—31–34 leaves for tall varieties, 28–30 for dwarf ones. Approximately 30–35% of total biomass is produced during this stage.
4. **Fruit Development Stage:** From the completion of flower differentiation to fruit maturity, the plant redirects nutrients to the fruits. Lower leaves yellow, and growth slows down. After harvest, the mother plant is cut back, and a new sucker takes over, starting the next growth cycle.
Bananas have specific nutritional requirements. They are a potassium-loving crop, requiring more potassium than any other fruit tree. The average N:P2O5:K2O ratio throughout the growing season is approximately 1:0.19:3.72. Nutrient needs vary by variety and plant type. For example, medium-stalk bananas require about 5.9 kg N, 1.1 kg P2O5, and 22 kg K2O per 1000 kg of fruit, while dwarf varieties need slightly less. Calcium and magnesium are also crucial, with calcium absorption being 0.69 times that of nitrogen and magnesium 0.2 times.
Nutrient uptake varies across growth stages: 40.5%, 45.5%, and 52.6% during the early stages; 40.2%, 37.2%, and 31.0% during fruit maturation; 19.3%, 17.8%, and 16.4% during vegetative growth; and 42.0%, 43.0%, and 37.0% during fruit development. The overall N:P2O5:K2O ratio remains consistent at around 1:0.2:3.5 to 4.5, allowing for uniform fertilizer application throughout the growth cycle.
Fertilization practices for bananas are intensive, with 10 to 15 applications per year. Organic fertilizers are commonly used in winter and spring, applied in trenches or holes near the base of the plant. During the growing season, 75% of the total fertilizer is applied before planting, followed by regular top-dressing. After the first 10 large leaves appear, two applications per month are recommended, using 3–5% of the total fertilizer. Tissue culture seedlings benefit from a 0.2% compound fertilizer solution every 7 days for 4–6 weeks. As the plant progresses through its growth stages, the amount and frequency of fertilization increase accordingly.
In regions with acidic soils, such as southern China, magnesium deficiency is common, so 25–30 kg of magnesium sulfate per acre is often recommended. Boron deficiencies can be addressed with 0.2% borax spray applied 2–3 times during the growing season, significantly boosting yield. Overall, proper fertilization and nutrient management are critical for maximizing banana productivity and quality.