Autumn basal fertilization for jujube trees, ideally done before mid-September, is far more effective than spring fertilization. Trees that receive autumn basal fertilizer tend to sprout earlier, their leaves turn green faster, the fruiting period is longer, flower buds are more developed, and the fruit set rate is significantly higher. Therefore, it's best to apply it as early as possible. If autumn fertilization is missed or the amount is insufficient, spring application should be carried out immediately. The base fertilizer should primarily consist of organic materials, with a proper mix of nitrogen and phosphate fertilizers. It's especially important to combine any uncomposted manure with nitrogen and phosphorus to speed up decomposition. If there's not enough organic fertilizer, use a complete compound fertilizer or a specialized fertilizer designed for jujube trees.
In addition to basal fertilization, soil topdressing is also essential. Jujube trees typically require 2–3 topdressings per year. The first is applied before flowering, the second during the fruit enlargement stage, and the third to improve fruit quality.
1. **Pre-flowering topdressing** is usually applied in late May, just before the tree starts to flower. Its purpose is to supply nutrients needed for flowering and fruit setting, thereby increasing the fruit set rate. At this stage, nitrogen fertilizer is recommended, along with an appropriate amount of phosphate. A typical dose per tree includes 0.5–1.0 kg of urea, or 1.5–2.0 kg of ammonium bicarbonate, combined with 1.5–2.0 kg of superphosphate, or 0.5–0.8 kg of diammonium phosphate. Alternatively, 15–20 kg of well-rotted human manure can also be used.
2. **Fruit enlargement topdressing** should be applied from late June to early July to promote fruit growth and reduce physiological fruit drop. If this step is skipped or under-fertilized, the fruits may remain small and drop heavily. This topdressing should include nitrogen, phosphorus, and potassium. Using a specialized jujube tree fertilizer is ideal, with about 1.5–2.0 kg per tree.
3. **Quality improvement topdressing** is applied in early August, mainly focusing on phosphorus and potassium. This helps meet the plant’s needs for photosynthesis, enhances sugar accumulation and conversion, improves fruit color, sweetness, and juice content. The best options are diammonium phosphate and potassium sulfate, with 0.5–0.7 kg per tree, or 1.5–2.0 kg of professional jujube fertilizer.
Finally, foliar feeding is another important technique. Depending on the tree's nutritional status at different growth stages, various fertilizers and concentrations should be applied to the leaves. This method allows for quick nutrient absorption and can help correct deficiencies promptly. Always follow recommended concentrations to avoid leaf burn or over-fertilization.
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