Spinach is a biennial herb and one of the most popular leafy green vegetables. Its main root is thick, fleshy, pale red, sweet, and edible, while the lateral roots are underdeveloped. The leaves have short petioles, are arrow-shaped or oval, dark green in color, soft to the touch, and form the primary edible part of the plant.
Spinach thrives in cooler conditions and can tolerate temperatures as low as -6°C, but it does not perform well in high heat. The ideal growth temperature ranges between 15°C and 20°C. Seeds begin to germinate at 4°C, but their germination rate declines above 20°C, and the plant struggles when temperatures exceed 25°C. As a long-day plant, spinach grows faster with longer daylight hours, and drought can hinder its vegetative development. It prefers slightly acidic soil with a pH of 6 to 7 and requires ample nitrogen, along with moderate phosphorus and potassium for optimal growth. Sufficient nitrogen leads to larger, more vigorous leaves and higher yields.
(1) **Sowing**: Spinach is commonly sown using direct seeding methods such as broadcasting, drilling, or spot planting. High-quality varieties with round leaves are typically chosen. Autumn is the main season for cultivation, usually from late July to early September, with harvests occurring 30–40 days after sowing. Heat-resistant, early-maturing varieties like Union No. 1 are used for autumn planting. Autumn-winter sowing takes place in October and November, while spring planting is done from late February to March. Spring varieties should be selected to resist bolting and avoid spiny leaves. Early planting in spring may lead to premature bolting, so timing is crucial.
For early autumn sowing, which occurs during hot summer periods, seeds may struggle to germinate. Short-dormancy or two-year-old seeds are recommended. If using fresh seeds, they should be pre-treated by soaking in water for 12 hours, then kept at 4°C for 24 hours before germinating at 15–20°C. Alternatively, seeds can be soaked in well water to speed up germination. Seedlings usually emerge within 3–5 days. Due to high temperatures and drought in early autumn, sowing rates should be increased—about 10–15 kg per mu (666.7 m²). After September, when temperatures drop, no pre-germination treatment is needed, and sowing rates decrease to 4–5 kg per mu.
(2) **Field Preparation**: Choose fertile, moisture-retentive, slightly acidic soil. Apply base fertilizer before sowing, plow deeply, and create flat beds 1.5–2 meters wide. Water the field before sowing and ensure the soil remains moist after broadcasting the seeds.
(3) **Field Management**: In early autumn, high temperatures require topdressing combined with irrigation. A 20% diluted manure solution can be applied, and later, a 50% human urine solution helps reduce temperature. For wintering spinach, apply fertilizer before spring to prevent early bolting. After each harvest, apply nitrogen fertilizer to maintain productivity.
Weed control is essential since spinach grows slowly during the seedling stage. About 15 days before harvest, spraying 0.0015% gibberellic acid can promote earlier maturity and increase yield. Combining this with topdressing enhances the effect significantly.
(4) **Pest and Disease Control**: Common diseases include downy mildew and anthracnose, which affect the leaves. Insect pests such as leafminers and aphids also pose threats. Agricultural practices like crop rotation, proper spacing, and timely removal of infected plants help prevent these issues. Chemical controls include sprays like 64% antiviral (500x), 52.5% fast-eliminating net (1500x), and 70% thiophanate-methyl (700x). For pests, use 75% insecticide (3000–4000x), 0.5% Hisun (3250x), or 15% insecticide (1500–2000x).
(5) **Harvesting**: Autumn spinach can be harvested about 30 days after sowing, with subsequent harvests every 20 days. Spring-sown spinach is typically harvested once, depending on growing conditions.
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