Key Technical Points and Management Methods for Growing Overwintering Spinach
Spinach originated in Iran and was introduced to China from Nepal during the reign of Emperor Taizong of Tang. It is now one of the vegetables we commonly cultivate. Spinach can be divided by sowing time into spring spinach, summer spinach, autumn spinach and overwintering spinach. Overwintering spinach refers to spinach sown from mid-October to early November each year and harvested around the Spring Equinox of the following year. The market arrival of overwintering spinach can effectively fill a gap in the market, and its cultivation value is relatively high. So how should this overwintering spinach be grown? Qinnong.com will introduce it to you next: the cultivation techniques for overwintering spinach.
I. Selecting Varieties
Because overwintering spinach needs to grow throughout the entire winter, varieties with strong overwintering ability, strong cold tolerance, good quality, fast growth and high yield potential should be selected. Ordinary spinach varieties tend to bolt during the overwintering period, which reduces yield and quality and affects the value of the spinach.
II. Land Preparation
After the previous crop is harvested, stubble should be cleared in time. After that, each mu of land requires 5000 kg of decomposed organic fertilizer and 50-60 kg of ternary compound fertilizer, with deep plowing of more than 25 cm, after which it is leveled into flat beds 1.2 m to 1.5 m wide.
III. Sowing
The choice of sowing time is very important. Practice has shown that spinach during the overwintering period is relatively safe when it has 4-5 leaves, so sowing from late September to early October is appropriate. Spinach seeds germinate slowly. To shorten the emergence period, the seeds can be soaked in 20°C warm water for 12 hours one day before sowing, then removed, briefly air-dried and sown. If sowing is later, 4-5 days before sowing the seeds can be soaked in cold water for 12-24 hours, removed and piled indoors at a thickness of about 15 cm, covered with a hemp sack to keep warm, and turned once a day so that the temperature and humidity within the pile are even. The temperature should be kept at around 20°C. After 3-4 days, when more than 60% of the seeds show radicles, they can be sown. Coated seeds do not need soaking or germination acceleration. There are two sowing methods: dry sowing and wet sowing. Dry sowing means sowing and pressing first, then watering; wet sowing means watering before sowing, sowing after the water has seeped down, and covering with soil after sowing. Seeds that have been germinated must be wet-sown. There are two sowing patterns: broadcasting and drilling. Drilling requires sufficient subsoil moisture; when broadcasting, the seeds must be spread evenly, then covered with about 2 cm of soil. Generally, the seeding rate is 4-5 kg per mu, appropriately increased for late sowing. In addition, the sowing time of overwintering spinach also directly affects the overwintering ability of the seedlings, the harvest time and the yield.
IV. Routine Management
The routine management of overwintering spinach mainly targets three periods of overwintering spinach, including seedling-stage management, overwintering-stage management, and management during the vigorous regrowth period. The management methods required differ by period. Qinnong.com will now introduce them specifically for everyone.
1. Seedling-stage management: If the soil is dry after sowing, a light watering can be given. When the moisture condition is suitable, shallowly hoe the bed surface to loosen the topsoil and facilitate emergence. When 1-2 true leaves appear after emergence, keep the soil moist; at 3-4 true leaves, water can be appropriately controlled to promote root development and facilitate overwintering. If the seedlings are too dense, thin them once at 2-3 true leaves, with a spacing of 3-5 cm. If aphids cause damage, spray pesticide for control.
2. Overwintering-stage management: The period from when spinach stops growing until before regrowth in the following spring is the overwintering period. To prevent cold and drought damage, one freezing water can be applied before the soil freezes; where fertilization is insufficient, urine water can be mixed in with the irrigation. After the soil freezes, horse manure or pen manure can be spread to protect the seedlings through winter. Before regrowth, choose clear and warm weather, and after the frost has melted, splash fresh urine at 1000-2000 kg per mu, finishing by 3-4 pm.
3. Management during the vigorous regrowth period: In early March of the following year, spinach begins to regrow. Because the temperature is still low at this time, if the moisture condition is good, watering can be temporarily withheld and hoeing used to preserve moisture; if the moisture condition is poor and the temperature rises quickly, one watering can be given, with the amount preferably small rather than large. However, saline-alkali land can be watered appropriately to leach salts. In windbreak beds and sandy loam, where temperature rises quickly, watering should be done appropriately earlier. After spinach begins vigorous growth, the demand for fertilizer and water surges. During this period, the soil should be kept moist and not allowed to dry out. Topdressing and watering should be carried out promptly to promote vegetative growth and delay the bolting period. Generally, 15-20 kg of urea is topdressed per mu. Water after fertilizing. With sufficient fertilizer and water, spinach grows quickly and can be harvested in 10-15 days. Adopting windbreaks and flat film mulching in early spring (mulching for 7-10 days) can achieve the goals of earlier market arrival and high yield.
V. Pest and Disease Control
The main pests and diseases affecting overwintering spinach include downy mildew, anthracnose, viral disease and aphids. For downy mildew and anthracnose, at the early stage of onset, spray with 75% chlorothalonil 600-fold solution, 25% metalaxyl 700-800-fold solution, or 40% fosetyl-aluminum wettable powder 200-300-fold solution. For viral disease, in addition to practicing crop rotation, aphids and other virus-transmitting vectors should also be controlled in time. Aphids can be controlled with pesticides such as imidacloprid.
VI. Timely Harvesting
Generally, once the seedlings are more than 10 cm tall, they can be harvested in batches. About 15 days before a one-time harvest, 15-20 mg/kg of 920 can be sprayed on the leaves, and urea or ammonium sulfate should be added, which can advance the harvest and increase yield.
VII. Seed Saving
The sowing time for spinach used for seed saving can be slightly later than that for overwintering spinach. Drill sowing, with a row spacing of 20-23 cm. After regrowth in spring, successively pull out off-type plants and early-bolting male plants, leaving some vegetative male plants so that the plant spacing reaches about 20 cm. During the bolting period, excessive irrigation is not advisable, so as to avoid thin and weak flower stalks that lodge and reduce seed yield. After flowering, topdress, irrigate, and spray 1%-2% clear calcium superphosphate solution on the leaves to make the seeds plump. After the male plants set seed, pull out the male plants to improve ventilation and light penetration. When the stems and leaves are mostly withered and yellow and the seeds are mature, harvest, then after-ripen for several days and thresh.
The above is Qinnong.com's introduction to the cultivation techniques for overwintering spinach. From the above, it can be seen that among the cultivation techniques for overwintering spinach, the most critical step is the sowing time, which is also the key point that farmers should pay attention to.