Key Management Points for Potted Mango Seedlings in Winter
Choose a flat, open area with convenient drainage and irrigation, and avoid setting up seedbeds in windy gaps or areas where cold air easily accumulates. The size of the seedbed can be determined according to the terrain, generally 100 cm wide, with the length depending on the terrain. Dig the seedbed into a trough-shaped rectangle 5-8 cm below ground level. The soil in the trough should be loosened and leveled to help stabilize the seedlings, retain heat, and preserve moisture. After placing the seedlings, mound the surrounding soil up around the potted seedlings to form a soil-covered protective layer. Dig a drainage ditch on the opposite side across from the seedbed to facilitate drainage during the rainy season and irrigation during the dry season.
The shade shed can be set up according to the size of the seedbed, and the shade shed should extend 30-50 cm beyond the seedbed on all sides. The height of the shade shed frame should be 100-150 cm; if it is too high, it will not block the wind easily. Also set up a windbreak on the windward side to avoid damage from strong winds and cold air.
Leave a 50 cm field path between seedbeds for watering, weeding, and transporting seedlings. Frequently check the water needs of the mango seedlings and the protective performance of the shade shed. If water shortage or damage to the shade shed is found, water and repair the shade shed promptly.
During continuous drought, irrigation should use flooding, with water covering the seedbed and soil cover layer as the standard.
Fertilizing in winter is not advisable, but if seedlings bagged for 1 month are thin and weak, and the nutrient soil has low organic matter content, 0.5%-1% urea can be sprayed on the leaves to promote seedling growth. Entering autumn (around October), quick-acting nitrogen fertilizer should not be applied. Potassium sulfate at a concentration of 0.5% can be sprayed 1-2 times, with an interval of about 15 days, which can improve the cold resistance of the seedlings.
Hardening off is carried out in 2 periods. The 1st period is before winter begins. Generally, remove the shade shed in the evening and put it back up before the sun comes out the next day, or remove the shade shed on cloudy days and put it back up when there is sun. Note that during the hardening-off period, the local temperature cannot be lower than 15°C, and the extreme minimum temperature cannot be lower than 10°C; if the duration is short, it can reach around 8°C.
Before winter begins, if the seedling tissue is still tender, the seedlings can be exposed to the sun appropriately to increase leaf photosynthetic performance, speed up tissue maturation, and increase cold resistance. However, they should not be exposed to strong light for a long time, to avoid high-temperature scorching of the seedlings.
Around November, hardening off should stop about 1 month before the seedlings leave the nursery for field planting. This period is during the high-temperature season, so hardening off needs to be carried out gradually, starting with about 2 hours of sun exposure per day, then increasing the time day by day.
If after 1 week no damage to the seedlings is observed, the top cover of the shade shed can be removed to help improve seedling resistance and the survival rate after planting.
In winter, mango seedlings are prone to powdery mildew and aphid damage. Powdery mildew harms tender tissues and leaves, and can be controlled by spraying 15% triadimefon diluted with water 800-1000 times. Aphids mainly harm stems and leaves, and can be controlled by spraying 40% omethoate 1000-1500 times solution. In places with frequent rodent activity, rodent control should be done well, and methods such as poisoned bait trapping can be used.