How Big Should Tomato Seedlings Be Before Transplanting, Planting Out and Fertilizing? When Do They Flower?
SummaryTransplanting time: transplant and plant out when the seedlings are 20-25 days old and have 3-4 leaves. Soil preparation and planting out: make the planting beds into 50cm wide ridges, planting 4500 plants per mu. Temperature management: keep the daytime temperature at 25-30°C and the nighttime temperature at 15-17°C. Fertilizer and water management: when the fruit trusses reach the size of a walnut, apply 25kg of diammonium phosphate per mu, and spray an appropriate amount of foliar fertilizer again during the fruit-swelling stage. Flowering time: about 20 days after planting.
I. Transplanting Time
1. Sowing can be done in early to mid-July. Early sowing makes the plants prone to viral disease, while late sowing means low temperatures later on, which affects fruit ripeness and results in low yields. During the seedling-raising stage, avoid waterlogging, sunscald and damage from viral disease. The seedbed needs to be set up in a high, dry spot, and at the same time make raised beds, set up shade frames, and raise seedlings in nutrient paper bags or nutrient pots.
2. Transplant and plant out when the seedlings are 20-25 days old and have 3-4 leaves. If the seedlings show excessive vegetative growth during the seedling stage, spray 1-2 times with (500-1000)×10-6 chlormequat in good time.
II. Soil Preparation and Planting Out
Autumn tomatoes in the greenhouse are planted out relatively early, when the outside temperature is high. Before planting out, the shade-type greenhouse film needs to be put in place, with the surrounding film opened up, leaving only the upper part for rain protection and protection from strong light. After the film is in place, make the planting beds into 100cm wide, high, level beds, or 50cm wide ridges. Apply basal fertilizer well while making the beds and irrigate to full field capacity. If 2 fruit trusses are to be kept, the planting spacing is 25cm; if 3 fruit trusses are to be kept, the planting spacing is 30cm, planting about 4500 plants per mu.
III. Temperature Management
After planting out, ventilate day and night, ventilating from the bottom. Close off the area around the greenhouse, ventilating only at the middle and upper parts. When the outside temperature drops below 15°C, stop ventilating at night. Keep the daytime temperature at 25-30°C and the nighttime temperature at 15-17°C. After the whole greenhouse is sealed tight in late October, ventilate the greenhouse roof at noon to release moisture.
IV. Fertilizer and Water Management
1. 2-3 days after planting out, when soil moisture is suitable, cultivate and loosen the soil in good time, and hill up the ridges while loosening the soil. After the seedlings have recovered, water once. Later, to prevent excessive vegetative growth, water sparingly until large flower buds appear, then water thoroughly once, followed by shallow ploughing and root-establishing.
2. When the fruit trusses reach the size of a walnut, topdress and water, applying 25kg of diammonium phosphate per mu. After mid-October, to reduce humidity inside the greenhouse, stop watering, and spray an appropriate amount of foliar fertilizer again during the fruit-swelling stage.
V. Flowering Time
The flowering period of tomatoes is summer and autumn, generally about 20 days after planting. During the growing period, single-stem pruning is needed, keeping 3-4 well-shaped fruits per fruit truss; small-fruited varieties can keep 4-5 fruits, removing the rest. During the flowering period, treat with 2,4-D tomato hormone, which helps preserve flowers and fruits. Because temperatures are higher during the flowering period, the concentration used needs to be somewhat lower than for spring tomatoes.
VI. Pest and Disease Control
1. Growing autumn tomatoes requires preventing viral disease and late blight. Pay attention to controlling viral disease in the early stage. Besides selecting disease-resistant varieties, sowing at the right time, raising seedlings in nutrient pots and selecting disease-free seedlings for planting out, the greenhouse also needs to be covered in advance, which can significantly reduce the number of aphids. If diseased plants are found, they need to be pulled up in good time.
2. At the same time, wash hands with soapy water before replanting. In the middle and late stages, pay attention to controlling late blight. After planting, strengthen ventilation to lower the temperature, remove diseased leaves and fruits in good time, and spray thoroughly with agents such as zineb and chlorothalonil.