Detailed Explanation of the Key Technical Points for Year-Round Management of Greenhouse Strawberries

I. July to August

1. Soil disinfection and increased application of organic fertilizer. Use solar energy to disinfect the soil, apply 2000 kg of decomposed farmyard manure per mu, and spray the soil with 48% Lorsban 800-fold solution. After plowing, seal with plastic film for 7 to 10 days to kill underground pests. After removing the film, additionally apply 100 kg of cake fertilizer, 30 to 40 kg of superphosphate, and 30 kg of 45% nitrogen-phosphorus-potassium compound fertilizer. The amount of base fertilizer accounts for 70% of the total fertilizer application.

2. Land preparation and bed making. After the soil is disinfected, plow, rake level, and make ridges. Generally, the ridge height is 30 cm, the ridge surface width is 45 to 50 cm, the ridge bottom width is 55 to 60 cm, and the ditch bottom width is 30 cm.

II. September

1. Planting. The planting time is in early to mid-September. Plant 2 rows per bed in a "triangular" planting pattern, with a row spacing of 25 to 30 cm and a plant spacing of 15 to 20 cm. Determine the density according to the growth vigor of the variety; generally, plant 6000 to 8000 plants per mu. When planting seedlings, remove old leaves, diseased leaves, and runners, leaving 3 leaves and 1 heart. When planting, the arched back should face outside the bed (toward the ditch). The planting depth should be appropriate, so that it is deep enough not to bury the heart but shallow enough not to expose the roots.

2. Management after planting. After planting, water thoroughly to settle the roots, then water lightly 1 to 2 times a day to prevent drought until the seedlings survive. After the seedlings recover, they enter the flower bud differentiation stage. Fertilizer and water management should be strengthened, with controlled water and nitrogen to prevent excessive seedling growth. Apply 10 to 15 kg of nitrogen-phosphorus-potassium compound fertilizer per mu (the first time after the seedlings survive and the soil is loosened, the second time before film mulching) to promote flower bud differentiation. In addition, continue to do a good job of intertillage, weeding, and pest and disease control.

III. October to November

1. Covering with greenhouse film and plastic mulch. When the outdoor nighttime temperature drops to about 8°C, begin heat preservation. Late October to early November is the suitable period for heat preservation for forcing cultivation of greenhouse strawberries (the suitable period for covering the greenhouse). If heat preservation is too early, the indoor temperature is high, which is not conducive to axillary flower bud differentiation; if too late, the plants enter dormancy, causing plant dwarfing and unfavorable normal fruiting. EVA film and multifunctional drip-free film are suitable for the greenhouse film. When the nighttime greenhouse temperature is below 5°C, implement multi-layer covering for heat preservation. After the greenhouse film is covered, generally after the seedling-stage topdressing is completed (early to mid-November), carry out plastic mulch covering. First lay micro-drip tubes or soft tubes on the bed surface, then cover with plastic mulch. A 0.03 to 0.05 mm black opaque polyethylene film is suitable for the plastic mulch.

2. Management inside the greenhouse

(1) Temperature and humidity management. In the early stage of heat preservation, generally control the daytime temperature at 28°C to 30°C; control the nighttime temperature at 12°C to 15°C, and it must not be lower than 8°C; control indoor humidity at 85% to 90%. During the flowering period, generally control the daytime temperature at 22°C to 25°C, and it must not exceed 28°C. Too high or too low a temperature is unfavorable for pollination and fertilization; the nighttime temperature should preferably be about 10°C, and must not be lower than 8°C. If the nighttime temperature exceeds 13°C, axillary flower buds degenerate and stamen and pistil development is impeded; indoor humidity should preferably remain at 50% to 60%. Too high or too low humidity will cause poor pollination. Therefore, even in cold winter, during the day when the temperature is high at noon, the film should be uncovered for ventilation to reduce humidity inside the greenhouse.

(2) Fertilizer and water management. After the greenhouse strawberries are covered for heat preservation, it is exactly the flower bud development period, and soon afterward they bud, flower, and fruit. After the terminal inflorescence is harvested, axillary inflorescences again emerge and flower and fruit, placing a heavy burden on the plant. If fertilizer is not applied in time, premature senescence is likely to occur. Topdressing should be carried out at least 4 times, respectively before flowering, during fruit enlargement, during lateral inflorescence emergence, and during the lateral inflorescence fruiting period. Each time, apply 10 to 15 kg of 45% nitrogen-phosphorus-potassium compound fertilizer per mu, and spray the leaves once every 7 to 10 days with 0.3% urea plus 0.3% potassium dihydrogen phosphate liquid fertilizer.

The humidity inside the greenhouse is very high, which easily gives the false impression that there is no water shortage. Generally, water once before heat preservation and once before covering with plastic mulch. Afterward, supplement water appropriately in combination with topdressing or in the early morning when the edges of new leaves do not exude water. Greenhouse strawberries are especially suitable for drip irrigation. During the fruit development period, special attention should be paid to keeping the soil moist.

(3) Spraying gibberellin. After forcing cultivation begins heat preservation, when 2 new leaves have unfolded and 30% of buds have appeared, carry out the first gibberellin treatment to promote flower stalk elongation, which is beneficial for pollination and fertilization. Use 3 to 5 ml/kg or 5 to 8 mg/kg gibberellin per plant, spraying it on the seedling heart. After 7 days, depending on the inflorescence elongation, treat once more.

(4) Plant training. During the growth period, keep 8 to 10 leaves per strawberry plant. Generally, in addition to the main bud, retain 1 to 2 lateral buds. Excess lateral buds that appear should be removed early. Diseased and insect-damaged leaves, old leaves, and runners should be removed in time to ensure that nutrients are concentrated for supplying the fruit. During the young fruit stage, carry out appropriate fruit thinning, removing young fruits above the fourth fruit order of each inflorescence, mainly removing diseased fruit, small fruit, and malformed fruit. Finally, retain 12 to 15 fruits on the first inflorescence and 8 to 10 fruits on the second inflorescence, leaving 20 to 25 fruits per plant.

(5) Strengthen pest and disease control. During this period, the temperature inside the greenhouse is high and the humidity is high, so powdery mildew, gray mold, anthracnose, and other diseases are prone to occur, and control should be strengthened. Sulfur fumigant can be used (at 50 g sulfur per 180 sq m) for nighttime fumigation once every 7 days; or "Yixunling" smoke agent can be used at 4 tablets per 180 sq m for control; or 25% Shibaike 800 to 1000-fold solution can be sprayed for control. The main pests include aphids, mites, and others, which can be trapped and killed with yellow sticky insect adhesive boards; or sprayed with 10% abamectin-pyridaben 1500-fold solution or 10% imidacloprid 3000-fold solution; underground pests can be controlled with 48% Lorsban 800-fold solution.

(6) Releasing bees for pollination. In late November, the flowering period begins. Release one box of bees per standard greenhouse (30 m x 6 m) to increase the pollination rate of strawberry flowers and reduce the production of malformed fruit. A common method of artificial pollination is to gently smear the center of open flowers with a soft brush, or during full bloom, lightly brush over the inflorescences with a fine feather duster.