Key Technical Points for Growing Okra and Analysis of Its Economic Benefits
Okra has not been introduced into our country for long, and its growing range is very small; it is mainly used for export to Japan and other places. At present, the potential for developing okra production for export is very large, and at the same time, planting a few plants in each household is of very important significance for improving daily life and enhancing people's health. Okra has strong adaptability, grows vigorously, and is rarely harmed by diseases and pests. Growing okra is simple and easy, does not require much labor, uses little seed, has low cost, and gives high benefits. The growing techniques are introduced below:
[Environmental Requirements]
1. Temperature. Okra likes warmth and fears severe cold, and has strong heat tolerance. When the air temperature is 13°C and the soil temperature is about 15°C, the seeds can germinate. However, the optimum temperature for both seed germination and the growth period is 25-30°C. When the monthly average temperature is below 17°C, flowering and fruiting are affected; when the night temperature is below 14°C, growth is slow, the plants are short, the leaves are narrow, there are few flowers, and many flowers drop. At the optimum temperature of 26-28°C, there are many flowers, the fruit-setting rate is high, the fruits develop quickly, the yield is high, and the quality is good.
2. Water. Okra is drought-tolerant and moisture-tolerant, but not waterlogging-tolerant. If the soil moisture is too high during the germination period, it easily induces damping-off of the seedlings. If there is drought during the fruiting period, the plants grow poorly and the quality is poor, so the soil should always be kept moist.
3. Light. Okra is especially sensitive to light conditions and requires a long photoperiod and sufficient light. A sunny plot should be selected, ventilation and air movement should be strengthened, and reasonable close planting should be paid attention to in order to avoid mutual shading and effects on ventilation and light penetration.
4. Soil and nutrients. Okra has a relatively wide adaptability to soil and is not particular about soil fertility, but loam or sandy loam with deep soil layers, loose fertility, and good drainage is more suitable. In the early stage of growth, fertilizer should mainly be nitrogen, while in the middle and late stages more phosphorus and potassium fertilizer are needed. However, if there is too much nitrogen fertilizer, the plants easily grow excessively, flowering and fruiting are delayed, and the node position of fruit setting rises; if nitrogen fertilizer is insufficient, the plants grow poorly and flowering and fruit setting are affected.
[Propagation]
1. Germination period. From sowing to the flattening of 2 cotyledons is the germination period, requiring about 10-15 days. When sown at the optimum temperature of 25-30°C, they germinate and emerge in 4-5 days. Usually, direct sowing in the open field takes about 7 days for the seedlings to emerge, and plastic film mulching can advance emergence by 2-4 days.
2. Seedling period. From the flattening of 2 cotyledons to the opening of the first flower, about 40-45 days are needed. Generally, after the cotyledons fully unfold, the first true leaf unfolds after 15-25 days. After that, one true leaf appears every 2-4 days, among which the first and second true leaves are round. Growth is slow during the seedling period, and even more so when the soil temperature is too low.
3. Flowering and fruiting period. From the beginning of flowering to the end of harvest, about 85-120 days are needed. After emergence, the first flower opens after 50-55 days. The first and second flowers require a slightly longer number of days from flowering to harvest. After that, as the temperature rises, the harvest time shortens. Usually, the first harvest can be made about 70 days after sowing. At the optimum temperature of 28-32°C during the day and 18-20°C at night, they can be harvested 4 days after flowering. After flowering and fruiting, okra grows faster and its vigor increases, especially growing faster under high temperatures; in July, one true leaf unfolds every 3 days, while in September it takes 4-5 days for one true leaf to unfold.
[Open-field Cultivation]
1. Cultivation season. Okra likes warmth and fears frost, so the entire growth period should be arranged within the frost-free period, and the flowering and fruiting period should be in the warm and humid season of each region. For open-field cultivation, in both the north and south, sowing is mostly from April to June, and harvest is from July to October. In North China, sowing is generally from mid-to-late April to May. In cold northern regions, solar greenhouses and plastic tunnels are often used for centralized seedling raising, and after the late spring frost in early spring has passed, the seedlings are transplanted to the field.
2. Land preparation and bed making. Okra avoids continuous cropping and cannot follow fruit vegetables in rotation, so as to avoid root-knot nematodes. It is best to choose root vegetables, leafy vegetables, and so on as the previous crop. Soil with deep layers, fertility, looseness, and good water and fertilizer retention is more suitable. After the previous crop is harvested before winter, deep plowing should be done in time. Apply 75,000 kg of decomposed barnyard manure and 300 kg of nitrogen-phosphorus-potassium compound fertilizer per hectare evenly, mix well, rake level, and make beds. Open-field cultivation mostly uses two methods: first, planting in large and small rows, with large rows 70 cm apart, small rows 45 cm apart, bed width 200 cm, 4 rows per bed, and plant spacing 40 cm; second, narrow-ridge double-row planting, with ridge width 100 cm, two rows per ridge, row spacing 70 cm, plant spacing 40 cm, and furrow width 50 cm. If planted in a single row at the field edge, roadside, or riverside, plant spacing is 60 cm, with 3 plants per hole, giving good ventilation and light penetration and being convenient for management.
3. Sowing and seedling raising
(1) Direct sowing method. Okra is mostly directly sown. Before sowing, soak the seeds for 12 hours, then place them at 25-30°C to promote germination. After about 24 hours, the seeds begin to sprout, and when 60%-70% of the seeds have "broken their mouths," sow them. Hole sowing is suitable, with 3 plants per hole and a hole depth of 2-3 cm. In each region, sowing should be done at the proper time after the final frost period; water first, then sow, and then cover with about 2 cm of soil. Direct sowing uses 10 kg of seed per hectare, while seedling transplanting uses about 3 kg of seed per hectare.
(2) Seedling transplanting method. In northern regions, seedlings are mostly raised by sowing in cold frames and solar greenhouses in early to mid-March. The bed soil is prepared by mixing 6 parts garden soil, 3 parts decomposed organic fertilizer, and 1 part fine sand. Before sowing, soak the seeds to promote germination, level the seedbed, sow in spots at a spacing of 10 cm between plants and rows, and cover with about 2 cm of soil. After sowing, the seedbed soil temperature should be kept at 25°C, and they will germinate and emerge in 4-5 days. The seedling age is 30-40 days, and they are transplanted when the seedlings have 2-3 true leaves. It is best to use root-protecting seedling measures such as plastic pots and nutritional soil blocks to cultivate strong seedlings of the proper age.
4. Field management
(1) Thinning. The first thinning is done when the heart breaks, removing weak and remaining small seedlings. The second thinning is done when there are 2-3 true leaves, keeping strong seedlings. When there are 3-4 true leaves, the seedlings are finalized, keeping 1 plant per hole.
(2) Intertillage, weeding, and hilling. After the seedlings emerge or are transplanted, when the temperature is relatively low, intertillage should be carried out twice in succession to raise the soil temperature and promote recovery of the seedlings. Before the first flower opens, intertillage should be strengthened so as to moderately restrain seedling growth and favor root development. After flowering and fruiting, the plants grow faster, and intertillage should be done after each watering and topdressing. Before the rows close, intertillage and hill up the soil to prevent the plants from lodging. In areas with many summer rainstorms and wind, it is best to insert bamboo poles about 1 m long or branches near the plants to prevent lodging.
(3) Watering and fertilizing
① Watering. During the growth period, okra requires relatively high air and soil humidity. When water is lacking within 20 days after sowing, manual sprinkler irrigation in the morning and evening is suitable. After the seedlings are somewhat larger, mechanical sprinkler irrigation or furrow irrigation can be used. The hot summer season is exactly the peak harvest period of okra, when water demand is high and the surface temperature is high, so watering should be done before 9 a.m. and after sunset in the afternoon, avoiding watering under high temperatures that harms the roots. During the rainy season, pay attention to drainage to prevent seedling death. Throughout the growing period, the soil should be kept moist.
② Topdressing. On the basis of applying sufficient base fertilizer, topdressing should be done appropriately, and nitrogen fertilizer should not be applied alone. The first is the full-seedling fertilizer, applied after emergence, with 90-120 kg of urea per hectare. The second is the seedling-promoting fertilizer, applied in furrows after final thinning or transplanting, with 225-300 kg of compound fertilizer per hectare. During the flowering and fruiting period, apply one heavy fertilizer, with 30,000-45,000 kg of diluted human manure, or 300-450 kg of nitrogen-phosphorus-potassium compound fertilizer. In the middle and late stages of growth, apply topdressing multiple times in small amounts as appropriate to prevent premature aging of the plants.
(4) Plant adjustment. Under normal conditions, okra plants grow vigorously, with thick main and side branches and large leaves, often delaying flowering and fruiting. The branch-twisting method can be adopted, that is, twisting the leaf stalks into a curved and drooping shape to control vegetative growth. In the middle and late stages of growth, promptly remove the old leaves on each node below the harvested tender fruits, which can not only improve ventilation and light conditions and reduce nutrient consumption, but also prevent the spread of diseases and pests. For those harvesting tender fruits, timely pinching can promote fruit setting on side branches and increase early yield. For those harvesting seed fruits, timely pinching can promote the aging and ripening of seed fruits, favor full grains, and improve seed quality.
5. Harvesting. From sowing to the formation of the first tender fruit, okra needs about 60 days. After that, the entire harvest period lasts 60-70 days, and the whole growth period can reach about 120 days or even longer. The standard for picking commercial fresh fruits of okra is a fruit length of 8-10 cm, the fruit surface bright green, and the seeds inside the fruit not yet aged. If harvesting is not timely, the flesh ages, fiber increases, and the commercial edible value is greatly reduced. Generally, after the first fruit is harvested, in the early stage it is harvested once every 2-4 days, and as the temperature rises, the harvest interval shortens. In the peak fruiting period in August, harvest once a day or every other day. After September, as the temperature drops, harvest once every 3-4 days. When harvesting, it is best to use scissors and wear gloves to avoid the bristles or prickly tumors on the stems, leaves, and fruits injuring the skin, which causes unbearable itching; at this time, washing with soapy water or lightly roasting over a fire can reduce the degree of pain and itching. Usually, tender fruits harvested 4 days after the flowers fade have the best quality. The yield per hectare is mostly about 1,500-3,000 kg.
6. Disease and pest control
Viral disease. The main one is viral disease. This disease is spread by aphids, so aphids should be controlled in time. In the early stage of plant disease, spray the leaves with 500-800 times dilution of Virus A or 100 times dilution of 83-antagonist for control, once every 5-7 days, for 3-4 consecutive sprays.
Insect pests. The main ones are aphids and ants. You can choose 50% pirimicarb or pirimor wettable powder at 2,000-2,500 times dilution; or 40% dimethoate emulsifiable concentrate at 1,000 times dilution for spray control.
Benefit analysis
Okra's growth period is 7 months, and it can be intercropped with Chinese toon trees, that is, after the Chinese toon trees are moved out in April, okra is transplanted in. This can save the cost of building a greenhouse. Here the cost is calculated on the basis of rebuilding a greenhouse.
◆ Input
Greenhouse construction cost: at the current price level, about 13,000 yuan is needed, and under normal conditions it can be used for 6-8 years. Calculated at 6 years of use, the annual depreciation is about 2,167 yuan.
Land contract cost: contract fees vary from place to place; calculated at 1,000 yuan.
Seed cost: about 100 yuan.
Fertilizer cost: only 500-800 yuan per mu, calculated here at 800 yuan.
Water and electricity cost: 200 yuan.
Labor cost: about 3,000 yuan. Farmers developing small-scale cultivation themselves may not count labor cost.
Total input: 7,267 yuan
◆ Output
The yield of okra per mu is 2,200-2,500 kg. At a selling price of 15 yuan/kg and calculated at a yield of 2,200 kg per mu, the income per mu can reach 33,000 yuan.
◆ Profit
22,000 yuan - 7,267 yuan = 25,733 yuan.