How to Grow Cowpeas for High Yield? Latest High-Yield Cultivation Technique Tutorial
Cowpeas require high temperatures and have strong heat tolerance. The optimal growing temperature is 20-25°C. In summer, they can still set pods normally at high temperatures above 35°C and do not drop flowers. However, they are not frost-tolerant; prolonged low temperatures below 10°C inhibit growth. Cowpeas are short-day crops, but the long cowpeas grown as vegetables are mostly neutral to day length and are not very strict about sunlight requirements. Varieties such as Hongzuiyan and Zhijiang 28-2 can be cultivated in spring, summer, and autumn in southern China. Cowpeas adapt to a wide range of soils; any field with good drainage and loose soil can be planted. The pods are tender, and during the pod-setting period, adequate fertilizer and water are required.
Sowing and Seedling Raising
Early-maturing cultivation of cowpeas generally requires strong seedlings. The sowing time should be determined according to local climatic conditions, cultivation facilities, and management measures. For cultivation under small arch tunnels, sowing can be done in mid-to-late March; for greenhouse cultivation, sowing can be done in early-to-mid March; for greenhouse-within-greenhouse cultivation, sowing can be done from late February to early March. In some areas, the sowing time is delayed until late April or early May, and direct sowing can be used.
Before sowing, select plump, pest-free, undamaged seeds, and sun-dry them for 1-2 days on a sunny day. If necessary, seeds can be treated with chemicals before sowing. Prepare the seedbed before sowing; the nutrient soil in the seedbed should be no less than 5 cm thick. The seedbed soil should be at appropriate moisture, not too wet, otherwise the seeds are prone to rot. When sowing, scatter the seeds in the seedbed soil without overlapping. After sowing, cover with loose fine soil 1.5-2 cm thick, press lightly, then spread sparse rice straw and cover with plastic film to retain heat and moisture. After sowing, maintain the seedbed temperature at 25-30°C.
Seedlings begin to emerge 4-5 days after sowing. When about 30% of the seeds have emerged, promptly remove the plastic film and rice straw. When most seeds have emerged, lower the seedbed temperature, keeping the daytime temperature at around 20°C, not exceeding 25°C, and the nighttime minimum not below 15°C. If the temperature is too high, the small arch tunnel can be opened to cool down, but cold wind must be prevented from blowing directly into the seedbed to avoid cold damage. Begin hardening the seedlings 4-5 days after complete emergence. During hardening, the nighttime minimum temperature must not be below 10°C. Transplant when the first pair of true leaves has formed but not yet fully expanded. To protect the root system, nutrient pot seedling raising can be used if conditions permit.
Land Preparation and Base Fertilizer Application
Cowpeas are not waterlogging-tolerant and have a long growing period, requiring substantial nutrients during growth. Choose soil with high, dry terrain, deep soil layers, rich organic matter, and convenient drainage and irrigation. Prepare the land and apply base fertilizer 10-15 days before transplanting. Generally, apply 1500-2000 kg of fully decomposed human manure or chicken/duck manure, 15-20 kg of superphosphate, and 75-100 kg of plant ash per mu. This can be applied in furrows or broadcast. After land preparation, the bed surface width should be 100-110 cm, the furrow width 40 cm, and the bed height 20-25 cm. After leveling the bed surface, cover with plastic film.
Transplanting
Although cowpeas have a well-developed root system, their roots have weak regeneration ability, so small seedlings are preferable for transplanting. Generally, transplant when the cotyledons have expanded and the first pair of true leaves has not yet fully expanded; those raised in nutrient pots can be transplanted slightly later. Transplanting should be done on a sunny day at the end of a cold spell and the beginning of warm weather. Before transplanting, water the seedbed thoroughly, then lift the seedlings, discarding abnormal seedlings with damaged cotyledons or distorted true leaves. Cowpeas are transplanted in double rows, with hole spacing of 24-27 cm and 2-3 plants per hole. When transplanting, the plastic film opening should be small. After transplanting, water immediately to settle the roots, then seal the opening with soil.
Post-Transplanting Management
1. Replanting
After transplanting, check promptly. Seedlings that are missing or have damaged basal leaves should be replanted in time. After replanting, water thoroughly immediately to ensure these seedlings can grow in sync with other normal seedlings.
2. Water Management
After cowpeas recover from transplanting and before flowering and pod setting, strictly control water, otherwise plants will grow excessively, flowering nodes will rise, lateral buds will sprout, and the middle and lower parts of the plant will easily become bare vines (no pods). Generally, water once every 3-5 days after transplanting to help seedlings recover, then in principle do not water. Too much water at the early flowering stage will cause excessive vegetative growth, consuming too many nutrients and preventing flower buds from getting enough nutrients, leading to flower and pod drop. After pods set, the plant enters vigorous growth, growing stems and leaves while continuously flowering and setting pods. Water demand increases, so more water should be supplied to promote pod elongation and expansion, increase pod number, and maintain good plant vigor. Generally, begin watering when young pods are 2-3 cm long, then water every 5-7 days, but prevent waterlogging after rain.
3. Topdressing
The principle of topdressing cowpeas is “apply less before flowering, more after flowering, and heavily during pod setting.” Generally, after seedlings survive, apply a seedling-promoting fertilizer once, with 1000 kg of 15%-20% decomposed human manure per mu. After flowering, apply 1500 kg of 20% concentration decomposed human manure. After pod setting, apply 2000 kg of 20% concentration decomposed human manure and 10 kg of superphosphate, then apply once every week thereafter; alternatively, apply 15 kg of compound fertilizer per mu each time. In the late growth stage of cowpeas, apply heavy topdressing 2-3 times consecutively, using 15-20 kg of compound fertilizer each time, to promote vigorous plant growth, continue producing flower clusters, increase pod-setting rate, extend the harvest period, and increase yield.
4. Timely Trellising
Generally, when the plant begins to “throw vines,” set up trellises and guide the vines to prevent them from tangling with each other, which facilitates ventilation and light penetration and reduces flower and pod drop. Generally, use 2-2.5 m long bamboo poles to build an A-frame trellis, inserting one pole per hole, 10-15 cm from the plant base, inserting 15-20 cm into the soil. Place a bamboo pole at the crossing point of the upper 4/5 and tie it tightly with rope as a crossbeam. After trellising, guide the vines counterclockwise 2-3 times so the stems grow along the trellis, then let them grow naturally. The bamboo poles used for cowpea trellising are relatively long, so operate carefully during trellising to avoid puncturing the greenhouse film with the pole tips. After trellising, especially after entering the harvest period, promptly remove old and diseased leaves from the base according to plant growth conditions.
Pest and Disease Control
Common cowpea diseases include rust, gray mold, sclerotinia rot, and anthracnose. Pests are mainly aphids, pod borers, and thrips. Measures should be taken to control them promptly.
Harvesting
Cowpeas reach the initial harvest period 40-50 days after transplanting. Generally, cowpeas reach commercial maturity about 10-12 days after flowering and can be harvested successively. The specific harvest standard is pods that are plump, show the variety's characteristic color, and have not yet “bulged" at the seeds. Harvesting too early results in low yield; if harvesting is too late, pods easily become fibrous and old, and cowpeas suffer severe flower and pod drop, so harvesting should be timely.