Detailed Explanation of the Technical Specifications for Scientific Fertilization of Cowpea
Cowpea (scientific name Vigna unguiculata), commonly known as horn bean, ginger bean, belt bean, hanging bean pod. Cowpea is divided into two types, long cowpea and rice cowpea, and belongs to the legume family. Cowpea is an annual plant of the legume family. The stem has three types: dwarf, semi-vining, and vining. In southern cultivation, the vining type is predominant, followed by the dwarf type. It is an annual twining herbaceous plant of the Fabaceae (Papilionaceae), with 3 leaflets; the terminal leaflet is rhombic-ovate, 5-13 cm long, 4-7 cm wide, with an acute apex and a nearly rounded or broadly cuneate base, hairless on both sides; the lateral leaflets are obliquely ovate; the stipules are ovate, about 1 cm long, with the attachment point extending downward into a short spur. The calyx is bell-shaped and hairless; the corolla is pale purple, about 2 cm long, with pale yellow hairs on the inner upper part of the style. The pod is linear, pendulous, and can reach up to 40 cm long. The flowering and fruiting period is from June to September.
Morphological Characteristics of Cowpea
Annual twining, herbaceous vine or nearly erect herb, sometimes twining at the apex. The stem is nearly hairless. Pinnately compound leaves with 3 leaflets; stipules lanceolate, about 1 cm long, with the attachment point extending downward into a short spur, with linear striations; leaflets ovate-rhombic, 5-15 cm long, 4-6 cm wide, with an acute apex, entire or nearly entire margins, sometimes pale purple, hairless. Racemes axillary, with long peduncles; 2-6 flowers clustered at the apex of the inflorescence, with fleshy glands often present between the pedicels; the calyx is light green, bell-shaped, 6-10 mm long, with lanceolate teeth; the corolla is yellowish-white with a slight greenish-purple tinge, about 2 cm long, each petal having a claw, the standard petal is oblate, about 2 cm wide, with a slightly concave apex and slight auricles at the base, the wings are slightly triangular, and the keel is slightly curved; the ovary is linear and hairy. The pod is pendulous, erect or spreading, linear, 7.5-70 (90) cm long, 6-10 mm wide, slightly fleshy and inflated or firm, with multiple seeds; the seeds are oblong-elliptic or cylindrical or slightly kidney-shaped, 6-12 mm long, yellowish-white, dark red, or other colors. The flowering period is from May to August.
The leaves are trifoliate compound leaves, with flower stalks 20-25 cm long emerging from the leaf axils, bearing 2-4 pairs of flowers at the tip, white, red, pale purple, or yellow, usually setting only two pods; the pods are slender, varying by variety, about 30-70 cm long, with colors including dark green, light green, red-purple, or reddish mottling. Each pod contains 16-22 seeds, kidney-shaped, including red, black, reddish-brown, red-white, and black-white bicolor seeds; the root system is well developed, with pink root nodules on the roots.
1) Cultivating strong seedlings: For protected cultivation, varieties that are mid-to-late maturing, high-yielding, disease-resistant, highly adaptable, and suitable for close planting should be selected. Generally, the root-protecting seedling method can reduce root damage and facilitate seedling recovery. Seed treatment methods, nutrient soil preparation, and seedbed soil disinfection methods are basically the same as for common bean. For seedling raising, the nutrient pot root-protecting method is generally used to reduce root damage when lifting seedlings and facilitate seedling recovery and strong growth after planting. The diameter of the nutrient pot is 8 cm. The nutrient soil should be loose and fertile garden soil that has not grown cotton or legume crops within 3 years; 2 parts decomposed chicken manure, 2 parts horse manure, and 4 parts garden soil can be thoroughly mixed, sieved, and placed in nutrient pots. Do not fill the soil too full; it is best to fill to 3/4 of the height of the nutrient pot. Arrange them neatly on the seedbed. The seedling bed should be evenly irrigated with 50% carbendazim wettable powder at 500 times dilution or 10% shuangxiaoling aqueous solution at 250 times dilution.
Before sowing, first water thoroughly to the bottom; after the water infiltrates, sow 3-4 seeds per nutrient pot and cover with 3 cm of nutrient soil. Strengthen seedling-stage management, ventilate and harden seedlings in a timely manner, control excessive seedling growth, and promptly remove diseased seedlings.
2) Apply heavy basal fertilizer and plant at the right time: Cowpea should not be continuously cropped; it is best to choose a plot that has not grown cotton or legume crops within 3 years. After the previous crop is harvested, clean the garden, apply more than 75,000 kg/ha of decomposed high-quality organic fertilizer, mix it evenly with the soil, and make beds or ridges. At planting, apply 300-4,500 kg/ha of superphosphate, 750-1,050 kg/ha of plant ash, or 150-225 kg/ha of potassium sulfate in furrows, mix evenly, and rake level.
Before planting, close the greenhouse and disinfect the soil with formalin at 50-100 times dilution at 1-1.5 kg/sq m, keep it sealed for one day and night, ventilate for 7-10 days, and then plant; or use 50% carbendazim wettable powder at 500 times dilution to spray and disinfect the greenhouse soil, roof, and surrounding surfaces.
When planting, to prevent aphids, lay silver-gray film on the ground, or hang silver-gray film strips around the greenhouse, with a strip width of 15 cm.
3) Skillfully apply topdressing: After planting, focus on seedling restraint, control excessive stem and leaf growth, promote reproductive growth, and facilitate the formation of more inflorescences. After pod setting, in combination with watering and trenching, apply 15,000 kg/ha of decomposed human feces and urine or 75-120 kg/ha of compound fertilizer as topdressing; afterward, apply urea at 75-150 kg/ha and potassium sulfate at 75-120 kg/ha once every two pod harvests, or apply topdressing once per harvest with the amount halved. To prevent premature plant senescence, after the first yield peak appears, attention must be paid to fertilizer and water management to promote the sprouting of lateral branches and the formation of lateral flower buds, and to keep the original inflorescences on the main vine continuing to flower and set pods, extending leaf age; in this way, about 20 days after the first full pod stage, a second full pod stage will appear, and pod setting can continue for about 30 days.
In the peak growth period, 0.3% potassium dihydrogen phosphate can be used for foliar fertilization to prevent premature senescence.
To promote early symbiotic nitrogen fixation by cowpea root nodules, a nitrogen-fixing bacterial agent can be used for seed dressing, with artificial inoculation of rhizobia, in the same way as for common bean.