What causes yellowing of cowpea vines?

Cowpea is a common vegetable, rich in nutrients and well loved by people, and it can be cultivated in most parts of our country. So, what causes yellowing of cowpea vines?

1. What causes yellowing of cowpea vines?

Yellowing of cowpea vines may be caused by infection with root rot, a lack of fertilizer, or excessively high temperatures. If it is infected with root rot, carbendazim, thiram, hymexazol or copper abietate can be used for root drenching. If it is a lack of fertilizer, some foliar fertilizers such as amino acid foliar fertilizers can be sprayed during the middle and late stages of cowpea seedling development, used together with fertilizers containing elements such as boron, calcium, magnesium, iron and zinc, which has a very noticeable effect on reducing yellowing of the upper leaves. If the temperature is too high, appropriate shading is needed.

2. Cultivation techniques for cowpea

1. Soil

It is best to choose fertile, loose loam or sandy loam, and rotate with legume crops for 2-3 years. Heavy clay soil or low-lying plots with poor drainage are not suitable.

2. Sowing and raising seedlings

Tezao 30: an extremely early-maturing variety. Few branches, with pods set mainly on the main vine. Under conventional open-field cultivation, it takes about 35 days from sowing to the first flower, and pods can be harvested 10-12 days later. The harvest period lasts 20-40 days, and the whole growth period is 80-100 days. The first flower node is low, and pods generally set at about 3 nodes on average. When sown at the same time, the first flowering stage and first harvest stage are 2-5 days earlier than those of Zhijiang 28-2, and the total yield is slightly higher than that of Zhijiang 28-2. The tender pods are light green, uniform, about 60 cm long, with a single pod weight of about 20 g, and good market quality.

Zhijiang 28-2: mid-early maturing, plant height about 2.5 m, few branches, relatively sparse leaves. The main vine begins to set pods at nodes 4-6, with many pods; the pods are greenish-white, generally 60-80 cm long, 0.9-1.1 cm in cross diameter, and a single pod weighs 25 g. Thick flesh, few fibers, not easy to age, and excellent quality. Tolerant of high temperature and drought, and resistant to mosaic virus disease. The growth period is 90-100 days, with a yield of 2000-2500 kg per mu.

3. Fertilization

Apply heavy base fertilizer: the base fertilizer should mainly be decomposed organic fertilizer, combined with a properly proportioned compound fertilizer, such as Jinkai nitro compound fertilizer (15-15-15, 16-16-16), a compound fertilizer with relatively high phosphorus and potassium content. The generally recommended amount is 50-60 kg per mu, and it should be deeply plowed into the soil;

Skillfully apply topdressing: cowpea needs less fertilizer during the seedling stage, and heavy watering and heavy fertilizing can easily cause excessive vegetative growth. To control excessive stem and leaf growth, promote reproductive growth, and prevent overly vigorous growth leading to fewer flowers and fruits, the supply of fertilizer and water should be appropriately controlled. When the seedlings are weak, Jinkai liquid seedling-raising fertilizer can be applied with irrigation, at 5 kg per mu. Entering the pod-setting stage, the fertilizer requirement of cowpea begins to increase. After flowering, topdress with Jinkai nitro compound fertilizers in ratios such as 22-8-15 and 17-5-23, generally 15-20 kg each time. Topdress once every two pod harvests, applying 10 kg of Jinkai nitro compound fertilizers in ratios such as 22-8-15 and 17-5-23.

4. Reasonable close planting

The sowing time should be determined according to different cultivation methods. For example, when using a greenhouse + small arch shed + plastic film cultivation, sowing and seedling raising can be carried out in mid to late February, and nutrient pot seedling raising can be used where conditions permit. During the seedling stage, ventilation should be appropriately strengthened to reduce humidity, preventing excessive humidity in the seedbed from producing leggy seedlings or causing damping-off disease. In early to mid-March, transplant into the greenhouse. The planting density is two rows per bed, with a plant spacing of 15-20 cm, 3 plants per hole. After transplanting, water an appropriate amount of rooting water, and seal the transplanting opening with soil in time. Alternatively, direct sow in the greenhouse in early March, with a plant spacing of 15-20 cm and 3-4 seeds per hole. For open-field cultivation in Henan Province, sowing in late March is generally appropriate.

5. Field management

Strengthen the greenhouse temperature to promote early seedling recovery. After transplanting under greenhouse cultivation, first keep the greenhouse closed for 5-6 days to maintain a relatively high greenhouse

temperature and promote early seedling recovery. If a cold wave occurs, straw curtains must be added over the small arch shed to prevent cold damage. When the greenhouse temperature exceeds 30°C, ventilation should be carried out in time to lower the temperature.

Set up trellises in time and prune reasonably. When the vine grows to 20 cm, trellises should be set up in time to guide the vines, and all lateral buds below the first inflorescence on the main vine should be removed. In cases where side branches grow out, they can also be pinched off after leaving 1 leaf, using the first node of the side vine to form an inflorescence. Side branches growing from the middle and upper parts of the main vine in the middle and late stages should be pinched off early in time. If fertilizer and water conditions are sufficient and the plant grows vigorously, these side branches should not be pinched too heavily, and side vines can be used as appropriate to bear fruit. When the main vine grows to more than 2.2 m, top and pinch it in time to control growth and promote the formation of flower buds on side branches, so as to avoid consuming nutrients. If fertilizer and water are sufficient, the plant's vegetative growth is too vigorous, and ventilation is poor, excessive leaves, branches, old leaves and diseased leaves can be removed.

When planting cowpea, it is necessary to ensure that the soil is loose and breathable and that the plant has sufficient nutrition, so as to prevent the cowpea seedlings and vines from turning yellow.