Cowpea has a well-developed root system, the main root is 20-80cm deep, mainly distributed in the 15-18cm soil layer, the root system has a weak capacity for renewal, and the rhizoma ****-generating capacity is weak. Cowpea stems are short, semi-decumbent and semi-pendulous. Each inflorescence usually has 2-4 pods, which are 30-100 cm long and 0.7-1 cm thick. It is almost cylindrical, hence the name cowpea. The pods are blue, green, light green and purple. Each pod contains 8-20 seeds.

I. Environmental requirements

1. Temperature. Cowpea is a heat tolerant vegetable. The minimum temperature for seed germination is 8-12℃ and the optimum germination temperature is 25-30℃. The suitable temperature for plant growth is 20 ~ 25℃. The suitable temperature for flowering and podding is 25 ~ 28℃, relatively heat-resistant. It can still grow, flower and set pods normally above 35℃. Cowpea is sensitive to low temperature, growth is inhibited below 10℃, freezes below 5℃ and dies at 0℃

2. Light. Cowpea is a crop with short sunshine, but most varieties do not have strict requirements for sunshine length. There is a tendency for shorter sunshine to result in early flowering, early pod formation and low flower nodes. Adequate light is required during flowering and pod setting or flower and pod drop will result.

3. Humidity. Cowpea has a deep root system with high water absorption capacity, low leaf transpiration and high drought tolerance. Cowpea needs moderate amount of moisture during growth. However, excessive soil moisture tends to cause yellowing of leaves, defoliation and even root rot, leading to seedling death. Flowering pods are not conducive to the activity of rhizomatous seedlings.

Two, seed selection

Cowpea likes temperature and heat resistance, and has a long growing season. After frost in late spring and before frost in early fall, choose the appropriate varieties according to different seasons and cultivate in spring, summer and fall to extend the supply cycle. Early spring cultivation should choose varieties with less stringent sunlight conditions. Cowpea can be divided into summer and fall sowing. To save seeds, select disease-free plants with low podding rates and concentrate on pods that are characteristic of the variety. Pairs of pods are the same size and seeds are neatly arranged. Select the lower and middle pods for seed and remove the upper pods in time to fill the seed. When the seed walls of the pods are soft enough and the skin is yellow, they can be picked, hung indoors, dried in the shade, and threshed. After drying, heat the seeds and store them in a pot in an airtight container, or place a few mothballs in the pot in an airtight container to avoid damaging the beans. If there are a few seeds, there is no need to thresh them. Hang the pods indoors in a ventilated area. They can be removed before planting and threshing next year. Seed viability is usually 1-2 years.

These are the notes on the environmental requirements of cowpea and how to do seed screening for your information and study.