Cowpeas are indigenous to Africa and can be cultivated on various soil types, even producing a crop on poor soils, but adding some compost and manure 3 to 4 weeks before planting can benefit growing.
Adding phosphorus (P) to the soil can improve seed set. Application of a phosphate fertiliser (F) is usually beneficial. Cowpea can grow in a pH range of 5,6 to 6,5 and prefers sandy soils but struggle in heavy wet soils. Putting nitrogen back into the soil (also called nitrogen fixation) is a characteristic of legumes,and is difficult in waterlogged soils.
Cowpeas is a summer crop which grows best when the minimum temperature is not lower than 10°C. Optimal growth temperature is around 30°C. It is more drought-tolerant than groundnuts, soybeans and sunflowers. In cooler areas, one should plant cowpeas in the middle of November and in warmer areas the crop can be planted during the middle of December.
Do not plant cowpeas at the beginning of the rainy season (beginning of October) or late in January because it can result in low yields and frost damage. Some insects are also more active late in the growing season. The planting date of cowpeas determines the use of the crop. For instance, if it is going to be used as grazing, it can be planted in October.
Plant seeds about 4 cm deep (width of matchbox) and 10 cm (just more than a hand width) apart. Do not compact the soil after planting, but firm it down to ensure good soil-seed contact. Pests like aphids and bollworm may be problems but it is important not to plant cowpeas successively on the same land because they are susceptible to nematodes.
The most important disease of cowpeas is stem rot. For grain production choose a cultivar such as Rhino or Glenda. For hay use Chappy or Bechuana White.
Harvesting Cowpeas
Cowpeas are harvested for grain when 90% of the pods have dried off. The whole plant is pulled up - this can be done as soon as the pods start to discolour.
When cowpeas are used as a vegetable, the green leaves and young pods can be picked by hand. Cowpea hay can be stored in bales or haystacks.
Commercial machinery can be used to thresh cowpeas, but the pods can also be put into a bag and then trampled or beaten with a stick to separate the seeds from the pods.