Performance of cowpea grown as an intercrop with maize of different populations
Cereal-cowpea intercrops have a record of low yields in the West African savannah. Two potential ways to improve the yield of cowpea (Vigna unguiculata Walp), when grown with maize (Zea mays L.), is by manipulating the plant population of maize and using adapted cowpea cultivars. A field trial was conducted at Samaru in northern Guinea savannah of Nigeria, to determine the performance of semi-determinate and indeterminate cowpeas grown under maize populations of 0, 17,777, 26,666, and 53,333 plants ha-1. The radiation transmitted into cowpea was reduced by 50, 30 and 15% for a maize population of 53,333, 26,666 and 17,777 plants ha-1 respectively, compared with 0 plants ha-1. Maize population of 0 to 26,666 plants ha-1 favoured better cowpea performance compared with 53,333 plants ha-1 because at these lower plant populations, maize plants had lower leaf area indices which allowed maize canopy to transmit more light into the understorey cowpea. The negative effects of shade were more pronounced in the semi-determinate cowpea than in the indeterminate. Therefore, in high maize populations, indeterminate spreading cowpeas should be grown; while semi-determinate cowpeas should be planted in low to moderate maize populations because of their intolerance to severe shade.
Key Words: Vigna unguiculata, Zea mays