The effect of double-rowed corn (Zea mays L.) at varying spacings on light incidence, plant height, leaf area, percent protein and yield of interplanted cowpeas (Vigna unguiculata L. Walp)

Abstract

Growth parameters of interplanted cowpeas (Vigna unguiculata) including plant height, leaf area, dry weights of leaves, stems, flower clusters, green pods, and seed as well as soluble and total protein of each plant part were measured to determine their variability as affected by 1, 2 and 3 m spacings for both corn and cowpeas were held constant. Photosynthetically active radiations (PAR) interception was measured across data rows at cowpea canopy height to determine the effect of the associated corn on the PAR availability over 3 sampling periods. A significant difference was observed between 1, 2 and 3 m spacings and between the 3 sampling periods. The % PAR received over the trial period for the 1, 2 and 3 m treatments was 71, 69, and 90%, respectively, of direct PAR. Percent PAR decreased over the 3 sampling periods from 88 to 79 to 63% as corn height increased. The 2 m treatment, which received the lowest average % PAR, consistently showed an increase over the 1 and 3 m treatments for many of the parameters measured, including yield of dry seed per ha and seed protein yield per ha.