Time of planting and weed suppression abilities of some legumes intercropped with maize in the Guinea savanna zone of Ghana

Abstract

Field experiments were conducted in the field at Nyankpala in the Northern Region of Ghana to determine the appropriate time of intercropping soybean, cowpea and groundnut with maize for optimum yield; and to compare the weed suppression abilities, vis-a-vis maize yields, of these legumes. The legumes were intercropped with the cereal 0, 2 and 4 weeks after planting (WAP) the maize. The intercrop components were arranged in a 1:1 spatial arrangement. The nonintercropped treatments served as sole crops. The experimental plots were laid out in a randomized complete block design (RCBD) with four replications for each treatment. Results showed that leaf area index, shoot biomass, nodule number, pod number, grain yield and land equivalent ratio (LER) decreased with delay in intercropping. However, LER values indicated that the intercrops had yield advantage over the sole crop maize. The appropriate time of intercropping maize with the legumes for optimum maize yield is very early (before or at 2 WAP maize). Results also showed that cowpea suppressed more weeds in the maize field than groundnut and soybean. Cowpea-maize intercrop gave a maize yield of 2988 kg/ha which was not significantly different from the sole maize yield of 3291 kg/ha at 2 WAP maize.