Abstract
Intercropping still remains a widespread practice in tropical developing countries. The cassava (Manihot esculenta}-cowpea (Vigna unguiculata) intercrop system was identified as one of the four major cropping systems in the forest, forest-savannah transition, and southern Guinea savannah zones of West and Central Africa. The objectives of the study were to evaluate the relative times of planting cowpea, cowpea row arrangements, and cassava variety in cassava-cowpea intercrop systems on yield and productivity, and economic returns of the systems. The study was conducted on farmers' fields in 2000-2002 in the forest-savannah transition and coastal savannah zones of Ghana. An incomplete block factorial design was used to assign a combination of (i) three cassava varieties [Afisiafi, Abasafitaa, and Local (farmer's variety)]; (ii) two relative times of planting cowpea [i.e., cowpea planted 2 weeks before cassava or 4 weeks after cassava (4 WAC)]; and (iii) three cowpea row arrangements (A1 = 1 row cassava-2 rows cowpea, A2 = 1 row cassava-3 rows cowpea, and A3 = 1 row cassava-5 rows cowpea) to farmers. The A1 and A2 arrangements with cowpea planted 4 WAC after Afisiafi or local cassava varieties were the most productive systems. Productivities or efficiencies of land use (land equivalent ratio) ranged from 37-53% for Afisiafi and 48-91 % for the local variety over the sole crops. Abasafitaa, Afisiafi, and local cassava in 4 WAC yielded 46-6l, 45--89, and 49-89% of sole crop yields, respectively. Asetenapa cowpea yielded 20% higher under the local cassava variety than the improved ones. Averaged over both years, cowpea planted four weeks after Afisiafi and local cassava varieties under the A1 arrangement, gave the highest net benefits (U.S. $592.00-U.S. $881.00), were not dominated by other systems, and also gave high marginal rate of return over the other systems. Sole cowpea gave the least net benefits (U.S. $165.00). Therefore, cowpea (Asetenapa) planted four weeks after Afisiafi or local cassava varieties using the A1 (1 row cassava-2 rows cowpea) arrangement is recommended for further demonstration and potential adoption by farmers.
