Twenty-eight (28) cowpea genotypes were evaluated in a multi-location trial across the Guinea Savannah agro-ecological zone of Ghana from June to October 2007. The three locations which were among the major cowpea producing areas in northern Ghana included Damongo, Yendi and Nyankpala. The objectives of the study were to: (1) assess cowpea grain yield and its selection criteria for maize-cowpea intercropping condition (2) determine whether cowpea lines selected under sole-crop conditions are productive under cowpea-maize additive series intercropping system. Even though there was significant genotype x location interaction effect for grain yield, the interaction did not complicate selection strategy. Selection for intercropping systems may be done under sole cropping due to similar heritability values, non-significance of genotype x cropping system interaction and lower error associated with evaluations under sole cropping compared to intercropping system. SARC 14-88, SARC 14-110, SARC 14-208, SARC 14-78, IT 95K-193-2 and IT 97K-499-35 were identified as the most intercrop-adapted genotypes. Such promising grain yielding genotypes could be used for grain yield improvement using intercrop susceptibility index (ISI), earliness to flower as well as grain yield under sole cropping system as selection criteria for maize-cowpea additive series intercropping system.

Keywords: genotype, cropping system, genotype by environment interaction, savannah zones

Field trials on sesame were conducted at the Manga Agricultural Research Station during the 2009 and 2010 cropping seasons to determine the optimal rate of nitrogen fertilizer and intra-row spacing for sesame production. Consistently, intra-row spacing of 30 and 40cm produced the best results in both seasons in terms of grain yield. Sesame grain yield increased significantly with increase in the rate of nitrogen fertilization, implying that sesame yields could be boosted through an increase in nitrogen fertilizer application. Marginal insignificant yield response was observed with increased nitrogen level attaining the peak at 80kgN/ha. Main effects of nitrogen rates and intra-row spacing significantly (P<=0.001) affected most of the traits evaluated more than the interaction effects. Plant spacing of 75cm x 30cm at N application of 80kgN/ha recorded the highest grain yield (273kg/ha) in 2009 while 75cm x 30cm at 0kgN/ha (control) recorded the least grain yield (60kg/ha) in 2010. Even though there was no significant interaction effect on plant population, the interaction effects of 20 cm and 30cm at 80kg N/ha produced the highest plant populations of 6.9 and 7.1 respectively. Sesame plant height was significantly (P<=0.001) influenced by N application with plant height increasing with increase in N rate, attaining a maximum height of 142cm at 60kgN/ha. Even though there was no significant interaction effect on plant population, the interaction effects of 20 cm and 30cm at 80kg N/ha produced the highest plant populations of 6.9 and 7.1 respectively. Sesame plant height was significantly (P<=0.001) influenced by N application with plant height increasing with increase in N rate, attaining a maximum height of 142cm at 60kgN/ha in 2009.

Keywords: Sesame, intra-row spacing, nitrogen fertilizer rate, main effect, interaction effect.