Multilocational characterization of selected herbaceous and shrub legumes was carried out over a 3-yr period at lowland and midlatitude sites in the moist savanna agroecological zone in Nigeria where a south–north gradient exists for rainfall, length of growing season, and insolation. One study site each was located in coastal–derived savanna (DS), southern Guinea savanna (SGS), and northern Guinea savanna (NGS). A fourth site was located in the plateau of the NGS. Only one legume cover crop, lablab, produced adequate ground cover and good weed suppression in three locations irrespective of rainfall amount, duration, and distribution. Velvetbean was superior to other legume cover crops in the lowland savanna locations where rainfall exceeded 1,100 mm/yr but not in the plateau of the NGS where rainfall was less than 1,000 mm. Pigeonpea grew luxuriantly and produced canopy cover that effectively suppressed weeds in the DS where rainfall was high. Centurion grew well and suppressed weeds effectively only in the SGS site where rainfall of 1,120 mm was well distributed over a 5-mo period. Sunnhemp grew well and suppressed weeds only in the NGS study sites where rainfall duration was 4 mo and the length of the growing period was short. Weed density was negatively correlated (P < 0.05) with percentage ground cover of those legume cover crops that were effective in weed suppression in all locations. Redundancy analysis revealed significant associations between weed species and cover crops at each of the locations.
Nomenclature: Centurion, Centrosema pascuorum Mart. Ex Benth. #3 CENPA; lablab, Lablab purpureus (L.) Sweet # LABPU; pigeonpea, Cajanus cajan (L.) Millsp. # CAJCA; sunnhemp, Crotalaria ochroleuca G. Don # CROOC; velvetbean, Mucuna pruriens (L.) DC. var. utilis (Wright) Burck # MUCPR.
Additional index words: Legume ground cover, weed density, weed species composition.
Abbreviation: WAP, weeks after planting; DS, coastal–derived savanna; SGS, southern Guinea savanna; NGS, northern Guinea savanna; RDA, redundancy analysis.
