Response of cowpea (Vigna unguiculata (L.) Walp.) to nitrogen and inoculation in Trinidad

Abstract

The effects of N and inoculation on cowpea cv. 'Los Banos Bush Sitao No. I' (Vigna ungulculata (L) Walp.) In Trinidad were studied in dry season on field trials on a St. Augustine loam (Orthoxic Tropudult). Fertilizer N applied at 30, 60, 90 and 120 kg ha-1 failed to give any significant yield response over 0 kg ha-1 N, and nodulation was inhibited when more than 30 kg ha-1 was applied. In a subsequent experiment, inoculation with a mixture of two effective local strains did not give a significant yield difference over uninoculated and N-fed treatments. Pod yields in both experiments were low, ranging between 4500 and 5350 kg ha-1. It appears that effective natural nodulation with Indigenous rhizobia can supply most or all of the N required for optimum yield of cowpea.