Abstract

MAYZ FIGUEROA, Juliana. Effectiveness of cowpea rhizobial strains under different phosphorus regimes. Rev. colomb. biotecnol [online]. 2011, vol.13, n.2, pp.162-169. ISSN 0123-3475.

In Venezuela, cowpea is an alternative to animal protein due to its high consumption and nutritious value, so it has stimulated the implementation of programs to reactivate the small and medium producers economy, in order to increase its production and to have major high quality protein availability at low cost; so that, the studies carry on to improve its cultivation, are well-aimed. The effectiveness of slow (sg) and fast (fg) growing rhizobial strains was evaluated in cowpea (Vigna unguiculata (L.) Walp) cultivar TC9-6 at various phosphorus regimes (0, 20, 40 and 80 kgP₂O₅ ha^-1 ): randomized block design with factorial arrangement. Plants were cultivated in 4 kg savannah soil: 45 days, and the strains in yeast and mannitol broth: 5 (fg: JV91) and 10 (sg: JV94) days. The inoculation (2 ml each time) was applied at sowing time and 6 days later. Phosphorus utilization (40-80 kgP₂O₅ ha^-1 ) increa- sed nodulation (nodule number, total and individual dry weight) and favoured nodule red colour appearance; also, incremented shoot dry matter weight, height, leaves number and nitrogen concentration. Values were similar with both strain types (similar effectiveness) and to the two doses (40-80 kgP₂O₅ ha^-1 ), with lower estimations to 0 and 20 kgP₂O₅ ha^-1 . Accordingly with the results, the doses of 40 and 80 kgP₂O₅ ha^-1 were the most favourable to cowpea growth and nodulation.

Keywords : Vigna unguiculata; Rhizobium; growth; nodulation; phosphorus.

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