potentiality of some Sudanese Acacia species for nodulation and nitrogen fixation

Inaam A. ElTahir, Hashim M. Babiker, Nouri O. Mukhtar, Muawia E. Hamad


Pot experiments were carried out to investigate the capability of seven Acacia species (A. seyal, A. senegal, A. nilotica, A. polycantha, A. mellifera, A. nubica and A. tortilis) for nitrogen fixation and to assess the efficiency of isolated and re-inoculated rhizobia for nodulation and N fixation. Also, the amount of N fixed by four Acacia species (A. seyal, A. senegal, A. mellifera and A. nubica) was estimated using 15N isotope dilution method with Tamarindus indica used as a reference plant. Fertilization was carried out by adding 20 kg N/ha (5% 15N atom excess) and 100 kg N/ha (1% 15N atom excess) to the fixing and to the non-fixing plants, respectively. Dry biomass, number of nodules, dry weight of nodules, N% and N content were determined. Plant tissue analysis was carried out for 15N and 14N. Result showed significant differences between the species in the growth parameters, with Acacia polycantha, A.seyal and A. mellifera giving the highest values. The inoculated plants gave the highest biomass and nodulation parameters. The study revealed a strong relationship between biomass and N content. The study also showed differences in N fixation among the tested Acacias  species(A. nubica, A. senegal, A. mellifera and A. seyal) both in terms of % N needed by the plant (60%, 58%, 53% and 50%)  and the total N fixed (0.063, 0.104, 0.098 and 0.078 g/plant, respectively).

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