African Journal of Biotechnology Vol. 1 (2), pp. 50–56, December 2002

ISSN 1684-5315  © 2002 Academic Journals  

Estimates of biological nitrogen fixation by Pterocarpus lucens in a semi arid natural forest park in Senegal using ¹⁵N natural abundance method

Sylla S N¹*, Ndoye I¹, Gueye M², Ba A T¹ and Dreyfus B³

¹UCAD, Faculté des Sciences et Techniques, Département de BV, BP 5005, Dakar, Sénégal.

²MIRCEN/Centre ISRA-IRD, BP 1386, Dakar, Sénégal.

³LSTM, IRD _ CIRAD, TA10/J, Campus de Baillarguet, 34398, Montpellier, France.

*Corresponding author; e-mail: Samba.sylla@ird.sn, tel: +221-8 49 33 22, fax: +221-8 32 16 75

Accepted 15 November 2002

Nitrogen (N₂) fixation by Pterocarpus lucens in a natural semi arid ecosystem, in Ferlo, Senegal was estimated using ¹⁵N natural abundance (∂¹⁵N) procedure. Other non-fixing trees accompanying P. lucens in the same area were also investigated as control. Results showed an important variation of ∂¹⁵N in leaves between the nitrogen-fixing tree (P. lucens) and reference plants, whereas no significant differences were recorded in amount of nitrogen (%). The relative ∂¹⁵N values (‰) were higher in non-fixing plants than in fixing plants considered. Calculations of %Ndfa gave rates ranging between 26% and 49%. The values of %Ndfa depend largely on soil and the reference plants. The contribution of nitrogen derived from fixation in leaves reached 28.9 kg.N/ha and 10.8 kg.N/ha in ferruginous and in sandy soil respectively.

Key words: Pterocarpus lucens, ¹⁵N natural abundance, semi arid lowland, biological nitrogen fixation, natural ecosystem.