Active N2 fixation in several Faidherbia albida provenances

For tree legumes, #Faidherbia albida$ is among those with low symbiotic capability, and for which significant improvement is needed. An experiment was conducted in the greenhouse, using the 15N isotope dilution technique to measure differences in the proportion (%Ndfa) and total N fixed in seven #F. albida$ provenances grown in an arenosol soil in Senegal. Total dry matter and N yield values were not significantly different among the seven provenances. In contrast, significant variability was measured in N2 fixation, with %Ndfa ranging from 0% in two provenances to 38% in the Kabrousse provenance. Also, total N fixed was highest in Kabrousse, 0.44 g N/plant, compared with the 0 to 0.26 g/plant fixed in the other provenances. Based on these results, Kabrousse was selected for further examination in the field, where still higher %Ndfa values were obtained, 54, 58, and 54% at 3, 6 and 15 months after transplanting (MAT), respectively. These are higher than the commonly reported values of %Ndfa for #F. albida$, and indicate the potential of screening as a tool for obtaining higher N2 fixation in NFTs. Total N fixed, unlike %Ndfa, which remained fairly constant during the three harvest periods, increased from 0.54 at 3 MAT to 1.41 g N/plant at 15 MAT. (Résumé d'auteur