Abundance of Legume Nodulating Bacteria in Soils of Diverse Land Use Systems in Cameroon

Abstract

Improving biological nitrogen fixation through legume nodulating bacteria (LNB) inoculation requires knowledge on the abundance and effectiveness of indigenous population in the ferralsols. The Most Probable Number method (MPN) was used to determine the naturally occurring LNB population in 64 representative soils of four sites in the humid forest zone of Cameroon. Nodulation Macroptilium atropurpureum was examined under tubes experiment in four location sites: Bertoua, Ebolowa, Bokito and Yaounde, and within each of the locations, in four land use systems (LUSs) of different levels of disturbance: mixed farm; fallows; cocoa plantation and forest. The LNB population size varied from 0.78 to 5.25 log units of soil depending on the land use. The most disturbed LUSs (farms and fallows) exhibiting the highest number of LNB on average. Undisturbed ones (cocoa plantation and forest) showed the lowest number of LNB. The percentage of the need for inoculation was more frequent in the forests (94%) and plantations (75 %). It is low in the in the fallows (25%) and the farms (44 %). In total 60 % of the soils analysed need inoculation. These results are important for future investigations on alternative inoculant strains for improving legume production in Cameroon.