Influence de la décomposition de la nécro-masse des espèces végétales tropicales sur le pH et la structure génétique des communautés bactériennes d’un sol ferrugineux tropical au Sénégal

Abstract

Objectives: This study was conducted to follow the influence of Faidherbia albida A. CHEV., Azadirachta indica A. JUSS., Casuarina equisetifolia FORSK., Andropogon gayanus KUNTH. and Eragrostis tremula STEUD. litters on soil pH and the genetic structure of bacterial communities of a lixisol. Methodology and Results: The litter weight loss was followed during the rainy season for 90 days in an experimental plot at Ecole Nationale Superieure d’Agriculture (E.N.S.A) of Thies. The study of the pH and the genetic structure of microbial communities was carried out in laboratory by mixing the grinded litters with 30 g of soil, the whole incubated for 140 days. The PCR-DGGE technique was used to study the genetic structure of soil microbial communities. Results have shown that at 90 days, that decomposition rate was 90% for A. indica and E. tremula, 75.5% for C. equisetifolia, and 31% for A. gayanus and F. albida. litter decomposition tended to decrease the pH compared to the control without litter amendment, and the decrease was more significant in soils amended with F. albida litters. The analysis of the genetic structure of microbial communities showed that after 140 days of incubation, although the litter effect reported, the difference between treatments is reduced. E. tremula, A. gayanus and C. equisetifolia diverged while A. indica and F. albida got closer (98% of similarity). Conclusions et Application : The study has shown that the input of organic matter to the soil, influences the pH and at the same time the microbial communities, but not in the same manner.