By using crop rotation and introducing legume crops, farmers can improve the structure of the system and change soil characteristics for the better. At the same time, the bacterial community is stimulated and enzyme activity is intensified, while an optimal nutritional regimen is created. Another improvement that comes from growing legumes is that it creates conditions for the accumulation and storage of soil humidity (Insam and Domsch 1988; Wardle 1992, Kowalchuk et al, 2002, Sharma1, et al, 2005). The aim of the paper is to study the way in which species Vicia sativa, organic matter and soil humidity index can influence the structure of the bacterial community in moderately-gleyed eutric cambisol. Ten samples of soil were collected as biologic material from two experimental fields sown with Vicia sativa, which is going to be incorporated into the soil as "green fertilizer". The biologic material was processed and conditioned at the Microbiology Laboratory at Banat University of Agricultural Sciences and Veterinary Medicine, Timisoara. The microorganisms in the root area and near-root area (experiment I and II) were isolated on YMA growth medium, using the plate culture method (Borozan, 2006). In parallel we looked for the presence of bacteria specific for legumes and root node bacteria belonging to genus Rhizobium (experiment I). We noticed changes in the microbial balance in the rhizosphere and rhizoplane. These changes were characterized by increases of UFC/g soil, the largest number being recorded on the rhizoplane (in experience II in particular).  In this last variant, the microbial segment is the most reduced, which proves the fact that quantitative changes in the microbial balance in the root and near-root zone of the soil is determined by the substances eliminated by vetch into the soil.  Of the two experiments, the second experience gives the highest number of UFC/g soil. The statistical data revealed a certain contribution of the humidity index and humus content in the evolution of UFC/g soil.  In what the formation of root nodules on the root of Vicia sativa is concerned, when the plant grows on slightly gleyed eutric cambisol (1st experiment), we noticed numeric variation of these, for similar values of the humidity index and humus content.

bacterial community, rhizosphere, rhizoplan, Genus Rhizobium, Vicia sativa

Presentation: oral