INFLUENCE OF IRRIGATION ON MICROBIAL COMMUNITIES AND SOIL ORGANIC MATTER EVOLUTION IN THE CHERNOZEM IN MARCULESTI

摘要

Anthropic interventions, such as irrigation can induce major changes in soil fundamental regims with implications in the whole ecosystem equilibrium. The increase of soil moisture causes decrease of temperature, modifies nutritional conditions for microflora and finally changes soil climax. Research have been carried out in order to assess changes in microbiological activity and taxonomic composition of microflora in irrigated chernozem in Marculesti as compared with non-irrigated control. The paper presents the results concerning the distribution of bacterial and fungal counts in the horizons of soil profile, species composition of each community and the level of CO_2 released by micrbflora as a consequence of its metabolic activities. Data analysis showed that the development of fungal and bacterial microflora was stimulated by increased humidity from irrigated plot. The release of CO_2 was, generally more intense in the horizons of irrigated soil profile when compared with non-irrigated one. Increments in bacterial and fungal counts on soil horizons have been recorded in irrigated soil when compared with non-irrigated, as well as changes in taxonomical composition and species diversity. Soil increased humidity and lowered temperature induced taxonomical changes, with dominance of Fusarium-Penicillium fungal association and Bacillius megaterium-Bacillus circulans bacterial associations in irrigated soil. Irrigation induced changes in soil biological quality and organic matter turn-over processes revealed by increased quantities of fulvic acid fractions Ⅰ-Ⅱ and sub-fractions B-C of aggressive fulvic acids in ascendant chromatograms.