Influence of agricultural practices on microbial population in Argentinean Rollin Pampa soil

FLOCCO, CG; CUADRADO, V; MERINI, LJ; GIULIETTI, AM

Capital Federal

Congreso; VII Congreso Latinoamericano y III Congreso Argentino de Biotecnología, BIOLATINA; 2006

Rolling Pampa region is Argentina`s prime agricultural land where intensive practices are carried out. Plots are chiefly used with an annual rotation scheme of crops such as corn, soybean, and wheat; also pastures for feeding cattle are cultivated. In the last two decades, the implementation of the “no-till system” became a widespread agricultural practice in this region. This implies the use of agrochemicals, like herbicides, which became an irreplaceable tool for pre and post emergent weed control. The objective of this work was to analyze the composition of the bacterial communities of three soils with different histories of crop cultures and herbicides regimes. In this way, PCR-single strand- conformation polymorphism (SSCP) of partial 16S rRNA genes was used as a genetic profiling technique followed by DNA sequencing of the highly abundant or specific bands of each profile. The dendograms obtained revealed a higher degree of similarity between the two soils with pasture, either a wild one (CC soil) or a seeded one (CPDB), regardless the fact that only CPDB soil has a history of use of herbicides (2,4-DB). The third soil (CMA) had a smaller degree of similarity with the two pastures, but it can not be said if this is attributable to the different crop use (planted alternatively with maize and soy bean), to the different herbicide regimes (atrazine and glyphosate vs. phenoxy herbicides) or to both factors. Nevertheless, these results suggest that the kind of crop cultured would be the main variable affecting the microbial communities composition in these soils, and that the presence or not of an herbicide treatment would not significantly affect soil biodiversity.