Impact of extensive agriculture on argentinean soils microbial diversity as revealed by 16s rRNA pyrosequencing

Argentina has over 30 million hectares under intensive agriculture, three times that of de European surface, and it is the third world producer of soybean and maize. Since the sustainable exploitation of natural resources is an important issue in the current global agenda, we are interested to investigate how intensive agriculture impact in soil microbial diversity. We used the 454 pyrosequencing technology to produce a dataset 718,226 pyrotags covering the V4 16s rRNA region from three different sites (each one disturbed and undisturbed) in the pampa humeda region. Additionally, we analyzed dynamical changes over a one-year period in one of these sites from another dataset of 413,667 pyrotags covering five different time points. In general, we showed that there is no dramatic impact on microbial diversity and species evenness even under intensive agriculture management in the pampa humeda soils, although we detected some specific proportional variations from phylums down to species adapted to each condition. Interestingly, we also found dynamical changes in the microbiota during the analyzed timeframe that were more related to the climate variables than to the agriculture management. Moreover, to our knowledge, the complete dataset of 1,131,893 pyrotags is one of the largest analyses in soil to date.