Microbial soil diversity: qPCR and PLFA from communities in response to sustainable agricultural intensification.

DANNAE SERRI; CAROLINA PEREZ BRANDÁN; DIEGO CHAVARRIA; FERNANDO SALVAGIOTTI; SILVINA BACIGALUPPO; JOSE MERILES; SILVINA VARGAS GIL

Rio de Janeiro, Brasil

Congreso; XXI Congreso Mundial de Suelos; 2018

In agricultural ecosystems, the replacement of natural vegetation by the introduction of high-productivity crop species implies significant changes in the structure of the soil microbial community. The hypothesis of this work was that the reduction in the diversity of plants would simultaneously diminishsoil microbial diversity, affecting important ecological functions. To counteract these effects, the sustainable intensification of agricultural systems, through the combination of different plant species and/or the use of winter service crops. This could contribute to the diversification of the system increasing soil microbial diversity. The objective of this work was to evaluate the response of soil microbial diversity to the sustainable intensification of agricultural systems. This study was conducted at the Oliveros Agricultural Experimental Station, Instituto Nacional de Tecnología Agropecuaria (INTA), Santa Fe province, Argentina. The field trial was performed under no-tillage and started in 2006, and soil sampling was carried out in 2015 and 2016. The treatments were different agricultural sequencescombining soybean (S), maize (M) and wheat (T) crops, including the alternative of T as a winter service crop (C). In this way, the treatments tending to the sustainable intensification of the agricultural system were: S-S; C-S; M-T / S and M-T / S-C. The structure of soil microbial communities were studied by quantitative real-time polymerase chain reaction (qPCR) and fatty acid phospholipid profiles (PLFA). Total bacteria (16S rDNA) and total fungi (18S rDNA) were determined by qPCR; and Gram-positive bacteria (GP), Gram-negative bacteria (GN), total bacteria and total fungi, arbuscular mycorrhizal fungi, Actinomycetes and total biomass (TPLFA) by PLFA. A greater abundance of 16S rDNA was registered for M-T/S-C and S-S, being the copies g dry soil-1 of 5,6E+26 and 4,9E+26, respectively. Similarly, the abundance of 18S rDNA was significantly higher for M-T/S-C and S-S, with its value of 4.2E+28 copies g dry soil-1, exceeding by 90% and 47% the treatments M-T/S and C-S respectively. Regarding PLFA, a significantly higher percentage of GN bacteria was observed in the M-T/S-C treatment, which registered 26% more than soybean monoculture (S-S). The remaining microbial groups did not show statistically significant differences for the sequences under study. Although TPLFA did not present significant differences for the treatments evaluated, there was a lower percentage in S-S.