Soil factors involved in the diversity and structure of soil bacterial communities in commercial organic olive orchards in Southern Spain

Nowadays, there is a tendency in olive production systems to reduce tillage or keep a vegetative cover to reduce soil erosion and degradation. However, there is scarce information on the effects of different soil management systems (SMS) in soil bacterial community composition of olive groves. In this study, we have evaluated the effects of soil type and different SMS implemented to control weeds in the structure and diversity of bacterial communities of 58 soils in the two geographic areas that best represent the organic olive production systems in Spain. Bacterial community composition assessed by frequency and intensity of occurrence of terminal restriction profiles (TRFs) derived from terminal restriction fragment length polymorphism (T-RFLP) analysis of amplified 16S ribosomal deoxyribonucleic acid were strongly correlated with soil type/field site (Eutric/Calcaric) that differed mainly in soil particle size distribution and soil pH, followed by a strong effect of SMS, in that order. Canonical discriminant (CD) analysis of TRFs properly classified all of the olive orchard soils as belonging to their respective soil type or SMS. Furthermore, only a small set of TRFs were enough to clearly and significantly differentiate soil samples according to soil type or SMS. Those specific TRFs could be used as bioindicators to assess the effect of changes in SMS aimed to enhance soil quality in olive production systems. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.Financial support for this research was provided by Projects AGL2008-00344 and AGL2009–12936-C03-01 from ‘Ministerio de Ciencia e Innovación’, AGL-2012–37521 and ‘Ministerio de Economia y Competitividad’ of Spain and Projects P08-AGR-03528, P08-AGR-03643 and P10-AGR-5908 from ‘Consejería de Economía, Innovación y Ciencia’ of Junta de Andalucía and FEDER financial support from the European Union. S. Aranda was recipient of a PhD. grant from ‘Consejo Nacional de Ciencia y Tecnología’ (CONACYT) México.Peer Reviewe