Organic amendments and land management affect bacterial community composition, diversity and biomass in avocado crop soils
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Background and aims
The avocado-producing area of southern Spain includes conventional orchards and organic orchards that use different organic amendments. To gain insight into the effects of these amendments, physicochemical properties and microbial communities of the soil were analysed in a representative set of commercial and experimental orchards.
The population size of several groups of culturable microorganisms was determined by plating on different selective media. Bacterial community structure was studied by denaturing gradient gel electrophoresis (DGGE)
Commercial composts showed the largest effects, especially the animal compost, enhancing the population sizes of some microbial groups and affecting bacterial community structure in superficial and deep soil layers. Moreover, animal and vegetal compost, manure and blood meal addition are related to high bacterial diversity in the superficial soil layer.
All of the organic amendments used in this study affect soil properties in one or more of the characteristics that were analysed. Culturable microbial population data revealed the most evident effects of some of the organic treatments. However, molecular analysis of soil bacterial communities by DGGE allowed the detection of the influence of all of the analysed amendments on bacterial community composition. This effect was stronger in the superficial layer of the avocado soil.
KeywordsOrganic crop Community structure Microbial diversity Manure Compost Almond shells DGGE
We want to thank David Sarmiento from SAT “TROPS” for assistance in sampling design and sample collection. We would also like to thank the owners of the orchards in which the study was conducted, the members of our laboratory for their inestimable help with the microbial analysis and Juan A. Torés for his assistance during various parts of the project. We are especially grateful to Jose M. Farré for his helpful ideas and discussion, which were absolutely essential for this project, and for allowing us to include his experimental orchards in the study. This work was supported by Plan Estratégico BIOÁNDALUS, CICE-Junta de Andalucía (BIOÁNDALUS 08/1/l1.1), and by Plan Nacional I+D+I from Ministerio de Ciencia e Innovación (MCI) (AGL08-05453-C02-01), co-financed by FEDER funds (EU). N. Bonilla was supported by a PhD fellowship from the FPU program of MCI.
Electronic supplementary material
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