In Situ Dynamics and Spatial Heterogeneity of Soil Bacterial Communities Under Different Crop Residue Management

Abstract

The effect of the location of wheat residues (soil surface vs. incorporated in soil) on their decomposition and on soil bacterial communities was investigated by the means of a field experiment. Bacterial-automated ribosomal intergenic spacer analysis of DNA extracts from residues, detritusphere (soil adjacent to residues), and bulk soil evidenced that residues constitute the zone of maximal changes in bacterial composition. However, the location of the residues influenced greatly their decomposition and the dynamics of the colonizing bacterial communities. Sequencing of 16S rRNA gene in DNA extracts from the residues at the early, middle, and late stages of degradation confirmed the difference of composition of the bacterial community according to the location. Bacteria belonging to the γ-subgroup of proteobacteria were stimulated when residues were incorporated whereas the α-subgroup was stimulated when residues were left at the soil surface. Moreover, Actinobacteria were more represented when residues were left at the soil surface. According to the ecological attributes of the populations identified, our results suggested that climatic fluctuations at the soil surface select populations harboring enhanced catabolic and/or survival capacities whereas residues characteristics likely constitute the main determinant of the composition of the bacterial community colonizing incorporated residues.

No-till and cover crops shift soil microbial abundance and diversity in Laos tropical grasslands

“…However, no reference was found regarding the effect of soil available P, Al content, and/or CEC changes on bacterial genetic structure. While we show that the quality of crop residues strongly influenced bacterial abundance, this factor did not appear influent regarding bacterial community structural changes, contrary to other studies (Nicolardot et al 2007;Pascault et al 2010). Finally, tillage could partly explain the differences in bacterial genetic structure observed between conservation (NTs) and conventional (CT) cropping systems, by modifying microbial access to crop residues and soil moisture content (Nicolardot et al 2007).…”

“…External agricultural inputs such as organic amendments (animal or green manure), mineral fertilizers, and pesticides affect in different ways soil microorganisms (Dick 1992;Bunemann et al 2006). Crop rotation and plant diversity are also important to maintain soil microbial diversity and activity (Nicolardot et al 2007;Pascault et al 2010). In conventional agriculture, tillage has generally the greatest impact on biological properties since physical disturbance changes soil water content, temperature, aeration, and the degree of mixing of crop residues within the soil matrix (Dick 1992;Buckley and Schmidt 2001;Kladivko 2001).…”

“…Among human activities, agricultural practices affect the physical and chemical characteristics of the soil in which microorganisms live, thereby affecting their abundance, diversity, and activity (Dick 1992;Kladivko 2001;Bunemann et al 2006;Nicolardot et al 2007;Pascault et al 2010). External agricultural inputs such as organic amendments (animal or green manure), mineral fertilizers, and pesticides affect in different ways soil microorganisms (Dick 1992;Bunemann et al 2006).…”

“…Molecular tools such as soil DNA concentration and real-time quantitative PCR of bacteria and fungi were used as bioindicators to evaluate the effect of agricultural practices on soil microbial abundance Smith and Osborn 2009;Chemidlin Prevost-Boure et al 2011). The genotyping of the soil bacterial community structure was assessed by a DNA fingerprinting approach, the automated ribosomal intergenic spacer analysis technique, that has been demonstrated to be sensitive and relevant for evaluating modifications in microbial community composition consecutive to land use management changes (Pascault et al 2010;Lejon et al 2007). The relationships between the soil physicochemical properties and the abundance and diversity of soil microbial communities were statistically tested to deduce an early environmental evaluation of these cropping systems.…”

Dynamiques de décomposition des résidus de cultures sur des exploitations pratiquant l'agriculture de conservation en région Grand Est, France

“…La dynamique de décomposition des résidus, dans ces conditions, est beaucoup moins étudiée que dans des conditions de mélange au sol lors d'un labour profond. En général, les études existantes s'appuient sur des cinétiques de décomposition avec des sacs à litières (technique du litter-bag) ou la mise en place de microparcelles (Lynch et al, 2016 ;Pascault et al, 2010), qui s'éloignent des conditions réelles de décomposition sur des parcelles d'agriculteurs (taille des brins, contact avec le sol, accès de la macrofaune, etc.). La dynamique de décomposition a une incidence directe sur la libération des nutriments que ces résidus contiennent.…”