Impact of management of cover crop-soybean agroecosystems on rhizosphere microbial communities

摘要

Knowledge of the rhizosphere and use of quality microbial bioinputs are tools to achieve agricultural sustainability. The impact of management of cover crop-soybean agroecosystems on rhizosphere microbial communities was evaluated. A field experiment in a randomized complete block design with factorial arrangement in sub-divided plots was performed. Effects of fertilization (0 and 45 kg center dot ha(-1)), oats, rye and control without cover crops, plant growth promoting rhizobacteria (PGPR) co-inoculation of Azospirillum brasilense and Pseudomonas fluorescens, and three sampling times on microbial counts, community-level physiological profiles (CLPP) and terminal restriction fragment length polymorphism (T-RLFP) were studied. CLPP were drastically changed at three sampling times: before glyphosate, after glyphosate and at soybean harvest. Before glyphosate application, the interaction between PGPR inoculation and coverage treatments modified the functional and structural profiles of the rhizosphere microbial communities. Furthermore, the highest microbial counts and the greatest functional diversity indices were observed before glyphosate application but significantly decayed after glyphosate application and at soybean harvest, showing a permanent impact of glyphosate application on the rhizosphere microbial community functionality, which was confirmed with several statistical analyses. For the cover crop-soybean agroecosystems, we can conclude that the rhizosphere microbial communities showed high sensitivity to glyphosate. PGPR inoculation only increased the aerial biomass of rye at the jointing and grain-filling stages. Inoculated plants without fertilization and non-inoculated plants with fertilization showed similar aerial biomass production of this crop. This work demonstrates that different management decisions can change plant-microorganism relationships in the rhizospheres of cover crops and impact aboveground biomass production. A better understanding of microbial ecology will allow the sustainable use of available resources.