Dynamics of rhizosphere microbial communities of cover crops dried with glyphosate

Abstract

The use of cover crops (CC) may be associated with other management practices recommended to achieve high yields and collaborate to use available resources more efficiently. Glyphosate is a nonselective systemic herbicide, which is commonly used for drying CC. Here we included a review of the related topics and showed the effects of drying oats and rye with glyphosate, inoculation with two plant growth-promoting rhizobacteria, and nitrogen fertilization on rhizosphere microbial communities at field conditions in the western Pampas of Argentina. Rhizosphere samples were obtained at three times: Before drying the CC, a month after this, and at harvest time of soybean which was grown after each CC. Counts of viable cells and physiology of rhizosphere microbial communities were analyzed. The inclusion of CC dried with glyphosate modifies their associated rhizosphere microbial communities. Their numbers significantly decreased or increased. For some microorganisms, these changes were temporary because their amounts at soybean harvest time did not differ from those obtained when the sampling was done before drying CC with glyphosate application. Besides, our results indicate that the drying time must be chosen taking into account CC types and their phenology. This scientific information is evidence of changes on rhizosphere microbial communities due to the management of CC with glypho- sate in combination with or without both inoculation and fertilization of CC. These data are agronomic and environmentally relevant because they have shown that the type of management would impact on the quality and health of the soil and therefore in agroecosystem sustainability.