Influence of different agricultural management practices on soil microbial community over dissipation time of two herbicides

• Published in: The Science of the total environment Vol. 646; pp. 1478 - 1488
• Main Authors: García-Delgado, Carlos, Barba-Vicente, Víctor, Marín-Benito, Jesús M., Mariano Igual, J., Sánchez-Martín, María J., Sonia Rodríguez-Cruz, M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2019
• Subjects: Agriculture - methods; Amended soil; Dissipation; Herbicide; Herbicides - analysis; Irrigation; Microbial diversity; Repeated application; Soil; Soil Microbiology; Soil Pollutants - analysis; Microbial diversity; Irrigation; Amended soil; Repeated application; Herbicide; Dissipation
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.07.395

Soil microbiology could be affected by the presence of pesticide residues during intensive farming, potentially threatening the soil environment. The aim here was to assess the dissipation of the herbicides triasulfuron and prosulfocarb, applied as a combined commercial formulation, and the changes in soil microbial communities (through the profile of phospholipid fatty acids (PLFAs) extracted from the soil) during the dissipation time of the herbicides under field conditions. The dissipation of herbicides and the soil microbial structure were assessed under different agricultural practices, such as the repeated application of herbicides (twice), in unamended and amended soils with two organic amendments derived from green compost (GC1 and GC2) and with non-irrigation and irrigation regimes. The results obtained indicate slower dissipation for triasulfuron than for prosulfocarb. The 50% dissipation time (DT50) decreased under all conditions for the second application of triasulfuron, although not for prosulfocarb. The DT50 values for both herbicides increased in the GC2 amended soil with the highest organic carbon (OC) content. The DT50 values decreased for prosulfocarb with irrigation, but not for triasulfuron, despite its higher water solubility. The herbicides did not have any significant effects on the relative population of Gram-negative and Gram-positive bacteria during the assay, but the relative abundance of Actinobacteria increased in all the soils with herbicides. At the end of the assay (215 days), the negative effects of herbicides on fungi abundance were significant (p < 0.05) for all the treatments. These microbiological changes were detected in non-irrigated and irrigated soils, and were more noticeable after the second application of herbicides. Actinobacteria could be responsible for the modification of herbicide degradation rates, which tend to be faster after the second application. This study makes a useful contribution to the evaluation of the soil environment and microbiological risks due to the long-term repeated application of herbicides under different agricultural management practices. [Display omitted] •Agricultural practices affected herbicide dissipation and soil microbial structure.•Repeated applications of herbicides accelerated the degradation of triasulfuron but not prosulfocarb.•Higher content of organic matter resulted in increased herbicide residues in soils.•Herbicides promoted the relative abundance of Actinobacteria and reduced fungi.•The changes on soil microbiology produced by herbicides modify their degradation rates.