Abrupt versus gradual application of pesticides: effects on soil bacterial and fungal communities

Abstract

Pesticides are a major anthropogenic input to the environment and a factor in global change that puts pressure on soil microbial communities. However, the effects of different rates of pesticide application on soils remain poorly understood. This study investigates how abrupt versus gradual pesticide applications influence soil bacterial and fungal communities. Employing high-throughput sequencing, we examined the microbial diversity and community composition in response to ten commonly used pesticides. Bacterial communities exhibited minimal changes across treatments, whereas fungal communities responded strongly to pesticide exposure. Gradual applications reduced the relative abundance of dominant fungal taxa, resulting in an overall increase in community evenness. This effect was particularly pronounced for two herbicides and a triazole fungicide, which induced substantial shifts in fungal composition. Conversely, abrupt pesticide applications resulted in transient disruptions but did not promote the long-term proliferation of rare fungal variants. These findings suggest that prolonged exposure to pesticides exerts strong selective pressures on fungi, potentially altering fundamental soil functions such as nutrient cycling and decomposition. Future research should focus on the long-term responses of soil microbial communities to pesticide application and the cumulative effects of chronic low-dose exposure to provide a more comprehensive understanding of how they shape microbial communities. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/644867v2_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@8660a8org.highwire.dtl.DTLVardef@33ce7borg.highwire.dtl.DTLVardef@139113eorg.highwire.dtl.DTLVardef@19b388b_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFungal communities were more responsive to pesticides than bacterial communities C_LIO_LIHerbicides caused strong non-target effects, similar to those of fungicides C_LIO_LIGradual pesticide applications altered fungal diversity and community composition C_LIO_LIRare fungal taxa proliferated under gradual exposure, increasing evenness C_LIO_LIProlonged exposure exerted greater selective pressure than abrupt application C_LI