Differences in bacterial functional profiles from loamy sand and clay loam textured soils under fungicide QuadrisR impact

The non-target effect of the fungicide Quadris^R on the bacterial community from grassland loamy sand (LS) and cropland clay loam (CL) soils with unknown history of fungicide usage was investigated. Quadris^R was applied to soil mesocosms at 0.0 mg kg^-1 (Az0), 2.90 mg kg^-1 (Az1), 14.65 mg kg^-1 (Az2) and 35.0 mg kg^-1 (Az3) calculated towards the active ingredient azoxystrobin (Az). Response of bacterial communities to Quadris^R was investigated during a 120-day incubation experiment, evaluating the shifts in bacterial catabolic profiles by the community-level physiological profiling (CLPP) technique and Biolog EcoPlates^TM method. Quadris^R decreased the overall catabolic activity (AWCD) of soil bacterial communities and the rate of decrease was independent of soil type and fungicide concentration. Fungicide affected negatively the utilisation of amines and positively that of amino acids in both soil types, whereas the effects on other carbon guilds (carbohydrates, carboxylic acids and polymers) corresponded closely to the respective soil type and fungicide concentration. Results indicated the presence of non-target effects of Quadris^R on bacterial functioning; hence, it is important to address the fungicide side-effects on soil health.