Changes in functional structure of soil bacterial communities due to fungicide and insecticide applications in canola

• Published in: Agriculture, ecosystems & environment ecosystems & environment, 2009-04, Vol.130 (3), p.109-114
• Main Authors: Lupwayi, Newton Z., Harker, K. Neil, Dosdall, Lloyd M., Turkington, T. Kelly, Blackshaw, Robert E., O’Donovan, John T., Cárcamo, Héctor A., Otani, Jennifer K., Clayton, George W.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Brassica napus; canola; foliar application; functional diversity; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; lambda-cyhalothrin; microbial activity; microbial communities; Non-target effects; nontarget organisms; Oilseed rape; Pesticides; population structure; rhizosphere; soil bacteria; Soil microbial biomass; Soil microbial diversity; species diversity; vinclozolin
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2008.12.002

The fungicide vinclozolin and insecticide λ-cyhalothrin are widely used to control canola ( Brassica spp.) diseases and insect pests, respectively, in Canada. We investigated non-target effects of these pesticides, applied at recommended rates, on soil microbial biomass, functional bacterial diversity and functional community structure of soil bacteria (by evaluating patterns of C substrate utilization) in canola rhizosphere and bulk soil at three locations in Alberta from 2002 to 2004. Experimental treatments were (a) untreated control, (b) vinclozolin fungicide foliar application, (c) λ-cyhalothrin insecticide foliar application, and (d) vinclozolin and λ-cyhalothrin applications. No significant pesticide effects on soil microbial biomass or functional bacterial diversity were observed, but the functional structures of soil bacteria were altered. In 1 of 12 cases, the control treatment had a different soil bacterial community structure from the 3 pesticide treatments. The fungicide treatment had different bacterial community structures from the control or insecticide treatments in 3 of 12 cases, the insecticide treatment had different community structures from the control or fungicide treatments in 4 of 12 cases, and the combined fungicide and insecticide treatment had different community structures from the other treatments in 3 of 12 cases. Therefore, evaluating soil bacterial functional structures revealed pesticide effects that were not detected when bacterial diversity or microbial biomass were measured in canola rhizosphere or bulk soil.