Soil carbon and nitrogen mineralization as affected by atrazine and glyphosate

• Published in: Biology and fertility of soils Vol. 35; no. 1; pp. 35 - 40
• Main Authors: HANEY, R. L, SENSEMAN, S. A, KRUTZ, L. J, HONS, F. M
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-02-2002
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical control; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Organic matter; Parasitic plants. Weeds; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Phytopathology. Animal pests. Plant and forest protection; Soil science; Weeds; Agricultural chemical product; Microbial activity; Laboratory study; Ecotoxicology; Cultivated soil; Pesticides; Organic phosphonate; Nitrogen; Microbial biomass; Carbon; Glyphosate; Herbicide; Agroecosystem; Biogeochemistry; Mineralization; Triazine derivatives; Soil biology; Soil interaction; Atrazine; Chemical weed control
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/s00374-001-0437-1

Atrazine alone and atrazine plus glyphosate were added to soil to determine their effect on soil microbial activity as measured by C and N mineralization (Cmin, Nmin) and soil extractable atrazine without the use of radiolabelled isotopes. Atrazine alone was added to soils as a formulated product (Aatrex 4L) at a field rate of 2 x (94 mg kg super(-1)), 4 x (188 mg kg super(-1)), and 6 x (282 mg kg super(-1)) with an assumed soil penetration depth of 58 mm. Glyphosate, as Roundup Ultra, was added along with atrazine to soil in equal amounts bringing the total cumulative herbicide amount to 2 x (188 mg kg super(-1)), 4 x (376 mg kg super(-1)) and 6 x (564 mg kg super(-1)) assuming a 2-mm soil penetration depth for glyphosate. Atrazine plus glyphosate stimulated microbial activity more than atrazine alone. During 56 days of incubation, mineralized C and N were highly correlated (r super(2) = 0.93). In addition, the C and N added from the herbicides were correlated with the amounts of C and N mineralized above the controls and were highly correlated (r super(2) = 0.93 for Cmin and r super(2) = 0.97 for Nmin). Cmin was greatest during the first 7 days of incubation after herbicide application while Nmin was greatest during the day 14 to day 28 period indicating a possible substrate shift from glyphosate to atrazine since atrazine has more N relative to C than glyphosate. Atrazine extracted from soil at four time periods (day 7, 14, 28, and 56) showed similar degradation curves (DT sub(50) = 10.5 days) for the atrazine and atrazine-glyphosate treatments for all rates, with the exception of the 6 x rate after 14 days and the 2 x rate after 28 days of incubation where glyphosate appeared to slightly enhance the degradation of atrazine.