Rapid Development of Enhanced Atrazine Degradation in a Dundee Silt Loam Soil under Continuous Corn and in Rotation with Cotton

Abstract

Mississippi Delta cotton (Gossypium hirsutum L.) production in rotation with corn (Zea mays L.) was evaluated in field experiments from 2000 to 2005 at Stoneville, Mississippi. Plots maintained under minimum tillage were established in 2000 on a Dundee silt loam with treatments including continuous cotton or corn and alternate cotton-corn rotations. Mineralization and dissipation of 14C [ring]-labeled atrazine were evaluated in the laboratory on soils collected prior to herbicide application in the first, second, third, and sixth years of the study. In soils collected in 2000, a maximum of 10% of the atrazine was mineralized after 30 days. After 1 year of herbicide application, atrazine-treated soils mineralized 52-57% of the radiolabeled atrazine in 30 days. By the sixth year of the study, greater than 59% of the atrazine was mineralized after 7 days in soils treated with atrazine, while soils from plots with no atrazine treatment mineralized less than 36%. The data also indicated rapid development of enhanced atrazine degradation in soils following 1 year of corn production with atrazine use. Atrazine mineralization was as rapid in soils under a rotation receiving biannual atrazine applications as in soils under continuous corn receiving annual applications of atrazine. Cumulative mineralization kinetics parameters derived from the Gompertz model (k and ti) were highly correlated with a history of atrazine application and total soil carbon content. Changes in the soil microbial community assessed by total fatty acid methyl ester (FAME) analysis indicated significant interactions of cropping system and sampling date, with FAME indicators for soil bacteria responsible for differences in community structure. Autoclaved soil lost all ability to mineralize atrazine, and atrazine-mineralizing bacteria were isolated from these plots, confirming the biological basis for atrazine mineralization. These results indicate that changes in degradative potential of a soil can occur rapidly and some changes in soil properties may be associated with cropping systems, which can contribute to enhanced atrazine degradation potential.

Metabolism and Persistence of Atrazine in Several Field Soils with Different Atrazine Application Histories

“…However, the experimental reapplication of atrazine after two decades without any additional atrazine treatment resulted in a slightly enhanced degradation of the chemical within the time frame of the investigation (Figure 1(d)). This may support previous observations of an enhanced atrazine mineralization after a single annual atrazine application (32).…”

“…It should be taken into account that certain microbes in this soil have native atrazine-degrading ability. Similar degradation patterns for soils from plots to which atrazine was not directly applied have been reported previously, and in these studies atrazine degradation in the control soils was attributed to the transport of degrading organisms from implements used for bed formation, tractor tires, harvesting equipment, and irrigation or runoff (32). Mineralization was significantly higher under slurried conditions in BS (Si = 95-99.95%) and BC (Si = 75-99.95%), which can be explained by a disaggregation of soil particles and homogeneous distribution of degrading strains and atrazine molecules in solution resulting in an increased microbial accessibility.…”

Simulation of branched serial first‐order decay of atrazine and metabolites in adapted and nonadapted soils

“…30,2011soils observed in the laboratory, half-lives decreased with increasing temperature and moisture. These ranges are in agreement with earlier studies [6][7][8][9][10] reflecting the growth of microbial communities capable of using atrazine as an energy source in soils with repeated applications of atrazine. The average halflife (over both temperature and moisture controls) fit to concentrations observed in the adapted Mississippi soils (6.2 d) was less than that fit to the concentrations in the adapted Colorado soils (7.5 d); the half-life fit to the Nebraska porewater concentrations was in between (6.6 d).…”

Degradation of Sulfadiazine by Microbacterium lacus Strain SDZm4, Isolated from Lysimeters Previously Manured with Slurry from Sulfadiazine-Medicated Pigs

“…This indicates that microbial adaptation and selection processes require reasonably long time periods of exposure to take place in pristine soils. Long-term as well as repeated exposure has often been reported to enhance the biodegradation of xenobiotics or other poorly degradable substances like atrazine in soils (27,28). After long-term and repeated exposure of agricultural soils to veterinary antibiotics, accelerated biodegradation and partial mineralization of sulfamethazine were detectable (29).…”