Microbial adaptation for accelerated atrazine mineralization/ degradation in Mississippi Delta soils

Abstract

Most well-drained Mississippi Delta soils have been used for cotton production, but corn has recently become a desirable alternative crop, and subsequently, atrazine use has increased. Between 2000 and 2001, 21 surface soils (0 to 5 cm depth) with known management histories were collected from various sites in Leflore, Sunflower, and Washington counties of Mississippi. Atrazine degradation was assessed in 30-d laboratory studies using 14C-ring–labeled herbicide. Mineralization was extensive in all soils with a history of one to three atrazine applications with cumulative mineralization over 30 d ranging from 45 to 72%. In contrast, cumulative mineralization of atrazine from three soils with no atrazine history was only 5 to 10%. However, one soil with no history of atrazine application mineralized 54 and 29% of the atrazine in soils collected in 2000 and 2001, respectively. Methanol extracted 15 to 23% of the 14C-atrazine 7 d after treatment in soils having two applications within the past 6 yr, whereas 65 to 70% was extracted from no-history soils. First-order kinetic models indicated soil with 2 yr of atrazine exposure exhibited a half-life of less than 6 d. Most probable number (MPN) estimates of atrazine-ring mineralizing-microorganisms ranged from 450 to 7,200 propagules g−1 in atrazine-exposed soils, and none were detected in soils with no history of atrazine use. Although most soils exhibited rapid atrazine mineralization, analysis of DNA isolated from these soils by direct or nested polymerase chain reaction (PCR) failed to amplify DNA sequences with primers for the atzA atrazine chlorohydrolase gene. These results indicate that microbial populations capable of accelerated atrazine degradation have developed in Mississippi Delta soils. This may reduce the weed control efficacy of atrazine but also reduce the potential for off-site movement. Studies are continuing to identify the genetic basis of atrazine degradation in these soils.

<i>In-Situ</i> Biostimulatory Effect of Selected Organic Wastes on Bacterial Atrazine Biodegradation

“…Cropping and herbicide history for at least the past two years before soil sample collection was obtained. Several researches have established relationship between soil characteristics and atrazine degradation parameters [16]. The correlation of more rapid atrazine mineralization in atrazine contaminated soil (ALA) is consistent with observation of others [17,18].…”

Differential Responses to Preemergence and Postemergence Atrazine in Two Atrazine‐Resistant Waterhemp Populations

“…This situation is similar to soils that exhibit enhanced atrazine degradation. After repeated applications, soil microorganisms can metabolize and accelerate atrazine degradation, which reduces the period of effective weed control (Zablotowicz et al, 2006;Shaner and Hager, 2014).…”

Selection of Herbicides Targeting the Use in Crop Systems Cultivated With Showy Crotalaria

“…From an agricultural point of view, this practice negatively undertakes various factors of the production environment because it reduces the diversity of the organisms that make up the microfauna of the soil, increases the pressure of pests, diseases and weeds, and reduces the residual activity of herbicides (Gasparim et al, 2005;Zablotowicz et al, 2006).…”