Mineralization of atrazine in agricultural soil: Inhibition by nitrogen

Abstract

Microbial mineralization of atrazine was characterized in soils and liquid media in the presence of nitrogen fertilizer concentrations representing typical field applications. The mineralization of atrazine in soils varied between 6 and 99% after 18 d of incubation. Half-lives of between 0.99 and more than 18 d were obtained. Mineralization kinetics and degree are related by a reciprocal trend to concentrations of available nitrogen in the soil. In liquid media, half-lives were calculated as 0.12 d in the absence of fertilizer nitrogen and as 79 d in the presence of 1,000 mg/L of KNO3-N. Only 20% of atrazine was mineralized after 18 d of incubation in the presence of this concentration of KNO3-N, whereas greater than 90% mineralization occurred after 2 d of incubation in liquid medium without KNO3-N. The results demonstrate that the mineralization of atrazine is inhibited even at fertilizer nitrogen levels lower than typical field applications. Inhibition in soil is lower than that in liquid medium, possibly because of the higher complexity of the soil system. This may explain why atrazine that infiltrates to the groundwater is persistent. The microbial consortium of the soils was characterized, and seven species were identified. The degrading capacity of these species suggests that only three species are involved in the degradation of atrazine.

Atrazine biodegradation in the lab and in the field: enzymatic activities and gene regulation

“…The influence of nitrogen compounds on the efficiency of atrazine elimination has been a focus of research, since most degrading strains use atrazine as a nitrogen source and agricultural soils are often rich in nitrogen due to routine fertilization. Numerous studies have established that nitrogen amendments have a negative effect on atrazine biodegradation by indigenous microbial populations in soils (Entry et al, 1993;Alvey and Crowley, 1995;Abdelhafid et al, 2000a,b;Guillén Garcés et al, 2007). The effect of nitrogen sources on atrazine degradation has also been tested in pure cultures of several degrading strains (Bichat et al, 1999;Gebendinger and Radosevich, 1999;García-González et al, 2003).…”

Agronomic and environmental implications of enhanceds-triazine degradation

“…It was postulated that this relationship could be exploited to alter s ‐triazine persistence in adapted soils. For example, under laboratory conditions, the addition of exogenous N to pure culture and native s ‐triazine‐adapted soils transiently suppressed s ‐triazine degradation by adapted microbial populations, with the suppression level depending primarily on the bacterial population responsible for degradation and the N source applied 82, 89, 114, 125–130. Additionally, atrazine‐catabolizing genes, particularly atzDEF , are subject to a complex regulatory circuit that is modulated by N availability and the presence of degradation products, e.g.…”

Estado Actual De La Investigación Sobre Plaguicidas en México

“…Sus resultados indicaron una mayor degradabilidad de clorpirifos (83 %) y su producto metabólico 3,5,6-tricloro-2-piridinol (TCP) (30 %), en suelos suplementados con B. thuringiensis. En el caso de atrazina, Guillén-Garcés et al (2007) caracterizaron la mineralización microbiana en suelos y líquidos en presencia de fertilizante nitrogenado, sus resultados mostraron que únicamente un 20 % de atrazina se mineralizó después de 18 días en presencia de nitrógeno, mientras que más del 90 % de mineralización ocurrió después de un día, sin la presencia de nitrógeno.…”