Resumen

BOCCOLINI, Mónica Fabiola et al. Impacto de la aplicación prolongada de urea sobre bacterias nitritantes de un Argiudol típico, Argentina. Cienc. suelo [online]. 2016, vol.34, n.1, pp.21-31. ISSN 1850-2067.

Ammonia oxidation to nitrite is a critical step in the nitrogen (N) cycle and is performed by ammonia-oxidizing bacteria (AOB) also called Nitrifying. Agricultural management can affect the AOB community due to the prolonged use of nitrogen fertilizers such as urea which tend to increase soil acidity. After 12 years of urea application, size, activity, AOB composition and chemical variables were investigated. The performed field experiment had a complete randomized block design with three replicates on a typical Argiudol soil located in Marcos Juárez, Southeastern Córdoba, Argentine. The treatments were: A control without N-application; B and C with 95 and 165 kg ha^-1 of urea as the N source respectively. Soil samples were collected before sowing and after corn harvest. The AOB community was studied through the most probable number method, shaken soil slurry, polymerase chain reaction and electrophoresis in denaturing gradient gel. Urea fertilization decreased soil pH, increased AOB abundance and diversity but did not significantly affect nitrifying potential. Bacterial community structure was dominated by members of the Group 3 of Nitrosospira in all the treatments. The results showed that the long-term urea fertilization in a typical Argiudol was a substrate source and not a limiting factor for the nitrifying bacteria. The fertilization effect was more evident in the sampling date before corn sowing.

Palabras clave : Nitrogen fertilization; Soil chemical properties; Community of ammonia-oxidizing bacteria; Denaturant gradient gel electrophoresis (DGGE).

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