Resumo

STUDDERT, GUILLERMO ALBERTO; DOMINGUEZ, GERMÁN FRANCO; ZAGAME, MARÍA CRISTINA  e  CARABACA, JUAN CARLOS. VARIACIÓN ESTACIONAL DE CARBONO ORGÁNICO PARTICULADO Y NITRÓGENO ANAERÓBICO. Cienc. suelo [online]. 2015, vol.33, n.1. ISSN 1850-2067.

Labile soil organic matter fractions (particulate (COP) organic carbon (CO) and nitrogen (N) released through anaerobic incubation (Nan)) are soil health indicators. However, COP and Nan contents may change in time limiting utility as indicators. The aim of this study was to evaluate seasonal variation of COP and Nan under different managements. Soil samples were taken at 0-5 and 5-20-cm depths at different moments between fall and spring in two years (2007 and 2009) from a complex of Mollisols under contrasting tillage systems (no-tillage (SD) and conventional tillage (LC)) and N fertilization (with and without N). Total CO (COT), COP and Nan contents were determined. In 2009, COP and Nan contents at 020 cm (4.8 g kg^-1 y 56.2 mg kg^-1, respectively) were higher than in 2007 (3.7 g kg^-1 y 47.0 mg kg^-1, respectively) and, in each year, they were higher under SD and with N, although not always significantly. Besides, in 2009, COT and COP did not change in time, but in 2007 they changed slightly and without clear trends. Nan decreased between July and October sampling times of each year, although significantly only in 2009. In July, Nan at 0-20 cm was 13.5 mg kg^-1 higher in 2009 than in 2007, whereas in October the difference was 6.7 mg kg^-1. There were inverse relationships between COP and Nan at 0-20 cm and corn response to N, but were significant only for Nan. Such relationships were different between SD and LC and among sampling moments. Given its scarce variation in time, the use of COP as an indicator would be possible regardless of the sampling time. Nan showed more variation in time; the possibility of using Nan as indicator would require more adjustments taking into account the sampling time and/or the previous conditions.

Palavras-chave : Particulate organic matter, potentially mineralizable nitrogen, no-tillage, conventional tillage.

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