Resumo

DIOVISALVI, Natalia Verónica; STUDDERT, Guillermo Alberto; DOMINGUEZ, Germán Franco  e  EIZA, Maximiliano Joaquín. Effect of two tillage systems under continuous cropping on organic carbon and nitrogen fractions and on the anaerobic nitrogen indicator. Cienc. suelo [online]. 2008, vol.26, n.1, pp.1-11. ISSN 1850-2067.

The organic carbon (CO) is a key component that determines many soil properties, and it is composed of labile (particulate CO, COP) and less labile fractions. Particulate CO is an early indicator of changes in CO due to management practices. On the other hand, anaerobic N (Nan) is an indicator of the soil capacity to mineralize N. The objective of this study was to evaluate the effect of no-tillage (SD), conventional tillage (LC) and N fertilization on total CO (COT), COP, total organic N (NOT), particulate organic N (NOP), and of Nan contents, and on their relationship with corn yield. Soil samples (0-5 and 5-20 cm-depths) were taken from two areas of a long term experiment started in 1997 on a Mollisol in Balcarce. There was greater concentration of COP, NOP, COT and NOT under SD compared to LC, especially in the soil surface layer. In general, there were no differences in Nan content between tillage systems. Nitrogen fertilization did not affect either CO and NO fractions or Nan contents. There were no significant relationships between the latter and corn yield or corn response to N fertilization. High CO contents and C returns through crop residues in both tillage systems could have caused the lack of differences expected. The observed results and trends would indicate that significant differences between tillage systems could be manifested in the near future.

Palavras-chave : Organic matter; Particulate organic matter; Tillage systems; Potentially mineralizable nitrogen.

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