Resumo

FERRARY LAGUZZI, Florencia et al. Fraccionamiento y mineralización de la materia orgánica en distintos sistemas de labranza en un inceptisol de Salta. Cienc. suelo [online]. 2014, vol.32, n.1, pp.63-72. ISSN 1850-2067.

Organic matter (MO) has an important influence on soil properties; it is composed of labile (particulate MO, MOP) and stable fractions (humified MO, MOH). Particulate MO is an early indicator of changes due to management practices. On the other hand, potentially mineralizable nitrogen (NPM) is an indicator of the soil capacity to mineralize nitrogen. The objective of this study was to evaluate the effect of four tillage systems (SL): conventional tillage (LC), minimum tillage with disc (LMd), minimum vertical tillage (LMv) and no tillage (SD) on total MO, MOP and MOH contents and on nitrogen mineralization (MN). Soil samples (0-5 and 0-20 cm) were taken froma long-term experiment started in 1990 on an Inceptisol (Udic Ustocrept) in Salta. Average concentrations of the following variables were found under SD and LMv, respectively: MO: 2.93% and 3.16%, MOP 9.62 and 10.98 g kg^-1 and MOH 13.62 and 14.63 g kg^-1. These values were greater than those found under LMd (2.19%, 7.08 g kg^-1 and 9.76 g kg^-1) and LC (1.35%, 3.23 g kg^-1 and 8.98 g kg^-1), for MO, MPO and MOH, respectively, in the soil surface layer. There was a higher quantity of mineralized nitrogen (18 mg N kg soil^-1) and potentially mineralizable nitrogen (32 mg N kg soil^-1) (CNM and NPM) under LMv compared to the other tillage systems:CNM: LC=6 mg N kg soil^-1, LMd and SD=10 mg N kg soil^-1; NPM: LC= 16 mg kg soil^-1, LMd= 20 mg kg soil^-1, SD= 19 mg kg soil^-1) in the topsoil. There were stronger dependency relationships between PMN and MOP (R²=0.65) that between the first and MOH (R²=0.32). Organic Matter, MOP, MOH, CNM and NPM were also evaluated as soil quality indicators (ICS). Particulate organic matter and especially the coarse fraction and the CNM were more sensitive indicators for detecting changes caused by different SL.

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