Resumen

SCHMIDT, Erica Susana  y  AMIOTTI, Nilda Mabel. Efecto de la secuencia de cultivos sobre las fracciones de materia orgánica y nitrógeno bajo siembra directa en la región pampeana semiárida sur. Cienc. suelo [online]. 2017, vol.35, n.1, pp.95-103. ISSN 1850-2067.

It is necessary to have an adequate level of residue in soil surface in order to express the benefits of no-tillage system (SD), which is achieved through proper planning of rotations. These studies are particularly important in semiarid regions, where the crop options are limited. The aim of this study was to analyze the effect of different crop sequences under SD on the content and quality of organic matter (OM) and its subsequent impact on nitrogen (N) stocks in soils of the southern semiarid pampean region. The experimental units were 13 plots under agricultural production, with different crop sequences: i) winter crops (Inv./Inv.), winter crops with prolonged fallow (Inv./Bar.) and winter and summer crops (Inv./Est.). Soil cover (%) was determined and sampling of topsoil (0-5 cm and 5-20 cm) was performed. The following soil variables were determined: pH, total organic carbon (YOC), particulate organic carbon (POC), total nitrogen (TN) and particulate nitrogen (PN). Soil cover was lower than 30% in Inv./Est. a condition that negatively affected the dynamics of OM and N. On the other hand, a higher amount of winter grain crops in the sequences resulted in a more elevated soil coverage together with higher stocks of TOC, POC, TN and PN. Monoculture of winter crops under SD should be considered in the analysis of the system sustainability for the study area, which in accord with our results, is at risk by introducing summer grain crops with low residues contributions in the management of crop sequence.

Palabras clave : Semiarid pampean region; Winter and summer crops; Soil size fractionation.

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