Organic nitrogen stock in pampean soil profiles

M MENDOZA; G BERHONGARAY; R ALVAREZ

Congreso; XXIII Congreso Argentino de la Ciencia del Suelo; 2012

Soil nitrogen stocks under contrasting vegetation types and land uses have not been assessed in the Pampas. Our objective was to determine organic nitrogen profiles under common scenarios of soil*vegetation*land use founded in the region. Samples from 250 sites widespread across the region, belonging to soils without petrocalcic horizons were used. Vegetation-land use treatments were: forest, uncropped sites under graminaceus vegetation, cropped soils under the pasture phase of a mixed rotation, cropped soils under the agricultural phase of the rotation and flooded lands. To 1 m depth nitrogen stocks were 14.4, 12.0, 10.8, 10.5 and 8.4 t ha-1 respectively.  Stocks were higher under forest than in uncropped soils, and in this treatment than in cropped sites. The phase of the rotation had no effect on nitrogen stocks. Flooded lands had the lowest nitrogen content. In all cases around 50 % of the nitrogen stored to 1 m was founded in the upper 25 cm of the profile.