Saturday, 15 July 2006

Productivity Index in Typic Natrudolls in Center-Southwestern of Buenos Aires Province, Argentina.

Gustavo A. Cruzate, Julio M. Sánchez, Gervasio Carboni, and Ricardo C. Díaz. INTA-CIRN-Instituto de Suelos, Las Cabañas y De Los Reseros CC 25, Castelar, Argentina

Until 1998, the mollic epipedon soils, argillic and natric horizon, in the Pampean region (Graph 1) were included in Natraquolls (IBC), Hapludolls (IHF), and Argialbolls (IAB). According to this classification, it was no possible to separate the natric horizon soils. In 1999, Natrudolls (IHA) were incorporated into the Key to Soil Taxonomy allowing the differentiation of Natrudolls from Natraquolls, with less land capability value. The objective of this study was to know the land capability of these type of soils. A total of seven soil profiles of Typic Natrudolls (IHAH, Soil Taxonomy, 2003) covering 800,000 ha in General Lamadrid,Coronel Suarez,Laprida and Coronel Pringles counties were analyzed. The area is a wide plain with non consolidated sediments of the quaternary,deposited by wind, and redistributed by water. The methodology included; 1)Topographic Argentine maps (IGM),INTA photo mosaic 3760-19-25-31,3763-24,and 3960-1 Scale 1:50.000;2)Geomorphological units of the province maps;3)Soil identification criteria; 4) Productivity index and parametric methods of soil evaluation; 5)Land Capability classification; 6) Keys to soil taxonomy (S.T. 2003); and 7) Soil survey laboratory methods manuals (1992). Twenty aerial INTA, photo mosaic information from five IGM data were used to compare landscape, permeability, and drainage. The variability of the productivity index was determined using the properties of the mollic epipedon and natric horizon variability. The results indicated that Typic Natrudolls are in low hills or extended plains, moderately slow permeability (3/4 class), average drainage (4-3 class). The mollic epipedon has 21-33 cm thickness, organic matter (4-4.50%), C/N between 11-12.5%, agriculture horizon of 21-35 cm, high organic matter and nitrogen. Natric horizon between 35-43 cm, 25-30% interchangeable sodium (PSI), 26.2 Cation exchange capacity meq/100 g and 7.1-10.3% of CO3Ca at 101-105 cm. The studied profiles had 50% of livestock pastures, and 50% as crop land (wheat, oat, corn), and IVws class of land capability. It was possible to identify the soils with higher productivity index, type of land management, and selection of forage species.

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