Resumo

ECHEVERRIA, Nora E; VALLEJOS, Adrián G  e  SILENZI, Juan C. Erodibility of soils in the south of the semiarid region of Argentina. Cienc. suelo [online]. 2006, vol.24, n.1, pp.49-57. ISSN 1850-2067.

Water erodibility of soils can be measured in the field using rainfall simulators or be predicted with mathematical models as USLE and WEPP. The objective of our research was to determine water erodibility of three representative soils in the southern semiarid region of Argentina, aiming to a comparison with the estimated by the WEPP and USLE models. In Bahía Blanca (SBB) and Cabildo (SC) soils -Petrocalcic Paleustolls- and Villarino (SV) soil - Petrocalcic Calciustoll, two consecutive rainfalls of 32 mm during 30 minutes were applied by a rainfall simulator. Soil loss owed to first and second rain indicated: SV 3,26 and 5,86 Mg ha^-1 h^-1; SC 2,04 and 5,53 Mg ha^-1 h^-1; SBB 0,75 and 2,66 Mg ha^-1. h^-1 Soil resistance to water erosion correlated to silt/clay ratio (r: 0,60); OC (r: 0,55) and structural stability (r: 0,56). Average runoff and sedimentation were: SV 12,4 10^-6 m s^-1 and 15,6 10-5 kg s^-1m^-2; SC 9,9 10^-6 m s^-1 and 13,5 10^-5 kg s^-1m^-2; SBB 9,6 10^-6 m s^-1 and 6,1 10^-5 kg s^-1m^-2. Behavior of SV soils is explained by a fast top sealing whilst SBB and SC is related to structural stability. In accord to WEPP the measured interill erodibility (Ki) was SV 2,5; SC 1,89 and SBB 1,39 (10⁶ kg s m^-4) whereas the estimated value was significantly higher, being SV 6,26; SC 10,2 and SBB 10,2 (106 kg s m^-4). Erosion indexes (IE) were SV 0,30; SC 0,21 and SBB 0,10 Mg MJ^-1, highly differing from estimated K, which confirms that nomograph predicted values have low confidence in soils with a higher than 65% sand content in texture.

Palavras-chave : Water erosion; Rainfall simulator; Soil loss; Runoff; Erodibility.

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