CR 09:41-46 (1997)  -  DOI:

Soil vulnerability in Uruguay: potential effects of an increase in erosive rainfall on soil loss

Carlos Víctora*, Aarón Kacevas, Héctor Fiori

Dirección de Suelos y Aguas, Dirección General de Recursos Naturales Renovables, Ministerio de Ganadería, Agricultura y Pesca, Avda. Garzón 456, Montevideo, Uruguay

Climate change is likely to modify rainfall patterns and their interaction with the soil. This paper addresses soil vulnerability in terms of soil loss resulting from increases in the amount of rainfall. Four agricultural soils from Uruguay were studied: 2 'Vertisol Rúptico' soils (Typic Pelluderts), 1 'Brunosol Subéutrico Típico' and 1 'Brunosol Subéutrico Lúvico' (Typic Argiudolls). A field rainfall simulator was used to produce rain events of controlled intensity. Three of the soils were exposed to a constant rain of 70 mm h-1, which is the intensity of 30 min erosive rain events with a return period of 2 yr. The remaining soil, which is characterized by a high infiltration rate, was exposed to 140 mm h-1 rain. A 20 mm rainfall was applied on soil previously wet to saturation of the A horizon. The surface was prepared as bare soil seedbed on natural slopes (which are 2 to 5% steep, depending on the soil). The results obtained were corrected for a constant slope according to the Universal Soil Loss Equation (USLE). Soil losses (in kg ha-1) for rainwater depths (amounts) of 5, 10, 15 and 20 mm respectively were: Vertisol (Serie Tala): 25, 136, 273 and 437; Vertisol (Serie Jesús María): 52, 291, 1233 and 2633; Brunosol (Serie Pando): 368, 961, 1725 and 2683; Brunosol (Serie Colonia Brause): 48, 60, 115 and 224. These results are indicative of: (1) a major difference in the degree of vulnerability among soils, and (2) an increase in the soil loss rate as a result of the increase in the amount of applied rainfall. The high sensitivity of the Uruguayan soils to climate-change-induced potential variations in rainfall pattern is thus confirmed.

Soil loss · Erosion · Erodibility · Rainfall · Typic Pelluderts · Argiudolls · Climate change · Soil vulnerability · Uruguay

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