Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/3/1996
Publication Date: N/A
Technical Abstract: In the Valley of Mexico, some soils have indurated horizons, called ¿tepetates¿, that appear at the surface once the topsoil is eroded. Infiltration is very low and a lot of runoff is produced, causing erosion and flooding. The objective of this study was to compare soil erosion, runoff and infiltration of four types of tepetate from three locations: Gray (Site 1), Brown and Yellow (Site 2), and Pink (Site 3). The soils were sieved, packed in a 0.14 m2 pan, prewetted and subjected to a 75 mm h-1 rain for 1 hour at 5 percent slope. The parameters were measured during the rain. Steady-state infiltration rates (Ia) varied from 15 to 55 mm h-1 and from 2 to 40 mm h-1 in the <8mm and <4mm aggregate size, respectively. Total runoff varied from 18 to 48 mm and from 24 to 75 mm in the <8mm and <4mm fractions. Total erosion was 217 g m-2 for the gray tepetate in the <8mm fraction and 1350 and 2354 g m2 for the brown and yellow tepetates in the <4mm fraction. The lower values of infiltration corresponded to the site 2 tepetates and the higher to the site 1 tepetate. The reverse order was found for total runoff and erosion. The relative magnitude in the results is explained by the presence of higher clay content in site 2 (37 to 46 percent) and the presence of high amounts of halloysite and smectite in the clay fraction. The increase in runoff and erosion and the decrease of infiltration in the <4mm aggregates may reflect the effect of tillage after natural tepetates are farmed. The parameters vary upon the type of tepetate. However, they suggest that erosion control practices are necessary to further prevent the productivity loss where tepetates exist.