Surface sealing and erosion on some high clay surface soils

Jose Miguel Reichert, Purdue University

Abstract

The soil resistance to detachment and transport of detached particles by erosive forces acting on the soil surface is largely determined by the physical-chemical composition of and processes acting on the soil-fluid interface during a rain. The effects of clay mineralogy, gypsiferous material (GM), surface boundary condition, rain intensity (P), and aggregate stability on water infiltration, runoff, and sediment yield were evaluated on twelve high clay content surface soils from different pedogenic environments. The experiment was conducted in the laboratory using simulated rainfall and small erosion pans (0.14 m$\sp2$). Steady-state infiltration rates were less for swelling than for non-swelling soils. GM increased infiltration and reduced soil and water losses for all five swelling and for only three of the seven non-swelling soils. Possibly, physical-chemical effects are predominant in sealing of swelling soils, whereas mechanical effects are predominant for non-swelling soils. Since the GM is a mixed and alkaline material, on soils with variable charge (highly weathered soils) the increased pH of the soil increases negative charges and enhances dispersion, and could be responsible for the increases in runoff and erosion observed in this study. For a sandy loam Oxisol, GM-flocculated clay obstructed pores and reduced infiltration. The Morin and Benyamini model effectively described infiltration, except for the sandy loam Oxisol. This soil showed a sinusoidal infiltration pattern, suggesting that sealing was a transient process. The crust consisted basically of a dense layer of lesser porosity and smaller pores than the soil below it. It was formed by raindrop impact and not by clay illuviation. On soils where GM increased infiltration, total porosity and planar porosity were increased; planar pores are thought to be more water conductive. Increases in rainfall rate had a lesser influence on dried-crust and wet-crust than on freshly-tilled soil. Dried-crust was the most erodible for half of the cases; possibly, rupture of the crust with shrinking rendered it more susceptible to pitting by raindrops. Runoff increased with wetting and drying cycles. Increased aggregate stability with capillary prewetting was not reflected in less erosion and runoff, probably due to differences in the rate of wetting and water-table height in the erosion pan. Soil textural parameters and "binding" agents (Fe and Al, and organic matter) were the independent variables that showed significance in the stepwise multiple linear regression for steady-states infiltration, runoff and sediment loss rates.

Degree

Ph.D.

Advisors

Norton, Purdue University.

Subject Area

Agronomy

COinS