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Residue Cover and Surface-Sealing Effects on Infiltration

Numerical Simulations for Field Applications

^a USDA-ARS-NPA, Great Plains Systems Research Unit, P.O. Box E, 301 S. Howes St., Fort Collins, CO 80522
^b USDA-ARS-NPA, Central Great Plains Research Unit, Akron, CO 80720

View larger version (72K): [in a new window]   Fig. 1. For residue distribution Type I, uniform residue patches are distributed evenly. The representative unit is simplified from a hexahedron to a cylinder. For residue distribution Type II, the residue area is simply switched with the sealed area

View larger version (19K): [in a new window]   Fig. 2. Representative soil cylinder with residues in the center and surface seal in the remaining area (Type I). R1 is the radius of the residue patch. R2 is the radius of the soil cylinder. D is the depth of the soil cylinder. Water may first run on to a residue-covered area from a surface-sealed area. Excess water from both the residue-covered area and surface-sealed area then become runoff, which is removed from the system

View larger version (38K): [in a new window]   Fig. 3. Relative infiltration vs. percentage residue cover, Prc, which is the percentage of residue-covered area of the total representative area (Type I). Relative infiltration is the cumulative infiltration at a value of Prc divided by cumulative infiltration at Prc = 100%. For different values of Prc, R1 is kept constant

View larger version (37K): [in a new window]   Fig. 4. Relative infiltration vs. percentage residue cover, Prc, which is the percentage of residue-covered area of the total representative area (Type I). Relative infiltration is cumulative infiltration at a value of Prc divided by cumulative infiltration at Prc = 100%. For different values of Prc, R2 is kept constant

View larger version (29K): [in a new window]   Fig. 5. Sensitivity of leveling-off value of Prc to rainfall intensity (Type I). The value of Prc, at which the cumulative infiltration equals 95% of the cumulative infiltration at 100% Prc, is defined as the leveling-off value of Prc

View larger version (29K): [in a new window]   Fig. 6. Sensitivity of leveling-off value of Prc to the residue-patch radius (Type I). The value of Prc, at which the cumulative infiltration equals 95% of the cumulative infiltration at 100% Prc, is defined as the leveling-off value of Prc

View larger version (31K): [in a new window]   Fig. 7. One-dimensional solution with the effective surface sealing Kce is compared with two-dimensional solutions with 4 degrees of surface sealing (Type I). Four combinations of soil textures and rainfall intensities were examined. For two-dimensional solutions, Kce/Ks represents percentage residue cover

View larger version (17K): [in a new window]   Fig. 8. Simulated results (Type I) are compared with field observations (after Baumhardt and Lascano, 1996; Lang and Mallett, 1984). The simulation input data are 65 mm h-1 rainfall intensity for a period of 1 h, 50-mm residue-patch radius, and Kc = 0.1Ks for surface sealing