EFFECT OF RESIDUE COVER, TILLAGE-INDUCED ROUGHNESS, AND SLOPE LENGTH ON EROSION AND RELATED PARAMETERS

NEROLI PEDRO COGO, Purdue University

Abstract

Studies of tillage-induced effects on soil erosion and related parameters were carried out under field conditions using simulated rainfall. Also, critical slope-length limits for two conservation tillage practices were investigated using extra-inflow additions to simulate longer slope lengths. Interpretation of the results involved principles and concepts used to develop current theories of erosion mechanics. Residue cover was shown to be the most important single parameter in reducing soil erosion, especially on a smooth soil surface. The roughness of the soil surface created by tillage was also shown to be of paramount importance, especially during those periods in which the soil is devoid of surface ground or canopy cover. The amount of secondary tillage partially offset the residue cover and roughness effects, however. Coefficient values for the parameters in the predictive equations varied depending on factors such as soil roughness, residue type and incorporation, and slope length. Because of the influence of roughness on erosion, the relative effectiveness of the mulch in reducing soil loss was shown to be the highest on a smooth, undisturbed soil surface. No critical slope-length limits for mulch were found on no-till and chisel plowing through a 135-m simulated slope length. Mulch was relatively more effective in reducing soil loss on the longer simulated slopes. Size distribution of the eroded aggregates was influenced by the tillage-induced parameters. Residue cover and soil roughness were both of paramount importance in determining the number of larger aggregates in the runoff water. The results also showed the soil to be dominantly eroded as aggregates rather than as primary soil particles. The primary particle composition of the eroded soil aggregates followed closely that of the original soil.

Degree

Ph.D.

Subject Area

Agronomy

COinS