RUNOFF AND EROSION RATES FROM SLIT, CONVENTIONAL, AND CHISEL TILLAGE UNDER SIMULATED RAINFALL

Abstract

ABSTRACT Runoff and erosion from reconstructed Letort silt loam under simulated rainfall were determined. Residue cover was varied in the presence of a small contoured slit. Four treatments, simulating field conditions, included a bare, smooth soil surface (representing conventional tillage after disking), a smooth soil surface with 30% residue cover (representing chisel tillage after disking), a smooth soil surface with a slit and 30% residue (representing slit tillage after disking), and a slitted soil surface with 50% residue (representing slit tillage without disking). The bare soil treatment produced the greatest runoff and erosion from the 30-min duration, 90-mm/h rainfall events. The two treatments with 30% residue cover produced 25% less runoff and 50% less erosion than the bare soil control treatment. In the slitted soil treatment, the slit provided a small impoundment which collected and stored all surface runoff until it filled and overflowed. The slit used in these experiments on a 300- x 1000-mm surface area stored 1.25-mm depth of surface runoff, the same depth of runoff produced from a 10-min duration, 90-mm/h rain on a Letort silt loam, or the equivalent of a 2-yr retum period rainfall event. After the slit overflowed, the erosion rates were approximately equal to the other conservation tillage treatment. Surface residue decreased surface runoff and erosion and increased the amount of water that infiltrated into the soil. The surface storage provided by the slit treatment further increased the opportunity for infiltration.