History, residue, and tillage effects on erosion of loessial soil

Studies have shown that no-till (NT) management reduces soil erosion relative to chisel/disk-tillage (CT) and that this benefit may increase over time. There are fewer data, however, to separate the erosion-reduction contributions of surface residue mulch from those of improved soil properties under NT. The objective of this study was to quantify these separate contributions for a silt loam soil (Glossic Fragiudalf) used for corn (Zea mays L.) production in northern Mississippi for five to ten years with either CT or NT. The experiment had ten treatments. Two were normal CT and NT managements in which a crop was planted but had not emerged prior to simulated rainfall. The other eight treatments had surface crop residues removed and comprised a 2 x 2 x 2 factorial arrangement of two tillage histories (CTh or NTh), two levels of tillage immediately prior to rainfall simulation (disturbed or not disturbed), and two levels of residue removal (residue removed just prior to simulated rainfall or residue removed one year prior to simulated rainfall). Simulated rainfall was applied at a rate of 65 mm h-1 in a three-storm sequence on 10.7 x 3.7 m areas. NT exhibited greater runoff but much lower sediment losses than CT. Residue removal doubled erosion for both tillage histories. Surface disturbance decreased runoff from the first storm following tillage but increased total soil loss 26% to 47%. With residues removed, long-term NTh resulted in one-third the soil loss of CTh, and similar benefits were observed with or without surface disturbance. This residual benefit of NTh was lost within one year of fallow after residue removal. These results demonstrate that the erosion resistance of NT areas is due to both residue cover and improved soil quality factors. Although the erosion-resisting soil quality factors developed over several years of NT management may be lost within a single year of fallow management, these factors may protect the soil from excessive erosion if NT fields that must occasionally be tilled are quickly returned to NT management.