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ARS Home » Midwest Area » West Lafayette, Indiana » National Soil Erosion Research Laboratory » Research » Publications at this Location » Publication #85227
Title: SURFACE ROUGHNESS CHANGES AS AFFECTED BY RAINFALL EROSIVITY, TILLAGE AND CANOPY COVER

Author
item ELTZ, FLAVIO - SANTA MARIA, BRAZIL
item Norton, Lloyd

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Tillage and plant cover are the two important factors that can be used for erosion control. Tillage causes the soil to become rough which stores water and prevents it from running and slows it when it does run. We studied how the tillage induced roughness changed as a result of the amount of natural rain and how this roughness was affected by soybean cover. We found that soybean cover did little to prevent roughness decline with rainfall. However, a very rough surface provided the most water storage and the roughness lasted longer. The significance of this research is that tillage operations that provide a very rough surface can provide a longer lasting storage of water to prevent soil erosion. The impact of this work is that changing to tillage operations such as chisel plowing can conserve our soil and water resource.

Technical Abstract: Surface roughness and canopy cover are important factors in preventing soil erosion. There is limited information on how soil surface roughness changes as a function of natural rainfall erosivity and canopy cover by plants. We hypothesize that canopy cover, tillage systems, and cumulative rainfall erosivity (CRE) would have unique effects on roughness. We tested this hypothesis on a Miami silt loam soil using a portable laser microtopographer. Tillage treatments of conventional (moldboard plowing + disking), chisel plowing and chisel plowing + dragging a chain produced three roughness levels. Surface cover was none (fallow) or soybean. Random roughness (RR), standard deviation (SD), tortuosity (T) and fractal roughness functions, expressed by D (fractal index) and l, the crossover length, were calculated from microtopography data. Chisel tillage had the greatest values of surface roughness, followed by chisel + chain and conventional tillage, as measured by the l index. All indices but D generally decreased with cumulative rainfall erosivity (CRE). The RR and SD indices decreased quadratically with CRE, with a decrease of 38 and 36 percent from its initial values, respectively, after 200 units CRE, while the T and l indices decreased exponentially, with a decrease of 40 and 60 percent from its initial values, respectively, after 200 units of CRE. Soybean cover lowered soil surface roughness 7 percent less than fallow, as measured by the l index. The l index was 50, 71 and 205 percent more sensitive to changes in CRE than RR, SD and T indices, respectively. The fractal roughness functions were the best approaches to characterize surface roughness at small scales, such as existing plant rows, mainly due to l index sensitivity to changes in CRE.