Surface roughness changes as affected by tillage and rainfall erosivity
Abstract
A two year field study was conducted to investigate the effects of different tillage systems, cumulative rainfall erosivity and a gypsiferous material on soil surface roughness, which was determined using a portable laser scanner. Tillage treatments for the natural rainfall experiment consisted of conventional (moldboard plowing + disking), chisel plowing and chisel plowing + a drug chain. Cover treatments consisted of bare soil and soybeans canopy. Four surface roughness indices were calculated from the elevation data files: Random Roughness (RR), Standard Deviation (SD), Tortuosity and Roughness Functions, expressed by D (Fractal index) and l. As a general tendency, all indices but D decreased with cumulative rainfall erosivity. Random Roughness and Standard Deviation indices decreased quadratically with cumulative rainfall erosivity, while Tortuosity and l indices decreased exponentially. The D index increased with cumulative rainfall erosivity. Soybean cover provided a decrease of 7% in the surface roughness decay, as measured by the l index, when compared with bare soil. The l index was the most sensitive index to changes in cumulative rainfall erosivity. The roughness functions, with D and l indices calculated, seems to be an appropriate way to characterize surface roughness at small scales. Depressional Storage decreased linearly with cumulative rainfall erosivity, with a decay rate depending on the initial values. Tillage treatments for the simulated rainfall experiment consisted of conventional (moldboard plowing + disking) and chisel plowing. Surface treatments consisted of bare soil and 5 t/ha of a gypsiferous material (GM). RR and SD indices decreased linearly with cumulative simulated rainfall erosivity, while Tortuosity and l indices decreased exponentially. The l index was the most sensitive index to changes in cumulative simulated rainfall erosivity. The GM cover did not have a significant effect in decreasing the surface roughness decay rate, nor decreasing the total amount of water infiltrating the soil nor the infiltration rates for conventional and chisel tillage treatments. The GM did have a positive effect in decreasing sediment concentration in runoff, decreasing the cumulative soil loss by 61 and 32% for conventional and chisel tillage treatments, respectively. The GM did not have a significant effect in the decay rate of the depressional storage.
Degree
Ph.D.
Advisors
Norton, Purdue University.
Subject Area
Agronomy|Agricultural chemicals
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