Changes of soil surface roughness under water erosion process

Abstract

The objective of this study was to determine the changing characteristics of soil surface roughness under different rainfall intensities and examine the interaction between soil surface roughness and different water erosion processes. Four artificial management practices (raking cropland, artificial hoeing, artificial digging, and contour tillage) were used according to the local agriculture customs of the Loess Plateau of China to simulate different types of soil surface roughness, using an additional smooth slope for comparison purposes. A total of 20 rainfall simulation experiments were conducted in five 1 m by 2 m boxes under two rainfall intensities (0.68 and 1.50 mm min À1 ) on a 15°slope. During splash erosion, soil surface roughness decreased in all treatments except raking cropland and smooth baseline under rainfall intensity of 0.68 mm min À1 , while increasing for all treatments except smooth baseline under rainfall intensity of 1.50 mm min À1 . During sheet erosion, soil surface roughness decreased for all treatments except hoeing cropland under rainfall intensity of 0.68 mm min À1 . However, soil surface roughness increased for the artificial hoeing and raking cropland under rainfall intensity of 1.50 mm min À1 . Soil surface roughness has a control effect on sheet erosion for different treatments under two rainfall intensities. For rill erosion, soil surface roughness increased for raking cropland and artificial hoeing treatments, and soil surface roughness decreased for artificial digging and the contour tillage treatments under two rainfall intensities. Under rainfall intensity of 0.68 mm min À1 , the critical soil surface roughness was 0.706 cm for the resistance control of runoff and sediment yield. Under rainfall intensity of 1.50 mm min À1 , the critical soil surface roughness was 1.633 cm for the resistance control of runoff, while the critical soil surface roughness was 0.706 cm for the resistance control of sediment yield. These findings have important implications for clarifying the erosive nature of soil surface roughness and harnessing sloped farmland.

Quantifying the changes of soil surface microroughness due to rainfall impact on a smooth surface

“…Table 1 summarizes the results of this study along with results from other studies focused on smooth surfaces, documenting the RR index values before and after the rainfall events, the cumulative rainfall, and the associated RR ratio. The present study, along with Vázquez et al (2008) and Zheng et al (2014) generally report an increase in RR with rainfall under the conditions examined. The Vázquez et al (2008) study, however, differs from the present study and that of Zheng et al (2014) in that it examined roughness evolution under successive rainfall events per run.…”

“…The present study, along with Vázquez et al (2008) and Zheng et al (2014) generally report an increase in RR with rainfall under the conditions examined. The Vázquez et al (2008) study, however, differs from the present study and that of Zheng et al (2014) in that it examined roughness evolution under successive rainfall events per run. Only the RR data collected on completion of the last rainfall succession in each run conducted by are presented in Table 1.…”

“…Rosa et al (2012) introduced an index (called the roughness index) estimated from the semivariogram to describe roughness, and an increase in the index with rainfall was observed under some conditions, and attributed to the fragmentation of aggregates and clods to smaller aggregates. Zheng et al (2014) also reported an increase in values of the RR after the application of rainfall on smooth soil surfaces. However, none of the above studies acknowledged or related the increasing trend in surface microroughness to rainfall impact on smooth surfaces.…”

“…In these studies, a decay of roughness due to precipitation action is predicted, since rainfall impact and runoff "smoothen" the rough edges of soil grains, aggregates, and clods, especially in the absence of cover (Potter, 1990;Bertuzzi et al, 1990;Vázquez et al, 2008;Vermang et al, 2013). There are few studies that have examined surfaces with initial microroughness less than 5 mm, a low roughness condition observed seasonally in some landscapes under bare conditions (e.g., Kamphorst et al, 2000;Vázquez et al, 2008;Zheng et al, 2014). Hereafter, for shortness, tests with initial RR less than 5 mm will be referred to as "smooth", whereas tests with initial RR greater than 5 mm will be referred to as "rough".…”

Effect of Soil Tillage and Plant Residue on Surface Roughness of an Oxisol Under Simulated Rain

“…According to Dalla Rosa et al (2012), the most common manner of expressing roughness is through the use of indices that represent the conformation of the soil surface. Among the different indices, the most used is the random roughness index (RR), which represents the chance distribution of the peaks and valleys resulting from clods of soil and organization of the aggregates (Zheng et al, 2013). The RR is calculated by the standard deviation of the heights of the microrelief after removal of the effect of the markings of soil tillage and the slope of the land (Allmaras et al, 1966).…”