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Title: Temporal variation in soil detachment under different land uses in the Loess Plateau of China

item Zhang, Xunchang

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2009
Publication Date: 6/2/2009
Citation: Zhang, G.H., Tang, M.K., Zhang, X.J. 2009. Temporal variation in soil detachment under different land uses in the Loess Plateau of China. Earth Surface Processes and Landforms. 34:1302-1309.

Interpretive Summary: Land use types and management practices such as tillage often have predominant effects on soil’s susceptibility to soil erosion in fields or watersheds. This study was conducted to evaluate the temporal effects of land use and management practices on soil erodibility (susceptibility to erosion) of undisturbed soil samples, which were taken from fields of five typical land uses (cropland, grassland, shrubland, wasteland, and woodland) in the Loess Plateau of China during the growing season. The intact soil samples were tested under a constant concentrated flow condition in flumes in laboratory. The results indicated that soil erodibility was significantly influenced by land uses. The erodibility in the cultivated crop lands was much greater than those in the undisturbed lands (grassland, shrubland, wasteland, and woodland). Temporal variation of soil erodibility was affected by tillage operations, soil consolidation, and root growth. The results indicated that conversion from croplands to grasslands and woodlands and from conventionally tilled croplands to no-till systems would considerably reduce soil loss rates in the Loess Plateau. The results can be useful to soil conservationists in evaluating the effectiveness of different land use types in controlling soil erosion in the region and to modelers in developing temporal adjustment of soil erodibility parameters in continuous soil erosion models.

Technical Abstract: Measurements of temporal variations in soil detachability under different land uses are badly needed to develop new algorithms or evaluate the existing ones for temporal adjustment of soil detachability in continuous soil erosion models. Few studies were conducted in the Loess Plateau to quantify temporal variations in detachment capacity under different land uses. The objectives of this study were to investigate the temporal variations of soil detachment capacity under different land uses and to further identify the potential factors causing the change in the Loess Plateau. Undisturbed soil samples were collected in the fields of cropland (millet, soybean, corn, and potato), grassland, shrub land, wasteland, and woodland and tested in a laboratory flume under a constant hydraulic condition. The measurements started in mid-April and ended in early October, 2006. The results showed that soil detachment capacity of each land use fluctuated considerably over time. Distinctive temporal variation in detachment capacity was found throughout the summer growing season of measurement in each land use. The maximum detachment capacities of different land uses varied from 0.019 to 0.490 kg per square meter per second and the minimum detachment capacities ranged from 0.004 to 0.092. Statistical analysis using a paired t-test indicated that soil detachment variations differed significantly at the 0.05 level between land uses in most cases. The major factors responsible for the temporal variation of soil detachment were tillage operations (such as planting, plowing, hoeing of weeds, harvesting), soil consolidation, and root growth. The influence of tillage operations on soil detachment depended on the degree of soil disturbance caused by the operations. The consolidation of the topsoil over time after tillage was reflected by increases in soil bulk density and soil cohesion. As soil bulk density and cohesion increased, detachment capacity decreased. The impact of root density was inconclusive in this study. Further studies were needed to quantify the effects of root density on temporal variations of soil detachment. This work provides useful information for developing temporal adjustments to soil detachment capacity in continuous soil erosion models in the Loess Plateau.