Soil erosion–runoff relations on cultivated land: Insights from laboratory studies

Land degradation in the form of soil erosion is a major problem in semiarid and arid regions. Understanding the processes and mechanisms affecting the generation of runoff and subsequent soil erosion in these regions is essential for the development of improved soil and water conservation and crop management practices. We performed a meta-analysis of both published and unpublished runoff and soil erosion data and the relations between them; data were obtained from numerous semiarid regions (211 samples, 720 simulations), exposed to drip type laboratory rain simulators. The samples varied in their intrinsic properties (e.g. texture and organic matter) and extrinsic conditions (e.g. rain properties and soil condition). Both runoff and soil erosion were considerably affected by the inherent soil and rain properties, and soil conditions within agricultural fields. The relation identified between soil loss and runoff could be expressed either as a nonlinear (exponential or power) or a linear function. Exponential and power functions applied mostly to situations where conditions tended to harm soil structural stability and enhance destabilization of surface aggregates (e.g. high rain kinetic energy, conventional tillage and sodicity). Linear functions applied to cases associated with conditions that enhanced the stability of soil structure (e.g. slow wetting, amendment with soil stabilizers, and minimum tillage in clay soil). The established soil loss–runoff relation (SLRR) contributed to a better understanding of the mechanisms governing overland flow and soil loss at the small plot scale. The relations identified might also assist in (a) further development of soil erosion models and research techniques to be linked with field-scale data (e.g. by using the connectivity concept) and (b) the design of more suitable management practices for soil and water conservation to decrease soil degradation. Highlights • Soil loss–runoff relations were studied in 211 semiarid soils under different extrinsic conditions. • Soil loss–runoff relations could be expressed as nonlinear (exponential or power) or linear. • Conditions that enhanced destabilization of surface aggregates resulted in nonlinear soil loss–runoff relations. • Linear soil loss–runoff relations were noted for conditions that stabilize soil structure (e.g. aggregate stability).