INTERCOMP • RESEARCH ARTICLE Effect of surface stone cover on sediment and solute transport on the slope of fallow land in the semi-arid loess region of northwestern China Tailong Guo & Quanjiu Wang & Dingqiang Li & Jie Zhuang Received: 18 December 2009 / Accepted: 21 May 2010 / Published online: 12 June 2010 # Springer-Verlag 2010 Abstract Purpose In the semi-arid loess region of northwestern China, use of stone and gravel as mulch has been an indigenous farming technique for improving crop produc- tion for over 300 years. However, systematic studies on the effects of stone covers on soil and water conservation have been rarely conducted, except for a few investigations and documentations on the stone cover effects on erosion and solute transport in such a highly erodible loess region. Materials and methods We experimentally examined the effects of surface stone cover on sediment erosion and solute transport using the water-scouring method on sloping land in a semi-arid region in China, which had been left fallow with alfalfa (Medicago sativa) for 3 years. All covered stones rested on the soil surface, and none were partly or completely embedded in the soil surface layer. Stone cover percentages were classified into three groups: 0% (no stone cover, the control treatment), 5.1%, and 20.8%. Two sizes of stones, SCA (7.6×7.6 cm) and SCB (18.4×18.4 cm), were used in the treatment of 5.1% stone cover. A dye method was used to measure flow velocities in the experiments. Each stone treatment had one replicate. Results and discussion The surface cover by stones influenced soil erosion processes, runoff generation, and solute transport. Runoff rate and sediment yield decreased as stone cover percentages increased from zero (no stone cover) to 20.8%. The effect of stone sizes on the runoff was not significant, whereas stone size type SCA caused lower sediment yield than SCB at the same stone cover percentage of 5.1%. Likewise, water flow velocity and the Froude numbers also decreased with increasing stone cover percentage. The Manning roughness increased with in- creasing stone cover percentage, ranging from 0.0296 to 0.0579 m −1/3 s. But the Reynolds numbers among different stone cover percentages and sizes remained nearly the same with a small variation from 483 to 486. Conclusions The study implied that stone cover percentage and size have important influences on sediment and solute concentration in runoff. Surface-covering stones reduced the velocity of runoff, increased surface roughness, decreased sediment yield in runoff, and consequently reduced the quantities of solute release from soil surface. Keywords Flow hydraulics . Soil erosion . Solute transport . Stone size . Surface stone cover Responsible editor: Marcel van der Perk. T. Guo : D. Li Guangdong Institute of Eco-environment and Soil Science, Guangdong Key Laboratory of Comprehensive Control of Agro-environment, No. 808 the Tianyuan Road, the Tianhe District, Guangzhou 510650 Guangdong, People’ s Republic of China T. Guo : Q. Wang (*) State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, No. 26 Xinong Road, YangLing, Shaanxi 712100, People’ s Republic of China e-mail: wquanjiu@163.com Q. Wang Xian University of Technology, Xian, Shaanxi 710048, People’ s Republic of China J. Zhuang Department of Biosystems Engineering and Soil Science, Institute for a Secure and Sustainable Environment, Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN 37996-4134, USA J Soils Sediments (2010) 10:1200–1208 DOI 10.1007/s11368-010-0257-8