ga uig ty o ent f Kw
P), CNRS, 14 Av Edouard Belin, F-31400 Toulouse, France a r t i c l e i n f o
Article history: © 2014 Elsevier B.V. All rights reserved.
IFT); and transport by nnell, 2005; Parlak and kely to operate within
Catena 126 (2015) 60–67
Contents lists available at ScienceDirect
Cate e lson soil ecosystem functions such as those associatedwith food productivity, water availability and its quality, biodiversity and regulation of greenhouse gas emissions, among others (Bationo et al., 2007; Hien et al., 1996; hillslopes during rainstorms, their effiiency is intimately linked to slope length (e.g., Chaplot and Le Bissonnais, 2003; Kinnell, 2005).
ST moves the detached soil particles radially away from their initialThese factors influence water erosion process, the main process by which soil and soil nutrients are lost from the soil matrix. The soil water erosion significantly impacts the soil organic carbon (SOC) pool (Berhe et al., 2007; Lal, 2003; Van-Oost et al., 2007) with huge consequences port (ST); (2) raindrop-induced flow transport (R flowwithout stimulation by drop impact (FT) (Ki Özaslan Parlak, 2010).
While all of these erosion mechanisms are li1. Introduction
In the sahelian region ofWest Africa, the combination of poor soil fertility with low and erratic rainfall, high soil and air temperature, surface crusting, low water-holding capacities and recurrent droughts are the main constraints to food productivity (Bationo and Buerkert, 2001).
The process of water erosion is complex, and can affect SOC through the combined action of detachment and transportmechanisms (Kinnell, 2005). These mechanisms are associated with raindrop impact and overland flow, either as Hortonian flow or saturation excess surface runoff (Hewlett and Hibbert, 1967). Once detachment has taken place, three types of transportmechanisms can be operative: (1) splash trans-Jacinthe et al., 2004; Lal, 2004; Martínez-Mena ⁎ Corresponding author at: P.O. Box: 7118Ouagadougou 36 60.
E-mail address: firstname.lastname@example.org (S.B. Maïga-Y http://dx.doi.org/10.1016/j.catena.2014.11.001 0341-8162/© 2014 Elsevier B.V. All rights reserved.19 on STRU crusts. These results on the relationship between soil crusting and sheet erosion should be further used to mitigate against the loss of SOC through the implementation of improved soil conservation techniques, as well as to improve soil erosion and/or SOC models.Received 7 April 2014
Received in revised form 23 October 2014
Accepted 1 November 2014
Available online xxxx
Soil surface feature
Soil organic carbon
Africaa b s t r a c t
Soil surface crusting influences water infiltration and runoff but its impact on soil organic carbon (SOC) losses by sheet erosion is largely unknown. Because there are different mechanisms of sheet erosion, from raindrop detachment and transport by raindrops interacting with flow (RIFT), to detachment and transport by flow, that require a certain slope length to be operative, this study examined the impact of slope length on SOC and nutrient losses. Field experiments were conducted on crusted soils in the Sahel region of Africa. Three replicates of micro-plots (1 m × 1 m), plots (10 m long × 5 m width) and long plots (25 m × 6 m) were installed for each crust type in the area (structural, STRU; desiccation, DES; gravel, GRAV; and erosion, ERO) and followed for each rainfall event in the 2012 rainy season. Sediment, SOC content in sediments and selected nutrients (NO3−; PO43−) in the runoff were analyzed to evaluate the annual losses by sheet erosion. SOC losses decreased significantly with increasing slope length from 0.24 g C m−1 on micro-plots to 0.04 g C m−1 on plots and to 0.01 g C m−1 on longplots and similar trendswere observed forNO3− and PO43− losses. This suggested a strong scale dependency of sheet erosion with the efficiency of transport by saltation and rolling by RIFT decreasing significantly with increasing slope length, by 6 folds in average between 1 and 10 m, with values between 1.8 on DES crusts andLaboratoire d'Océanographie et du Climat, Expérimentations et approches numériques, UMR 7159, 4, place Jussieu, 75252 Paris, Francee Géosciences Environnement Toulouse (GET), UMR 5563, IRD-Université de Toulouse, UPS (OM fImpact of sheet erosion mechanisms on or crusted soils in the Sahel
S.B. Maïga-Yaleu a,b,c,⁎, P. Chivenge d, H. Yacouba c, I. G
A. Bary a, V. Chaplot d,f a Laboratory of Analytical Chemistry, Radiochemistry and Electrochemistry (LACARE), Universi b Laboratory of Hydrology and Water Resources, International Institute of Water and Environm c Department of Training and Research, Regional Center AGRHYMET, BP 11011 Niamey, Niger d School of Agricultural, Earth & Environmental Sciences, Rabie Saunders Building, University o j ourna l homepage: www.et al., 2012). , Burkina Faso. Tel.:+22676 73 aleu).nic carbon losses from uemde a, H. Karambiri c, O. Ribolzi e, f Ouagadougou, 03 BP 7118, Burkina Faso al Engineering (Institute 2iE), 01 BP 594, Burkina Faso aZulu-Natal, Scottsville 3209, South Africa na ev ie r .com/ locate /catenalocation and is thus a relatively inefficient transport mechanism. In contrast, RIFT, which stimulates particles to roll and saltate, is much more efficient in transporting particles than ST. While ST is a point process which efficiency mainly depends on raindrop energy, the ability of
RIFT to move the detached soil material downslope tends to increase with increasing flow velocity and to some degree, flow depth, before thick layers of overland flow protect the soil surface from the impact of raindrops.
In-situ experimental designs involving runoff plots with different slope lengths thus, become important tools for the investigation of erosion mechanisms. Not only are water erosion mechanisms affected by slope length but also by factors such as raindrop energy, land cover and soil properties (e.g. texture, soil organic matter content, soil aggregation among others). Soil crusting is another important factor of control of water erosion, especially in the fragile Sahel region of Africa.