Modeling the effects of a partial residue mulch on runoff using a physically based approach
Introduction
Experimental knowledge about the effects of a mulch of vegetative residue on runoff is well established. Savabi and Stott (1994) proved that this porous media can store significant amounts of liquid water. Rutter et al. (1971) and later Scopel et al. (1998) showed that a mulch partly intercepts the rain and cuts down the quantity of water reaching the soil. Gilley and Kottwitz, (1994) observed an increase in soil retention capacity due to the modification of soil microtopography by mulch elements. Also, mulch elements act as a succession of barriers that block runoff and increase roughness (Gilley et al., 1991, Gilley and Kottwitz, 1992, Weltz et al., 1992). Consequently, runoff pathways are generally more sinuous, and runoff flow velocity lower on mulched soils (Abrahams et al., 1994, Poesen and Lavee, 1991). Finally, mulch tends to develop and strengthen topsoil structure through soil protection, macro-fauna activity and the incorporation of organic matter, which usually provides a high infiltration rate (Rao et al., 1998, Scopel et al., 1998, Valentin and Bresson, 1992, Zachmann and Linden, 1989).
However, very few authors have attempted to formalize or model these effects. Moreover, their models did not address all the previously listed effects but focused only on certain specific points. Gilley et al. (1991) modeled the uniform water flow on an impervious surface (∼7 m2) covered with glued residue, with the help of Darcy Weisbach's law. Yu et al. (2000) used Manning's equation to simulate overland flow on a mulched impervious soil (108 m2), at a 1 min time step. In both cases, modeling was in good agreement with experimental data and contributed to the determination of a friction factor that varies according to the type of residue used. However, the important role of the mulch in infiltration processes was not taken into consideration. Bristow et al. (1986), and later Bussière and Cellier, 1994, Gonzalez-Sosa et al., 1999, developed two similar mechanistic vertical 1D models to simulate the heat and water regimes of mulched soil. They simulated rain interception by mulch and percolation to the soil, and assumed that the rain that could not infiltrate into the soil was directly evacuated from the system, without considering runoff flow dynamics on the soil. The lack of accurate experimental data made calibration and validation of runoff processes impossible in these models.
Based on the early experimental results of Scopel et al. (1998), the present study consists in quantifying and modeling all the important effects (rain interception, soil infiltration and retention, velocity and pathway geometry of runoff flow) of a partial-covering mulch of corn residue on runoff. The methodology adopted consists of two parts: (1) obtaining a set of data that describe runoff dynamics at a short time step (20 s) on middle-scale runoff plots (RPs) (20 m2), (2) developing a physical model that accounts for the main processes that drive runoff on mulched soils, and calibrating and validating the latter on the experimental data.
Section snippets
Theory
Because we worked on a soil that tended to crust, we assumed that the topsoil layer strongly controlled infiltration (Vandervaere et al., 1998). Based on this concept, the model developed is composed of a production module for estimating runoff volume and a transfer module for assessing its flow dynamics to the plot outlet. The system on which the model was applied consisted of a RP that was simplified to a micro-catchment of two hillslopes drained by a single central channel (Fig. 1). The
Material and methods
Experimental data (rain and runoff dynamics), soil, mulch and plant properties, and parameters describing runoff flow were required to calibrate and validate the model. This information was obtained from measurements on different plots and is described in the subsections below. The methodology adopted for modeling consisted of three steps: (1) calibration of runoff production and transfer modules by means of an iterative procedure; (2) sensitivity analysis; (3) validation of the model.
Experiments
The results of the artificial runoff experiment are presented in Table 4. Tortuosity increased almost linearly with mulch biomass, its average from 1.09 on RP0 to 1.46 on RP4.5P (Table 4). Corresponding effective slope decreased from 0.064 to 0.048. Friction factor, derived from velocity and flow depth (Eq. (11)), was strongly affected by mulch biomass and increased on average from 0.20 on bare soil to 2.45 on RP4.5P. Width occupation varied from about 0.15 on mulched plot to approximately 0.40
Discussion
In this work, specific experiments were designed to assess quantitatively the main effects of a partial covering mulch of corn residue on runoff. Measurements showed that runoff was dramatically cut down by mulch, even for a small amount of residue. Runoff coefficient was reduced by 50% on average by applying only 1.5 t ha−1 of residue. This behavior was due to both short-term and long-term effects. At the cycle scale, the mulch stored up to 1.6 mm by rain interception, which reduced runoff
Conclusion
The objective of this work was to quantify and model the main effects of residue mulch on runoff processes. The experimental layout showed that runoff was dramatically cut down by mulch, even for a small amount of residue. In the short run (0–1 year), mulch intercepted rain, enhanced water flow concentration by dam effect, and slowed down runoff flow by increasing roughness and pathway tortuosity. In the long run (4 years), mulch ensured high topsoil water conductivity and sorptivity.
Acknowledgements
Financial and technical support from Centro Internacional de Mejoramiento del Maı́z y Trigo (CIMMYT) as well as Institut National de la Recherche Agronomique (INRA) is gratefully acknowledged. Special thanks to Jean-Claude Gaudu for his efficient technical assistance.
References (29)
- et al.
Resistance to overland flow on semiarid grassland and shrubland hillslopes, walnut gulch, southern Arizona
Journal of Hydrology
(1994) - et al.
Simulation of heat and moisture transfer through a surface residue-soil system
Agricultural and Forest Meteorology
(1986) - et al.
Modification of the soil temperature and water content regimes by a crop residue mulch : experiment and modelling
Agricultural and Forest Meteorology
(1994) - et al.
Effects of size and incorporation of synthetic mulch on runoff and sediment yield from interills in a laboratory study with simulated rainfall
Soil and Tillage Research
(1991) - et al.
Rainfall infiltration and runoff from an alfisol in semi-arid tropical India. 1. No-till systems
Soil and Tillage Research
(1998) - et al.
A production model of rainfall interception in forests. i. Derivation of the model from observations in a plantation of corsican pines
Agricultural Meteorology
(1971) - et al.
Morphology, genesis and classification of surface crusts in loamy and sandy soils
Geoderma
(1992) - Arreola Tostado, J., 1996. Etude et modélisation de l'effet des paillis sur le bilan hydrique—le cas du semis direct...
- et al.
Stics: a generic model for the simulation of crops and their water and nitrogen balance. i. Theory and parametrisation applied to wheat and corn
Agronomie
(1998) - de Condappa, D, 2000. Illustration de la méthode beer-kan en vue de la caractérisation hydrodynamique d'un sol, Dea,...
Representation of infiltration in adaptive rainfall-runoff models
Nordic Hydrology
Beginning of motion for selected unanchored residue materials
Journal of Irrigation and Drainage Engineering
Maximum surface storage provided by crop residue
Journal of Irrigation and Drainage Engineering
Cited by (89)
Microplastics in the soil environment: A critical review
2022, Environmental Technology and InnovationThe regional water-conserving and yield-increasing characteristics and suitability of soil tillage practices in Northern China
2020, Agricultural Water ManagementCombined effects of rainfall regime and plot length on runoff and soil loss in the Loess Plateau of China
2019, Earth and Environmental Science Transactions of the Royal Society of Edinburgh