A. Abd-elfattah and K. Wada, ADSORPTION OF LEAD, COPPER, ZINC, COBALT, AND CADMIUM BY SOILS THAT DIFFER IN CATION-EXCHANGE MATERIALS, Journal of Soil Science, vol.16, issue.2, p.271, 1981.
DOI : 10.1111/j.1365-2389.1981.tb01706.x

N. J. Barrow, Mechanisms of Reaction of Zinc with Soil and Soil Components Chapter Zinc in Soils and Plants, pp.15-32, 1993.

J. Bear, Dynamics of Fluids in Porous Media, Soil Science, vol.120, issue.2, 1972.
DOI : 10.1097/00010694-197508000-00022

C. Belmans, J. G. Wesseling, and R. A. Feddes, Simulation model of the water balance of a cropped soil: SWATRE, Journal of Hydrology, vol.63, issue.3-4, pp.271-286, 1983.
DOI : 10.1016/0022-1694(83)90045-8

D. A. Benson, R. Schumer, M. M. Meerschaert, and S. W. Wheatcraft, Fractional Dispersion, L??vy Motion, and the MADE Tracer Tests, Transp. Porous Media, vol.42, issue.12, pp.211-240, 2001.
DOI : 10.1007/978-94-017-1278-1_11

D. A. Benson, Application of a fractional advection-dispersion equation, Water Resources Research, vol.40, issue.11, 1998.
DOI : 10.1029/2000WR900031

D. A. Benson, S. W. Wheatcraft, and M. M. Meerschaert, Application of a fractional advection-dispersion equation, Water Resources Research, vol.40, issue.11, pp.1403-1412, 2000.
DOI : 10.1029/2000WR900031

B. Berkowitz and H. Scher, Anomalous Transport in Random Fracture Networks, Physical Review Letters, vol.79, issue.20, pp.4038-4041, 1997.
DOI : 10.1103/PhysRevLett.79.4038

B. Berkowitz, H. Scher, and S. E. Silliman, Anomalous transport in laboratory-scale, heterogeneous porous media, Water Resources Research, vol.146, issue.11, pp.149-158, 2000.
DOI : 10.1029/1999WR900295

R. L. Bertholf, H. Sigel, H. G. Seiler, and M. Dekker, Zinc " in " Handbook on Toxicity of Inorganic Compounds, pp.787-800, 1988.

A. E. Boekhold, Field scale behavior of cadmium in soil, 1992.

J. M. Boggs, L. M. Beard, L. S. Mcgee, and M. P. , Database for the second macrodispersion experiment, Electric Power Res. Inst, issue.2, 1993.

J. M. Boggs and E. E. Adams, Field study of dispersion in a heterogeneous aquifer: 4. Investigation of adsorption and sampling bias, Water Resources Research, vol.22, issue.13, pp.3325-3336, 1992.
DOI : 10.1029/92WR01759

J. M. Boggs, S. C. Young, L. M. Beard, L. W. Gelhar, K. R. Rehfeldt et al., Field study of dispersion in a heterogeneous aquifer: 1. Overview and site description, Water Resources Research, vol.24, issue.4, pp.28-3281, 1992.
DOI : 10.1029/92WR01756

C. Boutron, J. Candelone, and . Hong, Greenland snow and ice cores: unique archives of large-scale pollution of the troposphere of the Northern Hemisphere by lead and other heavy metals, Science of The Total Environment, vol.160, issue.161, pp.160-161, 1995.
DOI : 10.1016/0048-9697(95)04359-9

P. L. Brown, A. Haworth, S. M. Sharland, and C. J. Tweed, HARPHRQ: A Geochemical Speciation Program Based on PHREEQE, 1991.

D. P. Bruynzeel, G. Hennipman, and W. G. Van-ketel, Irritant contact dermatitis and chrome-passivated metal, Contact Dermatitis, vol.50, issue.3, pp.175-179, 1988.
DOI : 10.1111/j.1600-0536.1988.tb02889.x

C. M. Bouloutas, E. T. Zarba, and R. L. , A general mass-conservative numerical solution for the unsaturated flow equation, Water Resour. Res, vol.26, pp.1483-1496, 1990.

S. J. Chobanian, Accidental ingestion of liquid zinc chloride: Local and systemic effects, Annals of Emergency Medicine, vol.10, issue.2, pp.91-93, 1981.
DOI : 10.1016/S0196-0644(81)80345-9

C. and C. Interprofessionnel, Etude de la Pollution Atmosphérique, www.citepa..org, 2004.

A. Cortis and B. Berkowitz, Anomalous Transport in ???Classical??? Soil and Sand Columns, Soil Science Society of America Journal, vol.68, issue.5, pp.1539-1548, 2004.
DOI : 10.2136/sssaj2004.1539

J. H. Cushman and T. R. Ginn, Fractional advection-dispersion equation: A classical mass balance with convolution-Fickian Flux, Water Resources Research, vol.12, issue.6, pp.3763-3766, 2000.
DOI : 10.1029/2000WR900261

V. J. 32-dam and F. R. , Numerical simulation of infiltration, evaporation and shallow groundwater levels with the Richards' equation, J. Hydro, 2000.

V. J. 33-dam, J. Huygen, J. G. Wesseling, R. A. Feddes, P. Kabat et al., Theory of SWAP version 2.0. Simulation of water flow, solute transport and plant growth in the Soil-Water- Atmosphere-Plant environment, Report, vol.71, 1997.

V. J. 34-dam, Field-scale water flow and solute transport: SWAP model concepts, parameter estimation and case studies, 2000.

Y. P. Dang, K. G. Tiller, R. C. Dalal, and D. G. Edwards, Zinc speciation in soil solutions of Vertisols, Australian Journal of Soil Research, vol.34, issue.3, pp.369-383, 1996.
DOI : 10.1071/SR9960369

J. A. Davis and K. D. , Surface Complexation Modeling in Aqueous Geochemistry, Reviews in Mineralogy, vol.23, pp.177-260, 1990.

L. Dejonghe, Zinc???lead deposits of Belgium, Ore Geology Reviews, vol.12, issue.5, pp.329-354, 1998.
DOI : 10.1016/S0169-1368(98)00007-9

M. Dentz, A. Cortis, and H. Scher, Time behavior of solute transport in heterogeneous media: transition from anomalous to normal transport, Advances in Water Resources, vol.27, issue.2, pp.155-173, 2004.
DOI : 10.1016/j.advwatres.2003.11.002

A. J. Desbarats, An Interblock Conductivity Scheme for Finite Difference Models of Steady Unsaturated Flow in Heterogeneous Media, Water Resources Research, vol.28, issue.9, pp.2883-2889, 1995.
DOI : 10.1029/95WR02429

J. S. Dyson and R. E. White, A comparison of the convection-dispersion equation and transfer function model for predicting chloride leaching through an undisturbed, structured clay soil, Journal of Soil Science, vol.22, issue.2, pp.157-172, 1987.
DOI : 10.1111/j.1365-2389.1987.tb02133.x

C. Elinder, Zinc In: Handbook on the Toxicology of Metals, 1986.

B. Erdal and R. Chairman, Workshop on Fundamental Geochemistry Needs for Nuclear Waste Isolation, US DOE CONF8406134 National Technical Information Service, 1985.

F. J. Farrell, Angioedema and urticaria as acute and late phase reactions to zinc fume exposure, with associated metal fume fever-like symptoms, American Journal of Industrial Medicine, vol.75, issue.3, pp.331-337, 1987.
DOI : 10.1002/ajim.4700120308

R. A. Feddes, P. Kabat, P. J. Bakel-van, J. J. Bronswijk, and J. Halbertsma, Modelling soil water dynamics in the unsaturated zone ??? State of the art, Journal of Hydrology, vol.100, issue.1-3, pp.69-111, 1988.
DOI : 10.1016/0022-1694(88)90182-5

R. A. Feddes, P. J. Kowalik, and H. Zaradny, Simulation of field water use and crop yield, Simulation Monographs, vol.189, 1978.

L. Fishbein, Sources, transport and alterations of metal compounds: an overview. I. Arsenic, beryllium, cadmium, chromium, and nickel, Environmental Health Perspectives, vol.40, pp.43-64, 1981.
DOI : 10.1289/ehp.814043

M. Genuchten and . Th, A comparison of numerical solutions of the one-dimensional unsaturated???saturated flow and mass transport equations, Advances in Water Resources, vol.5, issue.1, pp.47-55, 1982.
DOI : 10.1016/0309-1708(82)90028-8

M. Genuchten, . Th, and . Van, A Closed-form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils1, Soil Science Society of America Journal, vol.44, issue.5, pp.892-898, 1980.
DOI : 10.2136/sssaj1980.03615995004400050002x

S. Goldberg, Adsorption Models Incorporated into Chemical Equilibrium Models " In Chemical Equilibrium and Reaction Models

F. Goodwin, Zinc compounds Krik- Othmer encyclopedia of chemical technology, pp.840-853, 1998.

R. Gorenflo and F. Mainardi, Fractional calculus and stable probability distributions, Arch. Mech, vol.50, issue.3, pp.377-388, 1998.

K. Harmsen, Behavior of heavy metals in soils " Thesis, 1977.

R. Haverkamp and M. Vauclin, A note on estimating finite difference interblock hydraulic conductivity values for transient unsaturated flow problems, Water Resources Research, vol.6, issue.2, pp.181-187, 1979.
DOI : 10.1029/WR015i001p00181

E. Hjortso, J. Qvist, and M. I. Bud, ARDS after accidental inhalation of zinc chloride smoke, Intensive Care Medicine, vol.89, issue.1, pp.17-24, 1988.
DOI : 10.1007/BF00254116

U. Hornung and W. Messing, Truncation errors in the numerical solution of horizontal diffusion in saturated/unsaturated media, Advances in Water Resources, vol.6, issue.3, pp.165-168, 1983.
DOI : 10.1016/0309-1708(83)90029-5

G. Huang, Q. Huang, H. Zhan, J. Chen, Y. Xiong et al., Modeling contaminant transport in homogeneous porous media with fractional advectiondispersion equation, Science in China Ser. D Earth Sciences, vol.48, 2005.

Q. Huang and G. Huang, Modeling adsorbing solute transport with fractional advection dispersion equation, Land and Water Management: Decision Tools and Practice Proceedings of 2004 International Commission of Agricultural Engineering Conference, pp.11-14, 2004.

Q. Huang, Modeling adsorbing solute transport with fractional advection dispersion equation, 2002.

G. Huang, Q. Huang, and Z. Hongbin, evidence of one-dimensional scaledependent fractional advection ? dispersion, J. of contaminant hydrology, 2006.

B. Hunt, Contaminant Source Solutions with Scale-Dependent Dispersivities, Journal of Hydrologic Engineering, vol.3, issue.4, pp.268-275, 1984.
DOI : 10.1061/(ASCE)1084-0699(1998)3:4(268)

E. A. Jenne, Chemical Modeling in Aqueous Systems. Speciation, Sorption, Solubility, and Kinetics, Symposium Series, vol.93, 1979.

E. A. Jenne, Geochemical Modeling: A Review " PNL-3574, 1981.

C. A. Johnson, M. G. Schaap, and A. K. , Model comparison of flow through a municipal solid waste incinerator ash landfill, Journal of Hydrology, vol.243, issue.1-2, pp.55-72, 2001.
DOI : 10.1016/S0022-1694(00)00404-2

P. Kabat, B. J. Broek, . Van-den, and R. A. Feddes, SWACROP: A water management and crop production simulation model, ICID Bulletin, vol.92, issue.41 2, pp.61-84, 1992.

A. Kabata-pendias and H. Pendias, Trace Elements in Soils and Plants, 1992.

A. Kabat-pendias and A. Karkowiak, Soils parameters as a base for the calculation of background heavy metals status " Int. Conf. Heavy metals in the environment, p.398, 1995.

M. V. Khire, C. H. Benson, and P. J. Bosscher, Water Balance Modeling of Earthen Final Covers, Journal of Geotechnical and Geoenvironmental Engineering, vol.123, issue.8, pp.744-754, 1997.
DOI : 10.1061/(ASCE)1090-0241(1997)123:8(744)

C. T. Kincaid, J. R. Morrey, and R. J. , Geohydrochemical Models for Solute Migration, Process Description and Computer Code Selection. EPRI EA-3417, 1984.

R. Lantzy and F. Mackenzie, Atmospheric trace metals: global cycles and assessment of man's impact, Geochimica et Cosmochimica Acta, vol.43, issue.4, pp.511-525, 1979.
DOI : 10.1016/0016-7037(79)90162-5

D. R. Leblanc, S. P. Garabedian, K. M. Hess, L. W. Gelhar, R. D. Quadri et al., Large-scale natural gradient tracer test in sand and gravel, Cape Cod, Massachusetts: 1. Experimental design and observed tracer movement, Water Resources Research, vol.247, issue.2, pp.895-910, 1991.
DOI : 10.1029/91WR00241

A. A. Levinson, Introduction to Exploration Geochemistry, 1974.

M. Lévy and B. Berkowitz, Measurement and analysis of non-Fickian dispersion in heterogeneous porous media, Journal of Contaminant Hydrology, vol.64, issue.3-4, pp.203-226, 2003.
DOI : 10.1016/S0169-7722(02)00204-8

W. L. Lindsay, Chemical equilibria in soils " Book, 2001.

T. Lioyd and W. Showak, Zinc and zinc alloys In: Grayson M ed. Encyclopedia of chemical technology Vitamins to zone refining, pp.835-836, 1984.

R. H. Loeppert, A. P. Schwab, and S. Goldberg, Chemical Equilibrium and Reaction Models, Special Publication Number, vol.42, 1995.

R. B. Mack, A hard day's knight, zinc phosphate poisoning, N.C. Med. J, vol.50, pp.17-18, 1989.

V. Maisonneuve and M. Vignoles, Etude de transfer des ETM ver les sols et les plantes, INRA, 2000.

J. Malo, J. Malo, A. Cartier, and J. Dolovich, Acute lung reaction due to zinc inhalation, Eur. Respir. J, vol.3, pp.111-114, 1990.

M. M. Meerschaert and C. Tadjeran, Finite difference approximations for fractional advection???dispersion flow equations, Journal of Computational and Applied Mathematics, vol.172, issue.1, pp.65-77, 2004.
DOI : 10.1016/j.cam.2004.01.033

D. C. Melchior and R. L. Bassett, Chemical Modeling in Aqueous Systems II, Symposium Series, vol.416, 1990.
DOI : 10.1021/bk-1990-0416

J. W. Mercer, C. R. Faust, W. J. Miller, and F. J. Pearson, Review of Simulation Techniques for Aquifer Thermal Energy Storage (ATES) " PNL-3769, 1981.

K. S. Miller and R. B. , An Introduction to the Fractional Calculus and Fractional Differential Equations, 1993.

J. Mortred and R. Gilkes, Zinc fertilizers In: Robson AD ed. Developments in plant and soil sciences Zinc in soils and plants, pp.33-44, 1993.

Y. Mualem, A new model for predicting the hydraulic conductivity of unsaturated porous media, Water Resources Research, vol.12, issue.4, pp.513-522, 1976.
DOI : 10.1029/WR012i003p00513

B. Nemery, Metal Toxicity and the Respiratory Tract, Journal of Occupational and Environmental Medicine, vol.32, issue.12, pp.202-219, 1990.
DOI : 10.1097/00043764-199012000-00003

D. K. Nordstrom and J. L. Munoz, Geochemical Thermodynamics The Benjamin, 1985.

D. K. Nordstrom and . J. Ball, Chemical Models, Computer Programs and Metal Complexation in Natural Waters In Complexation of Trace Metals in Natural Waters, pp.149-169, 1984.

D. K. Nordstrom, L. N. Plummer, T. M. Wigley, T. J. Woley, J. W. Ball et al., A Comparison of Computerized Chemical Models for Equilibrium Calculations in Aqueous Systems, Chemical Modeling in Aqueous Systems. Speciation, Sorption, Solubility, and Kinetics Symposium Series 93, pp.857-892, 1979.
DOI : 10.1021/bk-1979-0093.ch038

J. &. Nriagu and J. Pacyna, Quantitative assessment of worldwide contamination of air, water and soils by trace metals, Nature, vol.333, issue.6169, pp.134-139, 1989.
DOI : 10.1038/333134a0

F. Ohnesorge and M. Whilhelm, Zinc: Metals and their compounds in the environment, pp.1309-1333, 1991.

K. B. Oldham and J. Spanier, The Fractional Calculus " Academic, 1974.

Y. Pachepsky, D. A. Benson, and W. Rawls, Simulating Scale-Dependent Solute Transport in Soils with the Fractional Advective???Dispersive Equation, Soil Science Society of America Journal, vol.64, issue.4, pp.1234-1243, 2000.
DOI : 10.2136/sssaj2000.6441234x

L. Pan, A. W. Warrick, and P. J. Wierenga, Finite element methods for modeling water flow in variably saturated porous media: Numerical oscillation and mass-distributed schemes, Water Resources Research, vol.5, issue.6, pp.1883-1889, 1996.
DOI : 10.1029/96WR00753

L. Pang and B. Hunt, Solutions and verification of a scale-dependent dispersion model, Journal of Contaminant Hydrology, vol.53, issue.1-2, pp.21-39, 2001.
DOI : 10.1016/S0169-7722(01)00134-6

C. Papelis, K. F. Hayes, and L. J. , HYDRAQL: A Program for the Computation of Chemical Equilibrium Composition of Aqueous Batch Systems Including Surface-Complexation Modeling of Ion Adsorption at the Oxide/Solution Interface, 1988.

J. F. Pickens and G. E. Grisak, Scale-dependent dispersion in a stratified granular aquifer, Water Resources Research, vol.1899, issue.HY4, pp.1191-1211, 1981.
DOI : 10.1029/WR017i004p01191

F. Porter, Corrosion resistance of zinc and zinc alloys, 1995.

R. W. Potter, Computer modeling in low temperature geochemistry, Reviews of Geophysics, vol.25, issue.4, pp.850-860, 1979.
DOI : 10.1029/RG017i004p00850

W. H. Press, B. P. Flannery, S. A. Teukolsky, and W. T. Vetterling, Numerical Recipes, the Art of Scientific Computing, 1989.

K. Pruess, C. Oldenburg, and G. Moridis, TOUGH2 User's guide, Version 2
DOI : 10.2172/751729

URL : http://escholarship.org/uc/item/4df6700h.pdf

K. R. Rehfeldt, J. M. Boggs, and G. L. , Field study of dispersion in a heterogeneous aquifer: 3. Geostatistical analysis of hydraulic conductivity, Water Resources Research, vol.27, issue.4, pp.3309-3324, 1992.
DOI : 10.1029/92WR01758

N. Romano, B. Brunone, and A. Santini, Numerical analysis of one-dimensional unsaturated flow in layered soils, Advances in Water Resources, vol.21, issue.4, pp.313-324, 1998.
DOI : 10.1016/S0309-1708(96)00059-0

D. U. Rosenberg-von, Methods for the numerical solution of partial differential equations, 1969.

S. G. Samko, A. A. Kilbas, and M. O. , Fractional Integrals and Derivatives: Theory and Applications, Gordon and Breach, 1993.

B. R. Scanlon, M. Christman, R. C. Reedy, I. Porro, J. Simunek et al., Intercode comparisons for simulating water balance of surficial sediments in semiarid regions, Water Resources Research, vol.31, issue.IR2, 2002.
DOI : 10.1029/2001WR001233

C. Schmitz, World Non-Ferrous Metal Production and Prices, pp.1700-1976, 1979.

R. J. Serne, R. C. Arthur, and K. K. , Review of Geochemical Processes and Codes for Assessment of Radionuclide Migration Potential at Commercial LLW Sites, 1990.

P. Seuntjenus, D. Maltants, J. Simunek, J. Patyn, and J. D. , Sensitivity analysis of physical and chemical properties affecting field-scale cadmium transport in a heterogeneous soil profile, Journal of Hydrology, vol.264, issue.1-4, pp.185-200, 2002.
DOI : 10.1016/S0022-1694(02)00071-9

J. Simunek, M. Sejna, and M. T. Van-genuchten, The HYDRUS-1D software package for simulating the one-dimensional movement of water

J. E. Sonke, J. A. Hoogewerff, S. R. Van-der-laan, and A. Vangonsveld, A chemical and mineralogical reconstruction of Zn-smelter emissions in the Kempen region (Belgium), based on organic pool sediment cores, Science of The Total Environment, vol.292, issue.1-2, pp.101-119, 2002.
DOI : 10.1016/S0048-9697(02)00033-5

J. Spence and J. Mchenry, Development of regional corrosion maps for galvanized steel by linking the RADM engineering model with an atmospheric corrosion model, Atmospheric Environment, vol.28, issue.18, pp.3033-3046, 1994.
DOI : 10.1016/1352-2310(94)90348-4

G. Sposito and J. Coves, SOILCHEM: A Computer Program for the Calculation of Chemical Speciation in Soils " Kearny Foundation for Soil Science, 1988.

C. Stephan, F. Courchesne, W. Hendershot, and S. Sauvé, Speciation of zinc in soil solutions " 7 ème Conférence internationale sur la biogéochimie des éléments traces. 15-19 juin, 2003.

H. E. Stokinger, Zinc. In: Patty's Industrial Hygiene and Toxicology " 3rd rev, pp.2033-2049, 1981.

W. Stumm and J. Morgan, Aquatic chemistry: Chemical equilibria and rates in natural water, 1996.

C. C. Sturgis, P. Drinker, and A. J. Sinclair, Metal fume fever: I. Clinical observations on the effect of the experimental inhalation of zinc oxide by two apparently normal persons, J. Ind. Hyg, vol.9, pp.88-97, 1927.

E. A. Sudicky, Reply [to ???Comment on ???A natural gradient experiment on solute transport in a sandy aquifer: Spatial variability of hydraulic conductivity and its role in the dispersion process??? by E. A. Sudicky???], Water Resources Research, vol.22, issue.13, pp.2069-2082, 1986.
DOI : 10.1029/WR024i002p00318

N. Toride, F. Leij, M. Van-genuchten, and . Th, The CXTFIT code for estimating transport parameters from laboratory or field tracer experiments: Version 2.0 " Research Rep, U.S. Salinity Lab, vol.137, 1995.

F. Assche, W. Van-tilborg, and H. Waeterschoot, Environmental Risk Assessment for Essential Elements -Case Study Zinc " in " Report of the International Workshop on Risk Assessment of Metals and their Inorganic Compounds, ICME, pp.171-180, 1996.

A. W. Warrick, Soil Water Dynamics " Book, 2003.

A. W. Warrick, Numerical approximations of darcian flow through unsaturated soil, Water Resources Research, vol.49, issue.6, pp.1215-1222, 1991.
DOI : 10.1029/91WR00093

B. J. Wilkens and L. J. , Accumulation of cadmium and zinc from diffuse emission on acid sandy soils, as a function of soil composition, Water Air Soil Pollution, vol.96, pp.1-4, 1997.

L. L. Williams, effect of plant root intrusion on the water balance of landfill cover systems, M.Sc. thesis, 2005.

S. R. Yates, An analytical solution for one-dimensional transport in heterogeneous porous media, Water Resources Research, vol.24, issue.10, pp.2331-2338, 1990.
DOI : 10.1029/WR026i010p02331

S. R. Yates, An analytical solution for one-dimensional transport in porous media with an exponential dispersion function, Water Resources Research, vol.24, issue.8, pp.2149-2154, 1992.
DOI : 10.1029/92WR01006

W. W. Yeh, Review of Parameter Identification Procedures in Groundwater Hydrology: The Inverse Problem, Water Resources Research, vol.19, issue.1, pp.95-108, 1986.
DOI : 10.1029/WR022i002p00095

J. Zaidel and D. Russo, Estimation of finite difference interblock conductivities for simulation of infiltration into initially dry soils, Water Resources Research, vol.25, issue.9, pp.2285-2295, 1992.
DOI : 10.1029/92WR00914

G. M. Zaslavsky, Fractional kinetic equation for Hamiltonian chaos, Physica D: Nonlinear Phenomena, vol.76, issue.1-3, pp.110-122, 1994.
DOI : 10.1016/0167-2789(94)90254-2

R. Zhang, K. Huang, and J. Xiang, Solute movement through homogeneous and heterogeneous soil columns, Advances in Water Resources, vol.17, issue.5, pp.317-324, 1994.
DOI : 10.1016/0309-1708(94)90034-5

Y. Zhang, D. A. Benson, M. M. Meerschaert, and H. P. Scheper, On using random walks to solve the space-fractional advection-dispersion equations, J. Stat. Phy, vol.123, issue.1, pp.89-110, 2006.

L. Zhou and H. M. Selim, Application of the Fractional Advection-Dispersion Equation in Porous Media, Soil Science Society of America Journal, vol.67, issue.4, pp.1079-1084, 2003.
DOI : 10.2136/sssaj2003.1079