I (cm)I (cm)I (cm)I (cm)

TIME EVOLUTION OF SURFACE

SOIL HYDRAULIC PROPERTIES

GENERAL OUTLINE

I Main objectives and general presentation II Beer-kan method and field measurements III Theoretical treatment

MAIN OBJECTIVES

(1) Characterize the hydraulic properties of 4 plots : - identical initial agricultural history,

- four different treatments repeated since 1994.

(2) Emphasize the significant drift in soil properties in terms of temporal variability.

COLIMA

JALISCO

MEXICO

ZACATECAS NAYARIT

Sierra Los Manzanillos

El Grullo La Tinaja Ciudad Guzmán GUANA-JUATO AGS Guadalajara MICHOACAN Nevado de Colima Sierra Tapalpa PACIFIC OCEAN Municipio de San Gabriel 100 km GENERAL CONTEXT • Altitude : 1200 m • Latitude : 19.1° N • Mountain semi-arid tropical climate • Rain : 400 to 650 mm

PLOTS DESCRIPTION

Plot 4 : Direct Sowing, 4.5 t/ha (DS4.5) Plot 1 : Conventional Tillage (CT) Plot 2 : Direct Sowing, no residue (DS0)

GENERAL OUTLINE

I Main objectives and general presentation

II Beer-kan method and field measurements

III Theoretical treatment IV Results and conclusion

SOIL HYDRAULIC PROPERTIES

• Soil retention curve : Van Genuchten with Burdine condition

• Soil conductivity curve : Brooks and Corey

θ θ_s hh_g n = 1 + -m ₂ n m ₌ 1 -with θ θ_s η = K K_s

CUMULATIVE INFILTRATION IN SOIL

Cumulative infiltration in soil (I) is defined as :

with :

• h(θ) : soil retention curve,

• K(θ) : soil conductivity curve,

• IC : initial conditions (such as θ₀),

• BC : boundary conditions (such as h_surf).

BEER-KAN METHOD

time (h) 0 1 2 3 4 5 6 7 I (cm) 0 1 2 3 4 5 time (h) 0 1 2 3 4 5 6 7 I (cm) 0 1 2 3 4 5 time (h) 0 1 2 3 4 5 6 7 I (cm) 0 1 2 3 4 5 time (h) 0 1 2 3 4 5 6 7 I (cm) 0 1 2 3 4 5

Cumulative infiltration (I) vs time

Plot 2 : DS0 Plot 1 : CT Plot 4 : DS4.5 Plot 3 : DS1.5 0 cm 2 cm 50 cm

GENERAL OUTLINE

I Main objectives and general presentation II Beer-kan method and field measurements

III Theoretical treatment

SPECIAL CASE OF CRUSTED SOIL

If K_{s crust} < K_{s subsoil} then the crust controls entirely infiltration : S_{+ crust} < S_{+ subsoil} (*)

SCALING INFILTRATION : THEORY

• Dimensional log-shaped infiltration curve I(t) :

with :       ₋ + + − = − + + + I S K K t S K K I S K K_{s s s} 2 0 2 2 0 2 0) 2( ) _{ln 1} 2( ) ( 2

• Invariant nondimensional log-shaped infiltration curve I*(t*) :

(

)

*

* _{t ln 1 I}

I = + +

with : soil sorptivity (m.s-0.5_{) and initial conductivity (m.s}-1₎

2 2 0 * 2 0 * ) ( 2 . ) ( 2 . + + − = = − = = S K K and t t S K K and I I s t t s I I α α α α + S K₀ = K(θ₀)

SCALING

t

I

I

SCALING INFILTRATION : EXAMPLE

α

α

• A set of dimensional infiltration curves • 1 nondimensional infiltration curve

• A set of fitted scaling parameters α_I, α_t

SCALING

FROM SCALING FACTORS TO SOIL PARAMETERS

• Soil texture parameters :

m.n = function of cumulative particle size distribution

• Soil structure parameters :

α_t α_I = Ks - K0 θ_s = ε . 2m-M ⇒ h_g = f-1_{( g(}α I)) S₊ = f(h_g) S₊ = g(α_I) (3) (5) (4) (2) (1) 2 m.n η ₌ 3 +

GENERAL OUTLINE

I Main objectives and general presentation II Beer-kan method and field measurements III Theoretical treatment

COMPARISON OF

K

VALUES

Plot 4 (DS4.5)

Plot 1 (CT) Plot 2 (DS0)

Plot 3 (DS1.5)

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 0cm 2cm 50cm

K_s (m/s)

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 0cm 2cm 50cm

K_s (m/s)

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 0cm 2cm 50cm

K_s (m/s)

1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 0cm 2cm 50cm

COMPARISON OF SORPTIVITY

VALUES (S)

Plot 4 (DS4.5)

Plot 1 (CT) Plot 2 (DS0)

Plot 3 (DS1.5)

1.E-05 1.E-04 1.E-03 1.E-02 0cm 2cm 50cm

S (m/s0.5₎

1.E-05 1.E-04 1.E-03 1.E-02 0cm 2cm 50cm

S (m/s0.5₎

1.E-05 1.E-04 1.E-03 1.E-02 0cm 2cm 50cm

S (m/s0.5₎

1.E-05 1.E-04 1.E-03 1.E-02 0cm 2cm 50cm

COMPARISON OF

h

VALUES

Plot 4 (DS4.5)

Plot 1 (CT) Plot 2 (DS0)

Plot 3 (DS1.5)

h_g (m)

1.E-03 1.E-02 1.E-01 1.E+00 0cm 2cm 50cm

1.E-03 1.E-02 1.E-01 1.E+00 0cm 2cm 50cm

h_g (m)

1.E-03 1.E-02 1.E-01 1.E+00 0cm 2cm 50cm

h_g (m)

1.E-03 1.E-02 1.E-01 1.E+00 0cm 2cm 50cm

COMPARISON OF

θ

AND

m.n

VALUES

CONCLUSIONS

 The physically based Beer-Kan method is suitable to estimate properly

soil hydraulic properties h(θ) and K(θ).

 Different treatments can induce a significant temporal variability of

surface soil layer conductivity in the long run (5 years).

 A small quantity of residue (DS1.5) provides with good soil protection and