modelling water dynamics in coffee systems: parameterization of a mechanistic model over two...

Modelling water dynamics in coffee systems:Parameterization of a mechanistic model over two production cycles in Costa Rica.

Pablo Siles, Patrice Cannavo, Julie Sansoulet, Jean-Michel Harmand and Philippe Vaast

CATIE (Centro Agronómico Tropical de Investigación y Enseñensa), Turrialba, Costa Rica

CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement), Montpellier, France

Introduction

Water is key issue in the coffee regions of Central America:

– at plot level, complementarity /competition between coffee and various shade tree species

– at landscape level, coffee located in mountainous areas (erosion) and rainy zones providing water for communities downstream.

– Study with Inga (up to 6 species), predominant genus used in CA (70% shaded coffee)

Material and Methods

• Trial established at CICAFE, Central valley of Costa Rica, Date : 1997

• Optimal ecological conditions• High altitude (~1200 m), temperate (~22°C)• high rainfall (>3000 mm), 3 dry Months• slope < 5%

• Monoculture Coffee (MC): • Coffea arabica density : 5000 plants ha-1

• Agroforestry System (AFS)• Inga densiflora density : 277 trees ha-1

• Shade 40-55%

• Intensive fertilization regime:

Monitoring of water fluxes during 2 years

GR = I + E + T + Rn + ΔS + D

InterceptionI. densiflora

Coffee

Runoff

Transpiration

Soil evaporation

Gross Rainfall

Soil water stock

Drainage

Interception

I = GR - (Stemflow +Throughfall)

Transpiration : Sap flow (coffee & tree) Runoff

Soil water content Stemflow: Inga and coffee

Influence of shade trees on throughfall

Reduction in throughfall in AFS by 14.4% in 2004 and 7.6% in 2005

Gross rainfall (mmd-1)

0 10 20 30 40 50

Th

rou

ghfa

ll (m

m d-1)

0

10

20

30

40

50

60

AFSMC

Gross rainfall (mmd-1)

0 10 20 30 40 50 60

2004 2005

MC AFS MC AFS

LAI Coffee 4.71 4.64 4.60 3.80

LAI I. densiflora - 1.32 - 1.22

Influence of shade trees on stemflow

• Higher stemflow in AFS (41%) could be explained by differences in architecture of coffee plants (40 cm taller, longer branches) in spite of lower coffee LAI

• Low contribution of tree stemflow to the system (1% of rainfall)

Gross rainfall (mm d-1)

0 10 20 30 40

Co

ffe

e S

tem

flo

w (

mm

d-1)

0

1

2

3

4

5

6

7

AFSMC

Gross rainfall (mm d-1)

0 10 20 30 40 50 60

Tre

e S

tem

flo

w (

mm

d-1)

0

1

2

3

4

5

6

7

Influence of trees on rainfall interception

SystemTotal rainfall   Throughfall   Stemflow   Interception

(mm)   (mm) (%)   (mm) (%)   (mm) (%)

2004                    

AFS 1426 1038 72.8 167* 11.7 221 15.5

MC 1426 1214 85.1 84* 6.0 126 8.9

2005                    

AFS 1725 1324 76.8 204 11.8 196 11.4

MC 1725   1434 83.2   124 7.2   167 9.6

74% higher in AFS

18% higher in AFS

AFS MC

Throughfall* 77% 83%

Tree Stemflow 1% -

Coffee Stemflow 10.5% 7%

Interception 11.5% 10%

Transpiration 34% 25%

Runoff 3% 8%

Drainage (>200 m) 50.5% 57%

Order of magnitude of various components for 2005

I. densiflora

Coffee

Runoff

Transpiration

Soil evaporation

GrossRainfall

Soil water stock

Drainage

Interception

Adaptation of Model “HYDRUS”

0

0,1

0,2

0,3

0,4

0,5

0,6

So

il w

ater

co

nten

t (cm

3 cm

-3)

0

0,1

0,2

0,3

0,4

0,5

0,6

Soi

l wat

er

cont

ent

(cm

3 cm

-3)

Comparison of simulated (solid line) and observed (circles) soil volumetric water contents in the 0-30 and 60-90 cm soil layers in AFS with allocation of water uptake in the various soil layers according to root density

0-30 cm soil layer in AFS 60-90 cm soil layer in AFS

-5

15

35

55

75

95

115W

ater

flux

(m

m d

-1)

200 cm

Water drainage (in mm d-1) at 200 cm soil depth in AFS

0

500

1000

1500

2000

2500

3000

3500

4/24/2004 6/3/2004 7/13/2004 8/22/2004 10/1/2004 11/10/2004

date

Rai

nfal

l, dr

aina

ge (

mm

)0

100

200

300

400

500

600

700

800

900

1000

RE

T, r

unof

f (m

m)

Rainfalldrainage 200 cmRETRunoff

Cumulative values in AF system over wet season

Conclusion

• Shade trees modify the coffee architecture resulting in increased coffee stemflow and a lower throughfall

• Runoff was decreased in AFS due to coffee architecture and litter cover, hence less soil erosion and better water quality

• Lower runoff offsets higher interception in AFS, hence a higher infiltration in AFS

• Higher transpiration in AFS slightly lowers drainage in AFS

• The soil water content simulated adequately by the Hydrus model (one the first time this model is used in agroforestry)

• Sound basis to estimate the amount of water drainage and hence nutrient leaching (nitrate)

• No OVERGENERALIZATION, present AFS with only one tree species (Inga), Andosol (fast infiltration) and high rainfall regime (>2500 mm).

• The challenges are to use this approach 1) in more complex systems and 2) in conditions of lower precipitation and different soils (currently underway in India) and 3) upscaling.