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.