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
I = GR - (Stemflow +Throughfall)
Transpiration
I. densiflora
Interception
Interception
Soil evaporation
Coffee
Gross
Rainfall
Runoff
D Soil water stock
Drainage
Transpiration : Sap flow (coffee & tree)
Soil water content
Runoff
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
2004
LAI Coffee
LAI I. densiflora
2005
MC
AFS
MC
AFS
4.71
4.64
4.60
3.80
-
1.32
-
1.22
60
AFS
MC
Throughfall (mm d-1)
50
40
30
20
10
0
0
10
20
30
40
Gross rainfall (mmd-1)
50
0
10
20
30
40
Gross rainfall (mmd-1)
50
60
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)
7
7
AFS
MC
6
5
5
4
4
3
3
2
2
1
1
0
0
0
10
20
30
40
Gross rainfall (mm d-1)
0
10
20
30
40
Gross rainfall (mm d-1)
50
60
Tree Stem flow (mm d-1)
Coffee Stem flow (mm d-1)
6
Influence of trees on rainfall interception
System
Total rainfall
Throughfall
Stemflow
Interception
(mm)
(mm)
(mm)
(mm)
(%)
(%)
2004
(%)
74% higher in AFS
AFS
1426
1038
72.8
167*
11.7
221
15.5
MC
1426
1214
85.1
84*
6.0
126
8.9
2005
18% higher in AFS
AFS
1725
1324
76.8
204
11.8
196
11.4
MC
1725
1434
83.2
124
7.2
167
9.6
Transpiration
I. densiflora
Interception
Soil evaporation
Order of magnitude of various
components for 2005
Coffee
Gross
Rainfall
Runoff
D Soil water stock
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%
Drainage
Adaptation of Model “HYDRUS”
0,6
0,6
0,5
0,5
3
-3
Soil water content (cm cm )
Soil water content (cm3 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
0,4
0,3
0,2
0,4
0,3
0,2
0,1
0,1
0
0
0-30 cm soil layer in AFS
60-90 cm soil layer in AFS
115
200 cm
75
55
35
15
3500
3000
Water drainage (in mm d-1)
at 200 cm soil depth in AFS
Rainfall, drainage (mm)
-5
1000
Rainfall
drainage 200 cm
RET
Runoff
900
800
2500
700
600
2000
500
1500
400
300
1000
200
500
100
0
4/24/2004
6/3/2004
7/13/2004
8/22/2004
10/1/2004
0
11/10/2004
date
Cumulative values in AF system
over wet season
RET, runoff (mm)
-1
Water flux (mm d )
95
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.