The cause and effect of soil variability in the Ecuadorian Andes
Study area
The potato-pasture system in Carchi
• Fertile volcanic ash soils • Potato-pasture rotation• Seasonality almost absent• Market oriented production• Intensive use of external inputs
Research question
Provide accurate information about the economic and environmental consequences of agricultural systems and policies, considering the complex interactions between bio-physical processes and farm management decisions
The Tradeoff Analysis Model
Field evaluation
Crop/management decisions
Management evaluation
Tradeoff analysis
Scenario definition
0
50,000
100,000
150,000
200,000
250,000
Scale
Number ofobservations
Soil survey
100 625 2,500 10,000
62,500
250,000
Causes of soil variability
• Parent material
• Topography
• Tillage erosion
• Land management
• Climate
Cause 1. Parent material
Results
2r
R2
0
0.2
0.4
0.6
0.8
1 Crop growth
Pesticide leaching
Cause 2. Topography
Results
2r
R2
0
0.2
0.4
0.6
0.8
1 Crop growth
Pesticide leaching
Cause 3. Tillage erosion
Cause 3. Tillage erosion
Cause 3. Tillage erosion
Tillage erosion = f(distance, topography)
No tillage erosion
Strong tillage erosion
Results
R2
0
0.2
0.4
0.6
0.8
1 Crop growth
Pesticide leaching
Cause 4. Land management
Cause 4. Land management
Results
R2
0
0.2
0.4
0.6
0.8
1 Crop growth
Pesticide leaching
Cause 5. Climate
0
5
10
15
20
2500 2700 2900 3100 3300 3500
Altitude (m.a.s.l.)
Org
anic
mat
ter
(%)
Results
R2
0
0.2
0.4
0.6
0.8
1 Crop growth
Pesticide leaching
Detailed soil survey
Simulation
Inherent productivity
Carbofuran use
Potato/dairy ratio
Carbofuran leaching
Tillage erosion
Effect 1
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Carbofuran leaching
Low
High
Effects 2
0
250
500
750
1000
0 2 4 6 8 10
Tillage erosion (cm/yr)
Ca
rbo
fura
n l
ea
ch
ing
(g
/ha
/yr)
Causes of variation:• 62 % soil variation• 38 % price variation
Effects 3
0.0
25.0
50.0
75.0
100.0
0 250 500 750 1000 1250 1500
Carbofuran leaching (g/ha)
Cu
mu
lati
ve
pro
ba
bil
ity
(%
)
+50%
+25%
Observed prices
-25%
-50%
EPA limit
0
100
200
300
400
500
600
0 5 10 15 20 25 30
Year
Inc
rea
se
in
ca
rbo
fura
n l
ea
ch
ing
(g
/ha
/yr)
A: shallow topsoil, low tillage erosion rateB: deep topsoil, low tillage erosion rateC: shallow topsoil, high tillage erosion rateD: deep topsoil, high tillage erosion rate
Repercusions on soil variability
Repercusions on soil variability
0
1000
2000
3000
4000
5000
6000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Year
Inh
ere
nt
pro
du
cti
vit
y
(dry
we
igh
t/y
r/h
a)
0
50
100
150
200
250
300
350
400
450
500
Ca
rbo
fura
n l
ea
ch
ing
(g
/ha
/yr)
Inherent productivity base runInherent productivity with and without feedbacksCarbofuran leaching base runCarbofuran leaching without feedbacksCarbofuran leaching with feedbacks
Conclusions
Current research activities- Kenya -
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CENTURY
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Consortium for agricultural soils mitigation of greenhouse gases
www.tradeoffs.nlwww.tradeoffs.montana.nl
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