The cause and effect of soil variability in the Ecuadorian Andes

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

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Consortium for agricultural soils mitigation of greenhouse gases

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