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DIFFERENCES IN CROPPING SYSTEMS AND
SOIL ORGANIC CARBON DUE TO CLIMATE
CHANGE AND SOCIOECONOMIC FACTORS IN
POTATO-BASED CROPPING SYSTEMS IN THE
BOLIVIAN HIGHLANDS
Peter Motavalli, Jorge Cusicanqui, Javier
Aguilera, Corinne Valdivia, Magali Garcia,
Elizabeth Jiménez, and Roberto Miranda
STUDY AREA
The
Bolivian
highland
plateau region (Altiplano)
is a semi-arid region in
the Andes Mountains that
occupies
approximately
27% of the area of Bolivia
and has a range in
elevation
of
between
3600 and 4300 m.a.s.l.
STUDY AREA
Primarily
potato-based
cropping systems and
livestock
rearing
of
cows,
sheep
and
camelids (e.g., alpaca
and lama)
SANREM STUDY AREA IN BOLIVIA
A.
B.
Lake
Titicaca
Ancoraimes
La Paz
Umala
Altiplano
C. Ancoraimes
D. Umala
Chojňapata
Calahuancane
Kellhuiri
Cohani
Karkapata
Vinto Coopani
San Juan Cerca
Chinchaya
San José de Llanga
Lake Titicaca
CLIMATE CHANGE
The
Altiplano
region’s
climate is characterized by
high diurnal temperature
variations, frost risks, low
and irregular precipitation
and high risks of drought
during the growing season
(Garcia et al., 2007).
CLIMATE CHANGE
The region will experience
temperature increases of
up to 6C by the end of the
century (Bradley et al.,
2006, IPCC, 2007).
A consequence of global
climate change has and
will be a higher incidence
of extreme weather events
(Haylock et al., 2006;
Thibeault et al., 2008).
STUDY AREA IN BOLIVIA
Annual Rainfall
Distribution
Change in Minimum
Temperature
Average
annual rainfall
(mm yr-1)
ºC yr-1
Garcia and Seth (in prep.)
OBJECTIVES OF SOILS RESEARCH
To
survey
representative
indigenous farming communities
in the Altiplano of Bolivia to
determine perceived changes in
cropping practices in potatobased cropping systems due to
global climate change and socioeconomic factors.
To assess the effects of these
changes on soil total organic C
and other soil properties to
determine if soil degradation has
occurred.
MATERIALS AND METHODS
Village-level surveys and participatory workshops were
conducted in 4 to 5 villages situated at different relative
altitudes in the communities of Umala and Ancoriames.
MATERIALS AND METHODS
Replicated
soil
samples
were collected in Umala to
a 20 cm depth from
agricultural fields of the
same cropping system and
sandy soil type (locally
classified as “cha’lla” soil)
to determine changes in
soil properties with fallow
length.
MATERIALS AND METHODS
Replicate soil samples were
collected to a 20 cm depth
directly
underneath
or
between
“th’ola”
(Parastrephia lepidophylla),
a common component of
fallow
vegetation,
to
determine its effects on soil
properties during fallow.
CHANGES IN SOIL MANAGEMENT PRACTICES
20 years ago in Chinchaya
Present
(Yucra and Gilles, unpublished)
CHANGES IN SOIL
MANAGEMENT PRACTICES
Increase in production of some cash crops (e.g.
onion) and other income-generating activities
(e.g. dairy production, day labor)
Decrease in the length of the fallow period in the
crop rotation.
Reduction in planting of early season crops (e.g.,
fava beans and quinoa) due to early season
rainfall uncertainty.
CHANGES IN SOIL
MANAGEMENT PRACTICES
Greater tractor use for tillage in lower
elevation communities.
Loss of native species (e.g., th’ola) that
have multiple uses to restore soil fertility
during fallow period and are a fuel source.
COMMUNITY PERCEPTIONS OF SOIL RESOURCES
AND SOIL-RELATED PROBLEMS
• Soil-related problems are only one of several
factors limiting crop production.
• Soil management problems identified were:

Low soil quality and soil fertility
(low soil nutrient content, high clay content and stoniness)



Excessive water and wind-induced soil erosion
Insufficient soil moisture due to lower rainfall
Inadequate soil management practices
(Inappropriate tractor tillage practices, lack of a suitable crop
rotation strategy, insufficient soil fertility inputs, and
overgrazing by sheep)
EXAMPLES OF LOCAL SOIL CLASSIFICATION SYSTEM AND
PERCEIVED CHANGES IN SOIL PROPERTIES
Vinto Coopani community (Relative high elevation)
Soil type
Native
name Characteristics
Changes in use over time*
1.White soil
Pajre
oraque
Soft soil; spiny plants grow in it.
Before it was used for agriculture and
now it is not.
2.Clayey soil
Ňeq’e
oraque
The surface soil can be
cultivated but with erosion the
soil becomes hard like cement
The soil used to be much stronger
but it has been washed away.
3.Sandy/clayey
soil
Jach’oca
The soil has both clay and large
stones
The moisture content is decreasing
and there are more rocks.
4.Hard clay soil
Karpa
Has clay that is used for making
ceramics.
It has become less fertile.
5.Sandy soil
Saj’e
Little soil on surface and below Used to be more fertile because it
has gravel. Dries out quickly and was maintained in fallow longer.
is a very good for production.
6.Black soil
7.Fine sand soil
Chiar laqa The clay is neither hard or soft
Laqa
Oraque
Good soil with the color of skin;
it has very fine sand
* Observed changes in use of soil over the last 10 years.
Used to be more fertile because it
was maintained in fallow longer.
It appears to have more rocks.
EXAMPLES OF SOIL PROPERTIES OF SOIL TYPES BASED ON
LOCAL SOIL CLASSIFICATION SYSTEM
Exchangeable
Community
Soil type
Textural
class
Organic
matter
pHs
Vinto
Coopani
K
Ca
Mg
---------------- mg kg-1 -----------------
-- % --
San José
Bray1
P
CEC
EC
cmolc
kg-1
dS
cm-1
Sandy/ Cha’lla
Sand
0.3
5.5
35.0
166
311
44
3.1
0.1
Clayey/ Ňeq’e
Silt loam
2.4
7.5
20.5
424
4520
279
26.0
0.5
Silty/ Kaima
Silt loam
0.5
7.5
14.8
158
2337
125
13.1
0.3
Sandy/ Cha’lla
Loam
1.3
5.7
46.8
271
1102
148
8.9
0.3
Sandy/ clayey
/Jach’oca
Sandy loam
1.2
5.5
45.2
240
580
70
5.8
0.2
Clayey/ Ňeq’e
oraque
Clay loam
1.5
6.9
3.0
159
3763
578
24.3
0.2
EFFECTS OF FALLOW AND CROPPING
ON SOIL ORGANIC C IN UMALA
1.600
Uncropped land
y = 0.0141x + 1.0671
R² = 0.3649
1.400
Soil
total
organic
C (%)
Vinto Coopani
y = -0.0004x 2 + 0.0299x + 0.7586
R² = 0.868
1.200
SJ Circa
San Jose
1.000
Uncropped land
Kellhuiri
y = 0.0052x + 0.5403
R² = 0.8085
0.800
Uncropped land
0.600
y = 0.0017x + 0.4387
R² = 0.4908
0.400
0.200
-5
Years of
cropping
5
15
25
Years of fallow
35
45
55
EFFECTS OF TH’OLA AND CROPPING
ON SOIL PROPERTIES
Selected soil properties of sandy (ch’alla) soil collected directly underneath or between th’ola
plants or in farm field during first year of cropping in San José de Llanga in Umala.
Location of sampling
Total organic
Total
C
N
----------------- % --------------
p Hs
Neut.
acidity
-1
cmolc kg
Exchangeable
Soil test
Soil test
Bray1 P
K
Ca
Mg
-1
---------------------------- mg kg ---------------------------
CEC
-1
cmolc kg
Underneath th’ola
1.82
0.145
7.20
0.0
44.5
529
3152
208
18.8
Between th’ola
1.57
0.152
7.50
0.0
28.7
365
3485
185
19.9
1st year cropping
0.43
0.024
5.55
0.5
23.2
121
322
54
2.8
DMRT(0.05)*
0.81
0.047
0.42
0.1
17.8
261
1068
66
6.1
*Duncan’s Multiple Range Test (P < 0.05).
“Th’ola” is an evergreen shrub (Parastrephia lepidophylla)
that re-grows during fallow periods
CONCLUSIONS
Climate change and socioeconomic
factors in the Altiplano region have
led
to
changes
in
soil
and
management practices that have
generally reduced soil fertility and
soil
organic
matter.
The decreasing length of the fallow
period and reduction in native
vegetation (e.g. “th’ola”) caused by
competing uses and mechanized
tillage,
may
be
removing
an
important mechanism by which soil
fertility and soil organic matter are
restored.
CONCLUSIONS (CONT.)
Ongoing research is examining soil
management practices that may
increase soil fertility and soil
organic
matter
by
adding
conventional
and
alternative
organic soil amendments (e.g.
compost,
biofertilizers).
Additional research is needed to
identify suitable plants that could
be introduced for improved fallow
management.
QUESTIONS?
COMMENTS?
SUGGESTIONS?