Peter Motavalli, Jorge Cusicanqui, Javier Aguilera, Corinne Valdivia, Magali Garcia, Elizabeth Jim

1
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
2
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.

3
STUDY AREA

• Primarily potato-based cropping systems and
  livestock rearing of cows, sheep and camelids
  (e.g., alpaca and lama)

4
SANREM STUDY AREA IN BOLIVIA
5
CLIMATE CHANGE

• The Altiplano regions 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).

6
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).

7
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.)
8
OBJECTIVES OF SOILS RESEARCH

• To survey representative indigenous farming
  communities in the Altiplano of Bolivia to
  determine perceived changes in cropping practices
  in potato-based cropping systems due to global
  climate change and socio-economic factors.
• To assess the effects of these changes on soil
  total organic C and other soil properties to
  determine if soil degradation has occurred.

9
MATERIALS AND METHODS
10
MATERIALS AND METHODS
11
MATERIALS AND METHODS
12
CHANGES IN SOIL MANAGEMENT PRACTICES
20 years ago in Chinchaya
Present
(Yucra and Gilles, unpublished)
13
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.

14
CHANGES IN SOIL MANAGEMENT PRACTICES

• Greater tractor use for tillage in lower
  elevation communities.
• Loss of native species (e.g., thola) that have
  multiple uses to restore soil fertility during
  fallow period and are a fuel source.

15
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(Inappropriat
  e tractor tillage practices, lack of a suitable
  crop rotation strategy, insufficient soil
  fertility inputs, and overgrazing by sheep)

16
EXAMPLES OF LOCAL SOIL CLASSIFICATION SYSTEM AND
PERCEIVED CHANGES IN SOIL PROPERTIES
Vinto Coopani community (Relative high elevation) Vinto Coopani community (Relative high elevation) Vinto Coopani community (Relative high elevation) 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 Neqe 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 Jachoca 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 Saje Little soil on surface and below has gravel. Dries out quickly and is a very good for production. Used to be more fertile because it was maintained in fallow longer.
6.Black soil Chiar laqa The clay is neither hard or soft Used to be more fertile because it was maintained in fallow longer.
7.Fine sand soil Laqa Oraque Good soil with the color of skin it has very fine sand It appears to have more rocks.
Observed changes in use of soil over the last
10 years.
17
EXAMPLES OF SOIL PROPERTIES OF SOIL TYPES BASED
ON LOCAL SOIL CLASSIFICATION SYSTEM
Exchangeable Exchangeable Exchangeable
Community Soil type Textural class Organic matter pHs Bray1 P K Ca Mg CEC EC
-- -- ---------------- mg kg-1 ----------------- ---------------- mg kg-1 ----------------- ---------------- mg kg-1 ----------------- ---------------- mg kg-1 ----------------- cmolc kg-1 dS cm-1
San José Sandy/ Challa Sand 0.3 5.5 35.0 166 311 44 3.1 0.1
Clayey/ Neqe 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
Vinto Coopani Sandy/ Challa Loam 1.3 5.7 46.8 271 1102 148 8.9 0.3
Sandy/ clayey /Jachoca Sandy loam 1.2 5.5 45.2 240 580 70 5.8 0.2
Clayey/ Neqe oraque Clay loam 1.5 6.9 3.0 159 3763 578 24.3 0.2
18
EFFECTS OF FALLOW AND CROPPING ON SOIL ORGANIC C
IN UMALA
19
EFFECTS OF THOLA AND CROPPING ON SOIL PROPERTIES
Selected soil properties of sandy (challa) soil
collected directly underneath or between thola
plants or in farm field during first year of
cropping in San José de Llanga in Umala.
Thola is an evergreen shrub (Parastrephia
lepidophylla) that re-grows during fallow periods
20
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. thola)
  caused by competing uses and mechanized tillage,
  may be removing an important mechanism by which
  soil fertility and soil organic matter are
  restored.

21
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.

22
QUESTIONS? COMMENTS? SUGGESTIONS?