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 6C 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?