Changes in soil organic C and N due to climate change and socioeconomic factors in potato-based cropping systems in the Bolivian Highlands

Global climate change and changes in migration and market conditions in the Bolivian Highlands (Altiplano) have reduced the use of traditional cropping practices and increased the risk of crop failure and food insecurity. The objectives of this research were to survey indigenous farming communities in the northern Altiplano of Bolivia to determine the actual and perceived changes in cropping practices in potato-based cropping systems and to assess the effects of these changes on soil total organic carbon (C) and total nitrogen (N) levels and the availability and composition of soil amendments. Village-level surveys were conducted using questionnaires and participatory techniques in 2006-2007 in four communities that were selected to represent communities situated at relatively low and high altitudes in the region. Samples of soil amendments, primarily animal manures, were obtained from each community to determine the range of composition of the materials. In addition, soil samples were collected to a 20 cm depth from agricultural fields that represented different stages of the common agricultural rotation practiced in the region and that had different lengths of fallow periods. A hypothesis of this research is that climate change and socioeconomic factors have caused lower soil total organic C and total N levels due to increased intensity of land use and the amount and type of tillage, and a decrease in the length of the fallow period that was traditionally used to restore soil fertility. The results of the analysis of the soil amendments and soils will be compared to community perceptions of changes in soil quality and management and any differences among the communities will be discussed. The findings of this research will assist in determining if appropriate management practices need to be identified to improve soil organic matter in order to possibly mitigate negative effects of climate change in the area.