Clima De Bolivia

The southern Bolivian Altiplano is one of the most arid places in this country, with many climatic constrains, the average rainfall for instance is around 200 mm per year with a huge inter annualvariability. There is the main area of quinoa production worldwide, therefore is important for the local economy. In the soil of quinoa production is possible to find volcanic rock fragments (VRF), dueto volcanic activity in the past. Because there is not enough information about the influence of these volcanic rocks on the soil and quinoa yield, the general objective is to determine the influenceof VRF on soil water holding capacity and on crop water productivity modelling.

The study area is located in Bolivia, specifically in Irpani at 19°37´ LS, 67°43´ LW and at 3700 m. a. s. l. Soilsamples were collected in order to determine their texture, gravel content and to categorize the volcanic rocks fragments, in four classes according their size, afterwards in laboratory the waterretention curve of samples composed by 15 and 30 vol% of VRF mixed with different soil textures were determined. The crop water productivity model was then used to test its sensitivity to volcanic rockfragments presence in the soil, with calibrated crop parameters of quinoa, historical climatic data from the agro climatic GIS library of Geerts et al. (2006), and under rainfed conditions as well as lowfertility.

Depending on the bulk density and volcanic rock fragment content vol%, the simulated grain yield did not change much, for silty loam soil containing 15 vol% of VRF under conditionsof Bolivian Altiplano, but as the content of volcanic rock fragment increased to around 30 vol% the reduction of simulated grain yield became significant. This was because of VRF can hold water atpermanent wilting point, which reduces the total available water of soils. The VRF contented in sandy soils of Irpani ranged from 12 to 30 mass% between 0 and 60 cm of depth. It can be concluded based...