Get reliable rangeland science

Soil organic carbon content is a central characteristic for sustaining the productive system and the provision of important ecosystem services, including carbon sequestration. Knowing the carbon stock in the soil is important in order to design and manage strategies for its conservation and capture. The main objective of this work is to characterize the carbon stock in livestock systems in Uruguay and explore estimation methods based on satellite information. Twelve farms with extensive mixed livestock production (cattle and sheep) located on the basaltic slope geomorphological region of Uruguay were evaluated. Three categories of soil were defined (superficial, medium and deep) with an average depth of 9.0, 18.5 and more than 30 cm depth respectively. This classification of soils was done through the normalized vegetation index (NDVI) obtained for selected dates when low soil water content was evident. The ability to maintain green vegetation due to soil water content is strongly linked to depth. Ten sites were randomly selected for each soil category also considering the representativeness of the main soil cartographic units (CONEAT) where 20 soil core samples up to 30 cm deep were extracted with a drill and divided into four strata: 0 to 5, 5 to 10, 10 to 20 and 20 to 30 cm. A specific sampling was performed for determining bulk density. The organic carbon stock was calculated for each soil category. The sampling locations were geo-referenced and the soil carbon values and average NDVI for the last 5 or 10 years was calculated for determination of correlations. The determined carbon stocks we found varied between 16 Mg/ha in extremely superficial soils and 144 Mg/ha up to 30 cm deep in deep soils. Based on these results, we now propose to develop a reliable method for estimating carbon stocks across the basaltic slope region using models based on remote sensing variables.