Fate of Carbon Around Excreta Patches.

Dung pats constitute nutrient and energy rich pulses that can contribute to soil carbon sequestration. This study evaluates changes in total and soluble soil organic C below and around dung pats. Soil samples from 0-10 and 10-20 cm depth were taken below and 30 cm away from dung pats that were recently deposited (within 1 hour of defecation), 3 days and 7 days old. Soluble organic C in the soil decreased over time, and was higher below the dung pats than away from the pats. Also, soluble organic C was higher on the 0-10 cm depth than the 10-20 cm depth. These trends suggest both vertical and lateral transport of soluble C fractions as important mechanisms of dung decomposition. Soil organic matter (SOM) (measured by loss on ignition) significantly increased with pat age both below and away from the dung pats suggesting C immobilization of the soluble C by microbial biomass. The magnitude of the changes in SOM indicates another mechanism of transport of organic matter is also contributing to SOM increase. It is hypothesized that invertebrate activity may be contributing to the changes in SOM.