Reductions in greenhouse gas emissions must be complimented with increases in negative emissions in order to stabilize atmospheric carbon dioxide concentrations and prevent catastrophic changes in climate. Soil carbon sequestration on arable lands is a negative emissions technology with high climate change mitigation potential that also confers agronomic co-benefits, but variability of soil organic C (SOC) stocks remains both a statistical and financial challenge for verifying SOC sequestration goals. This work is in two parts: 1) improving sampling methods for SOC assessment on rocky soils, and 2) reducing sampling requirements for mapping and modeling field-scale subsoil, topsoil and whole profile SOC stocks via remote and proximal sensing.