Among soil properties susceptible to land use changes, we focus on soil carbon and metal cations and their interactions. In Delaware Coastal Plain, we studied two soil profiles in agricultural field vs. forest which share same soil forming factors. XRD diffractograms confirmed that the two soils share almost identical mineralogy. Geochemical mass balance model is combined with total elemental chemistry to calculate the fractional mass losses of major oxide elements. Zr was used as an index element. We also conducted elemental analyses of sodium pyrophosphate extracts as a proxy for organic matter complexed pool. Average carbon content of A horizon in the farm soil is 0.96% which is less than half of carbon content in the forest soil (2.62%). The concentration of Ca and P in farmland are 0.28% and 0.07% respectively, which are significantly higher than 0.21% (Ca) and 0.04% (P) in the forest soil. The fractional mass losses of Ca P are greater by 35% and 75%, respectively in the farm soil, reflecting the fertilizer inputs. No significant difference in the total concentrations of Al and Fe was found between the two sites. However, the concentrations of C-complexed Al (Fe) per soil mass are 0.12% (0.09%) in the farm soil, which are significantly less than 0.22% (0.14%) in the forest soil. Further examination of the Al and Fe amounts per carbon mass revealed that Al and Fe were not proportionately lost with the farming-associated reduction of organic matter. Instead, the organic matter is diluted in Fe and Al during the reduction. In contrast, the liming at the farmland resulted in the 10 fold increase of Ca per mass of organic matter. This study suggests that land use changes may significantly affect the fates metal cations by altering carbon cycle, which in turn can contribute to stabilizing organic matter.