Davis, California

A 10-year study at the University of California, Davis monitored soil C gain and the rate of conversion of organic inputs to soil organic carbon. The highest rate of carbon accrual that they recorded was with an organic corn/tomato rotation, with external C inputs from composted manure. For the entire study, the conversion of crop residue carbon to soil carbon was 7.6%.

Soil Sci. Soc. Am. J. 69:1078–1085 (2005)