Sales of organic produce were estimated at $27.8 billion in 2004 with more than 31 million ha farmland organically managed. In organic farming, crop residues and animal manures are added to soils to improve soil tilth. Information on the decomposition rates of the added organic carbon (C) is a prerequisite for designing strategies to improve C sequestration in soils. The objectives of these studies were to: 1) Determine the decomposition rates of organic materials added to soils; 2) Investigate the effects of sweet potato cultivars on the decomposition rates of the added organic C; and 3) Establish relationships between Sweet potato yields and organic C levels in the soil. The experimental design was a completely randomized block design with four treatments (Control, cover crops alone, or in combination with broiler litter, or NPK), and four replicates. Every fall since 2002, cover crops were planted and incorporated into the soil. Three Sweet potato (Ipomoea batatas) cultivars were planted for 120 days and harvested. Soil samples were collected at 0-15 cm depth. A 20-g soil sample (oven-dry) was adjusted to 0.03 MPa with DI water and incubated in bottles at room temperature (20 ± 2^°C) for 30 days. The bottles were connected to an aerobic incubation apparatus consisting of a compressed air, a scrubber to remove N and CO₂ from the compressed air. A manifold of Tygon tubes distributed the CO₂-free air to the incubation bottles connected to test tubes containing a standard NaOH (0.2 M) to trap the CO₂ evolved. The CO₂ trapped in the NaOH solution was determined potentiometrically after precipitation of carbonate. The trapping solution was replaced with fresh solution on a regular basis. A non-linear regression approach for N mineralization was used to estimate the readily mineralizable organic C pools (C_o) and the first-order rate constant (k).