Organic matter contains about 5% nitrogen. A soil containing 3% organic matter could contain about 3,000 pounds of N per acre-furrow slice (2,000,000 lb x 0.05 x 0.03 = 3,000 lb N).
Higher OM levels help maintain higher CEC’s. This is important in the soil’s ability to hold, maintain, and supply nutrients for plant growth.
pH - Nutrient availability is pH dependent.
Others; Animal waste application, types of crops grown (C/N ratio).