1,000 kg of carbonaceous materials with a C:N ratio of 12:1 are applied to soil. 25% of the 400 kg of carbon in the materials is assimilated by microorganisms, reducing the C:N ratio to 8:1. This leaves 20.8 kg of nitrogen available for crops. An additional 39.2 kg of nitrogen is needed. Applying 85.2 kg of urea fertilizer which is 46% nitrogen would provide this amount. Fertilizer A, with 15% nitrogen content and costing RM8/kg of nitrogen, is a better buy than Fertilizer B at RM11.25/kg of nitrogen. One liter of liquid fertilizer containing 20