The contribution of agricultural soils to greenhouse gas emissions arises from emissions of nitrous oxide from the use of nitrogenous fertilizers, animal manures and from crop residues. Crop residue emissions are calculated using known values for the nitrogen content of individual crop varieties. The cultivation of crops does not, in general, lead to the sequestration, but rather to emissions of greenhouse gases. The annual inventory of greenhouse gas emissions, prepared by the Environmental Projection Agency, does not record data from emissions arising from individual crops as this is not required for reporting purposes under the United Nations Framework Convention on Climate Change.