Fertilizer replacement value
The extent to which a nutrient (N, P) in a manure or in a compost is as plant-available as that nutrient in a common mineral equivalent applied according to good agricultural practices, usually expressed as kg per 100 kg applied = fertilizer equivalency = ratio of apparent recoveries* (or of apparent efficiencies**) of a nutrient (often N) from manure and from a commonly used mineral fertilizer equivalent.