Fertilizer Replacement Value: Linking Organic Residues to Mineral Fertilizers

Organic residues of animal origin are an important nutrient source for crop production. Due to the presence of organic nutrients, manures are more difficult to manage than mineral fertilizers. The increasing diversification in available organic residues makes the need for a correct assessment of the fertilizing value. This chapter outlines the theoretical concept of the fertilizer replacement value (FRV) and explores how it is derived in science and applied in farming practices. It explains the nutrient pathways from land application of organic residues to crop uptake, identifying the different routes to nutrient losses. The chapter reviews the concept of FRVs and discusses methods of obtaining estimates, including potential pitfalls. It also describes some examples of how FRVs are applied in fertilizer plans, including mineral fertilizers and manures. Fertilizer plans or nutrient management plans aim to match nutrient supply from fertilizers, manures, and other sources to nutrient demand from crops