Balanced fertilization and regulating nutrient losses from agriculture

Balanced fertilization was introduced in the nineties as government policy to decrease nutrient losses from European agriculture. However, balanced fertilization is an ambiguous term and is not yet defined in operational terms. This paper discusses the pros and cons of balanced fertilization as a policy tool and suggests operational measures. Essential steps are the book-keeping of nutrients at farm and field levels, and the evaluation of soil fertility level and the nitrogen (N) and phosphate (P) surpluses relative to the vulnerability of the environment. The N surplus is a proximal indicator of total N losses, but information about site-specific environmental conditions is needed for the partitioning of the total N loss over N losses to the atmosphere, groundwater and surface water. The P surplus is a distal indicator of total P loss whilst a soil P test value is a proximal indicator. It is concluded that N and P surpluses combined with information about site specific environmental conditions and the agroecosystem itself, allow evaluation of the degree of balance between agriculture and the environment, as implicitly suggested by the term balanced fertilization.