Nutrient balances provide information about environmental pressures. A nutrient deficit (negative value) indicates declining soil fertility. A nutrient surplus (positive data) indicates a risk of polluting soil, water and air. The nutrient balance is defined as the difference between the nutrient inputs entering a farming system (mainly livestock manure and fertilisers) and the nutrient outputs leaving the system (the uptake of nutrients for crop and pasture production). Inputs of nutrients are necessary in farming systems as they are critical in maintaining and raising crop and forage productivity. However, a build up of surplus nutrients in excess of immediate crop and forage needs can lead to nutrient losses, representing not only a possible cause of economic inefficiency in nutrient use by farmers, but also a source of potential harm to the environment, through water pollution or air pollution, notably ammonia or greenhouse gas emissions. This indicator is presented for the two main nutrients, nitrogen and phosphorus, and is measured in tonnes of nutrient and in kilograms of nutrient per hectare of agricultural land.