Agricultural productivity and the nitrogen cycle

During the past 30 years agricultural production in the U.K. has consistently increased as the result of a number of technological changes. For example, cereal yields have doubled and milk yields from dairy cows have increased by one and a half times. Livestock numbers have also increased, particularly those of pigs and poultry. The use of fertilizer nitrogen has increased fivefold in the same period. This greater productivity means that not only have the inputs of nitrogen to agriculture increased but so also have the amounts circulating within agricultural systems. These changes are examined and the implications of their effects on the environment assessed.