Management of nitrogen for sustainable agricultural systems

A fundamental shift has taken place in world food production. In the past, the principal driving force in agriculture has been to increase the yield potential of food crops. Today, the drive for productivity is increasingly combined with a desire for sustainability. For farming systems to remain productive, and to be sustainable in the long-term, it is necessary to replenish the reserves of nutrients which are removed or lost from the soil. In the case of nitrogen (N), inputs into agricultural systems may be in the form of N-fertilizer, or occur via biological N2 fixation. The paper discusses the role of N2 fixation in tropical and temperate environments of the Asia-Pacific region and compares the relative recoveries and losses of organic and inorganic N by crop and forage species. Management strategies to manipulate N supply and control the extent of N losses are also considered. (author). 53 refs, 1 fig., 7 tabs