Efficiency of Fertilizer Nitrogen in Cereal Production: Retrospects and Prospects

Presently, 50% of the human population relies on nitrogen (N) fertilizer for food production. The world today uses around 83 million metric tons of N, which is about a 100‐fold increase over the last 100 years. About 60% of global N fertilizer is used for producing the world's three major cereals: rice, wheat, and maize. Projections estimate that 50 to 70% more cereal grain will be required by 2050 to feed 9.3 billion people. This will require increased use of N of similar magnitude if the efficiency with which N is used by the crop is not improved. Fertilizer N‐recovery efficiency by the first crop is 30 to 50%. The remaining N either remains in the soil, the recovery of which in the following crops is very limited (<7% of applied N up to six consecutive crops), or it is lost from the soil–plant system, causing serious disruptions in ecosystem functions. Much research has been conducted during the past decades to improve N‐use efficiency (NUE) by developing fertilizer management strategies based on a better synchronization between the supply and requirement of N by the crop. Importantly, some of these techniques are being adopted on a large scale by farmers. The two challenges ahead are to (1) improve farmers’ knowledge and (2) ensure that these techniques are cost‐effective and user‐friendly so that they provide attractive options for adoption.