50 year trends in nitrogen use efficiency of world cropping systems: the relationship between yield and nitrogen input to cropland

Nitrogen (N) is crucial for crop productivity. However nowadays more than of the N added to cropland is lost to the environment, wasting the, producing threats to air, water, soil and biodiversity, and greenhouse gas emissions. Based on FAO data, we have the trajectory followed, in the past 50 years, by 124 in terms of crop yield and total nitrogen inputs to cropland (manure, synthetic fertiliser, symbiotic fixation and atmospheric). During the last five decades the response of agricultural to increased nitrogen fertilization has evolved differently in the world countries. While some countries have improved their agroenvironmental, in others the increased fertilization has low agronomical benefits and higher environmental losses. Our also suggest that, in general, those countries using a higher of N inputs from symbiotic N fixation rather than from synthetic have a better N use efficiency.