Does food demand and rapid urbanization growth accelerate regional nitrogen inputs?

Under the broad pressures of food demand and urbanization growth, an excess of reactive nitrogen has been generated, which has led to multiple human health and environmental concerns. Efforts to address these concerns require an accurate assessment of the roles of food demand and rapid growth in urbanization. The Huai River Basin (HRB) was chosen for our study area because it exemplifies a region facing the double pressures of rapid urban development and food demand, as seen in other developing countries. Chemical N fertilizer was the largest source of nitrogen in the HRB, accounting for about 68% of the total input, followed by atmospheric N deposition (19%), biological nitrogen fixation (7%) and net food & feed import (6%). During the period 1990–2010, average grain yield increased from 354.5 to 494.2 t km−2 (a 39% increase), urbanization rate increased from 13% to 35% (a 22% increase), but the average growth rate of nitrogen input reached 63%. These results suggest that the driving force behind increasing nitrogen input may be attributable to food production, while rapid urban development did not accelerate the nitrogen input as expected. Instead, it will slow the increasing trend of nitrogen input. The accelerated trend in nitrogen inputs could be better managed by improving fertilizer efficiency, introducing cleaner energy sources, educating farmers for environmental awareness, and formulating economic development policies that explicitly consider the benefits of environmental protection.