Assessment of required increases in nitrogen use efficiencies in agriculture
Nitrogen (N) inputs in agriculture increased food production but also caused several environmental impacts. We present a spatially explicit estimation of required nitrogen use efficiencies (NUEs) to attain either current crop yields and target crop yields while complying with environmental standards within EU27. The standards refer to critical nitrogen deposition levels in terrestrial ecosystems, critical nitrogen concentrations in surface water and in groundwater. The calculated required NUEs to comply with the surface water standard are higher than for groundwater. For surface water the needed NUE increse is ofen higher than 0.3, whereas it mostly less than 0.2 for ground water.
Agricultural nitrogen (N) losses to air and water affect air and water quality. We used a spatially explicit N balance model to asses where agricultural N losses currently lead to an exceedance of critical N deposition levels on terrestrial ecosystems, critical NO3 concentrations in groundwater in view of drinking water quality and critical N concentrations in surface water in view of eutrophication impacts. We then calculated the N inputs at which critical N depositions or concentrations are just not exceeded (‘critical’ N inputs). Meeting air or water quality objectives by reducing N inputs to ‘critical’ N inputs, however, implies a reduction in yields. Even though Europe is one of the most food secure regions worldwide, yields will probably need to increase in the future in order to meet European and global demands without converting natural areas to cropland. This can be achieved by closing the gap between current yields and the “yield potential”, defined as the maximum yield for a given climate and soil, assuming optimal management.