Improving Nitrogen and Water Management in Crop Production on a National Scale

To meet the growing global demand for food and bioenergy, agricultural production must nearly double by 2050, placing additional pressures on water resources and nitrogen cycles. To address the global challenge, one focus has been on closing yield gaps wherever they occur with the development and adoption of more efficient technologies and management practices (TMPs). In general, synergies between good water and nutrient management can improve efficiencies of both and improve crop yield on a farm scale. However, TMPs proven to be efficient in nitrogen use at a farm scale do not necessarily lead to the reduction of nitrogen pollution on a regional to national scale, given the complex trade-offs and responses of markets, governments, and consumers. The same case applies to water use. For example, some water-efficient TMPs may enable the expansion of crops that require more water inputs. Therefore, it is critical to identify challenges and opportunities for improving nitrogen and water use efficiencies as they are integrated from farm scales to national scales.

Based on the Sustainable Agriculture Matrix (SAM) database, which has been developed to assess the impacts of agricultural production on sustainability, this study examines the historical trends of nitrogen and water use on a national scale for the period of 1961-2015, identifies key socioeconomic and ecological drivers for the trends, and characterizes the trade-offs or synergies between nitrogen and water use efficiencies. In addition, we quantify the differences in nitrogen and water use efficiencies among countries and crop types, and evaluate the opportunities in saving nitrogen and water use through international trade, technological improvement, or diet change.