Global Gridded Nitrogen Indicators: Influence of Crop Maps

Area of Science:

• Agricultural Science
• Environmental Science
• Geospatial Analysis

Background:

• Global Nitrogen (N) indicators are vital for assessing environmental impacts of N application.
• Accurate geospatial distribution of crop production data is essential for calculating these indicators.
• Existing crop maps vary, and their impact on N indicator calculations needs evaluation.

Purpose of the Study:

• To analyze the differences in global N Use Efficiency (NUE) and N surplus calculations using two distinct crop maps: SPAM and M3.
• To identify regions most affected by discrepancies in N indicator results due to differing crop maps.
• To evaluate the influence of crop inclusion/exclusion and aggregation on N indicator outcomes.

Main Methods:

• Utilized publicly available statistical and literature data.
• Integrated two global crop distribution maps (SPAM and M3) for calculations.
• Performed comparative analysis of N Use Efficiency (NUE) and N surplus indicators.

Main Results:

• Significant discrepancies in N indicator calculations were observed between SPAM and M3 crop maps.
• Regions like Central Asia, Russian Federation, Australia, Oceania, and North Africa showed the greatest impact from map differences.
• The M3 crop map yielded more plausible results for N indicator calculations compared to SPAM.

Conclusions:

• The selection of a crop map critically influences the accuracy of global N indicator assessments.
• Factors such as crop inclusion (e.g., grass crops) and aggregation levels affect N indicator outcomes.
• The M3 map is recommended for more reliable global N indicator calculations, aiding in understanding N use and overuse.