A high-resolution assessment on global nitrogen flows in cropland

Area of Science:

• Environmental Science
• Agricultural Science
• Global Biogeochemical Cycles

Background:

• Human activities, particularly agriculture, are the primary drivers of global nitrogen cycle alterations.
• Understanding nitrogen flows in croplands is crucial for food security and environmental sustainability.

Purpose of the Study:

• To conduct a comprehensive assessment of global nitrogen flows in croplands for the year 2000.
• To map nitrogen inputs, outputs, and balances at a high spatial resolution (5 arc-minutes).
• To evaluate national-level nitrogen stress and its relation to food insecurity.

Main Methods:

• Calculation of total nitrogen input (IN) and output (OUT) using global cropland data for 2000.
• Development of high-resolution (5 arc-minutes) spatial maps of nitrogen flows, soil, and surface balances.
• Aggregation of data to a per capita basis for national-level nitrogen stress assessment.

Main Results:

• Total nitrogen input (IN) was 136.60 trillion grams (Tg) N/year, with mineral fertilizers contributing nearly half.
• Total nitrogen output (OUT) was 148.14 Tg N/year, with crop uptake accounting for 55%.
• Global average nitrogen recovery was 59%, indicating significant ecosystem losses (nearly two-fifths of inputs).
• High-resolution mapping revealed spatial distribution of nitrogen flows and balances.
• Nitrogen scarcity or stress affects nearly 80% of African countries, exacerbating food insecurity.

Conclusions:

• Effective nitrogen management is critical to mitigate negative environmental impacts.
• Nitrogen stress is a significant issue in many developing nations, linked to poverty and food insecurity.
• The study highlights the urgent need for improved nitrogen use efficiency in global agriculture.