Quantifying the carbon footprint of crop production can help identify key options to mitigate greenhouse
gas emissions from agriculture. Using farm survey data from eastern China, the carbon footprints of three
major grain crops (rice, wheat and maize) were assessed by quantifying the greenhouse gas emissions
from individual inputs and farming operations with a full life cycle assessment methodology. The farm
carbon footprint in terms of farm area was estimated to be 6.0 ± 0.1, 3.0 ± 0.2, and 2.3 ± 0.1 t CO2-eq ha1,
and the product carbon footprint in terms of grain produced was 0.80 ± 0.02, 0.66 ± 0.03, and
0.33 ± 0.02 t CO2-eq t1 grain for rice, wheat and maize, respectively. Use of synthetic nitrogen fertilizers
contributed 44e79% and mechanical operations 8e15%, of the total carbon footprints. Irrigation and
direct methane emission made a significant contribution by 19% and by 25%, on average respectively for
rice production. However, irrigation was only responsible for 2e3% of the total carbon footprints in
wheat and maize. The carbon footprints of wheat and maize production varied among climate regions,
and this was explained largely by the differences in inputs of nitrogen fertilizers and mechanical operations
to support crop management. Moreover, a significant decrease (22e28%) in the product carbon
footprint both of wheat and maize was found in large sized farms, compared to smaller ones. This study
demonstrated that carbon footprint of crop production could be affected by farm size and climate
condition as well as crop management practices. Improving crop management practices by reducing
nitrogen fertilizer use and developing large scaled farms with intensive farming could be strategic options
to mitigate climate change in Chinese agriculture.