Optimum N rate for grain yield coincides with minimum greenhouse gas intensity in flooded rice fields

Dr Gilwon Kim1

1Western Sydney University, Hobartville, Australia

Excessive application of N fertilizer to rice results in water and atmospheric pollution including greenhouse gas (GHG) emissions. Therefore, N fertilizer management needs to be optimized taking into account grain yield, global warming potential (GWP, Mg CO2 eq. ha-1) and GHG intensity (GHGI, kg CO2 eq. kg-1 grain). However, the tradeoffs between the effects of N rate on rice grain yield, GWP and GHGI have not been adequately evaluated. Therefore, field experiments to determine the effect of N rate (as urea) on yield, GWP and GHGI were conducted in a typical flooded, transplanted rice paddy in a temperate environment. Methane (CH4) and nitrous oxide (N2O) emission rates were determined throughout the entire year (both during growing and fallow seasons) over two years. Rice grain yield showed a quadratic response to N rate, and the maximum yield (6.7-6.8 t ha-1) was achieved at 112-119 kg N ha-1, 50% higher than the yield of the control (0 kg N ha-1). Increasing N rate increased the seasonal N2O flux by 4.56-7.11 g N2O kg-1 N, but N2O flux contributed less than 7% of the total GWP. The GWP was mainly determined by the CH4 flux, which showed a relatively flat quadratic response to N rate, peaking at 124-138 kg N ha-1. Thus, GWP also showed a quadratic response to N rate, peaking at 122-130 kg N ha-1. The GHGI decreased as N rate increased and was the lowest (1.10-1.28 kg CO2-eq. kg-1 grain yield) at 104-112 kg N ha-1, approximately 20% lower than GHGI in the 0 N treatment. In conclusion, the N rate for maximum yield was similar to the N rate for minimum GHGI, mainly because of the small effect of N rate on CH4 emissions and the low magnitude of N2O emissions. Thus, GHGI was largely driven by grain yield, so the N rate for maximum grain yield was similar to the N rate for maximum GHGI. Proper N fertilization is essential in rice farming systems to increase crop productivity and reduce the global warming impact (GWP and GHGI).


Gil Won Kim



Hawkesbury Institute for the Environment (HIE)

Western Sydney University

E-mail: G.Kim@westernsydney.edu.au


Major Projects:

  1. How to reduce GHGs emission and increasing biomass productivities form pasture field
  2. The effect of N fertilization on carbon balance and GHGs emission in agricultural land
  3. Evaluation of CO2 emission factor from urea and calcium carbonate in agricultural land.


Scientific Publications (peer-reviewed paper)

  1. Jeong, S.T., Cho, S.R., Lee, J.G., Kim, P.J., Kim, G.W., 2019. Composting and compost application: Trade-off between greenhouse gas emission and soil carbon sequestration in whole rice cropping system. Journal of Cleaner Production 212: 1132-1142
  2. Cho, S.R., Jeong, S.T., Kim, G.Y., Lee, J.G., Kim, P.J., Kim. G.W., 2019. Evaluation of the carbon dioxide (CO2) emission factor from lime applied in temperate upland soil. Geoderma 337: 742-748
  3. Khan, M.I., Hwang, H.Y., Kim, G.W., Kim, P.J., Das, S., 2018. Microbial responses to temperature sensitivity of soil respiration in a dry fallow cover cropping and submerged rice mono-cropping system. Applied Soil Ecology 128: 98-108
  4. Jeong, S.T., Kim, G.W., Hwang, H.Y., Kim. P.J., Kim. S.Y., 2018. Beneficial effect of compost utilization on reducing greenhouse gas emissions in a rice cultivation system through the overall management chain. Science of The Total Environment 613: 115-122
  5. Kim, G.W., Alam, M.A., Lee, J.J, Kim, G.Y., Kim, P.J., Khan, M.I., 2017. Assessment of direct carbon dioxide emission factor from urea fertilizer in temperate upland soil during warm and cold cropping season. European Journal of Soil Biology 83: 76-83
  6. Kim, G.W., Gwon, H.S., Jeong, S.T., Kim, P.J., 2017. Influence of nitrogen fertilization on net ecosystem carbon budget in temperate mono-rice paddy. Geoderma 306: 58-66
  7. Hwang, H.Y., Kim, G.W., Kim, S.Y., Haque, M.M., Khan, M.I., Kim, P.J., 2017. Effect of cover cropping on the net global warming potential of rice paddy soil. Geoderma 292: 49-58.
  8. Kim, G.W., Das, S., Hwang, H.Y., Kim, P.J., 2017. Nitrous oxide emissions from soils amended by cover-crops and under plastic film mulching: Fluxes, emission factors and yield-scaled emissions. Atmospheric Environment 152: 377-388.
  9. Kim, G.W., Gwon, H.S., Jeong, S.T., Hwang, H.Y., Kim, P.J., 2016. Different responses of nitrogen fertilization on methane emission in rice plant included and excluded soils during cropping season. Agriculture Ecosystems & Environment 230: 162-168.
  10. Kim, G.W., Jeong, S.T., Kim, G.Y., Kim, P.J., Kim, S.Y., 2016. Evaluation of Carbon Dioxide Emission Factor from Urea during Rice Cropping Season: A Case Study in Korean Paddy Soil. Atmospheric Environment 139: 139-146.
  11. Haque, M.M., Kim, G.W., Kim, P.J., Kim, S.Y. 2016. Comparison of net global warming potential between continuous flooding and midseason drainage in monsoon region paddy during rice cropping. Field Crops Research 193: 133-142.
  12. Kim, G.W., Ho, A., Kim, P.J., Kim, S.Y. 2016. Stimulation of methane oxidation potential and effects on vegetation growth by bottom ash addition in a landfill final evapotranspiration cover. Waste Management 55: 306-312
  13. Atulba, S.L., Gutierrez, J., Kim, G.W., Kim, S.Y., Khan, M.I., Lee, Y.B., Kim, P.J. 2015. Evaluation of rice root oxidizing potential using digital image analysis. Journal of the Korean Society for Applied Biological Chemistry 58: 463-471.
  14. Haque, M.M., Kim, S.Y., Kim, G.W., Kim, P.J. 2015. Optimization of removal and recycling ratio of cover crop biomass using carbon balance to sustain soil organic carbon stocks in a mono-rice paddy system. Agriculture, Ecosystems & Environment 207: 119-125.
  15. Hwang, H.Y., Kim, G.W., Lee, Y.B., Kim, P.J., Kim, S.Y. 2015. Improvement of the value of green manure via mixed hairy vetch and barley cultivation in temperate paddy soil. Field Crops Research 183: 138-146.
  16. Gutierrez, J., Atulba, S.L., Kim, G.W., Kim, P.J. 2014. Importance of rice root oxidation potential as a regulator of CH4 production under waterlogged conditions. Biology and Fertility of Soils 50: 861-868.


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