Carbon and Nitrogen Footprints of Major Cereal Crop Production in China: A Study Based on Farm Management Surveys

doi:10.1016/j.rsci.2021.11.003

Abstract

Abstract:

Greenhouse gas (GHG) emissions and reactive nitrogen (Nr) releases are central environmental problems, which are closely linked to climate change, environmental ecology and crop production. Sustainable development of agriculture plays an important role in GHG emissions and Nr loss. The life cycle assessment (LCA) method was used to calculate the product and farm carbon footprints (CFs) and nitrogen footprints (NFs) in rice, wheat and maize production in China based on farm survey data. The results pinpointed that the CFs of rice, wheat and maize were 0.87, 0.30 and 0.24 kg/kg. Meanwhile, the computed NFs were 17.11, 14.26 and 6.83 g/kg, respectively. Synthetic nitrogen fertilizer applications and methane (CH₄) emissions were dominant CF sources, while ammonia (NH₃) volatilization was the main NF contributor. Moreover, significant decreases in CF and NF by 20%-54% and 33%-61%, respectively, were found in large-size farms (> 20 hm²) when compared to small-size farms (< 0.7 hm²). Furthermore, the significantly positive relationships between CF and NF indicated the potential for simultaneous mitigation in the regions with high agricultural inputs, like amounts of fertilizer. Based on our results, some effective solutions would be favorable toward mitigating climate change and eutrophication of the major cereal crop production in China, especially optimizing fertilizer use and farm machinery operation efficiencies, as well as developing large-size farms with intensive farming.

Key words: carbon footprint, nitrogen footprint, life cycle assessment, grain crop, sustainability

Xu Chunchun, Chen Zhongdu, Ji Long, Lu Jianfei. Carbon and Nitrogen Footprints of Major Cereal Crop Production in China: A Study Based on Farm Management Surveys[J]. Rice Science, 2022, 29(3): 288-298.

Figures/Tables 6

References 52

[1]	Breiling M, Hoshino T, Matsuhashi R. 1999. Contributions of rice production to Japanese greenhouse gas emissions applying life cycle assessment as a methodology. Keio Assoc Reposit Acad Resous, G38: 1-31.
[2]	Chen X H, Ma C C, Zhou H M, Liu Y, Huang X M, Wang M K, Cai Y Y, Su D, Muneer M A, Guo M C, Chen X J, Zhou Y, Hou Y, Cong W F, Guo J X, Ma W Q, Zhang W F, Cui Z L, Wu L Q, Zhou S G, Zhang F S. 2021. Identifying the main crops and key factors determining the carbon footprint of crop production in China, 2001-2018. Resour Conserv Recycl, 172: 105661.
[3]	Chen X P, Cui Z L, Fan M S, Vitousek P, Zhao M, Ma W Q, Wang Z L, Zhang W J, Yan X Y, Yang J C, Deng X P, Gao Q, Zhang Q, Guo S W, Ren J, Li S Q, Ye Y L, Wang Z H, Huang J L, Tang Q Y, Sun Y X, Peng X L, Zhang J W, He M R, Zhu Y J, Xue J Q, Wang G L, Wu L, An N, Wu L Q, Ma L, Zhang W F, Zhang F S. 2014. Producing more grain with lower environmental costs. Nature, 514: 486-489.
[4]	Chen Z D, Dikgwatlhe S B, Xue J F, Zhang H L, Chen F, Xiao X P. 2015. Tillage impacts on net carbon flux in paddy soil of the southern China. J Clean Prod, 103: 70-76.
[5]	Chen Z D, Chen F, Zhang H L, Liu S L. 2016. Effects of nitrogen application rates on net annual global warming potential and greenhouse gas intensity in double-rice cropping systems of the Southern China. Environ Sci Pollut Res Int, 23(24): 24781-24795.
[6]	Cheng K, Yan M, Nayak D, Pan G X, Smith P, Zheng J F, Zheng J W. 2015. Carbon footprint of crop production in China: An analysis of National Statistics data. J Agric Sci, 153(3): 422-431.
[7]	Cui Z L, Yue S C, Wang G L, Meng Q F, Wu L, Yang Z P, Zhang Q, Li S Q, Zhang F S, Chen X P. 2013. Closing the yield gap could reduce projected greenhouse gas emissions: A case study of maize production in China. Glob Chang Biol, 19(8): 2467-2477.
[8]	Davis K F, Rulli M C, Seveso A, D’Odorico P. 2017. Increased food production and reduced water use through optimized crop distribution. Nat GeoSci, 10: 919-924.
[9]	Feng S, Tan S, Zhang A, Zhang Q, Pan G, Qu F, Smith P, Li L, Zhang X. 2011. Effect of household land management on cropland topsoil organic carbon storage at plot scale in a red earth soil area of South China. J Agric Sci, 149(5): 557-566.
[10]	Galloway J N, Townsend A R, Erisman J W, Bekunda M, Cai Z C, Freney J R, Martinelli L A, Seitzinger S P, Sutton M A. 2008. Transformation of the nitrogen cycle: Recent trends, questions, and potential solutions. Science, 320: 889-892. PMID
[11]	Gan Y T, Liang C, Campbell C A, Zentner R P, Lemke R L, Wang H, Yang C. 2012. Carbon footprint of spring wheat in response to fallow frequency and soil carbon changes over 25 years on the semiarid Canadian prairie. Eur J Agron, 43: 175-184.
[12]	Guinée J B, Gorrée M, Heijungs R, Huppes G, Kleijn R, de Koning A, Oers L, Sleeswijk W A, Suh S, Haes U D, de Bruijn H, van Duin R, Huijbregts M A. 2002. Life Cycle Assessment:An Operational Guide to the ISO Standards. Dordrecht, the Netherlands: Kluwer Academic Publishers.
[13]	Hillier J, Hawes C, Squire G, Hilton A, Wale S, Smith P. 2009. The carbon footprints of food crop production. Int J Agric Sustain, 7(2): 107-118.
[14]	Hou H J, Peng S Z, Xu J Z, Yang S H, Mao Z. 2012. Seasonal variations of CH₄ and N₂O emissions in response to water management of paddy fields located in Southeast China. Chemosphere, 89(7): 884-892.
[15]	Huang J. 2016. Non-agricultural employment, planting scale and chemical fertilizer application: Based on empirical test on rural fixed observation points. [MS Thesis]. Nanjing, China: Nanjing Agriculture University. (in Chinese with English abstract)
[16]	Huang Y, Tang Y H. 2010. An estimate of greenhouse gas (N₂O and CO₂) mitigation potential under various scenarios of nitrogen use efficiency in Chinese croplands. Glob Change Biol, 16(11): 2958-2970.
[17]	Huang Z H, Wang P. 2008. Farmland transfer and its impacts on the development of modern agriculture: Status, problems and solutions. J Zhejiang Univ: Human Soc Sci, 38(2): 38-47. (in Chinese with English abstract)
[18]	IPCC(Intergovernmental Panel on Climate Change).2006.IPCC Guidelines for National Greenhouse Gas Inventories. [2021-02-27]. https://www.ipcc-nggip.iges.or.jp/public/2006gl/.
[19]	ISO(International Organization for Standardization). 2006 Environmental Management-Life Cycle Assessment-Requirements and Guidelines. [2021-03-05]. https://webstore.ansi.org/Standards/ISO/ISO140442006.
[20]	Jayasundara S, Wagner-Riddle C, Dias G, Kariyapperuma K A. 2014. Energy and greenhouse gas intensity of corn (Zea mays L.) production in Ontario: A regional assessment. Can J Soil Sci, 94: 77-95.
[21]	Leach A M, Galloway J N, Bleeker A, Erisman J W, Kohn R, Kitzes J. 2012. A nitrogen footprint model to help consumers understand their role in nitrogen losses to the environment. Environ Dev, 1(1): 40-66.
[22]	Leip A, Weiss F, Lesschen J P, Westhoek H. 2014. The nitrogen footprint of food products in the European Union. J Agric Sci, 152: 20-33.
[23]	Li J, Bai J, Overend R. 1998. Assessment of Biomass Resource Availability in China. Beijing, China: China Environmental Science Press. (in Chinese with English abstract)
[24]	Liu X H, Gao W S, Zhu W S. 2001. Mechanism and Technical Pattern of Straw Returning. Beijing, China: China Agriculture Press. (in Chinese)
[25]	Lu F, Wang X K, Han B, Ouyang Z, Zheng H. 2010. Straw return to rice paddy: Soil carbon sequestration and increased methane emission. J Appl Ecol, 21(1): 99-108. (in Chinese with English abstract)
[26]	Lorenz K, Lal R. 2009. Biogeochemical c and n cycles in urban soils. Environ Int, 35(1): 1-8. PMID
[27]	Ma Y C, Kong X W, Yang B, Zhang X L, Yan X Y, Yang J C, Xiong Z Q. 2013. Net global warming potential and greenhouse gas intensity of annual rice-wheat rotations with integrated soil-crop system management. Agric Ecosyst Environ, 164: 209-219.
[28]	Moldanová J, Grennfelt P, Jonsson Å, Simpson D, Spranger T, Aas W, Munthe J, Rabl A. 2011. Nitrogen as a threat to European air quality. In: Sutton M A, Howard C M, Erisman, J W, Billen G, Bleeker A, Grennfelt P, van Grinsven H, Grizzetti B. The European Nitrogen Assessment. Cambridge, UK: Cambridge University Press: 405-433.
[29]	Pandey D, Agrawal M. 2014. Carbon footprint estimation in the agriculture sector. In: Muthu S S. Assessment of Carbon Footprint in Different Industrial Sectors. Singapore: Springer: 25-47.
[30]	Pathak H, Jain N, Bhatia A, Patel J, Aggarwal P K. 2010. Carbon footprints of Indian food items. Agric Ecosyst Environ, 139: 66-73.
[31]	Pierer M, Winiwarter W, Leach A M, Galloway J N. 2014. The nitrogen footprint of food products and general consumption patterns in Austria. Food Policy, 49: 128-136.
[32]	Ray D K, Ramankutty N, Mueller N D, West P C, Foley J A. 2012. Recent patterns of crop yield growth and stagnation. Nat Commun, 3: 1293.
[33]	Rees W E. 1992. Ecological footprints and appropriated carrying capacity: What urban economics leaves out. Environ Urban, 4: 121-130.
[34]	Sefeedpari P, Ghahderijani M, Pishgar-Komleh S H. 2013. Assessment the effect of wheat farm sizes on energy consumption and CO₂ emission. J Renew Sustain Energy, 5: 023131.
[35]	Shen J B, Cui Z L, Miao Y X, Mi G H, Zhang H Y, Fan M S, Zhang C C, Jiang R F, Zhang W F, Li H G, Chen X P, Li X L, Zhang F S. 2013. Transforming agriculture in China: From solely high yield to both high yield and high resource use efficiency. Glob Food Secur, 2(1): 1-8.
[36]	Sommer S G, Schjoerring J K, Denmead O T. 2004. Ammonia emission from mineral fertilizers and fertilized crops. Adv Agron, 82: 557-622.
[37]	Stocker T F, Qin D, Plattner G K, Tignor M, Allen S K, Boschung J, Nauels A, Xia Y, Bex V, Midgley P M. 2013. Climate Change 2013:The Physical Science Basis, in Contribution of Working Group I (WGI) to the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). Cambridge, the United Kingdom: Cambridge University Press.
[38]	van Grinsven H J M, Holland M, Jacobsen B H, Klimont Z, Sutton M A, Jaap Willems W. 2013. Costs and benefits of nitrogen for Europe and implications for mitigation. Environ Sci Technol, 47(8): 3571-3579. PMID
[39]	Wang C, Zhou W, Li Z Z, Liu X M, Sun G, Xia W J, Wang X B, Liu G R. 2012. Effects of different nitrogen application rates on ammonia volatilization from paddy fields under double-harvest rice system. Plant Nutr Fertil Sci, 18(2): 349-358. (in Chinese with English abstract)
[40]	Wiedmann T, Minx J. 2008. A definition of carbon footprint. In: Pertsova C C. Ecological Economics Research Trends. Hauppauge, New York, USA: Nova Science Publishers: 1-11.
[41]	Xia Y Q, Yan X Y. 2012. Ecologically optimal nitrogen application rates for rice cropping in the Taihu Lake region of China. Sustain Sci, 7: 33-44.
[42]	Xu X M, Zhang B, Liu Y, Xue Y N, Di B S. 2013. Carbon footprints of rice production in five typical rice districts in China. Acta Ecol Sin, 33(4): 227-232.
[43]	Xue J F, Pu C, Liu S L, Zhao X, Zhang R, Chen F, Xiao X P, Zhang H L. 2016. Carbon and nitrogen footprint of double rice production in Southern China. Ecol Indic, 64: 249-257.
[44]	Xue X B, Landis A E. 2010. Eutrophication potential of food consumption patterns. Environ Sci Technol, 44(16): 6450-6456.
[45]	Yan M, Cheng K, Luo T, Yan Y, Pan G X, Rees R M. 2015. Carbon footprint of grain crop production in China: Based on farm survey data. J Clean Prod, 104: 130-138.
[46]	Yang T, Wu J N, Bao T, Li F B, Feng J F, Zhou X Y, Fang F P. 2021. Effects of tillage methods on distribution characteristics of CH₄ and N₂O in soil profile of double-cropping paddy field. Chin J Rice Sci, 35(1): 78-88. (in Chinese with English abstract)
[47]	Yu Y Q, Huang Y, Zhang W. 2013. Projected changes in soil organic carbon stocks of China’s croplands under different agricultural managements, 2011-2050. Agric Ecosyst Environ, 178: 109-120.
[48]	Zhang F S, Cui Z L, Chen X P, Ju X T, Shen J B, Chen Q, Liu X J, Zhang W F, Mi G H, Fan M S, Jiang R F. 2012. Integrated nutrient management for food security and environmental quality in China. Adv Agron, 116: 1-40.
[49]	Zhang W F, Dou Z X, He P, Ju X T, Powlson D, Chadwick D, Norse D, Lu Y L, Zhang Y, Wu L, Chen X P, Cassman K G, Zhang F S. 2013. New technologies reduce greenhouse gas emissions from nitrogenous fertilizer in China. Proc Natl Acad Sci USA, 110(21): 8375-8380.
[50]	Zhao M, Tian Y H, Ma Y C, Zhang M, Yao Y L, Xiong Z Q, Yin B, Zhu Z L. 2015. Mitigating gaseous nitrogen emissions intensity from a Chinese rice cropping system through an improved management practice aimed to close the yield gap. Agric Ecosyst Environ, 203: 36-45.
[51]	Zhou J, Su X W, Lai S K, Xu G P, Huang J Y, Yao Y L, Yang L X, Dong G C, Wang Y L. 2020 Differences in response of grain yield, nitrogen absorption and utilization to elevated CO₂ concentration in different rice varieties. Chin J Rice Sci, 34(6): 561-573. (in Chinese with English abstract)
[52]	Zou J W, Huang Y, Zheng X, Wang Y. 2007. Quantifying direct N₂O emissions in paddy fields during rice growing season in mainland China: dependence on water regime. Atmos Environ, 41: 8030-8042.

Item	Rice		Wheat		Maize
Item	Jiangxi	Hunan	Jiangsu	Anhui	Hebei	Jilin
Farm size (hm²) ^a	2.1 ± 0.5 a	2.6 ± 0.9 a	2.4 ± 1.1 a	1.6 ± 0.3 a	0.6 ± 0.2 b	0.8 ± 0.2 b
Grain yield (t/hm²) ^a	6.0 ± 0.1 a	5.4 ± 0.1 b	5.7 ± 0.8 a	6.0 ± 0.7 a	6.7 ± 0.6 a	7.7 ± 0.7 a
Diesel oil (kg/hm²)	107.1 ± 27.1	95.2 ± 33.4	131.9 ± 31.4	103.0 ± 29.0	104.1 ± 19.2	88.0 ± 10.3
Electricity for irrigation (kW/hm²)	27.3 ± 8.5	33.2 ± 7.1	-	-	91.8 ± 14.4	80.1 ± 10.9
Seed (kg/hm²)	78.6 ± 14.0	36.0 ± 17.8	44.2 ± 9.7	55.5 ± 6.6	44.6 ± 7.6	35.5 ± 5.1
Film (kg/hm²)	7.4 ± 1.1	7.0 ± 1.5	-	-	-	-
Herbicide (kg/hm²)	0.3 ± 0.1	0.3 ± 0.2	0.5 ± 0.2	0.3 ± 0.1	1.9 ± 0.4	1.4 ± 0.7
Insecticide (kg/hm²)	0.4 ± 0.2	0.3 ± 0.2	0.6 ± 0.2	0.5 ± 0.1	0.7 ± 0.2	0.6 ± 0.3
Fungicide (kg/hm²)	1.1 ± 0.4	0.8 ± 0.5	1.1 ± 0.5	1.0 ± 0.4	0.3 ± 0.1	0.2 ± 0.1
N fertilizer (kg/hm²)	363.2 ± 97.4	217.0 ± 96.3	272.4 ± 83.1	197.3 ± 57.1	172.8 ± 31.1	200.3 ± 37.0
P₂O₅ fertilizer (kg/hm²)	31.5 ± 14.1	36.1 ± 7.8	25.1 ± 9.7	35.2 ± 9.7	93.7 ± 30.1	107.6 ± 39.7
K₂O fertilizer (kg/hm²)	67.0 ± 23.0	86.9 ± 30.0	56.2 ± 18.6	78.1 ± 25.7	63.9 ± 16.7	91.1 ± 26.7
CH₄ (kg/hm²)	131.3 ± 19.5	121.1 ± 29.5	-	-	-	-
N₂O (kg/hm²)	1.9 ± 0.5	1.2 ± 0.5	2.0 ± 0.4	1.4 ± 0.3	1.3 ± 0.2	1.5 ± 0.3
NH₃ (kg/hm²)	149.0 ± 39.5	89.1 ± 40.0	90.9 ± 34.1	65.9 ± 23.1	47.2 ± 13.2	55.0 ± 21.2
NO₃^- (kg/hm²)	4.9 ± 0.5	2.9 ± 0.9	7.3 ± 1.0	5.3 ± 0.7	1.4 ± 0.1	1.6 ± 0.2
NH₄⁺ (kg/hm²)	1.6 ± 0.4	1.0 ± 0.5	0.7 ± 0.01	0.5 ± 0.01	0.1 ± 0.02	0.1 ± 0.03

Item	Rice		Wheat		Maize
Item	Jiangxi	Hunan	Jiangsu	Anhui	Hebei	Jilin
Farm size (hm²) ^a	2.1 ± 0.5 a	2.6 ± 0.9 a	2.4 ± 1.1 a	1.6 ± 0.3 a	0.6 ± 0.2 b	0.8 ± 0.2 b
Grain yield (t/hm²) ^a	6.0 ± 0.1 a	5.4 ± 0.1 b	5.7 ± 0.8 a	6.0 ± 0.7 a	6.7 ± 0.6 a	7.7 ± 0.7 a
Diesel oil (kg/hm²)	107.1 ± 27.1	95.2 ± 33.4	131.9 ± 31.4	103.0 ± 29.0	104.1 ± 19.2	88.0 ± 10.3
Electricity for irrigation (kW/hm²)	27.3 ± 8.5	33.2 ± 7.1	-	-	91.8 ± 14.4	80.1 ± 10.9
Seed (kg/hm²)	78.6 ± 14.0	36.0 ± 17.8	44.2 ± 9.7	55.5 ± 6.6	44.6 ± 7.6	35.5 ± 5.1
Film (kg/hm²)	7.4 ± 1.1	7.0 ± 1.5	-	-	-	-
Herbicide (kg/hm²)	0.3 ± 0.1	0.3 ± 0.2	0.5 ± 0.2	0.3 ± 0.1	1.9 ± 0.4	1.4 ± 0.7
Insecticide (kg/hm²)	0.4 ± 0.2	0.3 ± 0.2	0.6 ± 0.2	0.5 ± 0.1	0.7 ± 0.2	0.6 ± 0.3
Fungicide (kg/hm²)	1.1 ± 0.4	0.8 ± 0.5	1.1 ± 0.5	1.0 ± 0.4	0.3 ± 0.1	0.2 ± 0.1
N fertilizer (kg/hm²)	363.2 ± 97.4	217.0 ± 96.3	272.4 ± 83.1	197.3 ± 57.1	172.8 ± 31.1	200.3 ± 37.0
P₂O₅ fertilizer (kg/hm²)	31.5 ± 14.1	36.1 ± 7.8	25.1 ± 9.7	35.2 ± 9.7	93.7 ± 30.1	107.6 ± 39.7
K₂O fertilizer (kg/hm²)	67.0 ± 23.0	86.9 ± 30.0	56.2 ± 18.6	78.1 ± 25.7	63.9 ± 16.7	91.1 ± 26.7
CH₄ (kg/hm²)	131.3 ± 19.5	121.1 ± 29.5	-	-	-	-
N₂O (kg/hm²)	1.9 ± 0.5	1.2 ± 0.5	2.0 ± 0.4	1.4 ± 0.3	1.3 ± 0.2	1.5 ± 0.3
NH₃ (kg/hm²)	149.0 ± 39.5	89.1 ± 40.0	90.9 ± 34.1	65.9 ± 23.1	47.2 ± 13.2	55.0 ± 21.2
NO₃^- (kg/hm²)	4.9 ± 0.5	2.9 ± 0.9	7.3 ± 1.0	5.3 ± 0.7	1.4 ± 0.1	1.6 ± 0.2
NH₄⁺ (kg/hm²)	1.6 ± 0.4	1.0 ± 0.5	0.7 ± 0.01	0.5 ± 0.01	0.1 ± 0.02	0.1 ± 0.03

Input	Greenhouse gas emission (kg/hm²)			Reactive nitrogen emission (g/hm²)
Input	Rice	Wheat	Maize	Rice	Wheat	Maize
Diesel oil	504.7 ± 134.1	451.3 ± 149.7	479.3 ± 134.1	471.4 ± 139.8	547.3 ± 140.1	447.6 ± 77.1
Electricity for irrigation	24.8 ± 6.6	-	70.7 ± 13.1	3.6 ± 0.9	-	10.3 ± 1.8
Seed	105.4 ± 25.8	28.9 ± 4.6	77.3 ± 11.6	43.5 ± 10.6	12.0 ± 1.9	35.2 ± 5.8
Film	163.6 ± 23.8	-	-	86.6 ± 11.8	-	-
Herbicide	5.0 ± 1.7	6.6 ± 3.1	27.4 ± 8.3	1.1 ± 0.4	1.4 ± 0.7	5.8 ± 1.8
Insecticide	3.6 ± 1.6	5.6 ± 1.1	6.6 ± 2.1	1.6 ± 0.8	2.5 ± 0.6	2.9 ± 1.2
Fungicide	10.0 ± 5.0	11.0 ± 4.8	2.6 ± 1.2	6.7 ± 2.1	7.4 ± 2.8	1.8 ± 0.8
N fertilizer	443.9 ± 144.4	359.3 ± 107.1	285.4 ± 52.2	258.2 ± 86.3	209.0 ± 62.3	166.0 ± 30.6
P₂O₅ fertilizer	55.1 ± 17.1	49.1 ± 5.2	164.1 ± 18.9	18.3 ± 6.1	16.3 ± 1.6	54.4 ± 6.6
K₂O fertilizer	50.0 ± 17.1	43.6 ± 14.3	50.4 ± 14.1	2.3 ± 0.8	2.0 ± 0.7	2.3 ± 0.7
Total	1 366.0 ± 234.1	955.6 ± 194.4	1 163.8 ± 224.1	893.2 ± 187.2	797.9 ± 104.7	726.4 ± 100.7

Input	Greenhouse gas emission (kg/hm²)			Reactive nitrogen emission (g/hm²)
Input	Rice	Wheat	Maize	Rice	Wheat	Maize
Diesel oil	504.7 ± 134.1	451.3 ± 149.7	479.3 ± 134.1	471.4 ± 139.8	547.3 ± 140.1	447.6 ± 77.1
Electricity for irrigation	24.8 ± 6.6	-	70.7 ± 13.1	3.6 ± 0.9	-	10.3 ± 1.8
Seed	105.4 ± 25.8	28.9 ± 4.6	77.3 ± 11.6	43.5 ± 10.6	12.0 ± 1.9	35.2 ± 5.8
Film	163.6 ± 23.8	-	-	86.6 ± 11.8	-	-
Herbicide	5.0 ± 1.7	6.6 ± 3.1	27.4 ± 8.3	1.1 ± 0.4	1.4 ± 0.7	5.8 ± 1.8
Insecticide	3.6 ± 1.6	5.6 ± 1.1	6.6 ± 2.1	1.6 ± 0.8	2.5 ± 0.6	2.9 ± 1.2
Fungicide	10.0 ± 5.0	11.0 ± 4.8	2.6 ± 1.2	6.7 ± 2.1	7.4 ± 2.8	1.8 ± 0.8
N fertilizer	443.9 ± 144.4	359.3 ± 107.1	285.4 ± 52.2	258.2 ± 86.3	209.0 ± 62.3	166.0 ± 30.6
P₂O₅ fertilizer	55.1 ± 17.1	49.1 ± 5.2	164.1 ± 18.9	18.3 ± 6.1	16.3 ± 1.6	54.4 ± 6.6
K₂O fertilizer	50.0 ± 17.1	43.6 ± 14.3	50.4 ± 14.1	2.3 ± 0.8	2.0 ± 0.7	2.3 ± 0.7
Total	1 366.0 ± 234.1	955.6 ± 194.4	1 163.8 ± 224.1	893.2 ± 187.2	797.9 ± 104.7	726.4 ± 100.7

Crop	Carbon footprint (kg/kg)				Nitrogen footprint (g/kg)
Crop	Agricultural input	CH₄	N₂O		Agricultural input	NH₃	NO₃^‒	NH₄⁺ (× 10^-3)	N₂O
Rice	0.23 ± 0.04	0.55 ± 0.11	0.08 ± 0.001	0.15 ± 0.03		16.52 ± 2.10	0.16 ± 0.03	2.08 ± 0.70	0.21 ± 0.07
Wheat	0.20 ± 0.04	-	0.11 ± 0.001	14.17 ± 2.01		17.01 ± 1.41	19.12 ± 1.11	1.07 ± 0.01	0.17 ± 0.03
Maize	0.18 ± 0.03	-	0.06 ± 0.001	5.96 ± 2.37		6.86 ± 1.41	8.61 ± 2.13	0.18 ± 0.01	0.06 ± 0.02