Hi Stefano, probably you can use the Ecoinvent database: http://www.ecoinvent.ch/

Thank you very much, but actually we were looking for some scientific paper or opendata.

Stefano

Energy coefficients are available in published papers and literatures. I may suggest for few journals to consult: Biomass and bioenergy, Energy, Energy Conversionand Management, Energy for Sustainable Development etc.

Fehrenbach, H., Giegrich, J., Gärtner, S., Reinhardt, G., and Rettenmaier, N. (2007). Greenhouse gas balances for the German biofuels quota legislation. Methodological guidance and default values. A report prepared for the Federal Environment Agency, Germany. IFEU Institute, Heidelberg.

You might try searching the catalog at the US  National Agricultural Library. 

http://www.nal.usda.gov/

Open to all, and with lots of otherwise uncataloged US government and government financed reports.

the following information may be useful for your research

Abstract: Using the Farm Energy Analysis Tool (FEAT), we compare energy use and greenhouse gas (GHG) emissions from the cultivation of different crops, highlight the role of sustainable management practices, and discuss the impact of soil nitrous oxide (N2O) emissions and the uncertainty associated with denitrification estimates in the northeastern United States. 

Across all nonleguminous crops, the single greatest contribution to energy use was from N fertilizer, which ranged from 3175 MJ per ha per year (40% of the total) in hybrid poplar to 9209 MJ per ha per year (43% of the total) in corn silage (figure 1). The single greatest energy use contribution across the three legume crops was on-farm fuel use, which was also the second largest single energy use input across all nonleguminous crops. When averaged across all crops, N fertilizer accounted for 36% of the total energy use, followed by on-farm fuel (30%), then K2O (7%), lime (6%), the transportation of inputs (6%), P2O5 (5%), seed (5%), herbicide (4%), drying (2%), and insecticide (1%). These results show that N and on-farm fuel consumption are the main energy input drivers, representing 66% of the total energy across crops,

Ref: Energy Use and Greenhouse Gas Emissions from Crop Production Using the Farm Energy Analysis Tool

Gustavo G. T. Camargo, Matthew R. Ryan and Tom L. Richard

Bio Science, volume 63, Issue 4, pp 263-273, 2013.

bioscience.oxfordjournals.org/content/63/4/263.full

go thru this article

http://www.arpnjournals.com/jabs/research_papers/rp_2009/jabs_0309_118.pdf

http://www.fao.org/docrep/006/y5022e/y5022e04.htm

excellent answers! many, many thanks!!

Dear S.Fabiani

for estimate the energy requirement for product of chemical fertilizer its important that energy requirement of every form of chemical fertilizer is different. for example this amount is  66.14 MJ per kg for N fertilizer , and 12.44MJ per kg for phosphate fertilizer.

this paper guided you.

Dear Fabiani,

You can also visit www.iase.in. You can find there many papers on Energy in Agriculture. 

I suggest you to read following book. You can find good information in it.

CIGR Handbook of Agricultural Engineering Volume V

Energy and Biomass Engineering

Edited by CIGR–The International Commission of Agricultural Engineering

Volume Editor: Osamu Kitani

I suggested you to read a journal entitled, "Fadare, D. A., Bamiro, O. A., & Oni, A. O. (2010). Energy and cost analysis of organic fertilizer production in Nigeria.Energy, 35(1), 332-340". - Dr.O.D. Sam

http://www.fertilizerseurope.com/fileadmin/user_upload/publications/agriculture_publications/EFMA_Phosphorus_booklet__2_.pdf