Application of neutron-gamma analysis for determination of C/N ratio in compost

Authors: Yakubova, Galina; Kavetskiy, Aleksandr; Prior, Stephen - Steve; Torbert, Henry - Allen

Submitted to: American Society of Agronomy Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/2/2018
Publication Date: 2/4/2018
Citation: Yakubova, G.N., Kavetskiy, A.G., Prior, S.A., Torbert III, H.A. 2018. Application of neutron-gamma analysis for determination of C/N ratio in compost [abstract]. American Society of Agronomy Branch Meeting. CDROM.

Interpretive Summary:

Technical Abstract: Neutron-gamma analysis is based on the acquisition of gamma rays from neutron irradiated study objects. The intensity and energy of the registered gamma rays gives information on the types and amounts of elements in the studied object. The use of this method for measurements of soil carbon demonstrates the effectiveness for applications in soil science and agriculture due to the advantages over traditional laboratory chemical methods. Neutron gamma analysis is a nondestructive in situ method that requires no sample preparation and can perform multi-elemental analyses of large soil volumes in ~1 hour. These same advantages will apply when using this method for measurement of carbon and nitrogen in compost. Since assessing the C/N ratio is important in determining the quality of compost, this report will discuss the application of neutron gamma analysis in determining C/N ratios. Our discussion is based on Monte-Carlo (MC) computer simulations of neutron propagation into the medium, their interaction with medium nuclei, and the acquisition of gamma rays which appear due to this interaction. This method is widely used into the neutron physics area starting from the time of the “Manhattan Project.” Software packets for such simulations have been developed and are currently available; the software toolkit “Geant4” was used for our simulations. MC simulations of neutron propagation in compost and carbon and nitrogen gamma response from compost samples with different C/N ratios were determined. Simulations showed that the C to N gamma response ratio was directly proportional to the C/N mass ratio in samples ranging from 0-25. Our results showed that compost C/N ratio can be determined by measuring carbon and nitrogen gamma peak areas. Test measurements of C/N ratio in real compost were also conducted using neutron-gamma analysis. The results of these measurements were in a good agreement with MC simulations, and will be discussed in further detail. The economical, organizational, and radiation safety questions associated with the application of neutron gamma analysis will also be discussed. Based on our findings, it is possible to conclude that the application of neutron gamma analysis for determining C/N ratio of compost is quite effective and could be possibly used in compost fabrication.