Submitted to: Journal of Analytical & Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2005
Publication Date: 8/10/2005
Citation: Calderon, F.J., Reeves III, J.B., McCarty, G.W. 2005. Pyrolisis-MS and FT-IR analysis of fresh and decomposed dairy manure. Journal of Analytical & Applied Pyrolysis. 76:14-23. Interpretive Summary: In this study, we analyzed fresh and decomposed cattle manure using two techniques: Pyrolysis-Mass Spectrometry, as well as Fourier-transformed Infrared spectroscopy. Our results show that both technologies are sensitive to compositional changes during manure decomposition. Particularly, Pyrolysis-Mass Spectrometry allowed us to show that the quality of manure lignin changes during manure decomposition. Infrared spectroscopy results showed that proteins, lignins, and possibly fatty acids change during decomposition.
Technical Abstract: The ability to predict manure nitrogen mineralization is essential for optimizing crop growth while preventing N losses to the environment. However, estimating mineralizable manure N is problematic because of the wide variety of organic manure N forms, as well as the lack of a rapid standardized method. Fourier-transformed infrared spectroscopy (FT-IR) is a promising technology, since it can discern between different N functional groups in organic matter, in addition to being instantaneous and non-destructive. Likewise, analytical pyrolysis ' mass spectrometry (Pyrolysis-MS) has been used to study lignin and protein composition of forages. We carried out a 10 week laboratory incubation of manure-amended soil in order to test the sensitivity of FT-IR and Pyrolysis-MS to detect changes in manure during digestion in the animal and decomposition in soil. Four different dairy or beef manures were included. The manures (0.15 mg manure-N g-1 soil) were placed inside mesh bags during the soil incubation to allow for the recovery and analysis of fresh as well as decomposed manure. Infrared spectroscopy of the fresh and incubated manures shows that this technique is sensitive to changes in manure organic N after soil application. Bands associated with primary amines decrease during the incubation, while bands associated with proteins increase during manure decomposition. Bands associated with fatty acids tend to decrease during the incubation, possibly due to utilization as C sources. The spectroscopic data also shows lignin-specific signals increase during manure decomposition, suggesting that manure is lignified as it decomposes in soil. The pyrolysis-MS data shows qualitative changes in manure lignin during decomposition. The relative amounts of nitrogen containing pyrolyzates such as phenylacetonitrile and methylindole changed during the incubation, but the changes were not consistent across manures. In summary, this experiment shows that the use of manure bags is valuable in discerning between the N cycling dynamics of manure and soil, and that infrared spectroscopy, as well as analytical pyrolysis show potential as analytical tools to study manure decomposition in soil.