Fourier transform infrared and fluorescence spectral features of organic matter in conventional and organic dairy manure

Authors: He, Zhongqi; OHNO, TSUTOMU - University Of Maine

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2012
Publication Date: 5/15/2012
Citation: He, Z., Ohno, T. 2012. Fourier transform infrared and fluorescence spectral features of organic matter in conventional and organic dairy manure. Journal of Environmental Quality. 41:911-919.

Interpretive Summary: Although the organic dairy is currently a niche market, it has exhibited potential for growth in the U.S. dairy sector. Generally, organic dairy farming has significant differences from its conventional counterpart in respect to housing, grazing, animal nutrition, disease prevention, and veterinary treatment. Whereas organic matter is a major component in animal manure, this study investigated the effects of organic dairy farming management on the structural and functional properties of manure organic matter. We found no absolutely distinct difference in water extractable organic matter between the two types of dairy manure in respects to C and N contents, tested spectral features. However, based on the average values, we observed the general patterns on the impact of organic farming on the manure composition. That is, organic dairy manure contained less soluble C and N compounds; but more hydrophobic aliphatic groups. On the other hand, organic dairy manure contained less amino/protein N-related components. These differences might be attributed to more forage feedstuffs in organic dairy farming management and more protein additives in conventional dairy feedstuffs. Information derived from this study may be helpful in evaluating biodegradability of manure organic matter and the long-term fertility of the soil through organic matter deposition in organic mixed crop-dairy systems.

Technical Abstract: Organic dairy production has exhibited potential for growth in the U.S. dairy sector. Although organic dairy management may significantly affect availability, utilization, and cycling of manure nutrients, little information is available to aid organic dairy farmers in making nutrient and manure management decisions. In this work, we comparatively characterized 15 organic (OD) and seven conventional (CD) dairy manure samples by Fourier transform infrared (FT-IR) and fluorescence spectroscopies. FT-IR features of manure organic matter varied mainly in the 1650-1550 cm-1 range, reflecting the presence of different N compounds in these manure samples. Fluorescence data revealed five fluorophore components present in the water extracted organic matter from the manures. In respect to the difference between CD and OD samples, we found no absolutely distinct difference in whole and water extractable organic matter between the two types of dairy manure with respects to C and N contents, FT-IR and fluorescence spectral features. However, based on the average values, we observed general pattern differences on the effect of organic farming on the manure composition. That is, OD contained less soluble C and N compounds; but more hydrophobic aliphatic groups. The soluble organic matter in OD samples contained more stable humic- and lignin-related components and less amino/protein N-related components. These differences might be attributed to more forage feedstuffs in organic dairy farming management and more protein additives in conventional dairy feedstuffs. Information from this work may be useful in aiding organic dairy farmers in making nutrient and manure management decisions.