|ZHANG, MINGCHU - University Of Alaska|
|CAO, XIAOYAN - Old Dominion University|
|LI, YUAN - Old Dominion University|
|MAO, JINGDONG - Old Dominion University|
Submitted to: Organic Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2015
Publication Date: 5/18/2015
Citation: He, Z., Zhang, M., Cao, X., Li, Y., Mao, J., Waldrip, H.M. 2015. Potential traceable markers of organic matter in organic and conventional dairy manure using ultraviolet–visible and solid-state 13C nuclear magnetic resonance spectroscopy. Organic Agriculture. 5:113-122.
Interpretive Summary: Organic dairy (OD) production is drawing increasing attention because of public concerns about food safety, animal welfare and the environmental impacts of conventional dairies (CD) and other intensive livestock systems. Organic dairy farm management can differ considerably from their CD counterparts because OD farms adopt such management practices as allowing for more pasture grazing, feeding a higher proportion of forage in the diet, and not using synthetic amino acids, sub-therapeutic levels of antibiotics, or other and growth-promoting agents. In this work, we comparatively determined and analyzed the UV-vis spectral parameters of water soluble organic matter, and 13C NMR spectral features of whole organic matter between the two types of dairy manure. Our objectives were to get more in-depth insight on the differences in organic matter between OD and CD manures. Our observations indicate that the diet composition influenced dissolved organic matter components of dairy manure. Especially, a unique 13C NMR feature could be assigned to cuticle materials of plants. These compounds could serve as traceable marker components of forage required for organic dairy farming operation. Further confirmation of the relation of the 13C NMR feature with forage ingredients using manure from “control or known feeding” could help to provide a scientific basis for evaluation/authentication of OD farming programs.
Technical Abstract: Organic dairy (OD) production is drawing increasing attention because of public concerns about food safety, animal welfare and the potential environmental impacts of conventional dairy (CD) systems. However, very limited information is available on how organic farming practices affect the chemical composition and properties of dairy manure, which could influence nutrient cycling and soil fertility differently from CD manure. In this study, we compared the ultraviolet–visible (UV-vis) and 13C nuclear magnetic resonance (NMR) spectral features of dissolved and whole organic matter (OM), respectively, of CD and OD manure samples. With UV-vis analysis, we observed differences in absorptivities at 254 and 280 nm (SUVA254 and SUVA280) between the two types of manure, reflecting greater aromaticity of dissolved OM in OD than CD manure. Solid state 13C NMR spectroscopy revealed a greater abundance of NCH groups in CD than in OD manure, which was attributed to the inclusion of amino acid and protein additives in CD diets. The 13C NMR characteristics of triple peaks/shoulders at 26, 29, and 33 ppm were more evident in OD than in CD manures. This observation was presumably due to more forage feedstuff used on OD farms, as this 13C NMR feature was assigned to cutin and cutan from the outer cuticle of herbaceous plants. Thus, further 13C NMR research on the distinct spectral features of manure around 30 ppm may provide a scientific basis for the use of traceable marker components for evaluating the authenticity of OD farming programs.