Modified lignite and black coal (BC) are potential amendments for animal bedding to abate ammonia (NH3) emissions due to their large adsorption capacities for ammoniacal nitrogen (N). However, the ability of modified lignite and BC in reducing NH3 volatilization from livestock manure and the underlying mechanisms remain unknown. The present study has investigated the effect of lignite, modified lignite, BC and modified BC on NH3 volatilization from cattle manure, biological immobilization of manure ammoniacal N and manure properties. Modified lignite and BC reduced the NH3 volatilization from manure by 44 and 36%, respectively, which were comparable with original lignite (43%). The biological immobilization of applied stable isotope labelled 15N in lignite, modified lignite, BC and modified BC amended manures was 15, 18, 11 and 16%, respectively, which were significantly higher than that in unamended manure (4%, P < 0.001). In addition, NH4+-N concentrations of lignite, modified lignite and modified BC amended manures (7.0-7.3 mg g-1) were significantly higher than that of the unamended and original BC amended manures (3.3 and 4.8 mg g-1, respectively, P < 0.001). However, the manure pH in all treatments remained alkaline (pH > 8.2). Our results highlight that the adsorption and immobilization of manure ammoniacal N induced by amendments are the key drivers in reducing NH3 loss from manure, outweighing the pH effect. The findings of this study provide new insights into the mechanisms of coal amendments reducing NH3 loss from animal manure and their potential applications in intensive livestock systems.
Keywords: Amendment; Ammonia emission; Brown coal; Feedlot; Nitrogen loss; Waste management.
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