N2O emissions and N-Leaching from Spring and Fall Applications of Digestate, Raw Dairy Manure and Urea

Emily Ann Schwager1, Andrew VanderZaag2, Claudia Wagner-Riddle3, Anna Crolla4, Christopher William Kinsley4 and Edward Gregorich5, (1)University of Guelph, Guelph, ON, Canada, (2)Agriculture and Agri-Food Canada, Science and Technology Branch, Ottawa, ON, Canada, (3)University of Guelph, School of Environmental Sciences, Guelph, ON, Canada, (4)Campus d'Alfred, University of Guelph, Alfred, ON, Canada, (5)Agriculture and Agri-Food Canada, Ottawa, ON, Canada

Contact First Author: Emily Ann Schwager; schwager@uoguelph.ca

Abstract ID#: 33617

 

English Abstract:
Anaerobic digestion (AD) is a manure treatment technology that reduces CH4 emissions from manure storage and provides a nitrogen rich fertilizer for field crops. However, few studies have evaluated the environmental impacts of applying AD effluent (digestate) to agricultural soils, and interactions between soil type, climate and timing of application. In this study, N2O fluxes and N-leaching losses were measured for 2.5 years (October 2011 to May 2014) in Alfred, Ontario. The site consisted of two nearby fields with contrasting soil textures (sandy-loam vs. clay). Treatments included: fall- and spring-applied digestate (DG), fall- and spring-applied raw dairy manure (RM), spring urea (UR) and a zero-N control. N2O fluxes were measured using static chambers and N-leaching was estimated by sampling isolated tile drains (clay field) and zero-tension lysimeters in both fields. N2O emissions were higher in the second year of study (wet year) compared to the first (dry year). Peak N2O emissions occurred during spring thaw (March-April) and ~2 weeks following spring applications and tillage. There was no overall effect of timing (spring vs. fall) on annual N2O emissions, only a change on when emissions took place (at spring thaw for fall application and in late spring after spring manure application). DG had significantly higher N2O emissions compared to RM and UR in the sandy-loam field (pH=6.2), but there were no N source effects on N2O emissions in the clay field (pH=7.1). DG and RM treatments showed similar annual NO3 losses, while UR had the highest annual NO3 mass load in both fields measured using lysimeters and tile drains As such, lower N2O emissions from UR were potentially the result of greater NO3 leaching. Thus, simultaneous measurements of N2O and NO3 provide insight into potential pollutant trade-offs. Overall, N source effects were strongly linked to interactions with soil type and climate.
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