Nitrous Oxide Emission From Soil Receiving Anaerobically Digested Manure by-Products Application.

Anaerobic digestion (AD) of animal manure has become an environmentally attractive technology to meet the world’s increasing demand for energy. Anaerobically digested manure (ADM), often referred as digestate, is one of the final by-products of the biogas energy industry. The ADM is a nitrogen-rich material and its application increases crop yields, but could also increase soil nitrous oxide (N2O) emissions, which is an environmental concern. The objectives of this study were to investigate the N2O emissions from soil receiving various forms of ADM application. Two field sites were selected, one near Lethbridge, Southern Alberta, and another near St. Albert, Central Alberta. A complete randomized block design with six treatments, two application rates and four replications was used. The six treatments were: (1) control: no amendment (CK), (2) fresh manure (M), (3) ADM, (4) liquid removed from ADM to produce separated solids (SS), (5) SS processed into pellets (PE), and (6) urea-enriched SS processed into N:P balanced pellets (PEU). All amendments were applied at rates of 100 and 200 kg N per ha per yr. Barley was grown and harvested at the soft dough stage as forage for making silage feed. During the growing season, the rate of N2O emission was collected weekly using a vented static chamber at the Lethbridge site and every two weeks at the St. Albert site. Analysis of preliminary data indicates that crop yield and N2O emission from the ADM treatment were generally higher than from all other treatments, reflecting the higher water soluble N in the ADM and increases in soil moisture content following the amendment application. Two more years of field work is planned for much needed additional field data before meaningful conclusions can be drawn.