Transformation and utilization of anaerobically digested manure for crop production

Background

The process of anaerobic digestion of manure changes the form of nitrogen and phosphorus in manure from an organic form to an inorganic form. As a result, the nitrogen and phosphorus should be more plant available, but also may be more susceptible to loss to the environment.

Agronomic Approach

Two forms of manure were compared to urea as sources of nitrogen for grass growth. Raw dairy manure and anaerobically digested dairy manure (co-digested with pre-consumer food waste) were applied at equal amounts of total nitrogen. Grass yield and nitrogen uptake were monitored.

• Cumulative yields for years (analyzed separately)
• Weather conditions vary between years
• Biomass in 2009 than 2010 because of more favorable growing conditions
  
• AD dairy manure provides adequate crop fertility for forage production
• Increased N forage uptake in year 2 (most likely due to favorable weather conditions)
• AD broadcast application& Urea receiving plots had greatest biomass

Take Home Message

• AD manure reduces gaseous N loss
• Although small increase in N₂O, the benefits of methane removal and renewable energy creation outweigh this increase
• Nitrate leaching potential is lower in AD & non AD relative to Urea