Denitrification Losses In Manure Amended, Permanent Forage and Corn-Soybean-Wheat Rotations In Atlantic Canada.

Denitrification losses from agricultural fields are a known source of greenhouse gas emissions. Losses resulting from the use of organic amendments when used as a nitrogen source in crop production systems have the potential to be significantly higher when compared with systems using inorganic fertilizers. Using the acetylene blockage technique, growing season (GS) denitrification losses were measured in a permanent forage (PF) and a corn-soybean-wheat (CSW) rotation with or without tillage (T v NT). Spring-applied liquid dairy manure (LDM) was used as an N source for crop production at rates equivalent to 120 – 200 kg N ha^-1. Denitrification losses ranged between 0.7 and 31.0 kg N ha^-1 GS^-1 across all treatments and growing seasons. Cumulative losses over the four year study period were 42.2, 47.6 and 40.8 kg N ha^-1 for the PF, CSW-T and CSW-NT treatments respectively. There were no consistent differences between treatments over the four year study period. Large differences (~ 30 kg N ha^-1 GS^-1) in average denitrification rates between growing seasons, point towards non-treatment land management practices and weather conditions as being the major drivers for denitrification.