Reducing ammonia volatilization in a no-till soil by incorporating urea and pig slurry in shallow bands

Incorporation of broadcast pig slurry and urea into soil is incompatible with no-till production systems and alternative application methods that reduce NH(3)-N loss are required. The objective of this study was to assess the impact of incorporating urea and pig slurry in shallow furrows (banding) on NH(3) volatilization. A field study was conducted on a silty loam soil that had been under no-till for 2 years. Ammonia volatilization was measured for 29 days after urea and pig slurry (140 kg N ha(-1)) were broadcast or incorporated (5 cm) in bands. High urease activity and soil temperatures as well as an absence of rainfall combined to result in large losses of NH(3)-N from all treatments. Broadcast urea lost the greatest proportion of applied N (64%) followed by banded urea (31%), broadcast pig slurry (29%) and banded pig slurry (16%). High emissions from broadcast urea were consistent with previous reports of large volatilization losses on no-till soils. Presence of crop residues and associated high urease activity (288 mu g NH(4)-N g(-1) h(-1)) at the surface of no-till soils were likely important factors contributing to these high emissions. Incorporation of slurry and urea in bands was not as efficient in reducing volatilization as expected but not for the same reason. Relatively high emissions from banded slurry were the result of an incomplete incorporation of slurry in the shallow bands and indicate that the benefit of this practice is limited at high slurry application rates. In banded urea plots, hydrolysis of concentrated urea likely resulted in high localized NH(4) (+) concentrations and pH, which increased NH(3) source strength and emissions. Our results therefore suggest that incorporating urea in bands may not be as efficient for reducing NH(3) emissions as incorporation of broadcasted urea which results in lower soil urea concentrations.