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TECHNICAL REPORTS

Banding of Urea Increased Ammonia Volatilization in a Dry Acidic Soil

^a Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd., Québec City, QC, Canada, G1V 2J3
^b Institut de recherche et développement en agroenvironnement, Québec City, QC, Canada, G1P 3W8

^* Corresponding author (philippe.rochette{at}agr.gc.ca).

Received for publication June 27, 2008. Volatilization of ammonia following application of urea contributes to smog formation and degradation of natural ecosystems. The objective of this study was to evaluate the impact of (i) incorporation and banding of urea and (ii) surface broadcast of slow-release urea types on NH₃ volatilization in a dry acidic soil. Volatilization was measured using wind tunnels for 25 d after standard urea (140 kg N ha^–1) was broadcast, broadcast and incorporated (0–5 cm), or incorporated in shallow bands (3–5 cm) to a conventionally tilled silty loam soil. Urea supplemented with a urease inhibitor or coated with a polymer was also broadcast at the soil surface. Little N diffused out of the polymer-coated granules and ammonia losses were low (4% of applied N). Use of a urease inhibitor also resulted in a low NH₃ loss (5% of applied N) while maintaining soil mineral N at levels similar to plots where untreated urea was broadcast. The rate of hydrolysis of urea broadcast at the soil surface was slowed by the lack of moisture and NH₃ loss (9% applied N) was the lowest of all treatments with standard urea. Incorporation of broadcast urea increased emissions (16% applied N) by increasing urea hydrolysis relative to surface application. Furthermore, incorporation in band also increased emissions (27% applied N) due to a localized increase in soil pH from 6.0 to 8.7. We conclude that incorporating urea in bands in a dry acidic soil can increase NH₃ volatilization compared to broadcast application followed by incorporation.