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Ammonia Loss and Associated Reactions of Urea in Calcareous Soils
Author(s) -
Fenn L. B.,
Miyamoto S.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500030020x
Subject(s) - urea , chemistry , ammonia , ammonia volatilization from urea , leaching (pedology) , inorganic chemistry , soil water , calcareous , dissolution , environmental chemistry , organic chemistry , soil science , geology , paleontology
Urea in soil is a mobile compound which can be lost by leaching or ammonia (NH 3 ) volatilization. This research examined the contributions of water additions and chemical reactions in explaining the behavior of applied urea. Urea [CO(NH 2 ) 2 ] initially moves undissociated into the soil with added water. Ammonia losses from surface‐applied urea thus decreased with increasing amounts of applied water. Ammonia losses from urea were minimal if injected into the soil 2.5 cm or more, whereas NH 3 losses from (NH 4 ) 2 SO 4 (AS) were still high when placed 7.5‐cm deep. Application of AS produced chemically equivalent amounts of Ca and Mg whereas urea and NH 4 OH precipitated Ca and Mg. The amount of Ca and Mg precipitated increased with decreasing NH 3 losses. Precipitation of divalent cations enhanced adsorption of NH 4 on soil cation exchange sites, thereby reducing upward movement of NH 4 and subsequent NH 3 losses. The presence of Ca from reaction of AS with CaCO 3 enhanced upward movement of NH 4 and increased NH 3 losses.