Ammonia Loss and Associated Reactions of Urea in Calcareous Soils
1981
Fenn, L. B. | Miyamoto, S.
Urea in soil is a mobile compound which can be lost by leaching or ammonia (NH₃) volatilization. This research examined the contributions of water additions and chemical reactions in explaining the behavior of applied urea. Urea [CO(NH₂)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 NH₃ losses from (NH₄)₂SO₄ (AS) were still high when placed 7.5-cm deep. Application of AS produced chemically equivalent amounts of Ca and Mg whereas urea and NH₄OH precipitated Ca and Mg. The amount of Ca and Mg precipitated increased with decreasing NH₃ losses. Precipitation of divalent cations enhanced adsorption of NH₄ on soil cation exchange sites, thereby reducing upward movement of NH₄ and subsequent NH₃ losses. The presence of Ca from reaction of AS with CaCO₃ enhanced upward movement of NH₄ and increased NH₃ losses.
Show more [+] Less [-]AGROVOC Keywords
Bibliographic information
This bibliographic record has been provided by National Agricultural Library