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Effects of pasture management on N 2 O and NO emissions from soils in the humid tropics of Costa Rica
Author(s) -
Veldkamp Edzo,
Keller Michael,
Nuñez Marvin
Publication year - 1998
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/97gb02730
Subject(s) - fertilizer , soil water , nitrous oxide , pasture , agronomy , environmental science , nitrogen , tropics , legume , ammonium , nitrate , chemistry , ecology , biology , soil science , organic chemistry
Emissions of nitrous oxide (N 2 O) and nitric oxide (NO) from agricultural soils in the tropics are important in the global budgets of these trace gases. We made monthly measurements of N 2 O and NO emissions from pastures with three different management systems on volcanic soils in northwestern Costa Rica: traditional (no N input from fertilizer or legumes), pastures with a grass‐legume combination, and pastures fertilized with 300 kg N ha −1 1 yr −1 . Average annual N 2 O emissions were 2.7 ng N cm −2 h −1 from the traditional pastures, 4.9 ng N cm −2 h −1 from the grass‐legume pastures, and 25.8 ng N cm −2 h −1 from the fertilized pastures. Average annual NO emissions were 0.9, 1.3, and 5.3 ng N cm−2 h−1 from traditional, grass‐legume and fertilized pastures, respectively. In a separate experiment the effects of ammonium, nitrate, and urea‐based fertilizer mixtures on nitrogen oxide fluxes were compared. We measured nitrogen oxide fluxes following four different fertilization events. Nitrogen oxide fluxes were among the highest ever measured. The difference in soil water content between the fertilization events had a far greater effect on N 2 O and NO emissions than the effect of fertilizer composition. We conclude that the concept of “emission factors” for calculating N 2 O and NO emissions from different types of N fertilizer is flawed because environmental factors are more important than the type of N fertilizer. To estimate fertilizer‐induced N 2 O emission in tropical agriculture, stratification according to soil moisture regime is more useful than stratification according to fertilizer composition.