Open AccessNitric and nitrous oxide fluxes from intensifying crop agriculture in the seasonally dry tropical Amazon–Cerrado border region
Author(s) -
Huddell Alexandra,
Neill Christopher,
MaracahipesSantos Leonardo,
Cerri Carlos Eduardo Pellegrino,
Menge Duncan
Publication year - 2021
Publication title -
agrosystems, geosciences and environment
Language(s) - English
Resource type - Journals
ISSN - 2639-6696
DOI - 10.1002/agg2.20169
Subject(s) - nitrous oxide , agronomy , fertilizer , biome , human fertilization , tropics , environmental science , nitrogen , agroecosystem , ecosystem , agriculture , chemistry , biology , ecology , organic chemistry
Rapid expansion and intensification of crop agriculture in the tropics may accelerate ecosystem losses of reactive nitrogen (N). We quantified emissions of nitric oxide (NO) and nitrous oxide (N 2 O) in forest, single‐cropped soybean [ Glycine max (L.) Merr.], and N‐fertilized double‐cropped soybean–maize ( Zea mays L.) at three N fertilizer levels within the largest area of recent cropland expansion on earth, in the Amazon and Cerrado biomes in Brazil. The NO emissions were 2.1 kg N ha ‒1 yr ‒1 in forest, 0.6 kg N ha ‒1 yr ‒1 in soybean, and 1.3 kg N ha ‒1 yr ‒1 in soybean–maize. The N 2 O fluxes were <1.1 kg N ha ‒1 yr ‒1 across all land uses. As fertilization levels increased from 80 to 160 kg N ha −1 yr ‒1 in soybean–maize double‐cropped sites, NO emissions increased from 0.6 to 6.7 kg N ha −1 mo ‒1 in the month immediately after fertilization, but N 2 O emissions only increased from 0.6 to 1.8 kg N ha −1 mo ‒1 . These results indicate that NO emissions do not increase when forests are converted to croplands under current fertilization levels, and that NO will respond more strongly than N 2 O fluxes to increases in fertilizer applications. Our findings suggest that if N fertilization rates in the region were increased, NO fluxes could increase rapidly.