Measurements of CH4 uptake and N2O emissions in native, nitrogen-fertilized, and wheat-growing prairie soils from spring to late autumn, 1990 are reported. It is found that nitrogen fertilization and cultivation can both decrease CH4 uptake and increase N2O production, thereby contributing to the increasing atmospheric concentrations of these gases.

Methane and nitrous oxide fluxes in native, fertilized and cultivated grasslands

https://harvardforest.fas.harvard.edu/sites/harvardforest.fas.harvard.edu/files/publications/pdfs/Davidson_AgriForestMeterology_2002a.pdf

Minimizing artifacts and biases in chamber-based measurements of soil respiration

This Review discusses current knowledge regarding agriculture as a source for nitrous oxide — a major greenhouse gas. It offers an outlook on future developments about the consequences of increasing use of biofuels and the potential importance of aquaculture, as well as options for mitigation.

Global agriculture and nitrous oxide emissions

Emissions of nitrous oxide from intensively managed agricultural fields were measured over 3 years. Exponential increases in flux occurred with increasing soil water-filled pore space (WFPS) and temperature; increases in soil mineral N content due to fertilizer application also stimulated emissions. Fluxes were low when any of these variables was below a critical value. The largest fluxes occurred when WFPS values were very high (70-90%), indicating that denitrification was the major process responsible. The relationships with the driving variables showed strong similarities to those reported for very different environments: irrigated sugar cane crops, pastures, and forest in the tropics. Annual emissions varied widely (0.3-18.4 kg N 2 O-N ha -1 ). These variations were principally due to the degree of coincidence of fertilizer application and major rainfall events. It is concluded therefore that several years' data are required from any agricultural ecosystem in a variable climate to obtain a robust estimate of mean N 2 O fluxes. The emissions from small-grain cereals (winter wheat and spring barley) were consistently lower (0.2-0.7 kg N 2 O-N per 100 kg N applied) than from cut grassland (0.3-5.8 kg N 2 O-N per 100 kg N). Crops such as broccoli and potatoes gave emissions of the same order as those from the grassland. Although these differences between crop types are not apparent in general data comparisons, there may well be distinct regional differences in the relative and absolute emissions from different crops, due to local factors relating to soil type, weather patterns, and agricultural management practices. This will only be determined by more detailed comparative studies.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/1999JD900378

Nitrous oxide emissions from intensive agricultural systems: Variations between crops and seasons, key driving variables, and mean emission factors

Laboratory experiments were conducted to examine the effect of charcoal addition on N2O emissions resulting from rewetting of air-dried soil. Rewetting the soil at 73% and 83% of the water-filled pore space (WFPS) caused a N2O emission peak 6 h after the rewetting, and the cumulative N2O emissions throughout the 120-h incubation period were 11 ± 1 and 13 ± 1 mg N m−2, respectively. However, rewetting at 64% WFPS did not cause detectable N2O emissions (−0.016 ± 0.082 mg N m−2), suggesting a severe sensitivity to soil moisture. When the soils were rewetted at 73% and 78% WFPS, the addition of charcoal to soil at 10 wt% supressed the N2O emissions by 89% . In contrast, the addition of the ash from the charcoal did not suppress the N2O emissions from soil rewetted at 73% WFPS. The addition of charcoal also significantly stimulated the N2O emissions from soil rewetted at 83% WFPS compared with the soil without charcoal addition (P < 0.01). Moreover, the addition of KCl and K2SO4 did not show a clear d...

G. L. Hutchinson

Papers

Improved Soil Cover Method for Field Measurement of Nitrous Oxide Fluxes