Evaluation of N2O Emission Mitigation from Agricultural Fields: Average
Reduction of Fertilizers Containing Nitrification Inhibitor is -38%
Abstract
Field experiment data on reduction technology of nitrous oxide (N2O) emission from
agricultural fields were collected and statistically analyzed. The results indicated that
average reduction of fertilizers containing nitrification inhibitor and polymer-coated
fertilizers (PCF) were -38% and -35%, respectively.
Research Institute: Hiroko Akiyama, Kazuyuki Yagi, Xiaoyuan Yan,
National Institute for Agro-Environmental Sciences
Background and Purpose
Agricultural fields are an important anthropogenic source of atmospheric nitrous
oxide (N2O). Reducing N2O emission from agricultural fields now becomes an important
issue to mitigate global warming. The Third Assessment Report of the International
Panel on Climate Change stated that nitrogen fertilizer management such as the use of
nitrification inhibitor and slow-release fertilizers could tentatively cut N2O emissions
from nitrogen fertilizer use by -30% on a global scale. But to the present day there is no
sign of tangible data that contributes the evidence. This study aimed to quantitatively
evaluate the effect of these technologies.
Achievements
The evaluation of reduction technology should be based on field experiments, but it is
difficult to obtain average reduction rates through field experiments because such
results would vary widely with weather and soil conditions. For this reason, by
collecting literature values of field experiments and statistically analyzing them, the
average reduction effect was assessed. It was concluded that the average reduction
rates of fertilizer containing a nitrification inhibitor was -38% of conventional fertilizer
(Figure 2）, and it becomes apparent that the reduction rate was relatively stable. On
the other hand, the average reduction rate of polymer-coated fertilizer was -35%
depending on soil types. Thus, there were more reduction effects in heavy clay soil,
while Andosol, which occupies about 50% of upland soils in Japan, did not have a clear
reduction effect (Figure3). These results were the first report to quantitatively evaluate
potential reduction rates of N2O emission from agricultural lands and can be applied to
establish measures to control global warming.
① Fertilizer containing nitrification inhibitor is compound that delay bacterial
oxidation of NH4+ by depressing the activities of nitrifiers in soil.
② Polymer-coated fertilizer is a slow-release fertilizer that slows the rate of nutrient
release through coating. It is believed there is capability to improve nitrogen
efficiency and to restrain NO2.
Figure 1. N2O emission from agricultural fields
Note: In agricultural soil, there are two processes which can produce N2O. One is the
nitrification of NH+4 in fertilizers to NO3-, and another is the denitrification of NH4+ to
nitrogen gas (N2).
Figure 2. Reduction effect on N2O emission by nitrification inhibitors fertilizers
It is clarified that there are stable reduce effects by nitrification inhibitors fertilizers.
Figure 3. Reduction effect on N2O emission by polymer-coated fertilizers
Although the average reduction rate of polymer-coated fertilizer is -35%, it greatly
depends on the soil type with the biggest reduce effect for gleysol grassland and no clear
effect for Andosol upland fields.