**Author details**

More studies are necessary to evaluate the effectiveness of OAs in reducing N<sup>2</sup>

greatly reduced [15, 48–50]. [48] tested the effect of the NI DMPP in reducing N<sup>2</sup>

on irrigated rice in a Mediterranean environment, DMPP also reduced N<sup>2</sup>

availability; however, these factors are the main influencers of nitrification and denitrification

from changing the management practices, e.g., cultivation practices and application rates. To

from grassland after cattle slurry application. They found that DMPP reduced cumulative N<sup>2</sup>

emissions by 69 and 48% in autumn and spring, respectively. In another study using pig manure

so far, studies on the combination of OAs with NIs are scarce compared to the single treatments. In summary, OAs have the potential to be environmental-friendly if soil parameters like moisture and pH are carefully evaluated, and the best management practices, e.g., no tillage or split application, are applied. In addition, careful assessment of optimal OA rates, improved timing of OA application, and crop N demand or using a combination of OAs and stabilized

Overall, the N budget has to be understood first to estimate the potential benefit of EEF on N<sup>2</sup>

after harvest, rainy season) have to be assessed to determine the use of EEF effectively. Also, the contribution of nitrification, denitrification, and other processes concerning N turnover needs to be assessed in more detail. Especially, microbes, the drivers of these processes, need to be addressed in terms of changes in their activity, community structure, and abundance after EEF application and the subsequent changes in N turnover processes. In summary, more studies are necessary to assess the overall effectiveness of EEFs since their power in mitigat-

O emissions varies with many factors. An individual fertilizer plan and type which is optimized for the prevalent climate conditions, soil type, management practice, etc. would

The authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers' bureaus; membership, employment, consultancies, stock ownership, or other

with the assessment of an N balance approach to fully exploit their potential.

O emission peaks and the annual contribution of different periods (e.g., sowing,

volatilization, OAs should be incorporated into the soil to avoid contact with the atmo-

application mainly affects soil parameters like moisture, pH, O<sup>2</sup>

processes. Possibilities to influence and mitigate N<sup>2</sup>

84 Soil Contamination and Alternatives for Sustainable Development

fertilizers are some of the options to decrease N2

**3. Conclusion and recommendations**

be optimal in order to effectively reduce N<sup>2</sup>

sphere; however, this might increase N<sup>2</sup>

A possible option to mitigate N<sup>2</sup>

bination with NIs, N<sup>2</sup>

avoid NH<sup>3</sup>

emissions. N<sup>2</sup>

ing N2

**Conflict of interest**

O emissions. OA

O emissions

O emissions [50]. But

O

O

concentration, and substrate

O emissions after OA application mainly arise

O emissions due to higher N availability in the soil [20].

O emissions after OA application [20].

O emissions. The use of EEFs has to be combined

O emissions from OAs is to combine them with EEFs. In com-

O emissions from liquid manure like cattle slurry or pig manure can be

Yoshitaka Uchida\* and Isabell von Rein

\*Address all correspondence to: uchiday@chem.agr.hokudai.ac.jp

Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan
