北海道大学 大学院農学院 修士論文発表会,2014年2月7日

Effects of soil structure and nutrient status on N2O production
環境資源学専攻 地域環境学講座 土壌学 Zaimire Abudushalamu

Introduction
Soil aggregates play an important role to effect biological processes to influence N2O release from soil.
Moreover, the type of N inputs to the fields may affect the N2O emission in different ways, leading todifferent patterns of N2O emissions from N fertilizers. The study of incubation was carried out todetermine the effect of aggregate size, fertilizer management on N2O production.

Materials and Methods
Experiment 1. Soil samples were taken from 0-20 cm horizon of each field managed by chemicalfertilizer (F) and combination of chemical fertilizer and manure (FM) applications in Hokkaido (SZN,SHD) and FM in China (XJ). Air-dried soil samples were sieved with 2 and 4.5mm sieve. 20 g
air-dried sample was pre-incubated in a 1.8 L glass jar at 20 ℃ for 2 days. Soil sample was moistened
till field water capacity and then incubated again for 10 days (4 replicates). Gas concentrations ofnitric oxide (NO), carbon dioxide (CO2) and N2O were measured every 2 days. Soil chemical
properties were observed before and after incubation. Experiment 2. SHD and XJ soils were used
before fertilization. Five treatments including control (CK), ammonium nitrate, charcoal, plant residue
and cattle manure was selected as N source. Adding them to soil respectively with amount of 150 kg N
ha-1 after determined the total N. Incubation process was same with experiment 1.

Results and Discussion
Experiment 1. Larger aggregates of all soils showed higher values of WEOC, MBC, NH4+-N andNO3--N, and higher productions of N2O, compared to smaller aggregates. The high amount of MBC inlarger aggregates induced higher decomposition of organic matter, resulting in greater N2Oproductions and N mineralization. FM always showed the higher N2O production than F due to soilmineralization stimulated by manure application. The N2O production was higher in SZN soil thanSHD. This might be ascribed to WEOC consumption were higher in SZN. The result of N2O-N/NO-N
showed that the N2O production was derived from denitrification in SZN and XJ, but nitrification inSHD. The NO3--N concentration was significantly higher in XJ. Therefore, the highest N2O production
occurred in XJ due to denitrification which is enhanced by high NO3--N concentration. Experiment 2.
In all samples, cumulative N2O production increased with increasing WEOC consumption, which was
highest in cattle manure, and followed by the plant residue, chemical fertilizer, CK and charcoal.
Charcoal applied soils of both sites showed the lowest N2O flux, it could be explained by the charcoal
is able to changing microenvironment for the microbial growth due to adsorption. Especially in XJ.
NO3--N concentration of charcoal was lower than CK, decreasing N2O emission were partially causedby the ability of charcoal to adsorb NO3--N in the soil. Larger aggregates showed the higher N2O flux
due to mineralization, which was enhanced by WEOC consumption. It also showed the highest N2O
production happened in XJ because of high denitrification losses under high NO3--N concentration.

Conclusion
This study revealed that 1) larger aggregates of all treatments showed higher N2O production thansmaller aggregates because of association of higher amount of WEOC, MBC, NH4+-N and NO3--N
which is enhanced by manure application; 2) highest N2O production occurred in XJ owing todenitrification which is stimulated by high NO3--N concentration；3) The minimum N2O production
was found in charcoal applied soil due to adsorption on charcoal surface.